U.S. DEPARTMENT OF COMMERCE
Technology Administration
National Institute of Standards and Technology
NISTIR 6144
Office of Applied Economics
Building and Fire Research Laboratory
Gaithersburg, Maryland 20899
BEES 1.0
Building for Environmental and Economic Sustainability
Technical Manual and User Guide
Barbara C. Lippiatt
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NISTIR 6144
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Abstract
The BEES (Building for Environmental and Economic Sustainability) version 1.0 software
implements a rational, systematic technique for selecting environmentally and economically
balanced building products. The technique is based on consensus standards and designed to be
practical, flexible, and transparent. The Windows-based decision support software, aimed at
designers, builders, and product manufacturers, includes actual environmental and economic
performance data for 22 building products across a range of functional applications. BEES
measures the environmental performance of building products using the environmental life-cycle
assessment approach specified in the latest versions of ISO 14000 draft standards. All stages in
the life of a product are analyzed: raw material acquisition, manufacture, transportation,
installation, use, and waste management. Economic performance is measured using the American
Society for Testing and Materials (ASTM) standard life-cycle cost method, which covers the
costs of initial investment, replacement, operation, maintenance and repair, and disposal.
Environmental and economic performance are combined into an overall performance measure
using the ASTM standard for Multiattribute Decision Analysis. For the entire BEES analysis,
building products are defined and classified based on the ASTM standard classification for
building elements known as UNEFORMAT H
Key words: Building products, economic performance, environmental performance, green
buildings, life cycle assessment, life-cycle costing, multiattribute decision analysis, sustainable
development
Disclaimer
The United States Department of Commerce and NIST do not endorse any particular brand,
product, or service. The enclosed information is provided for comparing generic, U.S. industry-
average product classes only and no representations are made as to the quality or fitness of any
specific manufacturer's product. Users shall not in any way say or imply that the information
obtained from BEES is an endorsement of any particular product, service, or brand.
The BEES tool bears no warranty, neither express nor implied. NIST does not assume legal
liability nor responsibility for a User's utilization of BEES. NO WARRANTIES AS TO ANY
MATTER WHATSOEVER ARE MADE BY NIST, INCLUDING NO WARRANTY OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
111
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Acknowledgments
The BEES tool could not have been completed without the help of others. Thanks are primarily
due the NIST Building and Fire Research Laboratory (BFRL), Building Environment Division,
for its support of this work from its inception. The U.S. Environmental Protection Agency
(EPA), Pollution Prevention Division, and the NIST/BFRL Building Materials Division also
deserve thanks for their support. Deserving special thanks is the BEES environmental data
contracting team of Environmental Strategies and Solutions, Inc. and Ecobalance, Inc., for its
superb data development, documentation, and technical support. Also deserving special thanks
are the 125 BEES Beta Testers for their time spent reviewing the BEES Beta version, and their
comments leading to many improvements. The author is particularly grateful for the key
cooperation and support offered by a wide variety of manufacturers with products represented in
BEES. Their cooperation exceeded all expectations, and led to improvements in the underlying
BEES performance data. Thanks are also due colleagues from an early collaboration with EPA:
Greg Norris of Sylvatica, Inc. (formerly of the NIST Office of Applied Economics), James White
of the EPA National Risk Management Research Laboratory, EPA contractors Joel Todd and
Richard Pike of The Scientific Consulting Group, Inc., Hal Levin of Hal Levin and Associates, and
Pliny Fisk of the Center for Maximum Potential Building Systems, Inc. The comments of NIST
BFRL colleagues Hunter Fanney, Harold Marshall, Stephen Weber, Mark Ehlen, Amy Boyles, and
Julia Rhoten inspired many improvements. Thanks are also due Sandy Kelley for her wonderful
secretarial support.
IV
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Getting Started
System Requirements
BEES runs on a Windows 95 personal computer with a 486 or higher microprocessor, 32
Megabytes or more of RAM, at least 10 Megabytes of available disk space, and a 3.5 inch floppy
diskette drive. A printer is preferred but not required.
Installing BEES
Install BEES by inserting Disk 1 into any floppy drive (e.g., drive A) and running the BEES
setup program as follows:
In Windows 95, Select Start/Run, then type A:Setup and press Ok.
Running BEES
First-time BEES users may find it useful to read the BEES Tutorial, found in section 4 of this
report. The BEES Tutorial is a printed version of the BEES on-line help system, with step-by-
step instructions for running the software. The tutorial also includes illustrations of the screen
displays. Alternatively, first-time users may choose to double-click on the help icon installed in
the BEES program group at installation for an electronic version of the help system.
While running the BEES software, context-sensitive help is often available from the BEES Main
Menu. Context-sensitive help is also available through Help buttons on many of the BEES
windows.
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Contents
Abstract iii
Acknowledgments *................................. ........ ....................................*......*.*.......ป. iv
v
System Requirements [[[ v
Installing BEES [[[ v
Running BEES [[[ v
List of Tables.. ________ . _________ [[[ ______________________ viii
List of Figures... [[[ ...................................x
1 . Background and Introduction [[[ 1
2. The BEES Model ______ ................................................. _______________ .................................... ______ ........3
2.1 Environmental Performance [[[ 4
2.1.1 Goal and Scope Definition [[[ 4
2. 1.2 Inventory Analysis [[[ 6
2. 1.3 Impact Assessment [[[ 8
2. 1.4 Interpretation [[[ 20
2.2 Economic Performance [[[ 23
2.3 Overall Performance [[[ 26
2.4 Limitations [[[ 26
3. BEES Product Data [[[ 31
3.1 Portland Cement Concrete Product Alternatives (BEES Codes A1030, A2020, B101 1,
B1012.G2010) [[[ 31
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3.6 Floor Covering Alternatives (C3020) 61
3.6.1 Ceramic Tile with Recycled Windshield Glass (C30201) 61
3.6.2 Linoleum Flooring (C30202) 63
3.6.3 Vinyl Composition Tile (C30203) 67
4. BEES Tutorial 69
4.1 Setting Parameters 69
4.2 Defining Alternatives 71
4.3 Viewing Results 73
4.4 Browsing Environmental and Economic Performance Data 76
5. Future Directions[[[ 81
Appendix A. BEES Computational Algorithms 83
A.1 Environmental Performance 83
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List of Tables
Table 2.1 BEES Global Wanning Potential Equivalency Factors 11
Table 2.2 BEES Acidification Potential Equivalency Factors 12
Table 2.3 BEES Nullification Potential Equivalency Factors 13
Table 2.4 BEES Natural Resource Depletion Equivalency Factors 15
Table 2.5 Densities of BEES Building Products 16
Table 2.6 Volatile Organic Compound Emissions for Linoleum and Vinyl Composition
Tile 17
Table 2.7 BEES Indoor Air Performance Scores for Floor Covering Products 18
Table 2.8 Pairwise Comparison Values for Deriving Impact Category Importance
Weights 22
Table 2.9 Relative Importance Weights based on Science Advisory Board Study 22
Table 2.10 U.S. Rankings for Current and Future Consequences by Impact Category 23
Table 2.11 Relative Importance Weights based on Harvard University study 23
Table 3.1 Concrete Constituent Quantities by Compressive Strength of Concrete 34
Table 3.2 Energy Requirements for Portland Cement Manufacturing 35
Table 3.3 Life-Cycle Cost Data Specifications and Codes for Concrete Products 37
Table 3.4 Oriented Strand Board Sheathing Constituents 37
Table 3.5 Plywood Constituents 39
Table 3.6 Energy Requirements for Brick Manufacturing 42
Table 3.7 Masonry Cement Constituents 43
Table 3.8 Stucco Constituents 46
Table 3.9 Energy Requirements for Masonry Cement Manufacturing 46
Table 3.10 Density of Stucco by Type 47
Table 3.11 Blown Cellulose Constituents 48
Table 3.12 Energy Requirements for Blown Cellulose Insulation Manufacturing 48
Table 3.13 Fiberglass Batt Constituents 51
Table 3.14 Energy Requirements for Fiberglass Batt Insulation Manufacturing 51
Table 3.15 Blown Mineral Wool Constituents 54
Table 3.16 Energy Requirements for Mineral Wool Insulation Manufacturing 54
Table 3.17 Asphalt Shingle Constituents 56
Table 3.18 Seven Kilogram (15 pound) Roofing Felt Constituents 57
Table 3.19 Fourteen Kilogram (30 pound) Roofing Felt Constituents 58
Table 3.20 Fiber Cement Shingle Constituents 60
Table 3.21 Ceramic Tile with Recycled Glass Constituents 61
Table 3.22 Energy Requirements for Ceramic Tile with Recycled Glass Manufacturing 62
Table 3.23 Linoleum Constituents 63
Table 3.24 Energy Requirements for Cork Flour Production 65
Table 3.25 Energy Requirements for Linoleum Manufacturing 65
Table 3.26 Linoleum Raw Materials Transportation 66
Table 3.27 Vinyl Composition Tile Constituents 68
Table 3.28 Energy Requirements for Vinyl Composition Tile Manufacturing 68
Table 4.1 BEES Building Products Keyed to Environmental and Economic Performance Data
Codes 78
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Table 4.2 BEES Simulation Codes: All But Concrete Products 79
Table 4.3 BEES Simulation Codes: Concrete Products 79
IX
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List of Figures
Figure 2.1 Decision Criteria for Setting Product System Boundaries 5
Figure 2.2 BEES Inventory Data Categories 7
Figure 2.3 BEES Study Periods For Measuring Building Product Environmental and
Economic Performance 25
Figure 2.4. Deriving the BEES Overall Performance Score 27
Figure 3.1 Portland Cement Concrete Without Fly Ash Flow Chart 33
Figure 3.2 Portland Cement Concrete With Fly Ash Flow Chart 33
Figure 3.3 Oriented Strand Board Flow Chart 38
Figure 3.4 Softwood Plywood Flow Chart 40
Figure 3.5 Brick and Mortar Flow Chart 41
Figure 3.6 Stucco (Type C) Flow Chart 44
Figure 3.7 Stucco (Type MS) Flow Chart 44
Figure 3.8 Masonry Cement Flow Chart 45
Figure 3.9 Portland Cement Flow Chart 45
Figure 3.10 Blown Cellulose Insulation Flow Chart 48
Figure 3.11 Fiberglass Batt Insulation Flow Chart 50
Figure 3.12 Blown Mineral Wool Insulation Flow Chart 53
Figure 3.13 Asphalt Shingles Flow Chart 56
Figure 3.14 Clay Tile Flow Chart 58
Figure 3.15 Fiber Cement Shingles Flow Chart 60
Figure 3.16 Ceramic Tile with Recycled Glass Flow Chart 62
Figure 3.17 Linoleum Flow Chart 64
Figure 3.18 Vinyl Composition Tile Flow Chart 67
Figure 4.1 Setting Analysis Parameters 69
Figure 4.2 Viewing Impact Category Weights 70
Figure 4.3 Entering User-Defined Weights 71
Figure 4.4 Selecting Building Element for Bees Analysis 72
Figure 4.5 Selecting Building Product Alternatives 73
Figure 4.6 Setting Transportation Parameters 73
Figure 4.7 Viewing BEES Overall Performance Results 74
Figure 4.8 Viewing BEES Environmental Performance Results 74
Figure 4.9 Viewing BEES Economic Performance Results 75
Figure 4.10 Viewing BEES Environmental Impact Category Performance Results 76
Figure 4.11 Viewing BEES Environmental Performance by Life-Cycle Stage Results 77
Figure 4.12 Viewing BEES Embodied Energy Performance Results 77
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1. Background and Introduction
Buildings significantly alter the environment. According to Worldwatch. Institute, l
building construction consumes 40 percent of the raw stone, gravel, and sand used
globally each year, and 25 percent of the virgin wood. Buildings also account for 40
percent of the energy and 16 percent of the water used annually worldwide. In the United
States, about as much construction and demolition waste is produced as municipal
garbage. Unhealthy indoor air is found in 30 percent of new and renovated buildings
worldwide.
Negative environmental impacts arise from building construction and renovation. For
example, raw materials extraction can lead to resource depletion and biological diversity
losses. Building product manufacture and transport consumes energy, generating
emissions linked to global warming, acid rain, and smog. Landfill problems may arise
from waste generation. Poor indoor air quality may lower worker productivity and
adversely affect human health.
Selecting environmentally preferable building products is one way to reduce these
negative environmental impacts. However, while 93 percent of U.S. consumers worry
about their home's environmental impact, only 18 percent are willing to pay more to
reduce the impact, according to a survey of 3,600 consumers in 9 U.S. metropolitan
areas.2 Thus, environmental performance must be balanced against economic
performance. Even the most environmentally conscious building product manufacturer or
designer will ultimately weigh environmental benefits against economic costs. To satisfy
their customers, manufacturers and designers need to develop and select building
products with an attractive balance of environmental and economic performance.
Identifying environmentally and economically balanced building products is no easy task.
Today, the green building decisionmaking process is based on little structure and even
less credible, scientific data. There is a great deal of interesting green building
information available, so that in many respects we know what to say about green
buildings. However, we still do not know how to synthesize the available information so
that we know what to do in a way that is transparent, defensible, and truly
environmentally sound.
In this spirit, the U.S. National Institute of Standards and Technology (NIST) Green
Buildings Program began the Building for Environmental and Economic Sustainability
(BEES) project in 1994. The purpose of the BEES project is to develop and implement a
1 D.M. Roodman and N. Lenssen, A Building Revolution How Ecology and Health Concerns are
Transforming Construction, Worldwatch Paper 124, Worldwatch Institute, Washington, DC, March 1995.
11995 Home Shoppers survey cited in Minneapolis Star Tribune, 11/16796, p H4 (article by Jim
Buchta). According to another survey, Japanese consumers are willing to pay up to 25 percent more for
environmentally friendly products (Maurice Strong, Chairman, Earth Council Institute, "Closing Day
Keynote Address," Engineering and Construction for Sustainable Development in the 21st Century,
Washington, DC, February 4-8,1996, p 54)
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systematic methodology for selecting building products that achieve the most appropriate
balance between environmental and economic performance based on the decision
maker's values. The methodology is based on consensus standards and is designed to be
practical, flexible, and transparent The BEES model is implemented in publicly available
decision-support software, complete with actual environmental and economic
performance data for a number of building products. The intended result is a cost-
effective reduction in building-related contributions to environmental problems.
In 1997, the U.S. Environmental Protection Agency's (EPA) Environmentally Preferable
Purchasing (EPP) Program also began supporting the development of BEES. The EPP
program is charged with carrying out Executive Order 12873 (10/93), "Federal
Acquisition, Recycling, and Waste Prevention," which directs Executive agencies to
reduce the environmental burdens associated with the $200 billion in products and
services they purchase each year, including building products. Over the next several
years, BEES will be further developed as a tool to assist the Federal procurement
community in carrying out the mandate of Executive Order 12873.
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2. The BEES Model
The BEES methodology takes a multidimensional, life-cycle approach. That is, it
considers multiple environmental and economic impacts over the entire life of the
building product. Considering multiple impacts and life-cycle stages is necessary because
product selection decisions based on single impacts or stages could obscure others that
might cause equal or greater damage. In other words, a multidimensional, life-cycle
approach is necessary for a comprehensive, balanced analysis.
It is relatively straightforward to select products based on minimum life-cycle economic
impacts because building products are bought and sold in the marketplace. But how do
we include life-cycle environmental impacts in our purchase decisions? Environmental
impacts such as global wanning, water pollution, and resource depletion are for the most
part economic externalities. That is, their costs are not reflected in the market prices of
the products that generated the impacts. Moreover, even if there were a mandate today to
include environmental "costs" in market prices, it would be nearly impossible to do so
due to difficulties in assessing these impacts in economic terms. How do you put a price
on clean air and clean water? What is the value of human life? Economists have debated
these questions for decades, and consensus does not appear likely in the near future.
While environmental performance cannot be measured on a monetary scale, it can be
quantified using the evolving, multi-disciplinary approach known as environmental life-
cycle assessment (LCA). The BEES methodology measures environmental performance
using an LCA approach, following guidance in the International Standards Organization
14040 series of draft standards for LCA.3 Economic performance is separately measured
using the American Society for Testing and Materials (ASTM) standard life-cycle cost
(LCC) approach. These two performance measures are then synthesized into an overall
performance measure using the ASTM standard for Multiattribute Decision Analysis.4
For the entire BEES analysis, building products are defined and classified based on
UNIFORMAT K, the ASTM standard classification for building elements/
3 International Standards Organization, Environmental ManagementLife-Cycle AssessmentPrinciples
and Framework, Draft International Standard 14040,1996; ISO Environmental ManagementLife-Cycle
AssessmentGoal and Scope Definition and Inventory Anslysis, Committee Draft International Standard
14041.2, 1996; and ISO Environmental ManagementLife-Cycle AssessmentLife Cycle Impact
Assessment, Committee Draft International Standard 14042.1,1997; and ISO Environmental Management-
-Life-Cycle AssessmentLife Cycle Interpretation, Committee Draft International Standard 14043.1, 1996.
4 American Society for Testing and Materials, Standard Practice for Applying the Analytic Hierarchy
Process to Multiattribute Decision Analysis of Investments Related to Buildings and Building Systems,
ASTM Designation ฃ 176S-9S, West Conshohocken, PA, 1995.
5 American Society for Testing and Materials, Standard Classification for Building Elements and
Related Sitework-UNIFORMATII. ASTM Designation E 1557-96, West Conshohocken, PA, September
1996.
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2.1 Environmental Performance
Environmental life-cycle assessment is a "cradle-to-grave," systems approach for
measuring environmental performance. The approach is based on the belief that all stages
in the life of a product generate environmental impacts and must therefore be analyzed,
including raw materials acquisition, product manufacture, transportation, installation,
operation and maintenance, and ultimately recycling and waste management. An analysis
that excludes any of these stages is limited because it ignores the full range of upstream
and downstream impacts of stage-specific processes.
The strength of environmental life-cycle assessment is its comprehensive, multi-
dimensional scope. Many green building claims and strategies are now based on a single
life-cycle stage or a single environmental impact. A product is claimed to be green simply
because it has recycled content, or claimed not to be green because it emits volatile
organic compounds (VOCs) during its installation and use. These single-attribute claims
may be misleading because they ignore the possibility that other life-cycle stages, or other
environmental impacts, may yield offsetting impacts. For example, the recycled content
product may have a high embodied energy content, leading to resource depletion, global
warming, and acid rain impacts during the raw materials acquisition, manufacturing, and
transportation life-cycle stages. LCA thus broadens the environmental discussion by
.accounting for shifts of environmental problems from one life-cycle stage to another, or
one environmental medium (land, air, water) to another. The benefit of the LCA
approach is in implementing a trade-off analysis to achieve a genuine reduction in overall
environmental impact, rather than a simple shift of impact.
The general LCA methodology involves four steps.6 The goal and scope definition step
spells out the purpose of the study and its breadth and depth. The inventory analysis step
identifies and quantifies the environmental inputs and outputs associated with a product
over its entire life-cycle. Environmental inputs include water, energy, land, and other
resources; outputs include releases to air, land, and water. However, it is not these inputs
and outputs, or inventory flows, that are of interest. We are more interested in their
consequences, or impacts on the environment. Thus, the next LCA step, impact
assessment, characterizes these inventory flows in relation to a set of environmental
impacts. For example, the impact assessment step might relate carbon dioxide emissions,
a flow, to global warming, an impact. Finally, the interpretation step combines the
environmental impacts in accordance with the goals of the LCA study.
2.1.1 Goal and Scope Definition
The goal of the BEES LCA is to generate relative environmental performance scores for
building product alternatives based on U.S. average data. These will be combined with
relative, U.S. average economic scores to help the building community select
environmentally and economically balanced building products.
6 International Standards Organization, Environmental ManagementLife-Cycle AssessmentPrinciples
and Framework, Draft International Standard 14040,1996.
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The scoping phase of any LCA involves defining the boundaries of the product system
under study. The manufacture of any product involves a number of unit processes (e.g.,
ethylene production for input to the manufacture of the styrene-butadiene bonding agent
for stucco walls). Each unit process involves many inventory flows, some of which
themselves involve other, subsidiary unit processes. The first product system boundary
determines which unit processes are included in the LCA. In the BEES system, the
boundary-setting rule consists of a set of three decision criteria. For each candidate unit
process, mass and energy contributions to the product system are the primary decision
criteria. In some cases, cost contribution is used as a third criterion.7 Together, these
criteria provide a robust screening process, as illustrated in figure 2.1, showing how five
ancillary materials (e.g., limestone used in portland cement manufacturing) are selected
from a list of nine candidate materials for inclusion in the LCA. A material must have a
large contribution for at least one decision criterion to be selected. The weight criterion
selects materials A, B, and C; the energy criterion adds material E; and cost flags material
I. As a result, the unit processes for producing ancillary materials A, B, C, E, and I are
included in the system boundaries.
Ancillary
Material
A
B
C
D
E
F
G
H
I
Weight
Energy
Cost
(as a flag
when
necessary)
Included in
system
boundaries
Yes
Yes
Yes
No
Yes
No
No
No
Yes
negligible contribution
small contribution
large contribution
Figure 2.1 Decision Criteria for Setting Product System Boundaries
The second product system boundary determines which inventory flows are tracked for
in-bounds unit processes. Quantification of all inventory flows is not practical for the
following reasons:
1 While a large cost contribution does not directly indicate a significant environmental impact, it may
indicate scarce natural resources or numerous subsidiary unit processes potentially involving high energy
consumption.
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An ever expanding number of inventory flows can be tracked. For instance, including
the U.S. Environmental Protection Agency's Toxic Release Inventory (TRI) data
would result in tracking approximately 200 inventory flows arising from
polypropylene production alone. Similarly, including radionucleide emissions
generated from electricity production would result in tracking more than ISO flows.
Managing such large inventory flow lists adds to the complexity, and thus the cost, of
carrying out and interpreting the LCA.
Attention should be given in the inventory analysis step to collecting data that will be
useful in the next LCA step, impact assessment. By restricting the inventory data
collection to the flows actually needed in the subsequent impact assessment, a more
focused, higher quality LCA can be carried out.
Therefore, in the BEES model, a focused, cost-effective set of inventory flows is tracked,
reflecting flows that will actually be needed in the subsequent impact assessment step.
Defining the unit of comparison is another important task in the goal and scoping phase
of LCA. The basis for all units of comparison is the functional unit, defined so that the
products compared are true substitutes for one another. In the BEES model, the functional
unit for most building products is 0.09 square meters (1 square foot) of product service
for 50 years.8'9 Therefore, for example, the functional unit for the BEES roof covering
alternatives is covering 0.09 square meters (1 square foot) of roof surface for 50 years.
The functional unit provides the critical reference point to which all inventory flows are
scaled.
Scoping also involves setting data requirements. Data requirements for the BEES study
include:
Geographic coverage: The data are U.S. average data.
Time period covered: The data are a combination of data collected specifically for
BEES within the last 2 years, and data from the well-known Ecobalance LCA
database created in 1990.'ฐ Most of the Ecobalance data are updated annually. No
data older than 1990 are used.
Technology covered: When possible, the most representative technology is studied.
Where data for the most representative technology are not available, an aggregated
result is used based on the U.S. average technology for that industry.
2.1.2 Inventory Analysis
Inventory analysis entails quantifying the inventory flows for a product system. Inventory
flows include inputs of water, energy, and raw materials, and releases to air, land, and
water. Data categories are used to group inventory flows in LCAs. For example, in the
BEES model, flows such as aldehydes, ammonia, and sulfur oxides are grouped under the
8 All product alternatives are assumed to meet minimum technical performance requirements (e.g.,
acoustic and fire performance).
9 The functional unit for concrete products except driveways and sidewalks is 0.76 cubic meters (1 cubic
yard) of product service for 50 years.
10 Ecobalance, Inc., DEAM. Data for Environmental Analysis and Management, Rockville, MD,
1997.
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air emissions data category. Figure 2.2 shows the categories under which data are
grouped in the BEES system. Refer to the BEES environmental performance data files,
accessible through the BEES software, for a detailed listing of approximately 100
inventory flow items included in BEES.
Raw Materials
-Energy-
-Water-
Unit
Process
I
Intermediate Material
or Final Product
t
Air Emissions-
-Water Effluents -
-Releases to Land-
Other Releases
Figure 2.2 BEES Inventory Data Categories
A number of approaches may be used to collect inventory data for LCAs. These range
from:11
Unit process- and facility-specific: data from a particular process within a given
facility that are not combined in any way
Composite: data from the same process combined across locations
Aggregated: data combining more than one process
Industry-average: data derived from a representative sample of locations believed to
statistically describe the typical process across technologies
Generic: data whose representativeness may be unknown but which are qualitatively
descriptive of a process
Since the goal of the BEES LCA is to generate U.S. average results, data are primarily
collected using the industry-average approach. Data collection is done under contract
with Environmental Strategies and Solutions, Inc. (ESS) and Ecobalance, Inc., using the
Ecobalance LCA database covering more than 6,000 industrial processes gathered from
actual site and literature searches from more than IS countries. Where necessary, the data
are adjusted to be representative of U.S. operations and conditions. Approximately 90
11 U.S. Environmental Protection Agency, Office of Research and Development, Life Cycle Assessment.
Inventory Guidelines and Principles, EPA/600/R-92/245, February 1993.
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percent of the data come directly from industry sources, with about 10 percent coming
from generic literature and published reports. The generic data include inventory flows
for electricity production from the average United States grid, and for selected raw
material mining operations (e.g., limestone, sand, and clay mining operations). In
addition, ESS and Ecobalance gathered additional LCA data to fill data gaps for the
BEES products. Assumptions regarding the unit processes for each building product are
verified through experts in the appropriate industry to assure the data are correctly
incorporated in BEES.
2.1.3 Impact Assessment
The impact assessment step of LCA quantifies the potential contribution of a product's
inventory flows to a range of environmental impacts. There are several well-known LCA
impact assessment approaches.
Direct Use of Inventories. In the most straightforward approach to LCA, the impact
assessment step is skipped, and the life cycle inventory results are used as-is in the final
interpretation step to help identify opportunities for pollution prevention or increases in
material and energy efficiency for processes within the life cycle. However, this approach
in effect gives the same weight to all inventory flows (e.g., to the reduction of carbon
dioxide emissions and to the reduction of lead emissions). For most impacts, equal
weighting of flows is unrealistic.
Critical Volumes (Switzerland). The "weighted loads" approach, better known as the
Swiss critical volume approach, was the first method proposed for aggregating inventory
flow data.12 The critical volume for a substance is a function of its load and its legal
limit. Its load is the total quantity of the flow per unit of the product. Critical volumes can
be defined for air and water, and in principle also for soil and groundwater, providing
there are legal limit values available.
This approach has the advantage that long lists of inventory flows, especially for air and
water, can be aggregated by summing the critical volumes for the individual flows within
the medium being consideredair, water, or soil. However, the critical volume approach
is rarely used today due to the following disadvantages of using legal limit values:
Legal limit values are available only for certain chemicals and pollutants. Long-term
global effects such as global warming are excluded since there are no legal limits for
the chemicals involved.
Legal limit values often differ from country to country, and their basis is far from
being purely scientific. Socioeconomic factors, technical limitations (for example,
analytical detection limits), and the feasibility of supervision and control are also
taken into account when arriving at legal limits.
12 K. Habersattei, Ecobalance of Packaging Materials - State of1990, Swiss Federal Office of
Environment, Forests, and Landscape, Bern, Switzerland, February 1991, and Bundesamt fur
Umweltschutz, Oekobilanzen von Packstoffen. Schriftenreihe Umweltschutz 24, Bern, Switzerland, 1984.
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Ecological Scarcity (Switzerland). A more general approach has been developed in a
report from the Swiss Federal Office of Environment, Forests, and Landscape.13 With this
approach, "Eco-Points" are calculated for a product, using the "Eco-Factor" determined
for each inventory flow. Eco-Factors are based on current annual flows relative to target
maximum annual flows for the geographic area considered. The Eco-Points for all
inventory flows are added together to give one single, final score.
The concept used in this approach is appealing but has the following difficulties:
It is valid only in a specific geographical area.
Estimating annual and target flows can be a difficult and time consuming exercise.
The scientific calculation of environmental impacts is combined with political and
subjective judgment, or valuation. The preferred approach is to separate the science
from the valuation.
Environmental Priorities System (Sweden). The Environmental Priority Strategies in
Product Design System, the EPS System, was developed by the Swedish Environmental
Research Institute.14 It takes an economic approach to assessing environmental impacts.
The basis for the evaluation is the Environmental Load Unit, which corresponds to the
willingness to pay 1 European Currency Unit. The final result of the EPS system is a
single number summarizing all environmental impacts, based on:
Society's judgment of the importance of each environmental impact.
The intensity and frequency of the impact.
Location and timing of the impact.
The contribution of each flow to the impact in question
The cost of decreasing each inventory flow by one weight unit.
The EPS system combines indices of ecological, sociological, and economic effects to
give a total effect index for each flow. The total effect index is multiplied by the amount
of the flow to give the "environmental load unit." Although this methodology is popular
in Sweden, its use is criticized due to its lack of transparency and the quantity and quality
of the model's underlying assumptions.
Classification/Characterization. The classification/characterization approach to impact
assessment was developed within the Society for Environmental Toxicology and
Chemistry (SETAC). It involves a two-step process:I5ll6>17
13 Ahbe S. Braunschweig A., and R. Muller-Wenk, Methodikfur Oekobilanzen aufder bases
Okologischer Optimiemng. Schriftenreihn Umwelt 133, Swiss Federal Office of Environment, Forests, and
Landscape, October 1990.
14 Steen B., and S-0 Ryding, The EPS Enviro-Accounting Method, IVL Report, Swedish Environmental
Research Institute, Goteborg, Sweden, 1992.
15 SETAC-Europe, Life Cycle Assessment, B. DeSmet, et al. (eds), 1992.
-------
Classification of inventory flows that contribute to specific environmental impacts.
For example, greenhouse gases such as carbon dioxide, methane, and nitrous oxide
are classified as contributing to global warming.
Characterization of the potential contribution of each classified inventory flow to the
corresponding environmental impact. This results in a set of indices, one for each
impact, that is obtained by weighting each classified inventory flow by its relative
contribution to the impact. For instance, the Global Warming Potential index is
derived by expressing each contributing inventory flow in terms of its equivalent
amount of carbon dioxide.
This classification/characterization method does not offer the same degree of relevance
for all environmental impacts. For global and regional effects (e.g., global warming and
acidification) the method may result in an accurate description of the potential impact.
For impacts dependent upon local conditions (e.g., smog) it may result in an
oversimplification of the actual impacts because the indices are not tailored to localities.
The BEES model uses this classification/characterization approach because it enjoys
some general consensus among LCA practitioners and scientists.18 For the reason stated
above, and because BEES has a U.S. average scope, local impacts such as smog are not
included. The following global and regional impacts are assessed using the classification/
characterization approach: Global Warming Potential, Acidification Potential,
Nullification Potential, and Natural Resource Depletion. Indoor Air Quality and Solid
Waste impacts are also included in BEES, for a total of six impacts. Besides local
impacts, other potential environmental impacts are not included. For example, ozone
depletion, while an important global impact that has been successfully classified and
characterized, is excluded. The primary inventory flows that contribute to ozone
depletion (chlorofluorocarbons, halons, and chlorine-based solvents) are being phased
out. Thus, inventory flow data are quickly changing, and soon there will be little left to
report. Human health impacts are also not explicitly included in BEES because the
science is not yet sufficiently developed. If the BEES user has important knowledge
about these or other potential environmental impacts, it should be brought into the
interpretation of the BEES results.
The six BEES impacts are discussed below.
Global Warming Potential. The Earth absorbs radiation from the Sun, mainly at the
surface. This energy is then redistributed by the atmosphere and ocean and re-radiated to
space at longer wavelengths. Some of the thermal radiation is absorbed by "greenhouse"
gases in the atmosphere, principally water vapor, but also carbon dioxide, methane, the
chlorofluorocarbons, and ozone. The absorbed energy is re-radiated in all directions,
downwards as well as upwards, such that the radiation that is eventually lost to space is
16 SETAC, A Conceptual Framework for Life Cycle Impact Assessment, J. Fava, et al. (eds), 1993.
17 SETAC, Guidelines for Life Cycle Assessment: A "Code of Practice," F. Consoli, et al. (eds), 1993.
18 SETAC, Life-Cycle Impact Assessment: The State-of-the-Art, J. Owens, et al. (eds), 1997.
10
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from higher, colder levels in the atmosphere. The result is that the surface loses less heat
to space than it would in the absence of the greenhouse gases and consequently stays
wanner than it would be otherwise. This phenomenon, which acts rather like a 'blanket'
around the Earth, is known as the greenhouse effect.
The greenhouse effect is a natural phenomenon. The issue is the increase in the
greenhouse effect due to emissions generated by humankind. The resulting general
increase in temperature can alter atmospheric and oceanic temperatures, which can
potentially lead to alteration of circulation and weather patterns. A rise in sea level is
also predicted due to thermal expansion of the oceans and melting of polar ice sheets.
Global Wanning Potentials, or GWPs, have been developed to measure the increase.
Several models have been developed to calculate GWPs. The Intergovernmental Panel
on Climate Change (IPCC) has compiled a list of "provisional best estimates" for GWPs,
based on the expert judgment of scientists worldwide. " Because of its broad support,
this list has been used in the BEES model.
A single index, expressed in grams of carbon dioxide per functional unit of product, is
derived to measure the quantity of carbon dioxide with the same potential for global
warming:
global wanning index = S; w, x GWP,, where
w,=weight (in grams) of inventory flow i, and
GWP, = grams of carbon dioxide with the same heat trapping potential as one
gram of inventory flow i, as listed in table 2.1.
Table 2.1 BEES Global Warming Potential Equivalency Factors
GWP,
Flow ft) (COj-equivalents)
Carbon dioxide 1
Methane 24.5
Nitrous oxide 320
Acidification. Acidifying compounds may in a gaseous state either dissolve in water or
fix on solid particles. They reach ecosystems through dissolution in rain or wet
deposition. Acidification affects trees, soil, buildings, animals, and humans. The two
" International Panel on Climate Change (IPCQ), Report of Scientific Assessment Working Group of
IPCC, 1994.
11
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compounds principally involved in acidification are sulfur and nitrogen compounds.
Their principal human source is fossil fuel and biomass combustion. Other compounds
released by human sources, such as hydrogen chloride and ammonia, also contribute to
acidification.
An index for potential acid deposition onto the soil and in water can be developed by
analogy with the global wanning potential, with hydrogen as the reference substance.
The result is a single index for potential acidification (in grams of hydrogen per
functional unit of product), representing the quantity of hydrogen emissions with the
same potential acidifying effect:
acidification index = Z, w, x AP,, where
w, = weight (in grams) of inventory flow i, and
= grams of hydrogen with the same potential acidifying effect as one gram of
inventory flow i, as listed in table 2.2.20
Table 2.2 BEES Acidification Potential Equivalency Factors
Flowฎ
Sulfur oxides
Nitrogen oxides
Ammonia
Hydrogen Fluoride
Hydrogen Chloride
AP,
(Hydrogen-
Equivalents)
0.031
0.022
0.059
0.05
0.027
Nutrification Potential. Nullification is the addition of mineral nutrients to the soil or
water. In both media, the addition of large quantities of mineral nutrients, such as
nitrogen and phosphorous, results in generally undesirable shifts in the number of species
in ecosystems and a reduction in ecological diversity. In water, it tends to increase algae
growth, which can lead to lack of oxygen and therefore death of species like fish.
An index for potential nutrification can be developed by analogy with the global warming
potential, with phosphate ions as the reference substance. The result is a single index for
potential nutrification (in grams of phosphate ions per functional unit of product),
representing the quantity of phosphate ions with the same potential minifying effect:
20 CML, Environmental Life Cycle Assessment of Products: Background, Leiden, The Netherlands,
October 1992.
12
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nutrification index = I, w, x NP,, where
w, = weight (in grams) of inventory flow i, and
NP, = grams of phosphate ions with the same potential nullifying effect as one
grams of inventory flow i, as listed in table 2.3.21
Table 2.3 BEES Nutrification Potential Equivalency Factors
Flow (i)
Phosphates
Nitrogen Oxides
Ammonia
Nitrogenous Matter
Nitrates
Phosphorous
Chemical Oxygen Demand
NP,
(phosphate-
equivalents)
1
0.13
0.42
0.42
0.095
3.06
0.022
Natural Resource Depletion. Natural resource depletion can be defined as the
decreasing availability of natural resources. The resources considered in this impact are
fossil and mineral resources. It is important to recognize that this impact addresses only
the depletion aspect of resource extraction, not the fact that the extraction itself may
generate impacts. Extraction impacts, such as methane emissions from coal mining, are
addressed in other impacts, such as global wanning.
Some experts believe resource depletion is fully accounted for in market prices. That is,
market price mechanisms are believed to take care of the scarcity issue, price being a
measure of the level of depletion of a resource and the value society places on that
depletion. However, price is influenced by many factors other than resource supply, such
as resource demand and non-perfect markets (e.g., monopolies and subsidies).
Furthermore, resource depletion is at the heart of the sustainability debate. Thus, in the
BEES model, resource depletion is explicitly accounted for in the LCA impact
assessment.
To assess resource depletion, the amount of reserves of a resource, or resource base,
needs to be determined. For mineral resources, the reserve base is defined as follows:
21 CML, 1992.
13
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The reserve base encompasses those parts of the resources that have a
reasonable potential for becoming economically available within planning
horizons beyond those that assume proven technology and current
economics. It includes those resources that are currently economic,
marginally economic, and subeconomic.22
Reserve base quantities used in the BEES model are listed in table 2.4.
Once reserves are established, an equivalency factor can be derived for each resource that
will relate its inventory flow with the depletion of the resource. The equivalency factor
addresses how long a given resource will continue to be available at current extraction
levels, as well as the size of the reserve. Using equivalency factors, a single index is
produced for natural resource depletion:
^ ! i ^iproducQCQj
Depletion Index = 2j~~~ I - *wi = A - 5" *wi > where
T-'reservej *yearsj j (reserve, r
reserve, = reserves (in kilograms) for natural resource i (the larger the reserve, the
smaller the equivalency factor)
years, = years of remaining use for natural resource i (the longer available, the
smaller the equivalency factor)
production, = annual production (in kilograms/year) for natural resource i
Wj = the weight (in kilograms) of the inventory flow for resource i
The BEES natural resource depletion equivalency factors are shown in the last column
of table 2.4.
Solid Waste. Solid waste is an inventory outflow of the building products included in the
BEES model. The BEES inventory analysis tracks the weight of non-recyclable solid
waste resulting from the installation, replacement, and disposal of each building product
over the fifty-year study period. Equivalency factors have not been developed to consider
the ultimate fate of the non-recyclable solid waste (e.g., landfill leachate, gas or
incinerator emissions, ash). Thus, the Direct Use of Inventories Approach, described at
the beginning of this subsection, is used, with solid waste volume representing the solid
waste impact of the product. Solid waste volume (in cubic meters, or cubic feet, of waste
per functional unit of product) is derived as follows:
solid waste volume = (Z, w, ) / density, where
w, = weight (in kilograms) of non-recyclable solid waste inventory flow i, and
density = density of the product (in kilograms per 0.0283 cubic meter, or
kilograms per cubic foot), as listed in table 2.5.
"U.S. Department of the Interior, Bureau of Mines, Mineral Commodity Summary, 1994.
14
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Table 2.4 BEES Natural Resource Depletion Equivalency Factors
Inventory Flow
Oil (in ground)
Natural Gas (in ground)
Coal (in ground)
Bauxite (A12O,.2 H2O, ore)
Cadmium (Cd, ore)
Copper (Cu, ore)
Gold (Au, ore)
Iron (Fe, ore)
Lead (Pb, ore)
Manganese (Mn, ore)
Mercury (Hg, ore)
Nickel (Ni, ore)
Phosphate Rock (in ground)
Potash (KjO, in ground)
Silver (Ag, ore)
Tin (Sn, ore)
Uranium (U, ore)
Zinc (Zn, ore)
Units
kg of oil
kg of natural gas
kg of coal
dry kg of bauxite
kg of Cd content
kg of Cu content
kg of Au content
kg of Fe content
kg of Pb content
kg of Mn content
kg of Hg content
kg of Ni content
kg of rock
kg of K:O equivalent
kg of Ag content
kg of Sn content
kg of U content
kg of Zn content
Source of Data
World Energy Council
1995
World Energy Council
1995
World Energy Council
1995
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
US Bureau of Mines 1996
World Energy Council
1995
US Bureau of Mines 1996
Annual
Production
(*gW
(1)
3.2 E+12
2.0 E+12
4.5 E+12
1.1E+11
2.0 E+07
9.8 E+09
2.2 E+06
4.3E+11
2.8 E+09
7.3 E+09
3.1 E+06
9.2 E+08
1.4E+11
2.6E+10
1.4 E+07
1.8 E+08
3.3 E+07
7.1 E+09
Reserve Base
(kg)
(2)
2.4 E+14
I.3E+14
3.0E+15
2.8E+13
9.7 E+08
6.1E+1I
6.1 E+07
1.0 E+14
1.2E+11
5.0 E+12
2.4 E+08
1.1E+11
3.4E+13
1.7E+13
4.2 E+08
l.OE+10
1.3E+10
3.3E+11
Years of Remaining
Use
(3)=(2)/(l)
75
66
666
257
49
62
28
231
43
685
77
120
248
649
30
56
412
47
Equivalency
Factor
(4)=
I4W0JJ
5.6E-17
1.2E-16
5.0E-19
1.4E-16
2.1E-11
2.6E-14
5.9E-10
4.3 E-17
1.9E-13
2.9E-16
5.4 E- 11
7.6 E-14
1.2E-16
9.1 E-17
7.9 E- 11
1.8E-12
1.8E-13
6.5 E-14
I/I
Due 10 abundant resources, the depletion index has been set lo zero for the following resources Clay (in ground). Dolomite (CaCO.MgCO,, in ground). Feldspar (on). Gypsum (ore), Kaoli
ground). Sand (in ground), Sodium Chloride (NปCI. in ground or in tea) Note Chat local shortages of these resources may exist Local shortages an translated into higher transportation distal
they have no impact on die depletion factor
(AI,0,2SiO, 2H,O, ore), Limestone (in
and therefore higher emissions, but
-------
Table 2.5 Densities of BEES Building Products
Density
k8/0.0283m3(U)/tf)
Product
All Concrete Products 66 (145.51)
Roof and Wall Sheathing
- Oriented Strand Board 17 (37.48)
- Plywood 12 (26.46)
Exterior Wall Finishes
-Brick 60(132.28)
-Stucco 55(121.25)
Wall Insulation
- R-13 Cellulose 1.07(2.35)
-R-ll Fiberglass 0.23(0.50)
-R-15 Fiberglass 0.54(1.20)
- R-12 Mineral Wool 0.98 (2.15)
Roof Coverings
- Asphalt Shingles 89 (196.21)
-Clay Tile 60(132.28)
- Fiber Cement Shingles 44 (97.00)
R-30 Ceiling Insulation
-Cellulose 0.73(1.60)
- Fiberglass 0.23 (0.50)
-Mineral Wool 0.98(2.15)
Floor Coverings
- Ceramic Tile 61 (134.48)
- Linoleum 33 (72.75)
- Vinyl Composition Tile 59 (130.07)
Indoor Air Quality. Indoor air quality impacts are not included in traditional life-cycle
impact assessments. Most LCAs conducted to date have been applied to relatively short-
lived, non-building products (e.g., paper versus plastic bags), for which indoor air quality
impacts are not an important issue. However, the indoor air quality performance of
building products is of particular concern to the building community and should be
explicitly considered in any building product LCA.
Ideally, equivalency factors would be available for indoor air pollutants as they are for
global warming gases. However, there is little scientific consensus about the relative
contributions of pollutants to indoor air performance. In the absence of equivalency
factors, a product's total volatile organic compound (VOC) emissions is often used as a
measure of its indoor air performance. Note that total VOCs equally weights the
contributions of the individual compounds that make up the measure. Further, reliance on
VOC emissions alone may be misleading if other indoor air contaminants, such as
particulates and aerosols, are also present.
16
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Indoor air quality should be considered for the following building elements currently
covered in BEES: floor coverings, wall and roof sheathing, and wall and ceiling
insulation. Other BEES building elements are primarily exterior elements for which
indoor air quality is not an issue.
Floor Coverings. BEES currently includes three floor covering products: ceramic tile
with recycled windshield glass, linoleum, and vinyl composition tile. Data for three
components of their indoor air performance are consideredtotal VOC emissions from
the products themselves, indoor air performance for their installation adhesives, and
indoor air performance for associated maintenance products.
Recognizing the inherent limitations in using total VOCs to assess indoor air quality
performance, and in the absence of more scientific data, estimates of total VOC emissions
from the floor covering products are used as a proxy for their indoor air performance. As
shown in table 2.6, total VOCs for linoleum and vinyl composition tile flooring measured
in three laboratory studies are averaged to represent their indoor air performance.23
Ceramic tile is inert and emits no VOCs.24
Table 2.6 Volatile Organic Compound Emissions for Linoleum and Vinyl
Composition Tile
Floor Covering
Total Volatile Organic Compound Emissions
by Testing Laboratory
(Mg/m2/hr at 24 hours)
Air Quality
Sciences'
Linoleum 1.667
Vinyl Composition Tile 0. 1 55
Armstrong"
Ortech"'
1.192 0.511
0.203 0.179
Average
1.123
0.179
'Averages for three linoleum and two VCT emissions tests conducted in a test chamber designed in
accordance with ASTM D5116-90 at Air Quality Sciences Laboratory, Atlanta, Georgia, 1991-1992.
"Averages for four linoleum and ten VCT emissions tests conducted in a test chamber designed in
accordance with ASTM DS116-90 at Armstrong Research and Development Laboratory, Lancaster,
Pennsylvania, 1992-1997.
'"Ortech Corporation, Toronto, Canada, 1996. Ortech results indicating 65% less VOC emissions for vinyl
composition floor tile than linoleum are applied to average VCT emissions, 0.179 Mg/mVhr, measured at
the other two testing laboratories.
The second component of the BEES indoor air assessment for floor coverings is indoor
air performance for their installation adhesives. Both linoleum and vinyl composition tile
23 Note that vinyl composition tile has substantially lower polyvinylchloride (PVC) and plasbcizer
contents than vinyl sheet flooring and thus emits lower levels of VOCs. Some vinyl sheet flooring may
emit higher levels of VOCs than linoleum.
24 American Institute of Architects, Environmental Resource Guide, Ceramic Tile Material Report,
1996, p. 1.
17
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are assumed to be installed using a styrene-butadiene adhesive, and ceramic tile with
recycled glass using a styrene-butadiene cement mortar. Assuming indoor air impacts are
proportional to the amount of styrene-butadiene used per functional unit (as quantified in
the BEES environmental performance data files), styrene-butadiene usage may be used as
a proxy for indoor air performance as follows:
ceramic tile with recycled windshield glass0.00311 kg/m2 (0.00028 kg/ft2)
linoleum0.00878 kg/m2 (0.00079 kg/ft2)
vinyl composition tile0.00878 kg/m2 (0.00079 kg/ft2)
Finally, indoor air performance is assessed for periodic waxing of the floor coverings.
Assuming indoor air impacts are proportional to the amount of acrylic lacquer used per
year per functional unit (as quantified in the BEES environmental performance data
files), acrylic lacquer usage may be used as a proxy for indoor air performance as
follows:
ceramic tile with recycled windshield glassno waxing
linoleum0.5 grams (0.02 oz) of acrylic lacquer per functional unit, applied 4 times
per year
vinyl composition tile0.5 grams (0.02 oz) of acrylic lacquer per functional unit,
applied 2 times per year
To assess overall indoor air performance for BEES floor coverings, each product's
performance data for product emissions, installation adhesives, and maintenance are
normalized by dividing by the corresponding performance value for the worst performing
product, then averaged across performance categories as shown in table 2.7. By taking the
simple average, each performance category is weighted equally.
Table 2.7 BEES Indoor Air Performance Scores for Floor Covering Products
Floor
Covering
Ceramic Tile
w/ Glass
Linoleum
Vinyl
Composition
Tile
Normalized Indoor Air Performance Score
Product
Emissions
0*
100
16
Installation
Adhesives
35
100
100
Maintenance
0*
100
50
Average
12
100
55
*For this exercise, normalized scores of zero are assumed for tile emissions and maintenance
Note that due to shortcomings in indoor air science, the BEES indoor air performance
scores for floor coverings are based on heuristics. If the BEES user has better knowledge,
or simply wishes to test the effect on overall results of changes in relative indoor air
performance, these scores may be changed by editing the "total" and "use" columns of
18
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the "Indoor Air" rows of the BEES environmental performance data files for floor
coverings. Refer to section 4.4 for more information on these files.
Wall and Roof Sheathing. Indoor air quality is a concern for many wood products due to
their formaldehyde emissions. Formaldehyde is thought to affect human health,
especially for people with chemical sensitivity. Composite wood products using urea-
formaldehyde adhesives have higher formaldehyde emissions than those using phenol-
formaldehyde adhesives, and different composite wood products have different levels of
emissions. Composite wood products include particleboard, insulation board, medium
density fiberboard, oriented strand board (OSB), hardboard, and softwood and hardwood
plywood.
BEES assumes formaldehyde emissions is the only significant indoor air concern for
wood products. BEES currently analyzes two composite wood productsOSB and
softwood plywood. Most OSB is now made using a methylene diphenylisocyanate (MDI)
binder, which is the binder BEES uses in modeling OSB environmental performance.
OSB using an MDI binder emits no formaldehyde other than the insignificant amount
naturally occurring in the wood itself.25 Softwood plywood also has extremely low
formaldehyde emissions because it uses phenol-formaldehyde binders and because it is
used primarily on the exterior shell of buildings.26 Thus, neither of the two composite
wood products as modeled in BEES are thought to significantly affect indoor air quality.
Wall and Ceiling Insulation. Indoor air quality is also discussed in the context of
insulation products. The main issues are the health impacts of fibers, hazardous
chemicals, and particles released from some insulation products. These releases are the
only insulation-related indoor air issues addressed in BEES.
As a result of its listing by the International Agency for Research on Cancer as a
"possible carcinogen," fiberglass products are now required to have cancer warning
labels. The fiberglass industry has responded by developing fiberglass products that
reduce the amount of loose fibers escaping into the air. For cellulose products, there are
claims that fire retardant chemicals and respirable particles are hazardous to human
health. Mineral wool is sometimes claimed to emit fibers and chemicals that could be
health irritants. For all these products, however, there should be little or no health risks to
building occupants if they are installed in accordance with manufacturer's
recommendations. Assuming proper installation, then, none of these products as modeled
in BEES are thought to significantly affect indoor air quality.27
23 Alex Wilson and Nadav Malin, "The IAQ Challenge: Protecting the Indoor Environment,"
Environmental Building News, Vol. 5, No. 3, p 15.
26 American Institute of Architects, Environmental Resource Guide, Plywood Material Report, May
1996.
27 Alex Wilson, "Insulation Materials: Environmental Comparisons,1' Environmental Building News.
Vol. 4, No. 1, pp. 15-16
19
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2.1.4 Interpretation
At the LCA interpretation step, the impact assessment results are combined. Few
products are likely to dominate competing products in all six BEES impact categories.
Rather, one product may out-perform the competition relative to natural resource
depletion and solid waste, fall short relative to global warming and acidification, and fall
somewhere in the middle relative to indoor air quality and nullification. To compare the
overall environmental performance of competing products, the performance measures for
all six impact categories need to be synthesized.
Synthesizing the six impact category performance measures involves combining apples
and oranges. Global warming potential is expressed in carbon dioxide equivalents,
acidification in hydrogen equivalents, nullification in phosphate equivalents, natural
resource depletion as a factor reflecting remaining years of use and reserve size, solid
waste in non-recyclable volume to landfill, and indoor air quality as a dimensionless
score.
How can the diverse measures of impact category performance be combined into a
meaningful measure of overall environmental performance? The most appropriate
technique is Multiattribute Decision Analysis (MADA). MADA problems are
characterized by tradeoffs between apples and oranges, as is the case with the BEES
impact assessment results. The BEES system follows the ASTM standard for conducting
MADA evaluations of building-related investments.28
MADA first places all impact categories on the same scale by normalizing them. Within
an impact category, each product's performance measure is normalized by dividing by the
highest measure for that category. All performance measures are thus translated to the
same, dimensionless, relative scale from 0 to 100, with the worst performing product in
each category assigned the highest possible normalized score of 100. Refer to Appendix
A for the BEES environmental performance computational algorithms.
MADA then weights each impact category by its relative importance to overall
performance. In the BEES software, the set of importance weights is selected by the user.
Several derived, alternative weight sets are provided as guidance, and may either be used
directly or as a starting point for developing user-defined weights. The alternative
weights sets are based on an EPA Science Advisory Board study, a Harvard University
study, and a set of equal weights, representing a spectrum of ways in which people,
including the experts, value various aspects of the environment.
EPA Science Advisory Board study. In 1990, EPA's Science Advisory Board (SAB)
developed lists of the relative importance of various environmental impacts to help EPA
best allocate its resources. The following criteria were used to develop the lists:
28 American Society for Testing and Materials, Standard Practice for Applying the Analytic Hierarchy
Process to Multiattribute Decision Analysis of Investments Related to Buildings and Building Systems,
ASTM Designation E 1765-95, West Conshohocken, PA, 1995.
20
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The spatial scale of the impact
The severity of the hazard
The degree of exposure
The penalty for being wrong
Five of the BEES impact categories were among the SAB lists of relative importance:29
Relatively High-Risk Problems: global warming, indoor air quality
Relatively Medium-Risk Problems: acidification, nullification
Relatively Low-Risk Problems: solid waste30
The SAB did not explicitly consider natural resource depletion as an impact. For this
exercise, natural resource depletion is assumed to be a relatively medium-risk problem,
based on other relative importance lists.31
Verbal importance rankings, such as "relatively high-risk," may be translated into
numerical importance weights by following guidance provided by a MADA method
known as the Analytic Hierarchy Process (AHP).32 The AHP methodology suggests the
following numerical comparison scale:
1 Two impacts contribute equally to the objective (in this case environmental
performance)
3 Experience and judgment slightly favor one impact over another
5 Experience and judgment strongly favor one impact over another
7 One impact is favored very strongly over another, its dominance demonstrated in
practice
9 The evidence favoring one impact over another is of the highest possible order of
affirmation
2,4,6,8 When compromise between values of 1,3,5,7, and 9, is needed
Through an AHP process known as pairwise comparison, numerical comparison values
are assigned to each possible pair of environmental impacts. Relative importance weights
can then be derived by computing the normalized eigenvector of the largest eigenvalue of
the matrix of pairwise comparison values. Tables 2.8 and 2.9 list the pairwise comparison
values assigned to the SAB verbal importance rankings, and the resulting importance
weights computed for the six BEES impacts, respectively:
29 United States Environmental Protection Agency, Science Advisory Board, Reducing Risk: Setting
Priorities and Stretegies for Environmental Protection, SAB-EC-90-021, Washington, D.C., September
1990, pp 13-14.
30 The SAB report classifies solid waste under its low-risk groundwater pollution category (SAB,
Reducing Risk, Appendix A, pp 10-15).
11 See, for example, Hal Levin, "Best Sustainable Indoor Air Quality Practices in Commercial
Buildings," Third International Green Building Conference and Exposition-1996, NIST Special
Publication 908, Gaithersburg, MD, November 1996, p 148.
32 Thomas L. Saaty, MultiCriteria Decision Making: The Analytic Hierarchy Process-Planning.
Priority Setting, Resource Allocation, University of Pittsburgh, 1988.
21
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Table 2.8 Painvise Comparison Values for Deriving Impact Category Importance
Weights
Verbal Importance
Comparison
High vs. Medium
Medium vs. Low
High vs. Low
Painvise Comparison Value
2
2
4
Table 2.9 Relative Importance Weights based on Science Advisory Board Study
Impact Category Relative Importance Weight (%)
Global Wanning 27
Acidification 13
Nullification 13
Natural Resource Depletion 13
Indoor Air Quality 27
Solid Waste 7
Harvard University Study. In 1992, an extensive study was conducted at Harvard
University to establish the relative importance of environmental impacts.33 The study
developed separate assessments for the United States, The Netherlands, India, and Kenya.
In addition, separate assessments were made for "current consequences" and "future
consequences" in each country. For current consequences, more importance is placed on
impacts of prime concern today. Future consequences places more importance on impacts
that are expected to become significantly worse in the next 25 years.
Five of the BEES impact categories were among the studied impacts. Table 2.10 shows
the current and future consequence rankings assigned to these impacts in the United
States.
The study did not explicitly consider solid waste as an impact. For this exercise, solid
waste is assumed to rank low for both current and future consequences, based on other
relative importance lists.34
Verbal importance rankings from the Harvard study are translated into numerical, relative
importance weights using the same, AHP-based numerical comparison scale and pairwise
33 Vicki Norberg-Bohm et al, International Comparisons of Environmental Hazards: Development and
Evaluation of a Method for Linking Environmental Data with the Strategic Debate Management Priorities
for Risk Management, Center for Science & International Affairs, John F. Kennedy School of Government,
Harvard University, October 1992.
34 See, for example, Hal Levin, "Best Sustainable Indoor Air Quality Practices in Commercial
Buildings," p 148. As in the SAB report, solid waste is classified under groundwater pollution.
22
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Table 2.10 U.S. Rankings for Current and Future Consequences by Impact
Category
Impact Category Current Consequences Future Consequences
Global Warming Low High
Acidification High Low
Nullification Medium High
Natural Resource Depletion* Medium Medium
Indoor Air Quality Medium Low
'Average of consequences for hazards contributing to natural resource depletion.
comparison process described above for the SAB study. Sets of relative importance
weights are derived for current and future consequences, and then combined by weighing
future consequences as twice as important as current consequences.35 Table 2.11 lists the
resulting importance weights for the six BEES impacts. The combined importance weight
set is offered as an option in the BEES software. However the BEES user is free to use
the current or future consequence weight sets by entering these weights under the user-
defined software option.
Table 2.11 Relative Importance Weights based on Harvard University study
Relative Importance Weight Set
Impact Category Current Future Combined
Global Wanning
Acidification
Nullification
Natural Resource
Depletion
Indoor Air Quality
Solid Waste
8
33
16
16
16
11
38
10
19
14
10
9
28
17
18
15
12
10
2.2 Economic Performance
Measuring the economic performance of building products is more straightforward than
measuring environmental performance. Published economic performance data are readily
available, and there are well-established ASTM standard methods for conducting
economic performance evaluations. First cost data are collected from the R.S. Means
publication, 1997 Building Construction Cost Data, and future cost data are based on data
published by Whitestone Research in The Whitestone Building Maintenance and Repair
35 The Harvard study ranks impacts "high" in future consequences if the current level of impact is
expected to double in severity over the next 25 years based on a "business as usual" scenario. Vicki
Norberg-Bohm, International Comparisons of Environmental Hazards, pp 11-12.
23
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Cost Reference 1997. The most appropriate method for measuring the economic
performance of building products is the life-cycle cost (LCC) method. BEES follows the
ASTM standard method for life-cycle costing of building-related investments.36
It is important to distinguish between the time periods used to measure environmental
performance and economic performance. These time periods are different. Recall that in
environmental LCA, the time period begins with raw material acquisition and ends with
product end-of-life. Economic performance, on the other hand, is evaluated over a fixed
period (known as the study period) that begins with the purchase and installation of the
product, and ends at some point in the future that does not necessarily correspond with
product end-of-life.
Economic performance is evaluated beginning at product purchase and installation
because this is when out-of-pocket costs begin to be incurred, and investment decisions
are made based upon out-of-pocket costs. The study period ends at a fixed date in the
future. For a private investor, its length is set at the period of product or facility
ownership. For society as a whole, the study period length is often set at the useful life of
the longest-lived product alternative. However, when all alternatives have very long lives,
(e.g., more than SO years), a shorter study period may be selected for three reasons:
Technological obsolescence becomes an issue
Data become too uncertain
The further in the future, the less important the costs
In the BEES model, economic performance is measured over a 50-year study period, as
shown in Figure 2.3. This study period is selected to reflect a reasonable period of time
over which to evaluate economic performance for society as a whole. The same 50-year
period is used to evaluate all products, even if they have different useful lives. This is one
of the strengths of the LCC method. It adjusts for the fact that different products have
different useful lives when evaluating them over the same study period.
For consistency, the BEES model evaluates the use stage of environmental performance
over the same 50-year study period. Product replacements over this 50-year period are
accounted for in the environmental performance score, and end-of-life solid -waste is
prorated to year 50 for products with partial lives remaining after the 50-year period.
The LCC method sums over the study period all relevant costs associated with a product.
Alternative products for the same function, say floor covering, can then be compared on
the basis of their LCCs to determine which is the least cost means of providing that
function over the study period. Categories of cost typically include costs for purchase,
installation, maintenance, repair, and replacement. A negative cost item is the residual
value. The residual value is the product value remaining at the end of the study period. In
36American Society for Testing and Materials, Standard Practice for Measuring Life-Cycle Costs of
Buildings and Building Systems, ASTM Designation E 917-94, West Conshohocken, PA, March 1994.
24
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FACILITY LIFE CYCLE
50 years
ECONOMIC STUDY PERIOD
Site Selection
and
Preparation
Construction
and Outfitting
Operation
and Use
Renovation
or Demolition
Product
Manufacture
Raw
Materials
Acquisition
50 Year Use Stage-
ENVIRONMENTAL
STUDY PERIOD
Figure 2.3 BEES Study Periods For Measuring Building Product Environmental
And Economic Performance
the BEES model, the residual value is computed by prorating the purchase and
installation cost over the product life remaining beyond the 50-year period.37
The LCC method accounts for the time value of money by using a discount rate to
convert all future costs to their equivalent present value. Refer to Appendix A for the
BEES economic performance computational algorithm showing the discounting
technique.
Future costs must be expressed in terms consistent with the discount rate used. There are
two approaches. First, a real discount rate may be used with constant-dollar (e.g., 1997)
costs. Real discount rates reflect the portion of the time value of money attributable to the
real earning power of money over time and not to general price inflation. Even if all
17 For example, a product with a 40-year life that costs S10 per 0.09 square meters (S10 per square foot)
to install would have a residual value of $7.50 in year SO, considering replacement in year 40.
25
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future costs are expressed in constant 1997 dollars, they must be discounted to reflect this
portion of the time-value of money. Second, a market discount rate may be used with
current-dollar amounts (e.g., actual future prices). Market interest rates reflect the time
value of money stemming from both inflation and the real earning power of money over
time. When applied properly, both approaches yield the same LCC results. The BEES
model computes LCCs using constant 1997 dollars and a real discount rate. As a default,
the BEES tool uses a real rate of 3.6 percent, the 1997 rate mandated by the U.S. Office
of Management and Budget (OMB) for most Federal projects.38
2.3 Overall Performance
The BEES overall performance score combines the environmental and economic results
into a single score. To combine them, the two results must first be placed on a common
basis. The environmental performance score reflects relative environmental performance,
or how much better or worse products perform with respect to one another. The economic
performance score, the LCC, reflects absolute performance, regardless of the set of
alternatives under analysis. Before combining the two, the life-cycle cost is converted to
the same, relative basis as the environmental score by dividing by the highest-life-cycle
cost alternative. Then the two performance scores are combined into a relative, overall
score by weighting environmental and economic performance by their relative
importance values. The BEES user specifies the relative importance weights used to
combine environmental and economic performance scores and may test the sensitivity of
the overall scores to different sets of relative importance weights.
Figure 2.4 illustrates the synthesis of environmental and economic performance results
into the BEES overall performance score. In this example, the Harvard environmental
importance weight set, the 1997 OMB discount rate, and equal weights for environmental
and economic performance are used. Refer to Appendix A for the BEES overall
performance computational algorithm.
2.4 Limitations
Properly interpreting the BEES scores requires placing them in perspective. There are
inherent limits to applying U.S. industry-average LCA and LCC results and in comparing
building products outside the design context.
The BEES LCA and LCC approaches produce U.S. average performance results for
generic product alternatives. The BEES results do not apply to products manufactured in
other countries where manufacturing and agricultural practices, fuel mixes, environmental
M Office of Management and Budget (OMB) Circular A-94, Guidelines and Discount Rates for Benefit-
Cost Analysis of Federal Programs, Washington, DC, October 27,1992 and OMB Circular A-94,
Appendix C, March 1997.
26
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Carbon Dioxide
Methane
Nitrous Oxide
Global Warming
(CO 2-equivalents)
Acid
Rain
Nullification
Resource
Depletion
Indoor Air
Quality
Solid
Waste
28%
Environmental
Performance
Score
Economic
Performance
Score
3.6%/yr
Overall
Score
50%
Figure 2.4. Deriving the BEES Overall Performance Score
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regulations, transportation distances, and labor and material markets may differ.39
Furthermore, all products in an industry-average, generic product group, such as vinyl
composition tile floor covering, are not created equal. Product composition,
manufacturing technologies, fuel mixes, transportation practices, useful lives, and cost
can all vary for individual products in a generic product group. Thus, the BEES results
for the generic product group do not necessarily represent the performance of an
individual product.
The BEES LCA uses selected inventory flows converted to selected regional and global
environmental impacts to assess environmental performance. Those inventory flows
which currently do not have scientifically proven or quantifiable impacts on the
environment are excluded, such as mineral extraction and wood harvesting which are
qualitatively thought to lead to loss of habitat and an accompanying loss of biodiversity.
Human health impacts, such as the carcinogenic potential of glass fibers used in building
insulation, are also excluded because they cannot yet be quantified and in some cases
scientifically proven. Finally, since BEES develops U.S. average results, local impacts
such as smog are excluded even though the science is proven and quantification is
possible. If the BEES user has important knowledge about these or other potential
environmental impacts, it should be brought into the interpretation of the BEES results.
During the interpretation step of the BEES LCA, the six environmental impacts are
combined into a single environmental performance score using relative importance
weights. These weights necessarily incorporate values and subjectivity. BEES users may
test the effects on the environmental performance score of changes in the set of
importance weights.
The BEES environmental scores do not represent absolute environmental damage.
Rather, they represent proportional differences in damage, or relative damage, among
competing alternatives. Consequently, the environmental performance score for a given
product alternative can change if one or more competing alternatives are added to or
removed from the set of alternatives under consideration. Keep in mind, however, that
rank reversal, or a reordering of scores, is impossible. For example, when comparing
Products A, B, and C, if Product A has the best score and Product C the worst, Product A
will continue to score better than Product C when Product B is removed from the
alternative set. Finally, since they are relative performance scores, no conclusions may be
drawn by comparing scores across building elements. That is, if exterior wall finish
Product A has an environmental performance score of 60, and roof covering Product C
has an environmental performance score of 40, Product C does not necessarily perform
better than Product A (keeping in mind that lower performance scores are better). The
same limitation to comparing relative scores across building elements applies to the
overall performance scores.
39 Since most linoleum manufacturing takes place in Europe, linoleum is modeled based on European
manufacturing practices, fuel mixes, and environmental regulations. However, the BEES linoleum results
are only applicable to linoleum imported into the United States because transport from Europe to the
United States is built into the BEES linoleum data.
28
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There are limits inherent in comparing product alternatives without reference to the whole
building design context. This approach may overlook important environmental and cost
interactions among building elements. For example, the useful life of one building
element (e.g., floor coverings), which influences both its environmental and economic
performance scores, may depend on the selection of related building elements (e.g.,
subflooring). There is no substitute for good building design.
Environmental and economic performance are but two attributes of building product
performance. The BEES model assumes that competing product alternatives all meet
minimum technical performance requirements40. However, there may be significant
differences in technical performance, such as acoustical performance, fire performance, or
aesthetics, that may outweigh environmental and economic considerations.
40 Environmental and economic performance results for wall insulation, and for concrete beams and
columns do consider technical performance differences. For wall insulation, BEES accounts for
differential heating and cooling energy use, based on insulation R-value, building location, and heating
fuel. For concrete beams and columns, BEES accounts for different compressive strengths.
29
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30
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3. BEES Product Data
The BEES model uses the ASTM standard classification system, UNIFORMAT H,4' to
organize building products into comparable groups. The ASTM standard classifies
building components into a three-level hierarchy: major group elements (e.g.,
substructure, shell, interiors), group elements (e.g., foundations, roofing, interior
finishes), and individual elements (e.g., slab on grade, roof coverings, floor finishes).
Elements are defined such that each performs a given function, regardless of design
specifications or materials used. The UNIFORMAT D classification system is well suited
to the BEES environmental and economic performance methodologies, which define
comparable products as those that fulfill the same basic function. The BEES model uses
the UNIFORMAT II classification of individual elements, the third level of the hierarchy,
as the point of departure for selecting functional applications for BEES product
comparisons.
3.1 Portland Cement Concrete Product Alternatives (BEES Codes A1030,
A2020, B1011, B1012, G2010)
Portland cement concrete, typically referred to as "concrete," is a mixture of portland
cement (a fine powder), water, fine aggregate such as sand or finely crushed rock, and
coarse aggregate such as gravel or crushed rock. The mixture creates a semi-fluid
material that forms a rock-like material when it hardens. Note that the terms "cement"
and "concrete" are often used interchangeably, yet cement is actually only one of several
concrete constituents.
Concrete is specified for different building elements by its compressive strength
measured 28 days after casting. Concretes with greater compressive strengths generally
contain more cement. While the compressive strength of concrete mixtures can range
from 0.69 to 138 Megapascals (100 to 20,000 pounds per square inch), concrete for
residential slabs, basements, driveways, and sidewalks often has a compressive strength
of 21 MPa (3000 psi) or less, and concrete for structural applications such as beams and
columns often have compressive strengths of 28 or 34 MPa (4000 or 5000 psi). Thus,
concrete mixes modeled in the BEES software are limited to compressive strengths of 21,
28, and 34 MPa (3000,4000, and 5000 psi).
To reduce costs, heat generation, and the environmental burden of concrete, fly ash may
be substituted for a portion of the portland cement in the concrete mix. Fly ash is a waste
material that is a result of burning coal to produce electricity. When used in concrete, fly
ash is a cementitious material and can act in a similar manner as cement by facilitating
compressive strength development.
41 American Society for Testing and Matenals, Standard Classification for Building Elements and
Related SiteworkUNIFORMAT II, ASTM Designation E 1557-93, West Conshohocken, PA, September
1993.
31
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BEES performance data apply to six building elements: 21 MPa (3000 psi) Slabs on
Grade, Basement Walls, Driveways, and Sidewalks; and 28 or 34 MPa (4000 or 5000 psi)
Beams and Columns. For each building element, concrete alternatives with 0%, 15%, and
20% fly ash content (by weight of cement) may be compared. While life-cycle costs
differ among building elements, the environmental performance for a given fly ash
content and compressive strength rating is the same. The detailed environmental
performance data for concrete products may be viewed by opening the following files
under the File/Open menu item in the BEES software:
A10301 .DBF0% Fly Ash Content Concrete
A10302.DBF15% Fly Ash Content Concrete
A10303.DBF20% Fly Ash Content Concrete
Within each of these three environmental performance data files, there are three complete
sets of environmental performance data corresponding to compressive strength ratings of
21,28, and 34 MPa (3000,4000, and 5000 psi).
BEES environmental performance data for concrete products are from the Portland
Cement Association LCA database. This subsection incorporates extensive
documentation provided by the Portland Cement Association for incorporating their LCA
data into BEES.42
Since comparisons within each building element are limited to concrete products, the
environmental performance data for all concrete mixes could be modeled from "cradle-to-
ready-mix plant gate" rather than from "cradle-to-grave" as for all other BEES products.
That is, environmental flows for transportation from the ready-mix plant to the building
site, installation (including concrete forms, reinforcing steel, welded wire fabric, and wire
mesh), and end of life are ignored. This modeling change does not affect environmental
performance results since BEES assesses relative environmental performance within a
given building element, and there will be no environmental performance differences
based on fly ash content for the ignored life-cycle stages.
Figures 3.1 and 3.2 show the elements of concrete production with and without fly ash.
Raw Materials. Table 3.1 shows quantities of concrete constituents for the three
compressive strengths modeled. Other materials that are sometimes added, such as silica
fume and chemical admixtures, are not considered. Typically, fly ash is an equal
replacement for cement. Quantities of constituent materials used in an actual project may
vary.
Portland Cement. Cement plants are located throughout North America at locations with
adequate supplies of raw materials. Major raw materials for cement manufacture include
42 Portland Cement Association, Concrete Products Life Cycle Inventory (LCI) Data Set for
Incorporation into the NISTBEES Model, PCA R&D Serial No. 2168, PCA Project 94-04a, prepared by
Michael Nisbet, JAN Consultants, 1998.
32
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Functional Unit
of Concrete
Without
Ply Ash
Portland
Cement
Production
Coarse
Aggregate
Production
Figure 3.1 Portland Cement Concrete Without Fly Ash Flow Chart
Functional Unit
of
Concrete With
Fly Ash
Figure 3.2 Portland Cement Concrete With Fly Ash Flow Chart
33
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Table 3.1 Concrete Constituent Quantities by Compressive Strength of Concrete
Concrete
Constituents
Cement and Fly Ash
Coarse Aggregate
Fine Aggregate
Water
Constituent Weight
in kilograms per cubic meter
(pounds per cubic yard)
21MPa
(SOOOpsi)
223 (376)
1127(1900)
831 (1400)
141 (237)
28MPa
(4000 psi)
279 (470)
1187(2000)
771 (1300)
141 (237)
34MPa
(SOOOpsi)
335 (564)
1187(2000)
712 (1200)
141 (237)
limestone, cement rock/marl, shale, and clay. These raw materials contain various
proportions of calcium oxide, silicon dioxide, aluminum oxide, and iron oxide, with
oxide content varying widely across North America. Since portland cement must contain
the appropriate proportion of these oxides, the mixture of the major raw materials and
minor ingredients (as required) varies among cement plants. BEES data for cement
manufacture is based on the average raw material mix and oxide content for all U.S.
cement plants for an ASTM C150 Type I/E cement, the most commonly used cement in
North America. The average raw materials for U.S. cement include limestone, cement
rock/marl, shale, clay, bottom ash, fly ash, foundry sand, sand, and iron/iron ore.
In the manufacturing process, major raw materials are blended with minor ingredients, as
required, and processed at high temperatures in a cement kiln to form an intermediate
material known as clinker. Gypsum is interground with clinker to form portland cement.
Gypsum content is assumed to be added at 5.15 percent (by weight) of portland cement.
Aggregate. Aggregate is a general term which describes a filler material in concrete.
Aggregate generally provides 60 to 75 percent of the concrete volume. Typically,
aggregate consists of a mixture of coarse and fine rocks. Aggregate is either mined or
manufactured.
Sand and gravel are examples of mined aggregate. These materials are dug or dredged
from a pit, river bottom, or lake bottom and require little or no processing. Crushed rock
is an example of manufactured aggregate. Crushed rock is produced by crushing and
screening quarry rock, boulders, or large sized gravel. Approximately half of the coarse
aggregate used in the United States is crushed rock.
Fly Ash. Fly ash is a waste material which is a result of burning coal to produce
electricity. In LCA terms, fly ash is an environmental outflow of coal combustion, and an
environmental inflow of concrete production. As in most LCAs, this waste product is
34
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assumed to be an environmentally "free" input material/3 However, transport of the fly
ash to the ready mix plant is included.
Energy Requirements: Portland Cement. Portland cement is manufactured using one of
four processes: wet process, dry process, preheater, or precalciner. The wet process is the
oldest and uses the most energy due to the energy required to evaporate the water. New
cement manufacturing plants are being constructed, and older plants converted, to use the
more energy efficient preheater/precalciner processes. As of 1995, the mix of production
processes was 30 percent wet, 27 percent dry, 19 percent preheater, and 24 percent
precalciner. Table 3.2 presents U.S. industry-average energy use by process and fuel type,
and, for all processes combined, average energy use weighted by the 1996 process mix.
Note that the production of waste fuels is assumed to be free of any environmental
burdens to portland cement production (LCA dictates that waste fuel production burdens
be allocated to the product whose manufacture generated the waste fuels).
Table 3.2 Energy Requirements for Portland Cement Manufacturing
Fuel Use
Coal
Petroleum Coke
Natural Gas
Liquid Fuels"
Wastes
Electricity
All Fuels:
Total Energy in kJ/kg
of cement (Btu/lb)
Cement Manufacturing Process'
Wet
49
18
9
1
16
7
100
6838 (2940)
Dry
45
31
8
1
6
9
100
6117(2630)
Preheater
67
6
10
2
4
12
100
4885 (2100)
Precalciner
60
8
16
1
3
12
100
4699(2020)
Weighted
Average
54
17
11
1
8
10
100
5745 (2470)
' Cement constitutes only 10 to IS percent by weight of concrete's total mass,
" Liquid fuels include gasoline, middle distillates, residual oil, and liquefied petroleum gas
Aggregate. In BEES, coarse and fine aggregate are assumed to be crushed rock, which
tends to slightly overestimate the energy use of aggregate production. Production energy
for both coarse and fine aggregate is assumed to be 155 kilojoules per kilogram of
aggregate (66.8 Btu/lb).
Fly Ash. Fly ash is a waste material with no production energy burdens.
41 The environmental burdens associated with waste products are typically allocated to the products
generating the waste.
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Round-trip distances for transport of concrete raw materials to the ready mix plant are
assumed to be 97 kilometers (60 miles) for portland cement and fly ash, and 80
kilometers (SO miles) for aggregate. The method of transport is truck, consuming 1.18
kilojoules per kilogram of material per kilometer (0.818 Btu per pound per mile).
Concrete, In BEES, concrete is assumed to be produced in a central ready-mix operation.
Energy use in the batch plant includes electricity and fuel used for heating and mobile
equipment. Average energy use is assumed to be 247 Megajoules per cubic meter of
concrete (0.179 MBtu/CYD, or about 45 Btu/lb of concrete).
Emissions. Emissions for concrete raw materials are from the Portland Cement
Association cement LCA database. Emissions include particulate matter, carbon dioxide
(CCb) , carbon monoxide (CO), sulfur oxide (SOx), nitrogen oxide (NO*), total
hydrocarbons, and hydrogen chloride (HC1). Emissions vary for the nine different
mixtures of compressive strength and fly ash content as shown in the concrete
environmental performance data files.
Cost The detailed life-cycle cost data for concrete products may be viewed by opening
the file LCCOSTS.DBF under the File/Open menu item in the BEES software. Life-cycle
cost data include first cost data (purchase and installation costs) and future cost data (cost
and frequency of replacement, and where appropriate and data are available, of operation,
maintenance, and repair). Costs are listed under the BEES codes listed in table 3.3. First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
3.2 Roof and Wall Sheathing Alternatives (B1020, B2015)
3.2.1 Oriented Strand Board Sheathing (B10201, B20151)
Oriented strand board (OSB) is made from strands of low density wood (e.g., lodgepole
pine, ponderosa pine, and white fir). A wax, primarily a petroleum-based wax, is used to
bind the strands. Methylene diphenylisocyanate (MDI) is also used as a binder material in
making most OSB. For the BEES system, 1.3 centimeter (1/2 inch) thick OSB boards are
studied. The flow diagram shown in Figure 3.3 shows the major elements of oriented
strand board production.
BEES performance data are provided for both roof and wall sheathing. Life-cycle costs
differ for the two applications, while the environmental performance data are assumed to
be the same. The detailed environmental performance data for OSB roof and wall
sheathing may be viewed by opening the file B10201.DBF under the File/Open menu
item in the BEES software.
36
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Table 3.3 Life-Cycle Cost Data Specifications and Codes for Concrete Products
Concrete Product
0% Fly Ash Content Slab on Grade
1 5% Fly Ash Content Slab on Grade
20% Fly Ash Content Slab on Grade
0% Fly Ash Content Basement Wall
15% Fly Ash Content Basement Wall
20% Fly Ash Content Basement Wall
0% Fly Ash Content Beams
15% Fly Ash Content Beams
20% Fly Ash Content Beams
0% Fly Ash Content Columns
15% Fly Ash Content Columns
20% Fly Ash Content Columns
0% Fly Ash Content Driveways &
Sidewalks
15% Fly Ash Content Driveways &
Sidewalks
20% Fly Ash Content Driveways &
Sidewalks
Specifications
10.2cm-15.2cm (4"-6") thick
10.2cm-15.2cm(4"-6") thick
10.2cm-15.2cm(4n-6") thick
20.3-38. 1cm (8"-15") thick
20.3-38. 1cm (8"-15") thick
20.3-38.1cm(8"-15") thick
3.0-7.6 mdO'-ZS1) span
3.0-7.6 m(10'-25') span
3.0-7.6 m(10'-25') span
40.6-61.0cm (16"-24") diameter
40.6-61.0cm (16"-24") diameter
40.6-61.0cm (16"-24") diameter
10.2cm-15.2cm (4"-6") thick
10.2cm-15.2cm (4"-6") thick
10.2cm-15.2cm(4"-6") thick
BEES Code
A1030.10
A1030.20
A1030.30
A2020.10
A2020.20
A2020.30
31011,10
B1011,20
81011,30
B1012.10
B1012,20
81012,30
G2010.10
G2010.20
G2010.30
Raw Materials. Production of the raw materials for oriented strand board sheathing is
based on the Ecobalance LCA database. The average diameter of the logs is assumed to
be 18 centimeters (7 inches), which occurs at a density of about 11 kilograms per square
meter (SO tons/acre). The MDI binder is added at about 0.26 kilograms per square meter
(O.OS Ibs per square foot) of 1.3 centimeter (1/2 inch) thickness. The wax used in the
binding of the strands is assumed to be petroleum-based wax. OSB constituents are
shown in Table 3.4.
Table 3.4 Oriented Strand Board Sheathing Constituents
Oriented Strand Board Constituents Physical Weight (%)
Wood (low density) 97
Methylene diphenylisocyanate (MDI) 2
Wax (petroleum-based) 1
Production requirements for OSB constituents are based on the Ecobalance LCA
database.
Energy Required. The energy requirement for OSB production is assumed to be 0.6 MJ
of electricity per kilogram (258 Btu per pound) of OSB produced.
37
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Transportation
Functional Unit of OSB
-Energyป
OSB production
MothylonB
Olphenyllsocyanate
(MDI) production
Wood Harvesting
Transportation
Figure 3.3 Oriented Strand Board Flow Chart
Emissions. Emissions data are from Forintek environmental impact study for wood
products.44
Transportation. Transportation of the raw materials to the oriented strand board
manufacturing facility is not taken into account (often manufacturing facilities are located
close to forests). However, transportation to the building site is modeled as a variable of
the BEES system.
Cost Installation costs for OSB sheathing vary by application. The detailed life-cycle
cost data for this product may be viewed by opening the file LCCOSTS.DBF under the
File/Open menu item in the BEES software. Its costs are listed under the following codes:
Bl 020,10Oriented Strand Board Roof Sheathing
B2015,10Oriented Strand Board Wall Sheathing
44 Fonntek Canada Corporation, Building Materials in the Context of Sustainable Development: Raw
Material Balances, Energy Profiles and Environmental Unit Factor Estimates for Structural Wood
Products, March 1993, p 27.
38
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Life-cycle cost data include first cost data (purchase and installation costs) and future cost
data (cost and frequency of replacement, and where appropriate and data are available, of
operation, maintenance, and repair). First cost data are collected from the R.S. Means
publication, 1997 Building Construction Cost Data, and future cost data are based on data
published by Whitestone Research in The Whitestone Building Maintenance and Repair
Cost Reference 1997, supplemented by industry interviews.
3.2.2 Plywood Sheathing (B10202, B20152)
Softwood plywood sheathing is made from lower density wood (e.g., lodgepole pine,
ponderosa pine, and white fir). Phenol formaldehyde is used in the manufacturing
process. For the BEES system, 1.3 centimeter (1/2 inch) thick plywood boards are
studied. The flow diagram shown in Figure 3.4 shows the major elements of softwood
plywood sheathing production.
BEES performance data are provided for both roof and wall sheathing. Life-cycle costs
differ for the two applications, while the environmental performance data are assumed to
be the same. The detailed environmental performance data for plywood roof and wall
sheathing may be viewed by opening the file B10202.DBF under the File/Open menu
item in the BEES software
Raw Materials. Production of the raw materials for plywood sheathing is based on the
Ecobalance LCA database. The average diameter of the logs, assumed harvested from
well-managed forests, is assumed to be 18 centimeters (7 inches), which occurs at a
density of about 11 kilograms per square meter (SO tons/acre). Phenol formaldehyde is
assumed to constitute 1.4% of the total mass of the product. Plywood sheathing
constituents are shown in Table 3.5.
Table 3.5 Plywood Constituents
Plywood Sheathing Physical Weight (%)
Constituents
Wood (low density) 98.6
Phenol formaldehyde 1.4
Production requirements for plywood sheathing are based on the Ecobalance LCA
database.
Energy Required. The energy requirement for plywood sheathing production is assumed
to be 0.45 MJ of electricity per kilogram (193 Btu per pound) of plywood produced.
39
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Transportation
Functional Unit of Plywood
Energy
QhnajrMtH
riyWrOOO
Phenol Formatdedyde
Production
Softwood Harvesting
Transportation
Figure 3.4 Softwood Plywood Flow Chart
Emissions. Emissions data are from the Forintek environmental impact study for wood
products.45
Transportation. Transportation of the raw materials to the plywood sheathing
manufacturing facility is not taken into account (often manufacturing facilities are located
close to forests). However, transportation to the building site is modeled as a variable of
the BEES system.
Cost Installation costs for plywood vary by application. The detailed life-cycle cost data
for this product may be viewed by opening the file LCCOSTS.DBF under the File/Open
menu item in the BEES software. Its costs are listed under the following codes:
B1020,20Plywood Roof Sheathing
B2015,20Plywood Wall Sheathing
45 Forintek Canada Corporation, Building Materials in the Context of Sustainable Development: Raw
Material Balances. Energy Profiles and Environmental Unit Factor Estimates for Structural Wood
Products, March 1993, pp 20-24.
40
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Life-cycle cost data include first cost data (purchase and installation costs) and future cost
data (cost and frequency of replacement, and where appropriate and data are available, of
operation, maintenance, and repair). First cost data are collected from the R.S. Means
publication, 1997 Building Construction Cost Data, and future cost data are based on data
published by Whitestone Research in The Whitestone Building Maintenance and Repair
Cost Reference 1997, supplemented by industry interviews.
3.3 Exterior Wall Finish Alternatives (B2011)
3.3.1 Brick and Mortar (B20111)
Brick is a masonry unit of clay or shale, formed into a rectangular shape while plastic,
then burned or fired in a kiln. Mortar is used to bond the bricks into a single unit. Facing
brick is used on exterior walls for an attractive appearance.
For the BEES system, solid, fired clay facing brick (10cm x 6.8cm x 20 cm, or 4" x 2-
2/3" x 8") and Type N mortar are studied. The flow diagram shown in Figure 3.5 shows
the major elements of clay facing brick and mortar production. The detailed
environmental performance data for this product may be viewed by opening the file
B20111 .DBF under the File/Open menu item in the BEES software.
Brick and Mortar
Figure 3.5 Brick and Mortar Flow Chart
41
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Raw Materials. Production of the raw materials for brick and mortar are based on the
Ecobalance LCA database. Type N mortar consists of 1 part (by volume) masonry
cement, 3 parts sand,46 and 6.3 liters (1.67 gallons) of water. Masonry cement is modeled
based on the assumptions outlined below for stucco exterior walls.
Energy Required. The energy requirements for brick production (drying and firing) are
listed in table 3.6. The production of the different types of fuel was based on the
Ecobalance LCA database.
Table 3.6 Energy Requirements for Brick Manufacturing
Fuel Use Manufacturing Energy
Total Fossil Fuel 2.88 MJ/kg (1238 Btu/lb)
% Coal 9.6 %
% Natural Gas (*) 71.9%
% Fuel Oil 7.8 %
% Wood 10.8 %
(*) Includes Propane
The mix of brick manufacturing technologies is 73 percent tunnel kiln technology and 27
percent periodic kiln technology.
The mortar is assumed to be mixed in a 8 Horsepower, gasoline powered mixer with a
flow rate of 0.25 cubic meters (9 cubic feet) of mortar per hour, running for five minutes.
Emissions. Emissions were based on AP-4247 data for emissions from brick
manufacturing for each manufacturing technology and type of fuel burned.
Transportation. Transportation of the raw materials to the brick manufacturing facility
was not taken into account (often manufacturing facilities are located close to mines).
However, transportation to the building site is modeled as a variable. Bricks are assumed
to be transported by truck and train (86% and 14%, respectively) to the building site. The
BEES user can select from among three travel distances.
Use. The density of brick is assumed to be 2.95 kilograms (6.5 pounds) per brick. The
density of the Type N mortar is assumed to be 2007 kilograms per cubic meter (125
pounds per cubic foot). A brick wall is assumed to be 80% brick and 20% mortar by
surface area.
End-Of-Life. The brick wall is assumed to have a useful life of 200 years. Seventy-five
percent of the bricks are assumed to be recycled after the 200 year use.
46 Based on ASTM Specification C 270-96.
" Clearinghouse for Inventories and Emission Factors, Version 4.0, EPA-454/C-95-001, CD-ROM, July
1995.
42
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Cost. The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code B2011, product code 10. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
3.3.2 Stucco (B20112)
Stucco is cement plaster used to cover exterior wall surfaces. For the BEES system, three
coats of stucco (two base coats and one finish coat) are studied. A layer of bonding agent,
polyvinyl acetate, is assumed to be applied between the wall and the first layer of base
coat stucco.
Figures 3.6 and 3.7 show the elements of stucco production from both portland cement
(for a base coat Type C plaster, finish coat Type F plaster) and masonry cement (for a
base coat Type MS plaster, finish coat Type F plaster). Since both cements are commonly
used for stucco exterior walls, LCA data for both portland cement and masonry cement
stucco were collected and then averaged for use in the BEES system. Figure 3.8 shows
the steps in the manufacture of masonry cement, and figure 3.9 the steps in the
manufacture of portland cement.
The detailed environmental performance data for stucco exterior walls may be viewed by
opening the file B20112.DBF under the File/Open menu item in the BEES software.
Raw Materials. The raw material consumption for masonry cement is based on Type N
masonry cement as shown in table 3.7.
Table 3.7 Masonry Cement Constituents
Masonry Cement Physical Weight
Constituent (%)
Portland Cement Clinker 50
Limestone 47.5
Gypsum 2A
Production of these raw materials is based on the Ecobalance LCA database.
Stucco consists of the raw materials listed in table 3.8.4S
48 Based on ASTM Specification C 926-94.
43
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44
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Masonry Cement
Figure 3.8 Masonry Cement Flow Chart
Portland Cement
Figure 3.9 Portland Cement Flow Chart
45
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Table 3.8 Stucco Constituents
Cementitious Materials (parts by volume) Sand
Type of Stucco Portland Masonry Lime per volume of
Cement Cement cementitious mat'l
Base Coat C 1
Finish Coat F 1
Base Coat MS
Finish Coat FMS
0.5 3.75
1.125 2.25
1 3.75
1 2.25
The coat of bonding agent is assumed to be 0.15 millimeters (0.006 inches) thick. The
bonding agent is polyvinyl acetate.
Production of sand, lime, and polyvinyl acetate is modeled from the Ecobalance database.
Energy Requirements. The energy requirements for masonry cement production are
shown in table 3.9.
Table 3.9 Energy Requirements for Masonry Cement Manufacturing
Fuel Use Manufacturing Energy
Total Fossil Fuel 2.72 MJ/kg (1169 Btu/lb)
% Coal 84 %
% Natural Gas 7%
% Fuel Oil 1 %
% Wastes 8 %
Total Electricity 0.30 MJ/kg (129 Btu/lb)
These percentages are based on average fuel use in portland cement manufacturing.
Stucco is assumed to be mixed in a 8 Horsepower, gasoline powered mixer with a flow
rate of 0.25 cubic meters (9 cubic feet) of stucco per hour, running for five minutes.
Emissions. Emissions for masonry cement production are based on AP-42 data for
controlled emissions from cement manufacturing. Clinker is assumed to be produced in a
wet process kiln.
Transportation. Transportation distance to the building site is modeled as a variable.
Use. The thickness of the three layers of stucco is assumed to be 1.6 centimeters (5/8
inch) each.
The densities of the different types of stucco are shown in table 3.10.
46
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Table 3.10 Density of Stucco by Type
Density
Type of Stucco kg/0.02 83m3(kg/ff)
Base Coat C 51.79
Finish Coat F 55.78
Base Coat MS 53.97
Finish Coat FMS 61.55
Cost. The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code B20JJ, product code 20. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
3.4 Wall and Ceiling Insulation Alternatives (B2012, B3014)
3.4.1 Blown Cellulose Insulation (B20121, B30141)
Blown cellulose insulation is produced primarily from post-consumer wood pulp
(newspapers), accounting for about 80% of the insulation by weight. Cellulose insulation
is treated with fire retardant. Ammonium sulfate, berates, and boric acid are used most
commonly and account for the other 20% of the cellulose insulation by weight. The flow
diagram shown in Figure 3.10 shows the elements of blown cellulose insulation
production.
BEES performance data are provided for thermal resistance values of R-13 for a wall
application and R-30 for a ceiling application. The detailed environmental performance
data files for this product may be viewed by opening the following files under the
File/Open menu item in the BEES software:
B20121.DBFR-13 Blown Cellulose Wall Insulation
B30141 .DBFR-30 Blown Cellulose Ceiling Insulation
Raw Materials. Blown cellulose insulation is composed of the materials listed in table
3.11. Production requirements for these constituents are based on the Ecobalance LCA
database.
47
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Post'Consunwr
Newspaper
Waste
Figure 3.10 Blown Cellulose Insulation Flow Chart
Table 3.11 Blown Cellulose Constituents
Blown Cellulose Insulation Physical Weight
Constituents
Pulp waste (newspapers)
Ammonium sulfate
Boric acid
80
15.5
4.5
Blown cellulose insulation manufacture involves the energy requirements as listed in
table 3.12.
Table 3.12 Energy Requirements for Blown Cellulose Insulation Manufacturing
Fuel Use
Manufacturing Energy
Electricity
0.35 MJ/kg (150 Btu/lb)
48
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Use. It is important to consider thermal performance differences when assessing
environmental and economic performance for insulation product alternatives. Thermal
performance affects building heating and cooling loads, which in turn affect energy-
related LCA inventory flows and building energy costs over the 50-year use stage. Since
alternatives for ceiling insulation all have R-30 thermal resistance values, thermal
performance differences are at issue only for the R-ll, R-12, R-13, and R-1S wall
insulation alternatives.
For wall insulation, thermal performance differences are separately assessed for 14 U.S.
cities spread across a wide range of climate and fuel cost zones, and for electricity,
distillate oil, and natural gas heating fuel types (electricity is assumed for all cooling).
When selecting wall insulation alternatives for analysis, the BEES user selects the U.S.
city closest to the building location, and the building heating fuel type, so that thermal
performance differences may be customized to these important contributors to building
energy use. A MIST study of the economic efficiency of energy conservation measures
(including insulation), tailored to these cities and fuel types, is used to estimate 50-year
heating and cooling requirements per functional unit of insulation.49 BEES environmental
performance results account for the energy-related inventory flows resulting from these
energy requirements. To account for the 50-year energy requirements in BEES economic
performance results, 1997 fuel prices by State,50 and U.S. Department of Energy fuel
price projections over the next 30 years51 are used to compute the present value cost of
operational energy per functional unit for each alternative R-value.
Cellulose insulation is typically blown into place. It is assumed to be blown at a rate of
1134 kilograms per hour (2500 Ibs/hr). During installation, there is negligible waste
because excess cellulose is typically added back into the hopper for re-blowing or is
simply placed by hand into wall or ceiling cavities.
Cost. Installation costs for blown cellulose insulation vary by application. The detailed
life-cycle cost data for this product may be viewed by opening the file LCCOSTS.DBF
under the File/Open menu item in the BEES software. Its costs are listed under the
following codes:
B2012.10R-13 Blown Cellulose Wall Insulation
63014,10R-30 Blown Cellulose Ceiling Insulation
Life-cycle cost data include first cost data (purchase and installation costs) and future cost
data (cost and frequency of replacement, and where appropriate and data are available, of
operation, maintenance, and repair). Operational energy costs for wall insulation
(discussed above under "Use") are found in the file USEENRGY.DBF. All other future
49 Stephen R. Petersen, Economics and Energy Conservation in the Design of New Single-Family
Housing. NBSIR 81-2380, National Bureau of Standards, Washington, D.C., 1981.
50 Therese K. Stovall, Supporting Documentation for the 1997 Revision to the DOE Insulation Fact
Sheet, ORNL-6907, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1997.
91 Sieglinde K. Fuller, Energy Price Indices and Discount Factors for Life-Cycle Cost AnalysisApril
1997. NISTIR 85-3273-12, National Institute of Standards and Technology, 1997. The year 30 DoE cost
esclation factor is assumed to hold for years 31-50.
49
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cost data are based on data published by Whitestone Research in The Whitestone Building
Maintenance and Repair Cost Reference 1997, supplemented by industry interviews.
First cost data are collected from the R.S. Means publication, 1997 Building Construction
Cost Data.
3.4.2 Fiberglass Batt Insulation (B20122, B20123, B30142)
Fiberglass batt insulation is made by forming spun-glass fibers into batts. Using a rotary
process, molten glass is poured into a rapidly spinning disc that has thousands of fine
holes in its rim. Centrifugal force extrudes the molten glass through the holes, creating
the glass fibers. The fibers are made thinner by jets, air, or steam and are immediately
coated with a binder and/or de-dusting agent. The material is then cured in ovens and
formed into batts.
The flow diagram shown in Figure 3.11 shows the elements of fiberglass ban insulation
production.
Figure 3.11 Fiberglass Batt Insulation Flow Chart
BEES performance data are provided for thermal resistance values of R-l 1 and R-l 5 for a
wall application, and R-30 for a ceiling application. The detailed environmental
performance data for fiberglass batt insulation may be viewed by opening the following
files under the File/Open menu item in the BEES software:
B20122.DBFR-l 1 Fiberglass Wall Insulation
B20123.DBFR-15 Fiberglass Wall Insulation
50
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B30142.DBFR-30 Fiberglass Ceiling Insulation
Raw Materials. Fiberglass batts are composed of the materials listed in table 3.13.
Table 3.13 Fiberglass Batt Constituents
Fiberglass Batt Constituents Physical Weight
High silica-content sand and 64
limestone
Binder (phenol formaldehyde) 6
Boron oxide 5
Glass cullet (industry average) 25
Production requirements for the fiberglass batt insulation constituents are based on the
Ecobalance LCA database.
Fiberglass batt production involves the energy requirements as listed in table 3.14.
Table 3.14 Energy Requirements for Fiberglass Batt Insulation Manufacturing
Manufacturing Energy
Fuel Use
Electricity 3.1 MJ/kg (1333 Btu/lb)
Natural Gas 17.17 MJ/kg (73 82 Btu/lb)
Emissions. Emissions associated with fiberglass batt insulation manufacture are based on
AP-42 data for the glass fiber manufacturing industry.
Use. It is important to consider thermal performance differences when assessing
environmental and economic performance for insulation product alternatives. Thermal
performance affects building heating and cooling loads, which in turn affect energy-
related LCA inventory flows and building energy costs over the 50-year use stage. Since
alternatives for ceiling insulation all have R-30 R-values, thermal performance
differences are at issue only for the R-ll, R-12, R-13, and R-15 wall insulation
alternatives.
For wall insulation, thermal performance differences are separately assessed for 14 U.S.
cities spread across a wide range of climate and fuel cost zones, and for electricity,
distillate oil, and natural gas heating fuel types (electricity is assumed for all cooling).
When selecting wall insulation alternatives for analysis, the BEES user selects the U.S.
city closest to the building location and the building heating fuel type, so that thermal
performance differences may be customized to these important contributors to building
energy use. A MIST study of the economic efficiency of energy conservation measures
51
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(including insulation), tailored to these cities and fuel types, is used to estimate 50-year
heating and cooling requirements per functional unit of insulation.52 BEES environmental
performance results account for the energy-related inventory flows resulting from these
energy requirements. To account for the 50-year energy requirements in BEES economic
performance results, 1997 fuel prices by State,53 and U.S. Department of Energy fuel
price projections over the next 30 years54 are used to compute the present value cost of
operational energy per functional unit for each R-value.
When installing fiberglass batt insulation, approximately 5% of the product is lost to
waste. Although fiberglass insulation reuse or recycling is feasible, very little occurs
now. Most fiberglass insulation waste is currently disposed of in landfills.
Cost. Purchase and installation costs for fiberglass batt insulation vary by R-value and
application. The detailed life-cycle cost data for this product may be viewed by opening
the file LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs
are listed under the following codes:
62012,20R-l 1 Fiberglass Batt Wall Insulation
82012,30R-15 Fiberglass Batt Wall Insulation
83014,20R-30 Fiberglass Batt Ceiling Insulation
Life-cycle cost data include first cost data (purchase and installation costs) and future cost
data (cost and frequency of replacement, and where appropriate and data are available, of
operation, maintenance, and repair). Operational energy costs for wall insulation
(discussed above under "Use") are found in the file USEENRGY.DBF. All other future
cost data are based on data published by Whitestone Research in The Whitestone Building
Maintenance and Repair Cost Reference 1997, supplemented by industry interviews.
First cost data are collected from the R.S. Means publication, 1997 Building Construction
Cost Data.
3.4.3 Blown Mineral Wool Insulation (B20124, B30143)
Blown mineral wool insulation is made by spinning fibers from natural rock (rock wool)
or iron ore blast furnace slag (slag wool). Rock wool and slag wool are manufactured by
melting the constituent raw materials in a cupola. A molten stream is created and poured
onto a rapidly spinning wheel or wheels. The viscous molten material adheres to the
wheels and the centrifugal force throws droplets of melt away from the wheels, forming
fibers. The fibers are then collected and cleaned to remove non-fibrous material. During
52 Stephen R. Petersen, Economics and Energy Conservation in the Design of New Single-Family
Housing, NBSER. 81-2380, National Bureau of Standards, Washington, D.C., 1981.
n Therese K. Stovall, Supporting Documentation for the 1997 Revision to the DOE Insulation Fact
Sheet, ORNL-6907, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1997.
54 Sieglinde K. Fuller, Energy Price Indices and Discount Factors for Life-Cycle Cost AnalysisApril
1997. NISTTR 85-3273-12, National Institute of Standards and Technology, 1997. The year 30 DoE cost
esclation factor is assumed to hold for years 31-50.
52
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the process a phenol formaldehyde binder and/or a de-dusting agent are applied to reduce
free, airborne wool during application. The flow diagram in Figure 3.12 shows the
elements of blown mineral wool insulation production.
Functional Unit of Insulation
Mineral Wool Production
Iron Ore Slag
Production
-Energy-
Diabase Rock
Production
Binder Production
Figure 3.12 Blown Mineral Wool Insulation Flow Chart
BEES performance data are provided for a thermal resistance value of R-12 for a wall
application, and R-30 for a ceiling application. The detailed environmental performance
data for blown mineral wool insulation may be viewed by opening the following files
under the File/Open menu item in the BEES software:
B20124.DBFR-12 Mineral Wool Wall Insulation
B30143 .DBFR-30 Mineral Wool Ceiling Insulation
Raw Materials. Mineral wool insulation is composed of the materials listed in table 3.15.
Production requirements for the mineral wool constituents are based on the Ecobalance
LCA database.
53
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Table 3.15 Blown Mineral Wool Constituents
Mineral Wool Constituents Physical
Weight (%)
Iron-ore slag (North American) 80
Diabase/basalt 20
Mineral wool production involves the energy requirements listed in table 3.16.
Table 3.16 Energy Requirements for Mineral Wool Insulation Manufacturing
Manufacturing Energy
Fuel Use
Natural Gas 15.85 MJ/kg (6814 Btu/lb)
Coke 6.38 MJ/kg (2473 Btu/lb)
Emissions. Emissions associated with mineral wool insulation production are based on
AP-42 data for the mineral wool manufacturing industry.
Use. It is important to consider thermal performance differences when assessing
environmental and economic performance for insulation product alternatives. Thermal
performance affects building heating and cooling loads, which in turn affect energy-
related LCA inventory flows and building energy costs over the 50-year use stage. Since
alternatives for ceiling insulation all have R-30 R-values, thermal performance
differences are at issue only for the R-ll, R-12, R-13, and R-15 wall insulation
alternatives.
For wall insulation, thermal performance differences are separately assessed for 14 U.S.
cities spread across a wide range of climate and fuel cost zones, and for electricity,
distillate oil, and natural gas heating fuel types (electricity is assumed for all cooling).
When selecting wall insulation alternatives for analysis, the BEES user selects the U.S.
city closest to the building location and the building heating fuel type, so that thermal
performance differences may be customized to these important contributors to building
energy use. A NIST study of the economic efficiency of energy conservation measures
(including insulation), tailored to these cities and fuel types, is used to estimate 50-year
heating and cooling requirements per functional unit of insulation.55 BEES environmental
performance results account for the energy-related inventory flows resulting from these
energy requirements. To account for the 50-year energy requirements in BEES economic
performance results, 1997 fuel prices by State,56 and U.S. Department of Energy fuel
91 Stephen R. Peterson, Economics and Energy Conservation in the Design of New Single-Family
Housing. NBSIR 81-2380, National Bureau of Standards, Washington, D.C., 1981.
"Therese K. Stovall, Supporting Documentation for the 1997 Revision to the DOE Insulation Fact
Sheet, ORNL-6907, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 1997.
54
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price projections over the next 30 years57 are used to compute the present value cost of
operational energy per functional unit for each R-value.
Mineral wool insulation is typically blown into place. It is assumed to be blown at a rate
of 1134 kilograms per hour (2500 Ibs/hr). During installation, there is negligible waste
because excess mineral wool is typically added back into the hopper for re-blowing or is
simply placed by hand into wall or ceiling cavities.
Cost. Purchase and installation costs for blown mineral wool insulation vary by
application. The detailed life-cycle cost data for this product may be viewed by opening
the file LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs
are listed under the following codes:
B2012.40R-12 Mineral Wool Wall Insulation
83014,30R-30 Mineral Wool Ceiling Insulation
Life-cycle cost data include first cost data (purchase and installation costs) and future cost
data (cost and frequency of replacement, and where appropriate and data are available, of
operation, maintenance, and repair). Operational energy costs for wall insulation
(discussed above under "Use") are found in the file USEENRGY.DBF. All other future
cost data are based on data published by Whitestone Research in The Whitestone Building
Maintenance and Repair Cost Reference 1997, supplemented by industry interviews.
First cost data are collected from the R.S. Means publication, 7997 Building Construction
Cost Data.
3.5 Roof Covering Alternatives (B3011)
3.5.1 Asphalt Shingles (B30111)
Asphalt shingles are commonly made from fiberglass mats filled with asphalt, then
coated on the exposed side with mineral granules for both a decorative finish and a
wearing layer. Asphalt shingles are nailed over roofing felt onto sheathing.
For BEES, a roof covering of 20-year asphalt shingles, roofing felt, and galvanized nails
is analyzed. The flow diagram shown in Figure 3.13 shows the elements of asphalt
shingle production. The detailed environmental performance data for this product may be
viewed by opening the file B30111.DBF under the File/Open menu item in the BEES
software.
51 Sieglinde K. Fuller, Energy Price Indices and Discount Factors for Life-Cycle Cost AnalysisApril
1997, NISTIR 85-3273-12, National Institute of Standards and Technology, 1997. The year 30 DoE cost
escladon factor is assumed to hold for years 31-50.
55
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Figure 3.13 Asphalt Shingles Flow Chart
Raw Materials. Asphalt shingles are composed of the materials listed in table 3.17.
Table 3.17 Asphalt Shingle Constituents
Asphalt Shingle
Constituents
Physical Weight
Asphalt
Filler
Fiberglass
Granules
1.9kg/m2(401bs/sq.)
4.2kg/m2(861bs/sq.)
0.2kg/m2(41bs/sq.)
3.7kg/m2(751bs/sq.)
Filler is assumed to be 50 percent dolomite and SO percent limestone. Granules
production is modeled as rock mining and grinding. Production requirements for the
asphalt shingle constituents are based on the Ecobalance LCA database.
Seven kilogram (fifteen pound) felt consists of asphalt and organic felt as listed in table
3.18. The organic felt is assumed to consist of 50 percent recycled cardboard and 50
percent wood chips. The production of these materials, and the asphalt, is based on the
Ecobalance LCA database.
Energy Requirements. The energy requirement for asphalt shingle production is
assumed to be 33 MJ of natural gas per square meter (2843 Btu per square foot) of
shingles.
56
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Table 3.18 Seven Kilogram (15 pound) Roofing Felt Constituents
7kg(15lb)
Felt Constituents Physical Weight
Asphalt 0.5 kg/ m2 (9.6 Ibs/sq.)
Organic Felt 0.3 kg/ m2 (5.4 Ibs/sq.)
Total: 0.8 kg/m2 (15 Ibs/sq.)
Emissions. Emissions associated with manufacturing asphalt shingles and roofing felt is
taken into account based on AP-42 data for asphalt shingle processing and saturated felt
processing.
Transportation. Transport of the asphalt shingle raw materials is taken into account. The
distance transported is assumed to be 402 km (250 mi) for all of the components. Asphalt
is assumed to be transported by truck, train, and pipeline in equal proportions. Dolomite,
limestone, and granules are assumed to be transported by truck and train in equal
proportions. Fiberglass is assumed to be transported by truck.
Transport of the raw materials for roofing felt is also taken into account. The distance
transported is assumed to be 402 km (250 mi) for all of the components. Asphalt is
assumed to be transported by truck, train, and pipeline in equal proportions, while the
cardboard and wood chips are assumed to be transported by truck.
Transport of the shingles, roofing felt, and nails to the building site is a variable of the
BEES system.
Use. Asphalt shingle and roofing felt installation is assumed to require 47 nails per square
meter (440 nails per square). Installation waste from scrap is estimated at 5 percent of the
installed weight. At 20 years, new shingles are installed over the existing shingles. At 40
years, both layers of roof covering are removed before installing replacement shingles.
Cost. The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code B3011, product code 10. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
3.5.2 Clay Tile (B30112)
Clay tiles are made by shaping and firing clay. The most commonly used clay tile is the
red Spanish tile. For the BEES system, a roof covering of 70-year red Spanish clay tiles,
57
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roofing felt, and nails is studied. Due to weight of the tile and its relatively long useful
life, 14 kilogram (30 pound) felt and copper nails are used. The flow diagram shown in
Figure 3.14 shows the elements of clay tile production. The detailed environmental
performance data for this product may be viewed by opening the file B30112.DBF under
the File/Open menu item in the BEES software.
Clay Tiles
Functional Unit
of Clay Tile Roofing
Figure 3.14 Clay Tile Flow Chart
Raw Materials. The weight of the clay tile studied is 381 kilograms (840 pounds) per
square, requiring 171 pieces of tile. Production of the clay is based on the Ecobalance
LCA database.
Table 3.19 Fourteen Kilogram (30 pound) Roofing Felt Constituents
14 kg (30 Ib)
Felt Constituents
Physical Weight
Asphalt
Organic Felt
Total:
0.9 kg/m2 (19.2 Ibs/sq.)
0.5kg/mz(10.81bs/sq.)
1.4kg/m2(301bs/sq.)
Fourteen kilogram (thirty pound) felt consists of asphalt and organic felt as listed in table
3.19. The organic felt is assumed to consist of 50 percent recycled cardboard and SO
percent wood chips. The production of these materials, and the asphalt, is based on the
Ecobalance LCA database.
58
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Energy Requirements. The energy required to fire clay tile is 6.3 MJ per kilogram (2708
Btu per pound) of clay tile. The fuel type is natural gas.
Emissions. Emissions associated with natural gas combustion are based on AP-42
emission factors.
Transportation. Transport of the clay raw material is taken into account, the distance
transported is assumed to be 402 km (250 mi) for the clay by train and truck. Transport of
the raw materials for roofing felt is also taken into account. The distance transported is
assumed to be 402 km (2SO mi) for all of the components. Asphalt is assumed to be
transported by truck, train, and pipeline in equal proportions, while the cardboard and
wood chips are assumed to be transported by truck. Transport of the tiles to the building
site is a variable of the BEES model.
Use. Clay tile roofing is assumed to require two layers of 14 kilogram (30 pound) roofing
felt, 13 galvanized nails per square meter (120 per square) for underlavment, and 37
copper nails per square meter (342 per square) for the tile (2 copper nails per tile).
Installation waste from scrap is estimated at 5 percent of the installed weight. One-fourth
of the tiles are replaced after 20 years, and another one-fourth at 40 years. All tiles are
replaced at 70 years.
Cost. The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code 53077, product code 20. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
3.5.3 Fiber Cement Shingles (B30113)
In the past, fiber cement shingles were manufactured using asbestos fibers. Now asbestos
fibers have been replaced with cellulose fibers. For the BEES study, a 45-year fiber
cement shingle consisting of cement, sand, and cellulose fibers is studied. Roofing felt
and galvanized nails are used for installation. The flow diagram shown in Figure 3.15
shows the elements of fiber cement shingle production. The detailed environmental
performance data for this product may be viewed by opening the file B30113.DBF under
the File/Open menu item in the BEES software.
Raw Materials. Fiber cement shingles are composed of the materials listed in table 3.20.
The filler is sand, and the organic fiber is wood chips. The weight of fiber cement
shingles is assumed to be 16 kilograms per square meter (325 pounds per square), based
on 36cm x 76cm x 0.4cm (14in x 30in x 5/32in) size shingles.
59
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Functional Unit of
Fiber Cement Shingles
Figure 3.15 Fiber Cement Shingles Flow Chart
Table 3.20 Fiber Cement Shingle Constituents
Fiber Cement Shingle
Constituents
Physical Weight
Portland Cement
Filler
Organic Fiber
90
5
5
Portland cement production requirements are identical to those noted above for stucco
exterior wall finish. Fourteen kilogram (30 pound) roofing felt is modeled as noted above
for clay tile roofing.
Production requirements for the raw materials is based on the Ecobalance LCA database.
Energy Requirements. The energy requirements for fiber cement shingle production are
assumed to be 33 MJ of natural gas and 11 MJ of electricity per square meter (2843 Btu
of natural gas and 948 Btu of electricity per square foot) of shingle.
Transportation. Transport of the raw materials is taken into account. The distance over
which all materials are transported is assumed to be 402 km (250 mi). Shingle materials
are assumed to be transported by truck. For roofing felt, asphalt is assumed to be
transported by truck, train, and pipeline in equal proportions, while the cardboard and
wood chips are assumed to be transported by truck.
Transport of the shingles to the building site is a variable of the BEES model.
60
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Use. Fiber cement shingle roofing requires one layer of 14 kilogram (30 pound) felt
underlayment, 13 nails per square meter (120 nails per square) for the underlayment, and
32 nails per square meter (300 nails per square) for the shingles. Installation waste from
scrap is estimated at 5 percent of the installed weight. Fiber cement roofing is assumed to
have a useful life of 45 years.
Cost. The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code B3011, product code 30. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
3.6 Floor Covering Alternatives (C3020)
3.6.1 Ceramic Tile with Recycled Windshield Glass (C30201)
Ceramic tile flooring consists of clay, or a mixture of clay and other ceramic materials,
which is baked in a kiln to a permanent hardness. To improve environmental
performance, recycled windshield glass can be added to the ceramic mix. For the BEES
system, 50-year ceramic tile with 75 percent recycled windshield glass content, installed
using a latex-cement mortar, is studied. The flow diagram shown in Figure 3.16 shows
the elements of ceramic tile with recycled glass production. The detailed environmental
performance data for this product may be viewed by opening the file C30201.DBF under
the File/Open menu item in the BEES software.
Raw Materials. For a 15cm x 15cm x 1cm (6in x 6in x l/2in) ceramic tile with 75 percent
recycled glass content, clay and glass are found in the quantities listed in table 3.21.
Table 3.21 Ceramic Tile with Recycled Glass Constituents
Ceramic Tile w/
Recycled Glass
Constituents
Recycled Glass
Clay
Total:
Physical Weight
475.5g(17oz)
156.9 g (6 oz)
632.4 g (23 oz)
Production requirements for clay are based on the Ecobalance LCA database. The
recycled windshield glass is environmentally "free." The transportation of the glass to the
61
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Ceramic Tile w/ Recycled G
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Use. The installation of the ceramic tile is assumed to require a layer of latex-mortar
approximately 1.3 centimeters (1/2 inch) thick. The relatively small amount of latex-
mortar between tiles is not included.
The ceramic tile with recycled glass is assumed to have a useful life of SO years.
Refer to section 2.1.3 for indoor air performance assumptions for this product.
Cost The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code C3020, product code 10. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
3.6.2 Linoleum Flooring (C30202)
Linoleum is a resilient, organic-based floor covering consisting of a backing covered with
a thick wearing surface. For the BEES system, a 2.5 millimeter (98 mil) sheet linoleum,
manufactured in Europe, and with a jute backing and an acrylic lacquer finish coat is
studied. A styrene-butadiene adhesive is included for installation. The flow diagram
shown in Figure 3.17 shows the elements of linoleum flooring production. The detailed
environmental performance data for this product may be viewed by opening the file
C30202.DBF under the File/Open menu item in the BEES software.
Raw Materials. Table 3.23 lists the constituents of 2.5 millimeter (98 mil) linoleum and
their proportions.
Table 3.23 Linoleum Constituents
Linoleum Constituents
linseed oil
pine rosin
limestone
wood flour
cork flour
pigment
backing (jute)
acrylic lacquer
Total:
Physical Weight (%)'
23.3
7.8
17.7
30.5
5.0
4.4
10.9
0.35
100.0
Physical Weight
670 g/m2 (2.2oz/ft2)
224g/m2(0.7oz/ft2)
509g/m2(1.7oz/ft2)
877g/m2(2.9oz/ft2)
144 g/m2 (0.5 oz/ft2)
127 g/m2 (0.4 oz/ft2)
313 g/m2 (1.0 oz/ft2)
10 g/m2 (0.03 oz/ft2)
2874 g/m2 (9.4 oz/ft2)
'Jonsson Asa, Anne-Marie Tillman, and Torbjom Svensson, Life-Cycle Assessment of Flooring Materials,
Chalmers University of Technology, Sweden, 1995.
63
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Linoleum
Figure 3.17 Linoleum Flow Chart
The cultivation of linseed is based on a United States agricultural model which estimates
soil erosion and fertilizer run-off,58 with the following inputs:59
Fertilizer: 35 kg nitrogen fertilizer per hectare (31 Ibs/acre), 17 kg phosphorous
fertilizer per hectare (15 Ibs/acre), and 14 kg potassium fertilizer per hectare (12
Ibs/acre)
Pesticides: 0.5 kg active compounds per hectare (0.4 Ibs/acre), with 20 percent lost to
air
Diesel farm tractor: 0.65 MJ per kilogram (279 Btu per pound) linseed
Linseed yield: 0.6 metric tons/hectare (536 Ibs/acre)
The production of the fertilizers and pesticides is based on the Ecobalance LCA database.
The cultivation of pine trees for pine rosin is based on the Ecobalance LCA data for
cultivated forestry, with inventory flows allocated between pine rosin and its coproduct,
turpentine.
The production of limestone is based on the Ecobalance data for open pit limestone
quarrying and processing.
51 Ecobalance, Life Cycle Assessment of Petroleum-Based Diesel Fuel and Biodiesel, US DOE/NREL &
US Department of Agriculture (not yet published).
lotting Jose and Komehs Blok, Life-cycle Assessment of Four Types of Floor Covering, Utrecht
University, The Netherlands, 1994.
64
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Wood flour is sawdust produced as a coproduct of wood processing. Its production is
based on the Ecobalance LCA database.
Cork flour is a coproduct of wine cork production. Cork tree cultivation is not included
but the processing of the cork is included as shown below.
Heavy metal pigments are used in linoleum production. Production of these pigments are
modeled based on the production of titanium dioxide pigment.
Jute used in linoleum manufacturing is mostly grown in India and Bangladesh. Its
production is based on the Ecobalance LCA database.
The production of acrylic lacquer is based on the Ecobalance LCA database.
Energy Requirements. Energy requirements for Unseed oil production include fuel oil
and steam, and are allocated on a mass basis between linseed oil (34%) and linseed cake
(64%). Allocation is necessary because linseed cake is a coproduct of linseed oil
production whose energy requirements should not be included in the BEES data.
Cork Flour production involves the energy requirements as listed in table 3.24.
Table 3.24 Energy Requirements for Cork Flour Production
Cork Product Electricity Use
Cork Bark 0.06 MJ/kg (26 Btu/lb)
Ground Cork 1.62 MJ/kg (696 Btu/lb)
Linoleum production involves the energy requirements as listed in table 3.25.
Table 3.25 Energy Requirements for Linoleum Manufacturing
Manufacturing Energy
Fuel Use
Electricity 2.3 MJ/kg (989 Btu/lb)
Natural Gas 5.2 MJ/kg (2235 Btu/lb)
Emissions. Tractor emissions for linseed cultivation are based on the Ecobalance LCA
database. The emissions associated with linseed oil production are allocated on a mass
basis between oil (34%) and cake (64%).
Since most linoleum manufacturing takes place in Europe, it is assumed to be a European
product in the BEES model. European linoleum manufacturing results in the following air
emissions in addition to those from the energy use:
65
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Volatile Organic Compounds: 1.6 g/kg (0.02S oz/lb)
Solvents: 0.94 g/kg (0.015 oz/lb)
Paniculate: 0.23 g/kg (0.004 oz/lb)
Transportation. Transport of linoleum raw materials from point of origin to a European
manufacturing location is shown in table 3.26. *ฐ
Table 3.26 Linoleum Raw Materials Transportation
Raw Material
linseed oil
pine rosin
limestone
wood flour
cork flour
pigment
backing (jute)
acrylic lacquer
Distance
4350 km (2703 mi)
1500 km (932 mi)
2000 km (1243 mi)
800 km (497 mi)
600 km (373 mi)
2000 km (1243 mi)
500 km (311 mi)
10,000 km (6214 mi)
500 km (311 mi)
Mode of Transport
Ocean Freighter
Train
Ocean Freighter
Train
Train
Ocean Freighter
Diesel Truck
Ocean Freighter
Diesel Truck
Transport of the finished product from Europe to the United States is included. Transport
of the finished product from the point of U.S. entry to the building site is a variable of the
BEES model.
Use. The installation of linoleum requires a styrene-butadiene adhesive.
Maintenance for this floor covering is assumed to be 0.5 grams (0.02 oz) of acrylic
lacquer applied 4 times per year.
Linoleum flooring has a useful life of 18 years.
Refer to section 2.1.3 for indoor air performance assumptions for this product.
Cost. The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code C3020, product code 20. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
60 Life-Cycle Assessment of Flooring Materials, Jonsson Asa, Anne-Marie Tillman, & Torbjorn
Svensson, Chalmers University of Technology, Sweden, 1995.
66
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3.6.3 Vinyl Composition Tile (C30203)
Vinyl composition tile is a resilient floor covering. Relative to the other types of vinyl
flooring (vinyl sheet flooring and vinyl tile), vinyl composition tile contains a high
proportion of inorganic filler. For the BEES study, vinyl composition tile is modeled with
a composition of milestone, plasticizer, and a copolymer of vinyl chloride-vinyl acetate.
A layer of styrene-butadiene adhesive is used during installation. Figure 3.18 shows the
elements of vinyl composition tile production. The detailed environmental performance
data for this product may be viewed by opening the file C30203.DBF under the File/Open
menu item in the BEES software.
Vinyl C
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Him BI ui
Buladtane
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Figure 3.18 Vinyl Composition Tile Flow Chart
Raw Materials. Table 3.27 lists the constituents of 30cm x 30cm x 0.3cm (12in x 12in x
1/8in) vinyl composition tile and their proportions.
A finish coat of acrylic latex is applied to the vinyl composition tile at manufacture. The
thickness of the finish coat is assumed to be 0.02S millimeters (0.98 mils).
The production of these raw materials, and the styrene-butadiene adhesive, is based on
the Ecobalance LCA database.
67
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Table 3.27 Vinyl Composition Tile Constituents
Vinyl Composition Tile Constituents
Limestone
Vinyl resins:
(10% vinyl acetate / 90% vinyl chloride)
Plasticizer: bis(2-ethylhexyl) phthalate
Physical Weight (%)
84
12
4
Energy Requirements. The energy requirements for the manufacturing process (mixing,
folding/calendaring, finish coating, die cutting) are listed in table 3.28.
Table 3.28 Energy Requirements for Vinyl Composition Tile Manufacturing
Fuel Use
Electricity
Natural Gas
Manufacturing
Energy
1.36MJ/kg(585Btu/lb)
0.85MJ/kg(365Btu/lb)
Emissions. Emissions associated with the manufacturing process arise from the
combustion of fuel oil and are based on AP-42 emission factors.
Use. Installing vinyl composition tile requires a layer of styrene-butadiene adhesive
0.002S millimeters (0.10 mils) thick.
It is assumed that maintenance for this floor covering involves 0.5 grams (0.02 ounces) of
acrylic lacquer twice a year.
The life of the flooring is assumed to be 18 years.
Refer to section 2.1.3 for indoor air performance assumptions for this product.
Cost. The detailed life-cycle cost data for this product may be viewed by opening the file
LCCOSTS.DBF under the File/Open menu item in the BEES software. Its costs are listed
under BEES code C3020, product code 30. Life-cycle cost data include first cost data
(purchase and installation costs) and future cost data (cost and frequency of replacement,
and where appropriate and data are available, of operation, maintenance, and repair). First
cost data are collected from the R.S. Means publication, 1997 Building Construction Cost
Data, and future cost data are based on data published by Whitestone Research in The
Whitestone Building Maintenance and Repair Cost Reference 1997, supplemented by
industry interviews.
68
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4. BEES Tutorial
To balance the environmental and economic performance of building products, follow
three main steps:
1. Set vour study parameters to customize key assumptions
2. Define the alternative building products for comparison. BEES results
may be computed once alternatives are defined.
3. View the BEES results to compare the overall environmental/economic
performance balance for your alternatives.
4.1 Setting Parameters
Select Analysis/Set Parameters from the BEES Main Menu to set your study parameters.
A window listing these parameters appears, as shown in figure 4.1. Move around this
window by pressing the Tab key.
Analysis Parameters
r* Environmental vs. Economic Performance Weights:
Environmental.; -'**--Tcn yg-^JErajjomic i .
Performance (Si): *L__J ,, * JPerformance (2^:
;
mrironmental Impart Categoiy Weights
^.OsiHOeSnei , '- _- ^ ' / "
.CQjEPA'SdenfificAdviswyBoanl-* ^L
Equal Weights
Discount Rate (%): rrr
(Excluding Inflation) '
Figure 4.1 Setting Analysis Parameters
The first set of parameters are your relative preference weights for environmental versus
economic performance. These values must sum to 100. Enter a value between 0 and 100
69
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for environmental performance reflecting your percentage weighting. For example, if
environmental performance is all-important, enter a value of 100. The corresponding
economic preference weight is automatically computed.
Next you are asked to select your relative preference weights for the six environmental
impact categories included in the BEES environmental performance score: Global
Warming Potential, Acidification Potential, Nullification Potential, Natural Resource
Depletion, Indoor Air Quality, and Solid Waste. You are presented with four sets of
alternative weights. You may choose to define your own set of weights, or select the
built-in weight sets derived from an EPA Scientific Advisory Board study, a Harvard
University study, or a set of equal weights. Press View Weights to display the impact
category weights for all four weight sets, as shown in figure 4.2. These may not be
changed. If you select the user-defined weight set, you will be asked to enter weights for
all six impacts, as shown hi figure 4.3. These six weights must sum to 100.
; Environmental Impact Category Weights
HHI3
I GloisaJwarm:! Acidifcatn: I NutrrfcaJn: I|Natresdepn:| Indoor Air rSebdwasterj
EPA Science Advisoiy Board-ba&
Haivard University Study-based
Equal Weights
^j~j"":i" '""'",. " ,' * .
27
28
17
13
17
17
*" ซ
13
18
17
f"," ซ ซ* * ,ป"
13
15
17
27
12
16
1
11
1(
- f
Figure 4.2 Viewing Impact Category Weights
Finally, enter the real (excluding inflation) discount rate for converting future building
product costs to their equivalent present value. All future costs are converted to then-
equivalent present values when computing life-cycle costs. Life-cycle costs form the basis
of the economic performance scores. The higher the discount rate, the less important to
you are future building product costs such as repair and replacement costs. The maximum
value allowed is 20%. A discount rate of 20% would value each dollar spent 50 years
hence as only $0.0001 in present value terms. The 1997 rate mandated by the U.S. Office
70
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i Environmental Impact Category Weights
f .
ser-Defined
"
,
Addificalion PrtentSW
'- - ~ *
' " * ' Nulrification RotentiaJ 1" |
_T" V. 1 ,,
-' * J - "
, " ~ , ปj .j. *~ -, " I 'ฃ" i I *""
~-_L * Natural Resource Depletion 117 ^ ^ " L-, ( _
" ~v'r>~ -I.*.,; --"I- "--'IndoorAfcQtfalily_|1G "-, /- , ,'.
A - \~S^4 -^Cv*- ? ' - '' 'ป,-' ' ' 21 ~i , '
ซ1"4:fc-'' '-7":?;Vvr * ,?ioirdwaste I16 ft 1 "J ฃ*** .;,;
< ^ >J^^ ^ 9* p 4* T /.^ >!ซ-ซ * OJ>1 r *U- <* *J^ ^ *" 1 IMUM**^ T* <~^ W " j. ^ Jty' **t
ป ,- - ป-fK i- ;,HO. * %>' *8 ~"*.~f '' 'I^1: .'.,"'. '
- T<*t,-v " _: i^,r3g^rj '
5 ' , I- ~ aJL*1 ปป<
so..
Figure 4.3 Entering User-Defined Weights
of Management and Budget for most Federal projects, 3.6%, is provided as the default
value.61
4.2 Defining Alternatives
Select Analysis/Define Alternatives from the Main Menu to select the alternative building
products you want to compare. A window appears as in figure 4.4.
Selecting alternatives is a two-step process.
1. Select the building element for which you want to compare alternatives.
Building elements are organized using the hierarchical structure of the
ASTM standard BEES classification system.62 Click on the down arrows
to display the complete lists of available choices at each level of the
hierarchy. BEES 1.0 contains environmental and economic performance
data for 12 individual building elements: slabs on grade, basement walls,
beams, columns, roof sheathing, exterior wall finishes, wall insulation,
61 Office of Management and Budget (OMB) Circular A-94, Guidelines and Discount Rates for Benefit-
Cost Analysis of Federal Programs, Washington, DC, October 27,1992 and OMB Circular A-94,
Appendix C, March 1997.
62 American Society for Testing and Materials, Standard Classification for Building Elements and
RelatedSitework-UNIFORMATII, ASTM Designation E 1557-93, West Conshohocken, PA, September
1993.
71
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i Building Element for Comparison
IBD3EI
- -
Individual Element
'J Floor Finishes
V?
Figure 4.4 Selecting BuUding Element for Bees Analysis
wall sheathing, roof coverings, ceiling insulation, floor coverings, and
driveways and sidewalks. Press Ok to select the choice in view.
2. Once you have selected the building element, you are presented with a
window of product alternatives available for BEES scoring, such as in
figure 4.5.63 Select an alternative with a mouse click. You may then be
presented with a window, such as hi figure 4.6, asking for the assumed
distance for transporting this product from the manufacturing plant to your
building site. Your choice affects the resource depletion, global warming,
and acidification impact category scores. You must select at least two
alternatives.
If you have already set your study parameters, next press Compute BEES Results to
compute and display the BEES environmental and economic performance scores.
63 If you have chosen the wall insulation element, you will first be asked, for the building in which
insulation will be installed, its location and fuel used for heating so that heating and cooling energy use
over the 50-year study period can be properly estimated. If you have chosen concrete beams or columns,
you will be asked for assumed compressive strength after selecting each product alternative.
72
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Select Building Product Alternatives
Ceramic Tile w/ Recycled Glas
{Linoleum
iVinyl Composition Tile
|nt!Siiip5SrBEES Results ' j-"-:
C
Figure 4.5 Selecting Building Product Alternatives
L, '* - *'' * "TCefamiclite w/ Recycled Glass 1,
Transportation Distancefrom Manufacture to Us
, (fr-jeOS km (500 mi)j
, Cl6ซ9kmflOOOmO I
Figure 4.6 Setting Transportation Parameters
4.3 Viewing Results
Once you have set your study parameters, defined your product alternatives, and
computed BEES results, BEES displays three summary graphs such as in figures 4.7, 4.8,
and 4.9. For all BEES graphs, the larger the value, the worse the performance. Also, the
values displayed across the back row are always the sum of the values in the preceding
rows.
1. The Overall Performance Results graph displays the weighted
environmental and economic performance scores and their sum, the
overall performance score.
2. The Environmental Performance Results graph displays the weighted
environmental impact category scores and their sum, the environmental
performance score. On this graph, if an alternative performs worst with
respect to all six environmental impact categories, it receives a score of
100, the worst possible score.
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^Economic Results
^Environmental Results
H32H1IEB3J
f
0)
Q.
Overall Performance
Product A Product C
Product B
lover*
Economtc-50%
I Environmertai-S0%
Figure 4.7 Viewing BEES Overall Performance Results
Environmental Performance
I
4)
0.
I EnvironmtntJl
I Solid Watt-10*
01AQ.12*
I Nottflojtion-18*
I Globjl Wjminj-28%
0.
Product A Product C
Product B
^/^aฃ*&i!^^
Figure 4.8 Viewing BEES Environmental Performance Results
x
74
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Economic Results
HHE
I
Economic Performance
*y.09m2(ซt2)
10.1
I
M
6
4
2
0
B Life-Cycle Cosl
ED FUire Cost-3.6%/yr
MM cost
Product A Product C
Products
' '
Figure 4.9 Viewing BEES Economic Performance Results
3. The Economic Performance Results graph displays the initial cost,
discounted future costs and their sum, the life-cycle cost.
BEES results are derived by using the BEES methodology to combine the BEES
environmental and economic performance data using your study parameters. The
methodology is described in section 2. The BEES environmental and economic
performance data, documented in section 3, may be browsed by selecting File/Open from
the Main Menu.
The displayed graphs are "live." Clicking on a graph column will bring up a window
displaying the column value, and from which you may customize colors, labels, and other
display attributes. Also note that columns and rows may be conveniently moved into and
out of view by pressing toolbar button numbers 5 though 10. The next 5 toolbar buttons
provide further functionality by offering alternative graph types. The Percent Stacked and
Pie Graph alternatives are particularly informative ways to display the BEES scores. Press
the Print toolbar button to print the graph. You can even copy an entire graph to the
clipboard and then paste it into another Windows application. You may then use the
application's graphics editor to resize the graph.
You may choose to display more detailed environmental performance graphs by selecting
Results/Environmental Performance from the Main Menu. You may display graphs for
75
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each environmental impact category, by life-cycle stage, and for embodied energy
performance, such as in figures 4.10,4.11, and 4.12.
To compare BEES results based on different parameter settings, simply select
Analysis/Set Parameters from the Main Menu, change your parameters, and press Ok.
Once the new graphs are displayed, select Window/Tile from the Main Menu to view
graphs side-by-side. Note that parameter settings are displayed on each graph's legend.
4.4 Browsing Environmental and Economic Performance Data
The BEES environmental and economic performance data may be browsed by selecting
File/Open from the Main Menu. Environmental data files are specific to products, while
there is a single economic data file, LCCOSTS.DBF, with cost data for all products. As
explained in section 3, some environmental data files map to a product in more than one
application, while the economic data are listed separately for each application. Table 4.1
lists the products by environmental data file name (all with the .DBF extension) and by
code number within the economic performance data file LCCOSTS.DBF
.^Global Warminq Results
HHE3
Global Warming
D Globjl Wjimin9-28%
DM.thJ
ICjfton Dioxidt
0.
Product A Product C
Products
Figure 4.10 Viewing BEES Environmental Impact Category Performance Results
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1-Environmentul Results
JL..J
B
by Life-Cycle Stage
Product A Product C
Products
| Environmental
I EndUTe
Dose
I Transport
iMfg
Raw Mans
i
Figure 4.11 Viewing BEES Environmental Performance by Life-Cycle Stage Results
by Fuel vs. Feedstock Energy
Product A Product C
Products
I Emo. Energy
I Fuel
Feedstock
Figure 4.12 Viewing BEES Embodied Energy Performance Results
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Table 4.1 BEES Building Products Keyed to Environmental and Economic
Performance Data Codes
Group Element
Foundations
Foundations
Foundations
Basement Construction
Basement Construction
Basement Construction
Superstructure
Superstructure
Superstructure
Superstructure
Superstructure
Superstructure
Superstructure
Superstructure
Exterior Closure
Exterior Closure
Exterior Closure
Exterior Closure
Exterior Closure
Extenor Closure
Exterior Closure
Extenor Closure
Roofing
Roofing
Roofing
Roofing
Roofing
Roofing
Interior Finishes
Interior Finishes
Interior Finishes
Site Improvements
Site Improvements
Site Improvements
Building Product
0% Fly Ash Content Slab on Grade
15% Fly Ash Content Slab on Grade
20% Fly Ash Content Slab on Grade
0% Fly Ash Content Basement Wall
15% Fly Ash Content Basement Wall
20% Fly Ash Content Basement Wall
0% Fly Ash Content Beams
15% Fly Ash Content Beams
20% Fly Ash Content Beams
0% Fly Ash Content Columns
15% Fly Ash Content Columns
20% Fly Ash Content Columns
Oriented Strand Board Roof Sheathing
Plywood Roof Sheathing
Brick & Mortar Extenor Wall
Stucco Exterior Wall
R-13 Cellulose Wall Insulation
R-l 1 Fiberglass Wall Insulation
R-15 Fiberglass Wall Insulation
R-l 2 Mineral Wool Wall Insulation
Onented Strand Board Wall Sheathing
Plywood Wall Sheathing
Asphalt Shingle Roof Covenng
Clay Tile Roof Covenng
Fiber Cement Shingle Roof Covenng
R-30 Cellulose Ceiling Insulation
R-30 Fiberglass Ceiling Insulation
R-30 Mineral Wool Ceiling Insulation
Ceramic Tile with Recycled Glass
Floor Covenng
Linoleum Floor Covering
Vinyl Composition Tile Floor Covenng
0% Fly Ash Content Dnveways and
Sidewalks
15% Fly Ash Content Dnveways and
Sidewalks
20% Fly Ash Content Driveways and
Sidewalks
Environmental
Data File Name
A10301
A 1 0302
A10303
A10301
A10302
A10303
A10301
A 10302
A10303
A10301
A10302
A10303
B10201
B10202
B20111
B20112
B2012I
B20122
B20123
B20I24
B10201
B 10202
B30111
B30112
B30113
B30I21
B30122
B30123
C3020I
C30202
C30203
A10301
A 10302
A 10303
Economic Data
Code
A1030.10
A 1030,20
A 1030,30
A2020.10
A2020.20
A2020.30
B1011,10
81011,20
81011,30
81012,10
81012,20
81012,30
81020,10
B 1020,20
82011,10
82011,20
82012,10
82012,20
82012,30
82012,40
82015,10
82015,20
83011,10
83011,20
83011,30
83012,10
83012,20
83012,30
C3020.IO
C3020.20
C3020.30
02010,10
G20 10,20
G20 10,30
The environmental performance data files are similarly structured, with 3 simulations in
each. The first column in all these files, "Sim," represents the transportation simulation
number for non-concrete products, or compressive strength simulation number for
concrete products. All files contain 3 sets of inventory data corresponding to the 3
simulations. The simulation codes are defined below in tables 4.2 and 4.3. For each
simulation, the environmental performance data file lists 97 environmental flows. Flows
marked "(r)" are raw materials inputs, "(a)" are air emissions, "(w)" are water effluents,
and "E" are energy usage. All quantities for concrete products except driveways and
78
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sidewalks are given per 0.76 cubic meters (1 cubic yard) of concrete, and for all other
products, including driveways and sidewalks, per 0.09 square meters (1 square foot) of
product. The column labeled 'Total" is the primary data column, giving total flow
quantities. Next are columns giving flow quantities for each product component, followed
by columns giving flow quantities for each life-cycle stage. The product component
columns sum to the total column, as do the life-cycle stage columns. The laindex column
is for internal BEES use.
The economic performance data file LCCOSTS.DBF lists for each cost the year of
occurrence (counting from year 0) and amount (in 1997 dollars) per 0.76 cubic meters (1
cubic yard) for concrete products except driveways and sidewalks, and cost (in 1997
dollars) per 0.09 square meters (1 square foot) for all other products (including driveways
and sidewalks).
Warning: If you change any of the data in the environmental or economic
performance data files, you will need to reinstall BEES to restore the original
BEES data.
Table 4.2 BEES Simulation Codes: All But Concrete Products
Simulation Code
1
2
3
Transportation Distance from
Manufacturing Plant to Building Site
Insulation Products
80 km (SO mi)
322 km (200 mi)
483 km (300 mi)
AU Other Non-
Concrete Products
161 km (100 mi)
805 km (500 mi)
1609 km (1000 mi)
Table 4.3 BEES Simulation Codes: Concrete Products
Simulation Code
1
2
3
Compressive Strength
21MPa(3000psi)
28MPa(4000psi)
34MPa(5000psi)
79
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80
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5. Future Directions
Development of the BEES tool does not end with the release of version 1.0. Plans to
expand and refine BEES include releasing updates every 12 to 18 months with model and
software enhancements as well as expanded building product coverage. A BEES training
program is also being considered. Listed below are a number of directions for future
research that have been proposed in response to obvious needs and through feedback
from the 125 BEES Beta version reviewers:
Proposed Model Enhancements
Conduct and apply research leading to the addition of more environmental impacts,
such as human health and resource extraction impacts
Update the BEES LCA methodology in line with future developments in the evolving
LCA field
Add a third performance measure to the overall performance scoreproduct technical
performance
Characterize uncertainty in the underlying environmental and cost data, and reflect
this uncertainty in BEES performance scores
Proposed Data Enhancements
Add building products covering many more building elements, and add more
products to currently covered elements
Refine all data to permit U.S. region-specific BEES analyses. This enhancement
would yield BEES results tailored to regional fuel mixes and labor and material
markets, and would permit inclusion of local environmental impacts such as smog
and locally scarce resources (e.g., water)
Permit greater flexibility in product specifications such as useful lives and product
composition
Every three years, revisit products included in previous BEES releases for updates to
their environmental and cost data
In support of the EPA Environmentally Preferable Purchasing Program, add key non-
building products to the BEES tool to assist the Federal procurement community in
carrying out the mandate of Executive Order 12873 (results of this effort may be
disseminated as a separate software tool)
Proposed Software Enhancements
Add feature permitting users to enter their own environmental and cost data for BEES
analysis
Display additional BEES graphs reporting more detailed results, such as the raw
environmental impact assessment scores before weighting and normalizing (e.g.,C02-
equivalents for the global wanning impact)
Revise product data file names and customize their column headings to be more
descriptive of their content
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Add feature permitting integrated sensitivity analysis so that the effect on BEES
results of changes in parameter settings may be displayed on a single graph
82
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Appendix A. BEES Computational Algorithms
A.1 Environmental Performance
BEES environmental performance scores are derived as follows.
EnvScorej = lAScorejit, where
EnvScorej = environmental performance score for building product alternative j;
p = number of environmental impact categories;
= weighted, normalized impact assessment score for alternative j with
respect to environmental impact k:
IAScorejk = - - *10Q ? where
Max {lAik, IA2k. . .
IVwtk = impact category importance weight for impact k;
m = number of product alternatives;
IA,k = raw impact assessment score for alternative j with respect to impact k:
n
lAjk = ^ lj* IMacton , where
1=1
i = inventory flow;
n = number of inventory flows in impact category k;
I,, = inventory flow quantity for alternative j with respect to
flow i, from environmental performance data file (See section 4.4.);
LAf actor, = impact assessment factor for inventory flow i
The BEES inventory flow scores, IScore^ which are displayed on graphs for single
impacts, are derived as follows:
IScoreij = IAScorejk*IPercentij , where
Iscorea = inventory flow score for alternative j with respect to flow i;
Iy*IAfactori
IPercentij = -
1=1
The BEES life-cycle stage scores, LCScore,f which are displayed on the life-cycle stage
graph, are derived as follows:
n
LCScoresj = ^]lScore,j*LCPercentsij, where
1-1
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LCScore, = life cycle stage score for alternative j with respect to stage s;
,j
LCPercentsu = - , where
IL,
s=l
1^=inventory flow quantity for alternative j with respect to flow i for life
cycle stage s;
r = number of life cycle stages
A.2 Economic Performance
BEES measures economic performance by computing the product life-cycle cost as
follows:
j = total life-cycle cost in present value dollars for alternative j;
C, = sum of all relevant costs, less any positive cash flows, occurring in year t;
N = number of years in the study period;
d = discount rate used to adjust cash flows to present value
A.3 Overall Performance
The overall performance scores are derived as follows:
LCG
Scorej =
EnvWt(EnvScorej) + EconWtl
Max(LCCi,LCC2 LCG,);
[SumEnvEconWti + SumEnvEconWt2+- -hSumEnvEconWtn]
.where
Score, = overall performance score for alternative j;
EnvWt, EconWt = environmental and economic performance weights, respectively
(EnvWt + EconWt = 1);
n = number of alternatives;
EnvScorej= (see section A.1);
LCCj = (see section A.2);
SumEnvEconWt= EnvWt(EnvScore,) + EconWtfLCC/MaxCLCCLLCCj,.. ..LCCJ]
84
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