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Reducing Urban Heat Islands
Compendium of Strategies
Cool Pavements
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Reducing Urban Heat Islands: Compendium of Strategies describes the
causes and impacts of summertime urban heat islands and promotes
strategies for lowering temperatures in U.S. communities. This compendium
was developed by the Climate Protection Partnership Division in the U.S.
Environmental Protection Agency's Office of Atmospheric Programs. Eva
Wong managed its overall development. Kathleen Hogan, Julie Rosenberg,
Neelam R. Patel, and Andrea Denny provided editorial support. Numerous
EPA staff in offices throughout the Agency contributed content and
provided reviews. Subject area experts from other organizations around the
United States and Canada also committed their time to provide technical
feedback.
Under contracts 68-W-02-029 and EP-C-06-003, Perrin Quarles Associates,
Inc. provided technical and administrative support for the entire
compendium, and Eastern Research Group, Inc. provided graphics and
production services.
For the Cool Pavements chapter, Cambridge Systematics, Inc. provided
support in preparing a June 2005 draft report on cool pavements under
contract to EPA as part of EPA's Heat Island Reduction Initiative.
Experts who helped shape this chapter include: Bruce Ferguson, Kim Fisher,
Jay Golden, Lisa Hair, Liv Haselbach, David Hitchcock, Kamil Kaloush, Mel
Pomerantz, Nam Tran, and Don Waye.
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Contents
Cool Pavements 1
1. How It Works 3
1.1 Solar Energy 5
1.2 Solar Reflectance (Albedo) 5
1.3 Thermal Emittance 6
1.4 Permeability 8
1.5 Other Factors to Consider 9
1.6Temperature Effects 10
2. Potential Cool Pavement Types 11
3. Benefits and Costs 23
3.1 Benefits 23
3.2 Costs 25
3.3 Benefit-Cost Considerations 26
4. Cool Pavement Initiatives 26
5. Resources 30
Endnotes 31
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Cool Pavements
Cool pavements refer to a range of
established and emerging materials.
These pavement technologies tend to
store less heat and may have lower surface
temperatures compared with conventional
products. They can help address the prob-
lem of urban heat islands, which result in
part from the increased temperatures of
paved surfaces in a city or suburb. Commu-
nities are exploring these pavements as part
of their heat island reduction efforts.
Conventional pavements in the United States
are impervious concrete* and asphalt, which
can reach peak summertime surface tem-
peratures of 120-150°F (48-67°C).2 These
surfaces can transfer heat downward to be
stored in the pavement subsurface, where it
is re-released as heat at night. The warmer
daytime surface temperatures also can heat
stormwater as it runs off the pavement into
local waterways. These effects contribute to
urban heat islands (especially at nighttime)
and impair water quality.
In many U.S. cities, pavements represent the largest
percentage of a community's land cover, compared
with roof and vegetated surfaces. As part of EPA's
Urban Heat Island Pilot Project, Lawrence Berkeley
National Laboratory (LBNL) conducted a series of
urban fabric analyses that provide baseline data on
land use and land use cover, including paved sur-
faces for the pilot program cities.1 Figure 1 shows
the percent of paved surfaces in four of these
urban areas, as viewed from below the tree canopy.
The data are from 1998 through 2002, depending
on the city. Paved areas, which can absorb and
store much of the sun's energy contributing to the
urban heat island effect, accounted for nearly 30 to
45 percent of land cover.
Figure 1: Paved Surface Statistics for Four U.S. Cities
Salt Lake City
Sacramento
Houston
Chicago
0 5 10 15 20 25 30 35 40 45 50
"When new, concrete has a high solar reflectance and generally is considered a cool pavement; however, it loses reflectance over time, as discussed in
Section 1.2.
COOL PAVEMENTS - DRAFT
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Figure 2: Conventional Pavement Temperatures
i L
This picture of Phoenix, Arizona, in the summer shows a variety of conventional pavements that reached
temperatures up to 150°F (67°C).
Defining Cool Pavements
Unlike a "cool" roof, a "cool" pavement has no standard, official definition. Until
recently, the term has mainly referred to reflective pavements that help lower sur-
face temperatures and reduce the amount of heat absorbed into the pavement.
With the growing interest and application of permeable pavements—which allow
air, water, and water vapor into the voids of a pavement, keeping the material cool
when moist—some practitioners have expanded the definition of cool pavements to
include permeable pavements as well. Ongoing permeable pavement research is im-
portant because these systems, compared with conventional pavement systems, react
differently and lead to different environmental impacts. Further, as we understand
better how pavements affect urban climates and develop newer, more environmen-
tal technologies, additional technologies that use a variety of techniques to remain
cooler are likely to emerge.
As concerns about elevated summertime
temperatures rise, researchers and policy-
makers are directing more attention to the
impact pavements have on local and global
climates. This chapter discusses:
• Pavement properties and how they
can be modified to reduce urban heat
islands
• Conditions that affect pavement proper-
ties
* Potential cool pavement technologies
• Cool pavement benefits and costs
Cool pavement initiatives and research
efforts
Resources for further information.
Given that cool pavements are an evolv-
ing technology and much is still unknown
about them, this compendium presents
basic information to give readers a general
understanding of cool pavement issues
to consider; it is not intended to provide
decision guidance to communities. Deci-
sion-makers can work with local experts
to obtain location-specific information to
REDUCING URBAN HEAT ISLANDS - DRAFT
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Why Have Communities Promoted Cool Roofs More Than Cool
Pavements?
A few decades ago when the concept of using cool roofs and pavements emerged,
researchers focused on radiative properties—surface solar reflectance and thermal
emittance—associated with these technologies. Scientists, engineers, and others
worked together through the standards-development organization ASTM Interna-
tional to create test standards for these properties that could apply to both roofs and
pavements. (See Section 4.1.) While researchers, industry, and supporters of energy
efficiency have helped advance cool roofing into the market, cool pavement has
lagged behind. Three factors, which differentiate pavements from roofs, may contrib-
ute to this difference:
1. Pavements are complex. Conditions that affect pavement temperatures, but not
roofing materials, include: (a) dirtying and wearing away of a surface due to daily
foot and vehicle traffic, affecting pavement surface properties; (b) convection
due to traffic movement over the pavement; and (c) shading caused by people
and cars, vegetation, and neighboring structures and buildings. These factors are
discussed in Sections 1.2 and 2.
2. Pavement temperatures are affected by radiative and thermal characteristics, un-
like cool roofs, where radiative properties are the main concern. This is discussed
in Section 1.3.
3. Pavements serve a variety of functions throughout an urban area. Their uses
range from walking trails to heavily trafficked highways (unlike cool roofs, which
generally perform the same function and are off-the-shelf products). Different
materials and specifications are needed for these different uses, and pavements
are often individually specified, making it difficult to define or label a cool pave-
ment.
further guide them in the pavement selec-
tion process. EPA expects that significant
ongoing research efforts will expand the
opportunities for updating existing technol-
ogies and implementing new approaches
to cool pavements. At the end of Sections 4
and 5 in this document, organizations and
resources with the most recent information
are listed. Communities will also continue
to implement new demonstration projects
and cool pavement initiatives. EPA intends
to provide updated information as it be-
comes available. Please visit .
1. How It Works
Understanding how cool pavements work
requires knowing how solar energy heats
pavements and how pavement influences
the air above it. Properties such as solar
energy, solar reflectance, material heat
capacities, surface roughness, heat transfer
rates, thermal emittance, and permeability
affect pavement temperatures.
COOL PAVEMENTS - DRAFT
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Reducing or Shading Pavements
Some efforts have emerged that focus on reducing the need to pave, particularly over
vegetated areas that provide many benefits, including lowering surface and air tem-
peratures. Communities have used various options to reduce the amount of paved
surface areas, such as lowering parking space requirements, connecting parking and
mass transit services, allowing for narrower street widths, or providing incentives for
multi-level parking versus surface lots.3
Concerned communities that move forward with paving often shade it with vegeta-
tion. The "Trees and Vegetation" chapter discusses the use of measures such as park-
ing lot shading ordinances as part of a heat island mitigation strategy.
Another option some local governments and private firms are considering involves
installing canopies that incorporate solar panels in parking lots. These photovoltaic
canopies shade surfaces from incoming solar energy and generate electricity that can
help power nearby buildings or provide energy for plug-in electric vehicles.4
For more information on urban planning and design approaches to minimize paved
surfaces, see , and for information on vegetated sur-
faces, see the "Trees and Vegetation" chapter of this compendium.
Figure 3: Solar Energy versus Wavelength Reaching Earth's Surface on a Typical Clear Summer Day
i.oo
ultraviolet ^—visible
infrared
200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600
Wavelength (in nanometers)
Solar energy intensity varies over wavelengths from about 250 to 2,500 nanometers. Figure 3 demonstrates this
variation, using a normalized measure of solar intensity on a scale of zero (minimum) to one (maximum). Currently,
reflective pavements are light colored and primarily reflect visible wavelengths. However, similar to trends in the
roofing market, researchers are exploring pavement products that appear dark but reflect energy in the near-infrared
spectrum.5 (See the "Cool Roofs" chapter of the compendium for more information.)
REDUCING URBAN HEAT ISLANDS - DRAFT
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1.1 Solar Energy
Solar energy is composed of ultraviolet
(UV) rays, visible light, and infrared en-
ergy, each reaching the Earth in different
percentages: 5 percent of solar energy is
in the UV spectrum, including the type of
rays responsible for sunburn; 43 percent of
solar energy is visible light, in colors rang-
ing from violet to red; and the remaining
52 percent of solar energy is infrared, felt
as heat. Energy in all of these wavelengths
contributes to urban heat island formation.
Figure 3 shows the typical solar energy
that reaches the Earth's surface on a clear
summer day.
1.2 Solar Reflectance (Albedo)
Solar reflectance, or albedo, is the per-
centage of solar energy reflected by a
surface. Most research on cool pavements
has focused on this property, and it is the
main determinant of a material's maximum
surface temperature.6 Albedo also affects
pavement temperatures below the surface,
because less heat is available at the sur-
face to then be transferred into the pave-
ment. Researchers, engineers, and industry
have collaborated to develop methods to
determine solar reflectance by measuring
how well a material reflects energy at each
wavelength, then calculating the weighted
average of these values.* (See Table 1 on
page 7.)
Conventional paving materials such as as-
phalt and concrete have solar reflectances of
5 to 40 percent, which means they absorb
95 to 60 percent of the energy reaching
them instead of reflecting it into the atmo-
sphere. (See Figure 4.) However, as Figure 4
also shows, these values depend on age and
Most existing research on cool pave-
ments focuses on solar reflectance,
which is the primary determinant of
a material's maximum surface tem-
perature. Many opportunities exist to
improve this property in pavements.
(See Table 2, beginning on page 15.)
Figure 4: Typical Solar Reflectance of
Conventional Asphalt and Concrete Pavements
over Time
Due to weathering and the accumulation of dirt, the
solar reflectances of conventional asphalt and concrete
tend to change over time. Asphalt consists largely of
petroleum derivatives as a binder mixed with sand or
stone aggregate. Asphalt tends to lighten as the binder
oxidizes and more aggregate is exposed through wear.
Concrete also uses sand and stone aggregate, but in
contrast to asphalt, typically uses Portland cement as
a binder.7 Foot and vehicle traffic generally dirty the
cement causing it to darken over time.
material, and thus usually change over time.
Figure 5 shows how changing only albedo
can significantly alter surface temperatures.
Although researchers, including those at
LBNL, have made light-colored pavements
with solar reflectances greater than 75 per-
cent,8 these high albedo pavements do not
have widespread commercial availability.
* Albedo is typically measured on a scale of zero to one. For this compendium, albedo is given as a percentage, so an albedo of 0.05 corresponds to a solar
reflectance of 5 percent. The"solar reflectance index" is a value on a scale of zero to 100 that incorporates both solar reflectance and thermal emittance in
a single measure to represent a material's temperature in the sun. (See Table 1 on page 7 or further explanation.)
COOL PAVEMENTS - DRAFT
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Figure 5: The Effect of Albedo on Surface Temperature
Albedo alone can significantly influence surface temperature, with the white stripe on the brick wall about 5-10°F
(3-5°C) cooler than the surrounding, darker areas.
1.3 Thermal Emittance
A material's thermal emittance determines
how much heat it will radiate per unit area
at a given temperature, that is, how readily a
surface sheds heat. Any surface exposed to
radiant energy will heat up until it reaches
thermal equilibrium (i.e., gives off as much
heat as it receives). When exposed to sun-
light, a surface with high emittance will
reach thermal equilibrium at a lower tem-
perature than a surface with low emittance,
because the high-emittance surface gives
off its heat more readily. As noted in Table
1 on page 7, ASTM methods can be used to
measure this property.
Thermal emittance plays a role in determin-
ing a material's contribution to urban heat
islands. Research from 2007 suggests albedo
and emittance have the greatest influence
on determining how a conventional pave-
ment cools down or heats up, with albedo
having a large impact on maximum sur-
face temperatures, and emittance affecting
minimum temperatures.9 Although thermal
emittance is an important property, there
are only limited options to adopt cool pave-
ment practices that modify it because most
pavement materials inherently have high
emittance values.10
REDUCING URBAN HEAT ISLANDS - DRAFT
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Standards for Measuring Solar Reflectance and Thermal
Emittance
To evaluate how "cool" a specific product is, ASTM International has validated labo-
ratory and field tests and calculations to measure solar reflectance, thermal emit-
tance, and the solar reflectance index, which was developed to try to capture the
effects of both reflectance and emittance in one number. (See Table 1 below.) Labo-
ratory measurements are typically used to examine the properties of new material
samples, while field measurements evaluate how well a material has withstood the
test of time, weather, and dirt.
The final method listed in Table 1 is not an actual test but a way to calculate the
"solar reflectance index" or SRI. The SRI is a value that incorporates both solar reflec-
tance and thermal emittance in a single value to represent a material's temperature
in the sun. This index measures how hot a surface would get compared to a standard
black and a standard white surface. In physical terms, this scenario is like laying a
pavement material next to a black surface and a white surface and measuring the
temperatures of all three surfaces in the sun. The SRI is a value between zero (as hot
as a black surface) and 100 (as cool as a white surface).
Table 1: Solar Reflectance and Emittance Test Methods
Property Test Method Equipment Used Test Location
Solar reflectance
Solar reflectance
Solar reflectance
Total emittance
Solar reflectance
index
ASTM E 903 - Standard Test Method
for Solar Absorbance, Reflectance,
andTransmittance of Materials Using
Integrating Spheres.
ASTM C 1 549 - Standard Test Method
for Determination of Solar Reflectance
Near Ambient Temperature Using a
Portable Solar Reflectometer
ASTM E 1 91 8 - Standard Test Method
for Measuring Solar Reflectance of
Horizontal and Low-Sloped Surfaces in
the Field
ASTM E408-71 - Standard Test Methods
for Total Normal Emittance of Surfaces
Using Inspection-Meter Techniques
ASTM E 1 980 - Standard Practice for
Calculating Solar Reflectance Index of
Horizontal and Low-Sloped Opaque
Surfaces
Integrating sphere spectro-
photometer
Portable solar reflectometer
Pyranometer
Portable, inspection-meter
instruments
None (calculation)
Laboratory
Laboratory or
field
Field
Laboratory or
field
COOL PAVEMENTS - DRAFT
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Pavement Surface and Subsurface Temperatures
This chapter mainly focuses on pavement surface temperatures, as most of the cited
studies focus on the surface layer. For conventional pavements, most of the impacts
at the surface tend to affect the subsurface similarly. For example, conventional
pavements with high solar reflectance generally reduce surface and subsurface tem-
peratures, as less heat is available at the surface to absorb into the pavement. How-
ever, permeable surfaces react differently. When dry, permeable pavement surface
temperatures may be higher than their impermeable equivalent; but preliminary
research shows that the subsurface generally is similar to or even cooler than the
conventional equivalent, because the permeable layer reduces heat transfer below.11
More information on subsurface heat transfer is needed to understand the potential
heat island impacts because the heat stored in the subsurface may significantly af-
fect nighttime temperature. Still, many complex interactions take place between the
surface and subsurface layers. These interactions are either briefly covered in Section
1.5 or beyond the scope of this chapter.
1.4 Permeability
Although originally designed for storm-
water control, permeable pavements are
emerging as a potential cool pavement.
These pavements allow air, water, and
water vapor into the voids of the pavement.
Permeable pavement technologies include
porous asphalt applications, pervious con-
crete applications, permeable pavers, and
grid pavements. To achieve both perme-
ability objectives and structural needs for
expected traffic load, these permeable
pavements benefit from proper design and
installation.12
When wet, these pavements can lower tem-
peratures through evaporative cooling. The
water passes through the voids and into the
soil or supporting materials below. (See Fig-
ure 6.) Moisture within the pavement struc-
ture evaporates as the surface heats, thus
drawing heat out of the pavement, similar
to evaporative cooling from vegetated land
cover. Some permeable pavement systems
Figure 6: Permeable versus
Conventional Asphalt
Permeable asphalt (foreground) allows water to
drain from the surface and into the voids in the
pavement, unlike conventional asphalt (mid- and
background).
contain grass or low-lying vegetation, which
can stay particularly cool because the sur-
face temperature of well-hydrated vegeta-
tion typically is lower than the ambient air
temperature.
REDUCING URBAN HEAT ISLANDS - DRAFT
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When dry, the extent to which permeable
pavements can influence temperatures is
more complex and uncertain. For example,
the larger air voids in permeable pave-
ments increase the available surface area.
These conditions may limit heat transfer
to the lower pavement structure and soils,
keeping heat at the pavement's surface
(and increasing daytime surface tempera-
tures), but reducing bulk heat storage (re-
ducing release of heat at nighttime).13 The
larger surface area also may help increase
air movement—convection—over the pave-
ment, transferring heat from the pavement
to the air. Overall, the limited transfer of
heat to the pavement subsurface layers
would reduce the release of heat during
the nighttime. Release of stored heat from
urban materials is a significant contributor
to the nighttime heat island experienced in
many cities.
More research is needed to better under-
stand the impacts of permeable pavement
on air temperatures and urban heat island
conditions. Given the complexity of these
cooling mechanisms, and the wide range of
conditions under which these pavements
function, further field testing and valida-
tion would help to quantify and clarify the
range of impacts and benefits of permeable
pavements on urban climates.
1.5 Other Factors to Consider
Pavement temperatures depend on a series
of factors. Reflective pavements increase
the albedo of the surface to limit heat gain,
whereas permeable pavements permit
evaporative cooling when the pavement is
moist, helping to keep it cool. As shown in
Table 2 (beginning on page 15), however,
actual conditions alter pavement proper-
ties, resulting in pavements that may not be
"cool" under all circumstances. This chapter
presents these issues for communities to
consider when making pavement choices.
Water Retentive Pavements
and Water Sprinkling in
Japan
Some cities in Japan, such as
Tokyo and Osaka, are testing the
effectiveness of water retentive
pavements as part of using
permeable pavements to reduce
the heat island effect. These porous
pavements can be asphalt or
concrete-based and have a sublayer
that consists of water retentive
materials that absorb moisture and
then evaporate it through capillary
action when the pavement heats
up. Some of these systems involve
underground water piping to
ensure the pavement stays moist.
Researchers have also tested water
sprinkling, where pavements are
sprayed with water during the
day. Some cities have used treated
wastewater. Results to date are
promising, as both water retentive
pavements and water sprinkling have
been effective in keeping pavement
temperatures low.14
Besides solar reflectance, emittance, and
permeability, other properties and factors
influence how readily pavements absorb or
lose heat.
• Convection. Pavement transfers heat to
the air through convection as air moves
over the warm pavement. The rate of
convection depends on the velocity
and temperature of the air passing over
the surface, pavement roughness, and
the total surface area of the pavement
exposed to air. Some permeable pave-
ments have rougher surfaces than con-
ventional pavements, which increases
COOL PAVEMENTS - DRAFT
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their effective surface area and creates
air turbulence over the pavement. While
this roughness can increase convection
and cooling, it may also reduce a sur-
face's net solar reflectance.
» Thermal Conductivity. Pavement with
low thermal conductivity may heat up
at the surface but will not transfer that
heat throughout the other pavement
layers as quickly as pavement with
higher conductivity.
* Heat Capacity. Many artificial materi-
als, such as pavement, can store more
heat than natural materials, such as dry
soil and sand. As a result, built-up areas
typically capture more of the sun's
energy—sometimes retaining twice as
much as their rural surroundings dur-
ing daytime.15 The higher heat capacity
of conventional urban materials con-
tributes to heat islands at night, when
materials in urban areas release the
stored heat.
» Thickness. The thickness of a pave-
ment also influences how much heat it
will store, with thicker pavements stor-
ing more heat.16
» Urban Geometry. The dimensions and
spacing of buildings within a city, or ur-
ban geometry, can influence how much
heat pavements and other infrastruc-
ture absorb. For example, tall buildings
along narrow streets create an "urban
canyon." (See Figure 7.) This canyon ef-
fect can limit heat gain to the pavement
during the day, when the buildings pro-
vide shade. But these same buildings
may also absorb and trap the heat that
is reflected and emitted by the pave-
ment, which prevents the heat from
escaping the city and exacerbates the
heat island effect, especially at night.
The overall impact of the urban canyon
effect will depend on how a specific
city is laid out, the latitude, the time of
year, and other factors.
More research is needed to determine the
exact impacts these properties have on
pavement temperatures and the urban heat
island effect.
1
Solar reflectance and thermal emittance
have noticeable effects on surface tempera-
tures, as discussed in Sections 1.2 and 1.3.
Depending on moisture availability, perme-
able pavements also can lower pavement
temperatures. Other properties, as noted in
Section 1.5, also influence pavement sur-
face and subsurface temperatures through
a variety of complex interactions. In gener-
al, lower surface temperatures will result in
lower near-surface air temperatures, with
the effect decreasing as one moves farther
away from the surface due to air mixing.
Location-specific conditions, such as wind
speed and cloud cover, can greatly influ-
ence surface and air temperatures.
Currently, few studies have measured the
role pavements play in creating urban heat
islands, or the impact cooler pavements
can have on reducing the heat island ef-
fect. Researchers at LBNL, however, have
estimated that every 10 percent increase
in solar reflectance could decrease sur-
face temperatures by 7°F (4°C). Further,
they predicted that if pavement reflec-
tance throughout a city were increased
from 10 percent to 35 percent, the air
temperature could potentially be reduced
by 1°F (0.6°C).17 Earlier research analyzed
a combination of mitigation measures in
the Los Angeles area, including pavement
and roofing solar reflectance changes, and
increased use of trees and vegetation. The
study identified a 1.5°F (0.8°C) temperature
improvement from the albedo changes.18 A
subsequent report analyzed the monetary
benefits associated with these temperature
improvements, and estimated the indirect
benefits (energy savings and smog reduc-
tions) of the temperature reduction in Los
10
REDUCING URBAN HEAT ISLANDS - DRAFT
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Figure 7: Urban Canyons
The row of three-and four-story townhouses on the left creates a relatively modest urban canyon, while the
skyscrapers on the right have a more pronounced effect.
Angeles from pavement albedo improve-
ments would be more than $90 million per
year (in 1998 dollars).1?
2. Potential Cool Pavement Types
Current cool pavements are those that have
increased solar reflectance or that use a
permeable material. Some of these pave-
ments have long been established—such
as conventional concrete, which initially
has a high solar reflectance. Others are
emerging—such as microsurfacing, which
is a thin sealing layer used for mainte-
nance.20 Some pavement applications are
for new construction, while others are used
for maintenance or rehabilitation. Not all
applications will be equally suited to all
uses. Some are best for light traffic areas,
for example. Further, depending on local
conditions—such as available materials,
labor costs, and experience with different
applications—certain pavements may not
be cost effective or feasible.
Generally, decision-makers choose pav-
ing materials based on the function they
serve. Figure 8 shows the proportions of
pavement used for different purposes in
four cities. Parking lots typically make up
a large portion of the paved surfaces in
urban areas. All current cool pavement
technologies can be applied to parking
lots, which may explain why many re-
search projects have been and are being
conducted on them.
COOL PAVEMENTS - DRAFT
11
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Figure 8: Percentage of Pavement Area by Type
of Use21
Sacramento Chicago Salt Lake Houston
City ,
Cities ;
LBNL conducted a paved surface analysis in four cities,
dividing the uses into four general categories. Roads
and parking lots make up the majority of paved areas.
Below are brief descriptions of potential
cool pavements and their typical uses:
• Conventional asphalt pavements,
which consist of an asphalt binder
mixed with aggregate, can be modified
with high albedo materials or treated
after installation to raise reflectance.
This material has been applied for de-
cades in a wide range of functions from
parking lots to highways.
• Conventional concrete pavements,
made by mixing Portland cement,
water, and aggregate, can be used in a
wide range of applications including
trails, roads, and parking lots.
• Other reflective pavements, made
from a variety of materials, are mostly
used for low-traffic areas, such as side-
walks, trails, and parking lots. Exam-
ples include:
- Resin based pavements, which
use clear tree resins in place of
petroleum-based elements to bind
an aggregate
- Colored asphalt and colored con-
crete, with added pigments or seals
to increase reflectance
Nonvegetated permeable pavements
contain voids and are designed to allow
water to drain through the surface into
the sublayers and ground below. These
materials can have the same structural
integrity as conventional pavements.
For example, some forms of porous
pavements, such as open-graded fric-
tion course (OGFC) asphalt pave-
ments, have been in use for decades
to improve roadway friction in wet
weather.22 Recently, rubberized asphalt
has been used on roads and highways
to reduce noise, and pervious concrete
applications are being studied for road-
way use. For some permeable pavement
options, the typical use may be for
lower traffic areas such as parking lots,
alleys, or trails. Examples of nonveg-
etated permeable pavements include:
- Porous asphalt
- Rubberized asphalt, made by mix-
ing shredded rubber into asphalt
- Pervious concrete
- Brick or block pavers, are gener-
ally made from clay or concrete,
and filled with rocks, gravel, or soil;
also available in a variety of colors
and finishes designed to increase
reflectance
Vegetated permeable pavements,
such as grass pavers and concrete grid
pavers, use plastic, metal, or concrete
lattices for support and allow grass or
other vegetation to grow in the inter-
stices. Although the structural integrity
can support vehicle weights compa-
rable to conventional pavements, these
materials are most often used in areas
where lower traffic volumes would
minimize damage to the vegetation,
such as alleys, parking lots, and trails,
and they may be best suited to climates
with adequate summer moisture.
12
REDUCING URBAN HEAT ISLANDS - DRAFT
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• Chip seals consist of aggregate bound
in liquid asphalt, and are often used to
resurface low-volume asphalt roads and
sometimes highways.
• Whitetopping is a layer of concrete
greater than 4 inches (10 cm) thick,
often containing fibers for added
strength. Typical applications include
resurfacing road segments, intersec-
tions, and parking lots.
• Ultra-thin whitetopping is similar
to whitetopping and can be used in
the same applications, but is only 2-4
inches (5-10 cm) thick.
• Microsurfacing is a thin sealing layer
used for road maintenance. Light-col-
ored materials can be used to increase
the solar reflectance of asphalt. Re-
searchers recently applied light-colored
microsurfacing material that consisted
of cement, sand, other fillers, and a liq-
uid blend of emulsified polymer resin,
and found the solar reflectance to be
comparable to that of new concrete.23
Table 2, beginning on page 15, provides
summary information for decision-makers
to consider. It is meant as a preliminary
guide, as more research and location-
specific data are needed. Table 2 includes
the following:
• A brief description of the technology
• The properties associated with it
• The potential impacts on pavement and
air temperatures
• Issues to consider
• Target functions.
Regarding impacts, the "+" sign indicates a
positive effect; for example, a technology
generally results in lower pavement tem-
peratures. A "-" signals a negative effect; for
example, a technology may lead to higher
air temperatures in certain conditions.
Slag and Fly Ash Cement
Slag and fly ash are sometimes added
to concrete to improve its perfor-
mance. Slag is a byproduct of pro-
cessing iron ore that can be ground
to produce cement, and fly ash is
a byproduct of coal combustion.24
These materials can make concrete
stronger, more resistant to aggressive
chemicals, and simpler to place. These
cements also reduce material costs
and avoid sending wastes to landfills.
A key heat island benefit of slag is its
lighter color, which can increase the
reflectivity of the finished pavement.
A 2007 study measured a solar reflec-
tance of almost 60 percent for cement
with slag, versus about 35 percent
for a conventional concrete mix.25 In
contrast, fly ash tended to darken con-
crete unless counterbalanced, such as
by added slag. However, substituting
fly ash for a portion of the Portland
cement reduces greenhouse gases and
other emissions associated with pro-
ducing Portland cement. Because of
such benefits, California's Department
of Transportation typically requires
use of 25 percent fly ash in cement
mixtures.26
Effects described in the table do not con-
sider magnitude, which may be influenced
by local conditions. Therefore, this infor-
mation is not intended for comparison.
The cool pavement technologies in Table
2 can have positive and negative impacts,
depending on actual conditions such as
moisture availability and urban design.
The points listed under "issues and consid-
erations" further illustrate the complexity
associated with cool pavements. These bul-
lets only discuss concerns related to urban
COOL PAVEMENTS - DRAFT
13
-------
heat islands and do not include other local
factors or priorities that decision-makers
generally consider when making pavement
choices.
Despite its limitations, Table 2 can be used
as a starting point. For example, using
Table 2, a city that generally uses asphalt
paving can identify alternative cool as-
phalt technologies for functions from bike
trails to roads. They can also discern that
high albedo pavements may be most effec-
tive in open areas, not surrounded by tall
buildings. Most communities will further
investigate the benefits and costs of the
technology, as discussed in Section 3, and
location-specific factors, such as political
acceptance and experience with the tech-
nology.
Filling in the Gaps
As more researchers and communi-
ties install cool pavement technolo-
gies, more data will be generated and
shared in forums such as the Trans-
portation Research Board Subcom-
mittee on Paving Materials and the
Urban Climate. (See Section 4 of this
chapter.)
14
REDUCING URBAN HEAT ISLANDS - DRAFT
-------
Table 2: Properties that Influence Pavement Temperatures—Impacts and Applications
NEW CONSTRUCTION
Pavement Type
Description of
Technology
Properties to Consider
Pavement Temperature
Impacts
Urban Climate Impacts
Issues and
Considerations
Target Use
Reflective Pavement Options
Asphalt pavement.
modified with high
albedo materials or
treated after installation
to raise albedo.
Asphalt pavements
consist of an asphalt
binder mixed with sand
or stone, referred to as
aggregate.
• Solar reflectance.
which initially may
be 5%, can increase
to 15-20% as con-
ventional asphalt
ages.27
• Using light-colored
aggregate, color pig-
ments, or sealants.
the reflectance of
conventional asphalt
can be increased.
• Maintenance ap-
plications such as
chip seals also can
increase solar reflec-
tance. (See below.)
• Urban geometry can
influence the effect
of high albedo pave-
ments.
+ Lowers pavement
temperature because
more of the sun's
energy is reflected
away, and there is less
heat at the surface to
absorb into the pave-
ment.
+ Can contribute to
lower air tempera-
tures day and night.
although air tempera-
tures are not directly
related to surface
temperatures and
many complicating
factors are involved.28
- Reflected heat can be
absorbed by the sides
of surrounding build-
ings warming the in-
terior of the building
and contributing to
the nighttime urban
heat island effect.
due to the additional
heat that needs to be
released from urban
infrastructure.
• Solar reflectance
increases over time.
and conventional
asphalt may reach a
reflectance of 20%
after seven years.29
(See Section 1.2.)
• Urban geometry.
in particular urban
canyons, influences
the impact reflective
pavements have on
the urban climate.
• Can be used in all
applications, such as
trails and roads.
• May be most effec-
tive when paving
large, exposed areas
such as parking lots.
-------
Table 2: Properties that Influence Pavement Temperatures — Impacts and Applications (continued)
NEW CONSTRUCTION (continued)
PavementType
Description of
Technology
Properties to Consider
Pavement Temperature
Impacts
Urban Climate Impacts
Issues and
Considerations
Target Use
Reflective Pavement Options (continued)
Concrete:
• Conventional
• Modified
Portland cement mixed
with water and ag-
gregate. Cured until it is
strong enough to carry
traffic.
• Initial solar reflec-
tance can be 40%.
• This can be raised
to more than 70%
using white cement
instead of gray ce-
ment mixtures.30
• Urban geometry can
influence the effect
of high-albedo pave-
ments.
+ Lowers pavement
temperature because
more of the sun's
energy is reflected
away, and there is less
heat at the surface to
absorb into the pave-
ment.
+ Can contribute to
lower air tempera-
tures day and night.
although air tempera-
tures are not directly
related to surface
temperatures and
many complicating
factors are involved.
- Reflected heat can be
absorbed by the sides
of surrounding build-
ings warming the in-
terior of the building
and contributing to
the nighttime urban
heat island effect.
due to the additional
heat that needs to be
released from urban
infrastructure.
• Solar reflectance
decreases overtime.
as soiling from traffic
darkens the surface.
• Conventional con-
crete may reach a
reflectance of 25%
after 5 years. 31 (See
Section 1 .2.)
• Urban geometry.
in particular urban
canyons, influences
the impact reflective
pavements have on
the urban climate.
• Can be used in all
applications, such as
trails and roads.
• May be most effec-
tive when paving
large, exposed areas.
such as parking lots.
-------
Table 2: Properties that Influence Pavement Temperatures—Impacts and Applications (continued)
NEW CONSTRUCTION (continued)
PavementType
Description of
Technology
Properties to Consider
Pavement Temperature
Impacts
Urban Climate Impacts
Issues and
Considerations
Target Use
Reflective Pavement Options (continued)
Other reflective
pavements:
• Resin based
• Colored asphalt
• Colored concrete
• Resin based pave-
ments use clear
colored tree resins in
place of cement to
bind the aggregate.
thus albedo is mainly
determined by ag-
gregate color.
• Colored asphalt or
concrete involve pig-
ments or seals that
are colored and may
be more reflective
than the conven-
tional equivalent.
These can be applied
when new or during
maintenance.
• These alternative
pavements will have
varying solar reflec-
tances based on the
materials used to
construct them.
• Urban geometry can
influence the effect
high-albedo pave-
ments have.
+ Lowers pavement
temperature because
more of the sun's
energy is reflected
away, and there is less
heat at the surface
to absorb into the
pavement.
+ Can contribute to
lower air tempera-
tures day and night.
although air tempera-
tures are not directly
related to surface
temperatures and
many complicating
factors are involved.
- Reflected heat can be
absorbed by the sides
of surrounding build-
ings warming the in-
terior of the building
and contributing to
the nighttime urban
heat island effect.
due to the additional
heat that needs to be
released from urban
infrastructure.
• As with concrete.
solar reflectance may
decrease overtime
as soiling from traffic
makes the pavement
darker and the sur-
face wears away.
• Urban geometry.
particularly urban
canyons, influences
the impact high-
albedo pavements
have on the urban
climate.
• Use depends on the
pavement applica-
tion. In general.
these alternative
pavements are used
for low-traffic areas.
such as sidewalks.
trails, and parking
lots.
• May be most effec-
tive when paving
large, exposed areas.
such as parking lots.
-------
Table 2: Properties that Influence Pavement Temperatures — Impacts and Applications (continued)
NEW CONSTRUCTION (continued)
PavementType
Description of
Technology
Properties to Consider
Pavement Temperature
Impacts
Urban Climate Impacts
Issues and
Considerations
Target Use
Permeable Pavement Options
Nonvegetated perme-
able pavements
• Porous asphalt has
more voids than con-
ventional asphalt to
a How water to drain
through the surface
into the base.
• Rubberized asphalt.
or crumb rubber, in-
volves mixing shred-
ded rubber into
asphalt. This material
is generally used to
reduce noise.
• Other porous
asphalts or open-
grade course friction
surfaces can also be
used for reducing
noise.32
• Provides cool-
ing through
evaporation.
• Solar reflectance of
these materials de-
pends on individual
materials (e.g., gravel
may be white and
very reflective). In
general, permeable
pavements may be
less reflective than
their nonpermeable
equivalent due to
the increased surface
area.33
• Increased convec-
tion may help cool
the pavement due
to increased surface
area.34
+ When wet, lowers
pavement tempera-
ture through evapora-
tive cooling.
-When dry, maybe hot
at the surface, but
subsurface generally
will be same tempera-
ture as nonpermeable
equivalent.
+ When moist, can
contribute to lower
air temperatures day
and night, through
evaporative cooling.
although air tempera-
tures are not directly
related to surface
temperatures and
many complicating
factors are involved.
-When dry, can
contribute to higher
daytime surface
temperatures, but
may not affect or may
even reduce night-
time air temperatures.
although air tempera-
tures are not directly
related to surface
temperatures and
many complicating
factors are involved.
• Cooling mecha-
nism depends on
available moisture.
Supplemental water-
ing may keep them
cooler.35
• Void structure may
aid in insulating the
subsurface from heat
absorption.
• More research
needed to deter-
mine permeable
pavement impacts
on pavement and air
temperatures.
• Structurally, avail-
able for any use.
Rubberized asphalt
and open-graded
friction course
asphalt are used on
roads and highways
and pervious con-
crete actively being
considered.
• Technologies often
applied to lower
traffic areas, such as
parking lots, alleys.
and trails.
• May be best in cli-
mates with adequate
moisture during the
summer.
-------
Table 2: Properties that Influence Pavement Temperatures—Impacts and Applications (continued)
NEW CONSTRUCTION (continued)
PavementType
Description of
Technology
Properties to Consider
Pavement Temperature
Impacts
Urban Climate Impacts
Issues and
Considerations
Target Use
Permeable Pavement Options (continued)
Nonvegetated
permeable pavements
(continued)
Vegetated permeable
pavements:
• Grass pavers
• Concrete
grid pavers
• Pervious concrete
has more voids than
conventional con-
crete to allow water
to drain through
the surface into the
base.
• Brick or block pavers
are generally made
from clay or concrete
blocks filled with
rocks, gravel, or soil.
• Plastic, metal, or
concrete lattices
provide support and
allow grass or other
vegetation to grow
in the interstices.
(see prior page)
• Provides cooling
through evapotrans-
piration.
• Sustainability of
vegetation may vary
with local conditions.
(see prior page)
+ Lowers pavement
temperatures
through evapotrans-
piration, particularly
when moist.
+ When dry may
still be cooler than
other pavement
options due to the
natural properties of
vegetation.
(see prior page)
+ In most conditions
will contribute to
lower air tempera-
tures day and night.
through evapo-
transpirationand
natural properties of
vegetation. Mois-
ture availability will
greatly increase its
effectiveness.
(see prior page)
• Cooling mecha-
nism depends on
available moisture.
Supplemental mois-
ture, for example
watering pavements.
may keep them
cooler.35
• More research
needed to determine
temperature impacts
from vegetated
pavements under
a wide range of
conditions.
(see prior page)
• Low-traffic areas.
such as alleys, park-
ing lots, and trails.
• May be best in cli-
mates with adequate
moisture during the
summer.
-------
Table 2: Properties that Influence Pavement Temperatures — Impacts and Applications (continued)
MAINTENANCE/REHABILITATION
PavementType
Description of
Technology
Properties to Consider
Pavement Temperature
Impacts
Urban Climate Impacts
Issues and
Considerations
Target Use
Reflective Pavement Options
Chip seals made with
high-albedo aggregate
• Chip seals describe
aggregate used to
resurface low-
volume asphalt
roads and some-
times for highway
surfaces.
• Solar reflectance of
chip seals will corre-
late with the albedo
of the aggregate
used. In San Jose, CA,
researchers identi-
fied albedo of 20%
for new chip seals.
which then decline
with age.37
• Urban geometry can
influence the effect
high-albedo pave-
ments have
+ Lowers pavement sur-
face and subsurface
temperature because
more of the sun's
energy is reflected
away, and there is less
heat at the surface
to absorb into the
pavement.
+ Can contribute to
lower air tempera-
tures day and night.
although air tempera-
tures are not directly
related to surface
temperatures and
many complicating
factors are involved.
- Reflected heat can be
absorbed by the sides
of surrounding build-
ings warming the in-
terior of the building
and contributing to
the urban heat island
effect.
• Solar reflectance
decreases overtime.
as soiling from traffic
makes chip seals
darker.
• Urban geometry, in
particular urban
canyons, influences
the impact high-
albedo pavements
have on the urban
climate.
• Chip seals are most
often used to resur-
face low-volume
asphalt roads.
although highway
applications also
exist.
• May be most effec-
tive when paving
large, exposed areas.
such as parking lots.
-------
n
O
O
Table 2: Properties that Influence Pavement Temperatures—Impacts and Applications (continued)
MAINTENANCE/REHABILITATION (continued)
PavementType
Description of
Technology
Properties to Consider
Pavement Temperature
Impacts
Urban Climate Impacts
Issues and
Considerations
Target Use
Reflective Pavement Options (continued)
Whitetopping
• Whitetopping is a
thick layer (thick-
ness greater than
4 inches or 10cm)
of concrete applied
over existing asphalt
when resurfacing
or can be applied to
new asphalt. It often
contains fibers for
added strength.
• Ultra-thin whitetop-
ping is generally 2-4
inches (5-1 Ocm)
thickand similarto
Whitetopping.
• The solar reflectance
of Whitetopping
material can be as
high as concrete.
• Urban geometry
can influence the
effect of high-albedo
pavements.
+ Lowers pavement sur-
face and subsurface
temperature because
more of the sun's
energy is reflected
away, and there is less
heat at the surface
to absorb into the
pavement.
+ Can contribute to
lower air tempera-
tures day and night.
although air tempera-
tures are not directly
related to surface
temperatures and
many complicating
factors are involved.
- Reflected heat can be
absorbed by the sides
of surrounding build-
ings, warming the in-
terior of the building
and contributing to
the urban heat island
effect.
• Solar reflectance
decreases overtime.
as soiling from traffic
makes whitetopped
surfaces darker.
• Urban geometry, in
particular urban
canyons, influences
the impact high-
albedo pavements
have on the urban
climate.
• Whitetopping and
ultra-thin whitetop-
ping are generally
used to resurface
road segments.
intersections, and
parking lots.
• May be most effec-
tive when paving
large, exposed areas.
such as parking lots.
I
D
-------
Table 2: Properties that Influence Pavement Temperatures — Impacts and Applications (continued)
MAINTENANCE/REHABILITATION (continued)
PavementType
Description of
Technology
Properties to Consider
Pavement Tempera-
ture Impacts
Urban Climate Impacts
Issues and Consider-
ations
Target Use
Reflective Pavement Options (continued)
Microsurfacing
with high-
albedo materials
• A thin sealing
layer used for road
maintenance.
• Light-colored
materials can be
used to increase
the solar reflec-
tance of asphalt.
• Solar reflectance of
microsurfacing will cor-
relate with the albedo
of the materials used.
• Researchers recently
measured solar reflec-
tances of microsurfac-
ing applications over
35%.38
+ Lowers pavement
surface and sub-
surface tempera-
ture because more
of the sun's energy
is reflected away.
and there is less
heat at the surface
to absorb into the
pavement.
+ Can contribute to lower
air temperatures day and
night, although air tem-
peratures are not directly
related to surface tempera-
tures and many complicat-
ing factors are involved.
- Reflected heat can be
absorbed by the sides of
surrounding buildings.
warming the interior of the
building and contributing
to the urban heat island
effect.
• Solar reflectance
may decrease over
time, if soiling from
traffic makes high-
albedo microsurfac-
ing materials darker.
• Urban geometry.
particularly urban
canyons, influences
the impact high-
albedo pavements
have on the urban
climate.
• Used to extend pavement
life and on worn pave-
ments that need improved
friction, such as low- to
medium-volume roads.
airport runways, and park-
ing areas.
-------
3. Benefits and Costs
Currently, few studies provide detailed
data on the benefits and costs of cool
pavements. This section aims to provide
a general discussion as a starting point
for decision-makers to consider and gives
examples where available. Again, decision-
makers will also consider location-specific
factors such as functionality of pavements
in the local climate, political acceptance,
and experience with the technology. Re-
sources and examples providing the latest
information are listed in Sections 4 and 5.
3.1 Benefits
Installing cool pavements can be part of
an overall strategy to reduce air tempera-
tures, which can result in a wide range of
benefits. The information below highlights
existing research in this area.
Reduced Energy Use
As noted earlier, researchers predicted that
if pavement reflectance throughout a city
were increased from 10 to 35 percent, the
air temperature could potentially be re-
duced by 1°F (0.6°C), which would result
in significant benefits in terms of lower
energy use and reduced ozone levels. For
example, an earlier, separate study esti-
mated over $90 million/year in savings
from temperature reductions attributed to
increased pavement albedo in the Los An-
geles area.39
Similarly, when permeable pavements
evaporate water and contribute to lower
air temperatures, they also provide other
energy benefits.40 Permeable pavements
can allow stormwater to infiltrate into
the ground, which decreases stormwater
runoff. With reduced runoff, communities
may realize energy savings associated with
pumping stormwater and maintaining con-
veyance structures. These cost savings may
Measuring Energy Savings
from Cool Roofs versus
Cool Pavements
Measuring the energy impacts from a
cool roof is relatively easy compared
with quantifying those from pave-
ment installations. With a roof, one
can measure energy demand before
and after the installation, and in a
controlled experiment, the change in
demand can be associated with the
roofing technology. In contrast, pave-
ments affect building energy demand
through influencing air temperature,
which is a more complex relation-
ship to isolate and measure.
be significant in areas where there are old,
combined sewers (where stormwater drains
into the sanitary sewer system).
Air Quality and Greenhouse Gas Emissions
Depending on the electric power fuel mix,
decreased energy demand associated with
cool pavements will result in lower as-
sociated air pollution and greenhouse gas
emissions. Cooler air temperatures also
slow the rate of ground-level ozone for-
mation and reduce evaporative emissions
from vehicles. A 2007 paper estimated
that increasing pavement albedo in cit-
ies worldwide, from an average of 35 to
39 percent, could achieve reductions in
global carbon dioxide (CO2) emissions
worth about $400 billion.41
Water Quality and Stormwater Runoff
Pavements with lower surface tempera-
tures—whether due to high solar reflec-
tance, permeability, or other factors—can
help lower the temperature of stormwater
runoff, thus ameliorating thermal shock to
COOL PAVEMENTS - DRAFT
23
-------
aquatic life in the waterways into which
stormwater drains.42 Laboratory tests with
permeable pavers have shown reductions
in runoff temperatures of about 3-7°F
(2-4°C) in comparison with conventional
asphalt paving.43
Permeable pavements allow water to
soak into the pavement and soil, thereby
reducing stormwater runoff, recharging
soil moisture, and improving water qual-
ity by filtering out dust, dirt, and pollut-
ants.44.45 Outdoor testing and laboratory
measurements have found that permeable
pavements can reduce runoff by up to
90 percent.46 Reducing runoff decreases
scouring of streams, and, in areas with
combined sewers, this flow reduction can
help minimize combined sewer overflows
that discharge sewage and stormwater into
receiving waters. The amount of water
that these pavements collect varies based
on the type of aggregate used and the po-
rosity of the pavements, as well as on the
absorptive ability of the materials support-
ing the pavement.
Increased Pavement Life and Waste Reduction
Reducing pavement surface temperatures
can increase the useful life of pavements
and reduce waste. Some simulations of
asphalt pavements showed that pavements
that were 20°F (11°C) cooler lasted 10
times longer than the hotter pavements,
and pavements that were 40°F (22°C) cool-
er lasted 100 times longer before showing
permanent damage.47
Quality of Life Benefits
Cool pavements may provide additional
benefits, such as:
• Nighttime illumination. Reflective
pavements can enhance visibility at
night, potentially reducing lighting
requirements and saving money and
energy. European road designers often
Figure 9: Slag Cement Airport Expansion
The Detroit Metro Airport used 720,000 square
feet (67,000 m2) of slag cement in an airport
terminal expansion project. In this region, the local
aggregate is susceptible to alkali-silica reaction,
whereas slag resists that form of corrosion
better than plain cement and is easier to place
in hot weather. This approach increased the life
expectancy of the paved surfaces, as well as
allowed for the use of a high-albedo product.48
take pavement color into account when
planning lighting.49
• Comfort improvements. Using reflec-
tive or permeable pavements where
people congregate or children play
can provide localized comfort benefits
through lower surface and near-surface
air temperatures.50
• Noise reduction. The open pores of
permeable pavements, such as an open-
graded course layer on highways, can
reduce tire noise by two to eight deci-
bels and keep noise levels below 75
decibels.51'52 Noise reduction may de-
cline over time, however, and some of
these pavements may not be as strong
and durable as conventional surfaces.
Researchers at the National Center of
Excellence at Arizona State University
are studying these issues.53
• Safety. Permeable roadway pavements
can enhance safety because better wa-
ter drainage reduces water spray from
moving vehicles, increases traction, and
may improve visibility by draining wa-
ter that increases glare.54
24
REDUCING URBAN HEAT ISLANDS - DRAFT
-------
3.2 Costs
Cool pavement costs will depend on many
factors including the following:
• The region
• Local climate
• Contractor
• Time of year
• Accessibility of the site
• Underlying soils
• Project size
• Expected traffic
• The desired life of the pavement.
Most cost information is project specific,
and few resources exist that provide
general cost information. For permeable
pavement, however, the Federal Highway
Administration (FHWA) has noted that
porous asphalt costs approximately 10 to
15 percent more than regular asphalt, and
porous concrete is about 25 percent more
expensive than conventional concrete.55
These comparisons pertain to the surface
layer only.
Table 3 (below) summarizes a range of
costs for conventional and cool pave-
ments, based on available sources. The
data should be read with caution, as many
project-specific factors—as highlighted
above—will influence costs. These costs
are estimates for initial construction or
performing maintenance, and do not
reflect life-cycle costs. Decision-makers
generally contact local paving associations
and contractors to obtain more detailed,
location-specific information on the costs
and viability of cool pavements in their
particular area.
Table 3: Comparative Costs of Various Pavements56
Basic Pavement Types
Example Cool Approaches
Approximate
Installed Cost, Estimated Service
$/sq ua re foot* Life, Yea rs
Asphalt (conventional)
Concrete (conventional)
Nonvegetated permeable pave-
ment
Vegetated permeable pave-
ment
Surface applications
New Construction
Hot mix asphalt with light aggregate,
if locally available
Portland cement, plain-jointed
Porous asphalt
Pervious concrete
Paving blocks
Grass/gravel pavers
Maintenance
Chip seals with light aggregate, if
locally available
Microsurfacing
Ultra-thin whitetopping
$0.10-$ 1.50
$0.30-$4.50
$2.00-$2.50
$5.00-$6.25
$5.00-$ 10.00
$1.50-$5.75
$0.10-$0.15
$0.35-$0.65
$1.50-$6.50
7-20
15-35
7-10
15-20
>20
>10
2-8
7-10
10-15
' Some technologies, such as permeable options, may reduce the need for other infrastructure, such as stormwater
drains, thus lowering a project's overall expenses. Those savings, however, are not reflected in this table. (1 square foot
= 0.09 m2)
COOL PAVEMENTS - DRAFT
25
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3,3 Benefit-Cost Considerations
Life-cycle cost assessments can help in
evaluating whether long-term benefits
can outweigh higher up-front costs. The
National Institute of Standards and Tech-
nology (NIST) has developed Building for
Environmental and Economic Sustainabil-
ity (BEES), a software tool that uses the
ISO 14040 series of standards to estimate
life-cycle costs from the production and
use of asphalt, Portland cement, fly ash
cement, and other paving materials.57 Al-
though not directly related to urban heat
island mitigation, this tool can help quan-
tify some of the impacts from a variety of
pavement choices.
Further, although permeable pavement
costs may be higher than conventional,
impermeable technologies, these costs are
often offset by savings from reduced re-
quirements for grading, treatment ponds,
or other drainage features, such as inlets
and stormwater pipes.58 For a community,
the cumulative reductions in stormwater
flows from sites can provide significant
savings in the municipal infrastructure.
If the community has combined sewers,
there could also be environmental, social,
and cost benefits from reducing combined
sewer overflows, as well as potentially
avoiding part of the increased infrastruc-
ture costs associated with combined sewer
operation.
In general, until more data on cool pave-
ment benefits and costs exist, communities
may need to think broadly to determine if
a cool pavement application is appropriate.
Sustainability initiatives, in some areas, are
motivating communities to try cooler alter-
natives, as discussed in Section 4.
The growing interest in lowering urban
temperatures and designing more sustain-
able communities has helped spur activ-
ity in the cool pavement arena. Most of
the effort has focused on research, due to
information gaps and the lack of specific
data quantifying cool pavement benefits.
More information on resources and exam-
ples are provided at the end of this sec-
tion and in Section 5. Highlights of some
cool pavement efforts are below:
» Arizona State University's National
Center of Excellence (NCE) SMART
Innovations for Urban Climate and
Energy. 59 This group is studying es-
tablished and emerging designs that
optimize albedo, emissivity, thermal
conductivity, heat storage capacity, and
density in laboratory and field sites.
NCE is developing models, particularly
for the Phoenix area but also beyond,
to help decision-makers predict the
effects of material properties, shading,
and energy use on urban temperatures.
» The National Academies of Science's
Transportation Research Board
(TRB) Subcommittee on Paving Ma-
terials and the Urban Climate. TRB
established this Subcommittee in Janu-
ary 2008 to help advance the science of
using pavements for heat island mitiga-
tion and addressing other urban climate
concerns.
• Trade association efforts. Represen-
tatives from the asphalt and concrete
trade associations are participating in
cool pavement efforts, such as the TRB
Subcommittee on Paving Materials and
the Urban Climate, as well supporting
research and training related to cool
pavement. For example, the National
26
REDUCING URBAN HEAT ISLANDS - DRAFT
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Asphalt Pavement Association has been
investigating high-albedo asphalt pave-
ments, the National Ready Mixed Con-
crete Association is leading seminars on
pervious concrete, and the Interlocking
Concrete Pavement Institute (ICPI) is
providing professional seminars on per-
meable pavements in cooperation with
the Low Impact Development Center
and North Carolina State University.60
These research efforts are expanding op-
portunities for identifying, applying, and
studying cool pavement technologies.
Sustainability or green building initiatives
are helping to encourage cool pavement
installations.
• Evanston, Illinois, includes permeable
pavements in its assessment of green
buildings.61
• Chicago's Green Alley program aims
to use green construction techniques to
repave over 1,900 miles of alleys, and
offers a handbook for installing per-
meable pavements for heat reduction,
stormwater management, and other
benefits.62
• Environmental rating programs such
as Leadership in Energy and Environ-
mental Design (LEED), Green Globes,
and EarthCraft award points to designs
that incorporate certain permeable
pavements or pavements of a certain
solar reflectance index. They also give
points for using local and recycled ma-
terials, such as slag, and reducing the
pavement used on a site.
Table 4 on page 28 summarizes other cool
pavement initiatives. Refer to the "Heat
Island Reduction Activities" chapter of this
compendium for further examples.
Growing Concern about
Synthetic Turf
Many communities have begun to
examine the health impacts from
synthetic turf surfaces, which include
the effects from high temperatures.
One researcher in New York found
that artificial sports fields could be
up to 60°F (16°C) hotter than grass,
potentially causing skin injuries to
athletes as well as contributing to the
heat island effect. These data, though
not directly related to pavements, can
help advance our understanding of
how different materials interact with
the urban climate.63
Figure 11: Grass Paving
This 300,000-square-foot (28,000 m2) parking lot
outside a stadium in Houston uses plastic grid
pavers that allow grass to grow in the open spaces.
COOL PAVEMENTS - DRAFT
27
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Alternative Paving under the Cool Houston Plan
While most communities have no, or limited, cool pavement experience, Houston's
heat island initiative recommends alternative pavements as part of the city's overall
approach to improving air quality and public health. The plan's three-tiered strategy
includes:
• Targeting alternative paving options for specific types of paved surfaces, such as
highways or parking lots, or expanding residential or commercial roadways. This
requires coordination with the Texas Department of Transportation and the Texas
Commission on Environmental Quality.
• Educating local and state decision-makers about public health, environmental
management, and public works maintenance benefits of alternative pavements.
• Combining and embedding alternative paving incentives into larger programs
and regulations, such as meeting Clean Air or Clean Water Act standards, with the
support of the Greater Houston Builders Association and the Texas Aggregates
and Concrete Association.
Table 4: Examples of Cool Pavement Initiatives
Type of
Initiative Description
Links to Examples
Research
Industry
National
laboratory
University-
supported
and similar
consortia
—Since 1928, the National Ready Mixed Concrete Association's
research laboratory has helped evaluate materials and set technical standards. Recent
projects include developing permeability tests and assessing concrete with high fly-
ash content.
—The Heat Island Group at Lawrence
Berkeley National Laboratory (LBNL) provides research and information about cool
paving and other heat island mitigation measures. The Cool Pavements section
describes the benefits of this technology, and published reports are included under
Recent Publications.
—Arizona State University's National Center
of Excellence collaborates with industry and government to research and develop
technologies to reduce urban heat islands, especially in desert climates.
—The Houston Advanced Research Center
(HARC) brings together universities, local governments, and other groups interested in
improving air quality and reducing heat islands. It has examined how cool paving could
be implemented in the Houston area to reduce urban heat island effects.
and —North Carolina State University has an
active permeable pavement research program, as well as a specialized collaborative
effort with ICPI and the Low Impact Development Center on permeable interlocking
concrete pavements.
28
REDUCING URBAN HEAT ISLANDS - DRAFT
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Table 4: Examples of Cool Pavement Initiatives (cont.)
Type of
Initiative Description
Links to Examples
Voluntary
efforts
Demonstration
programs
Outreach &
education
Tools
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
—
Poulsbo, Washington, used a $263,000 grant from the Washington Department of
Ecology to pave 2,000 feet of sidewalk with pervious pavement, making it one of the
largest pervious surface projects in the state.
—The nonprofit Heifer Interna-
tional used pervious pavement and other sustainable techniques for its new head-
quarters in Arkansas.
< www.epa.gov/heatisland/>—EPA's Heat Island Reduction Initiative provides infor-
mation on the temperature, energy, and air quality impacts from cool pavements and
other heat island mitigation strategies.
—EPA's Office of Water
highlights design options, including permeable pavements that reduce stormwater
runoff and water pollution.
—The Green Highways Partnership, supported by a number
of groups including EPA and the U.S. Department of Transportation is a public-private
partnership dedicated to transforming the relationship between the environment and
transportation infrastructure. The partnership's Web site includes a number of cool pave-
ment resources, especially with respect to permeable pavements.
—The University of Connecticut runs Nonpoint
Education for Municipal Officials (NEMO), which helps educate local governments
about land use and environmental quality.
—The National Institute of Standards and
Technology (NIST) has developed a software tool. Building for Environmental and
Economic Stability (BEES). The tool enables communities to conduct life cycle cost
assessments for various types of building initiatives, including pavement projects.
Policy
efforts
Municipal
regulations that
support cool
pavements
—The Cool Hous-
ton! Plan promotes cool paving as well as other techniques to reduce the region's
heat island.
—
Toronto's"Design Guidelines for'Greening'Surface Parking Lots"encourage reflective
and permeable pavements to reduce surface temperatures.
Although cool pavements are still in their
infancy compared with the other heat
island mitigation strategies—trees and veg-
etation, green roofs, and cool roofs—inter-
est and momentum are growing. Research
efforts these past few years have greatly
increased, particularly in the area of per-
meable pavements. As local and state trans-
portation and environmental agencies work
together to address energy, sustainability,
heat-health, and other concerns, communi-
ties can expect to see more cool pavement
installations. Activity in the private sector
has also been encouraging, as architects,
developers, and others are taking leader-
ship roles in advancing sustainable tech-
nologies. This chapter, which currently
provides a starting point for communities
and decision-makers, will evolve as more
information becomes available.
COOL PAVEMENTS - DRAFT
29
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5. Resources
The organizations below may provide additional information on alternative, or cool,
pavement technologies.
Program/Organization Role Web Address
The Federal Highway
Administration's (FHWA)
Office of Pavement
Technology
FHWAs Office of Planning,
Environment, and Realty
American Association
of State Highway and
Transportation Officials
Center for Environmental
Excellence (AASHTO)
Association of Metropolitan
Planning Organizations
(AMPO)
The American Concrete
Pavement Association (ACPA)
The Asphalt Pavement
Alliance (APA)
Interlocking Concrete
Pavement Institute (ICPI)
National Center for Asphalt
Technology (NCAT)
National Ready Mixed
Concrete Association
Portland Cement Association
(PCA)
The Office of PavementTechnology conducts research
and training related to asphalt and concrete pavements.
This office's Web site provides information regarding
transportation planning and the environment.
AASHTO created the Center for Environmental Excellence
in cooperation with the Federal Highway Administration
to offer technical assistance about environmental
regulations and ways to meet them.
AMPO supports local MPOs through training,
conferences, and assistance with policy development.
ACPA promotes concrete pavement by working with
industry and government.
A consortium of the National Asphalt Paving Association
(NAPA), the Asphalt Institute (Al),and state paving
associations, APA promotes hot mix asphalt through
research, development, and outreach. Individual state
asphalt associations are a good source for local paving
considerations.
ICPI has a document that compares permeable pavement
technologies and helps readers find certified installers.
NCAT provides up-to-date strategies for designing and
constructing asphalt pavements.
Since 1 928, the National Ready Mixed Concrete
Association's research laboratory has helped evaluate
materials and set technical standards. Recent projects
include developing permeability tests and assessing
concrete with high fly-ash content.
PCA represents cement companies in the United States
and Canada and conducts research, development, and
outreach.
30
REDUCING URBAN HEAT ISLANDS - DRAFT
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1 Statistics are from urban fabric analyses conducted by Lawrence Berkeley National Laboratory.
Rose, L.S., H. Akbari, and H. Taha. 2003. Characterizing the Fabric of the Urban Environment: A
Case Study of Greater Houston, Texas. Paper LBNL-51448. Lawrence Berkeley National Labora-
tory, Berkeley, CA.
Akbari, H. and L.S. Rose. 2001. Characterizing the Fabric of the Urban Environment: A Case
Study of Metropolitan Chicago, Illinois. Paper LBNL-49275. Lawrence Berkeley National Labora-
tory, Berkeley, CA. Akbari, H. and L.S. Rose. 2001. Characterizing the Fabric of the Urban Envi-
ronment: A Case Study of Salt Lake City, Utah. Paper LBNL-47851. Lawrence Berkeley National
Laboratory, Berkeley, CA. Akbari, H., L.S. Rose, and H. Taha. 1999. Characterizing the Fabric of
the Urban Environment: A Case Study of Sacramento, California. Paper LBNL-44688. Lawrence
Berkeley National Laboratory, Berkeley, CA.
2 Pomerantz, M., B. Pon, H. Akbari, and S.-C. Chang. 2000. The Effect of Pavements' Temperatures
on Air Temperatures in Large Cities. Paper LBNL-43442. Lawrence Berkeley National Laboratory,
Berkeley, CA. See also Cambridge Systematics. 2005. Cool Pavement Draft Report. Prepared for
U.S. EPA.
3 See, generally, U.S. EPA 2008. Green Parking Lot Resource Guide. EPA 510-B-08-001.
4 Golden, J.S., J. Carlson, K. Kaloush, and P. Phelan. 2006. A Comparative Study of the Thermal
and Radiative Impacts of Photovoltaic Canopies on Pavement Surface Temperatures. Solar
Energy. 81(7): 872-883. July 2007.
5 Kinouchi, T, T. Yoshinaka, N. Fukae, and M. Kanda. 2004. Development of Cool Pavement
with Dark Colored High Albedo Coating. Paper for 5th Conference for the Urban Environment.
Vancouver, Canada. Retrieved November 15, 2007, from .
6 National Center of Excellence on SMART Innovations at Arizona State University. 2007. What Fac-
tors Influence Elevated Pavement Temperatures Most During Day and Night? Case Study 1(1).
7 The Portland Cement Association thoroughly explains concrete cement at , and state and federal government sites, among others, define as-
phalt. Two useful ones are and
.
8 Levinson, R. and H. Akbari. 2001. Effects of Composition and Exposure on the Solar Reflec-
tance of Portland Cement Concrete. Paper LBNL-48334. Lawrence Berkeley National Laboratory,
Berkeley, CA.
9 National Center of Excellence on SMART Innovations at Arizona State University. 2007. What
Factors Influence Elevated Pavement Temperatures Most During Day and Night? Case Study
1(1).
10 Levinson, R., H. Akbari, S. Konopacki, and S. Bretz. 2002. Inclusion of Cool Roofs in Nonresi-
dential Title 24 Prescriptive Requirements. Paper LBNL-50451. Lawrence Berkeley National
Laboratory, Berkeley, CA.
11 See:
Haselbach, L. 2008. Pervious Concrete and Mitigation of the Urban Heat Island Effect. Un-
der review for the 2009 Transportation Research Board Annual Meeting.
Kevern, J., V.R. Schaefer, and K. Wong. 2008. Temperature Behavior of a Pervious Concrete
System. Under review for the 2009 Transportation Research Board Annual Meeting.
COOL PAVEMENTS - DRAFT 31
-------
12 For a general overview of permeable pavements, see Ferguson, B. 2005. Porous Pavements.
13 See, generally:
Haselbach, L. 2008. Pervious Concrete and Mitigation of the Urban Heat Island Effect. Un-
der review for the 2009 Transportation Research Board Annual Meeting.
Kevern, J., V.R. Schaefer, and K. Wong. 2008. Temperature Behavior of a Pervious Concrete
System. Under review for the 2009 Transportation Research Board Annual Meeting.
14 There are a number of resources available on Japan's efforts with water retentive pave-
ments, although there is no centralized source that compiles these initiatives. For examples
of the research and published summaries available, see the following (all Web sites accessed
September 17, 2008):
Karasawa, A., K. Toriiminami, N. Ezumi, K. Kamaya. 2006. Evaluation Of Performance Of
Water-Retentive Concrete Block Pavements. 8th International Conference on Concrete Block
Paving, November 6-8, 2006, San Francisco, California.
Ishizuka, R., E. Fujiwara, H. Akagawa. 2006. Study On Applicability Of Water-Feed-Type
Wet Block Pavement To Roadways. 8th International Conference on Concrete Block Paving,
November 6-8, 2006, San Francisco, California.
Yamamoto, Y. 2006. Measures to Mitigate Urban Heat Islands. Quarterly Review No. 18.
January 2006. Available online at .
Yoshioka, M., H. Tosaka, K. Nakagawa 2007. Experimental and Numerical Studies of the
Effects of Water Sprinkling on Urban Pavement on Heat Island Mitigation. American Geo-
physical Union, Fall Meeting 2007, abstract #H43D-1607.
Yamagata H., M. Nasu, M. Yoshizawa, A. Miyamoto, and M. Minamiyama. 2008. Heat island
mitigation using water retentive pavement sprinkled with reclaimed wastewater. Water
science and technology. 57(5): 763-771. Abstract available online at .
15 Christen, A. and R. Vogt. 2004. Energy and radiation balance of a Central European city. Interna-
tional Journal of Climatology. 24(ii):1395-l421.
16 Golden, J.S. and K. Kaloush. 2006. Meso-Scale and Micro-Scale Evaluations of Surface Pavement
Impacts to the Urban Heat Island Effects. The International Journal of Pavement Engineering.
7(1): 37-52. March 2006.
17 Pomerantz, M., B. Pon, H. Akbari, and S.-C. Chang. 2000. The Effect of Pavements' Temperatures
on Air Temperatures in Large Cities. Paper LBNL-43442. Lawrence Berkeley National Laboratory,
Berkeley, CA.
18 Taha, H. 1997. Modeling the impacts of large-scale albedo changes on ozone air quality in the
South Coast Air Basin. Atmospheric Environment. 31(11): 1667-1676.
Taha, H. 1996. Modeling the Impacts of Increased Urban Vegetation on the Ozone Air Quality in
the South Coast Air Basin. Atmospheric Environment. 30(20): 3423-3430.
19 Rosenfeld, A.H., J.J. Romm, H. Akbari, and M. Pomerantz. 1998. Cool Communities: Strategies
for Heat Islands Mitigation and Smog Reduction. Energy and Buildings. 28:51-62.
20 Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2008. Strategies for Design and Con-
struction of High-Reflectance Asphalt Pavements. Under review for the 2009 Transportation
Research Board Annual Meeting.
32 REDUCING URBAN HEAT ISLANDS - DRAFT
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21 Statistics are from urban fabric analyses conducted by Lawrence Berkeley National Laboratory.
Rose, L.S., H. Akbari, and H. Taha. 2003. Characterizing the Fabric of the Urban Environment: A
Case Study of Greater Houston, Texas. Paper LBNL-51448. Lawrence Berkeley National Labora-
tory, Berkeley, CA.
Akbari, H. and L.S. Rose. 2001. Characterizing the Fabric of the Urban Environment: A Case
Study of Metropolitan Chicago, Illinois. Paper LBNL-49275. Lawrence Berkeley National Labora-
tory, Berkeley, CA. Akbari, H. and L.S. Rose. 2001. Characterizing the Fabric of the Urban Envi-
ronment: A Case Study of Salt Lake City, Utah. Paper LBNL-47851. Lawrence Berkeley National
Laboratory, Berkeley, CA. Akbari, H., L.S. Rose, and H. Taha. 1999. Characterizing the Fabric of
the Urban Environment: A Case Study of Sacramento, California. Paper LBNL-44688. Lawrence
Berkeley National Laboratory, Berkeley, CA.
22 See, e.g., Mallick, R.B., PS. Kandhal, L.A. Cooley, Jr., and PE. Watson. 2000. Design, Construc-
tion, and Performance of New-generation Open-graded Friction Courses. Paper prepared for
annual meeting of Association of Asphalt Paving Technologists, Reno, NV, March 13-15, 2000.
23 Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2008. Strategies for Design and Con-
struction of High-Reflectance Asphalt Pavements. Under review for the 2009 Transportation
Research Board Annual Meeting.
24 More information on fly ash is available through EPA's Coal Combustion Products Partnership,
.
25 Boriboonsomsin, K. and F. Reza. 2007. Mix Design and Benefit Evaluation of High Solar Reflec-
tance Concrete for Pavements. Paper for 86th Annual Meeting of the Transportation Research
Board. Washington, D.C.
26 Office of the Governor. 2006. Statement by Gov. Schwarzenegger on U.S. EPA Award for Cali-
fornia's Leadership in the Construction Use of Waste Products. Retrieved July 15, 2008, from
27 Pomerantz, M., B. Pon, H. Akbari, and S.-C. Chang. 2000. The Effect of Pavements' Temperatures
On Air Temperatures in Large Cities. Paper LBNL-43442. Lawrence Berkeley National Labora-
tory, Berkeley, CA. See also Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2008. Strate-
gies for Design and Construction of High-Reflectance Asphalt Pavements. Under review for the
2009 Transportation Research Board Annual Meeting.
28 Aseda, T., V.T. Ca, and A. Wake. 1993. Heat Storage of Pavement and its Effect on the Lower
Atmosphere. Atmospheric Environment. 30(3): 413-427. 1996.
29 Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2008. Strategies for Design and Con-
struction of High-Reflectance Asphalt Pavements. Under review for the 2009 Transportation
Research Board Annual Meeting.
30 Levinson, R. and H. Akbari. 2001. Effects of Composition and Exposure on the Solar Reflec-
tance of Portland Cement Concrete. Paper LBNL-48334. Lawrence Berkeley National Laboratory,
Berkeley, CA.
31 Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2008. Strategies for Design and Con-
struction of High-Reflectance Asphalt Pavements. Under review for the 2009 Transportation
Research Board Annual Meeting.
32 National Center of Excellence on SMART Innovations at Arizona State University. 2007.
Alternative Paving—Recycling Crumb Rubber. Case Study, 1(3).
33 Haselbach, L. 2008. Pervious Concrete and Mitigation of the Urban Heat Island Effect. Under
review for the 2009 Transportation Research Board Annual Meeting.
COOL PAVEMENTS - DRAFT 33
-------
34 Haselbach, L. 2008. Pervious Concrete and Mitigation of the Urban Heat Island Effect. Under
review for the 2009 Transportation Research Board Annual Meeting.
35 Yamagata H., M. Nasu, M. Yoshizawa, A. Miyamoto, and M. Minamiyama. 2008. Heat island miti-
gation using water retentive pavement sprinkled with reclaimed wastewater. Water science and
technology. 57(5): 763-771. Abstract available online at .
36 Yamagata H., M. Nasu, M. Yoshizawa, A. Miyamoto, and M. Minamiyama. 2008. Heat island miti-
gation using water retentive pavement sprinkled with reclaimed wastewater. Water science and
technology. 57(5): 763-771. Abstract available online at .
37 Pomerantz, M., H. Akbari, S.-C. Chang, R. Levinson and B. Pon. 2003. Examples of Cooler Reflec-
tive Streets for Urban Heat-Island Mitigation: Portland Cement Concrete and Chip Seals. Paper
LBNL-49283. Lawrence Berkeley National Laboratory, Berkeley, CA.
38 Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2008. Strategies for Design and Con-
struction of High-Reflectance Asphalt Pavements. Under review for the 2009 Transportation
Research Board Annual Meeting.
39 Rosenfeld, A.H., JJ. Romm, H. Akbari, and M. Pomerantz. 1998. "Cool Communities: Strategies
for Heat Islands Mitigation and Smog Reduction," Energy and Buildings, 28, pp. 51-62.
40 Pomerantz, M., B. Pon, H. Akbari, and S.-C. Chang. 2000. The Effect of Pavements' Temperatures
on Air Temperatures in Large Cities. Paper LBNL-43442. Lawrence Berkeley National Laboratory,
Berkeley, CA.
41 Akbari, H., and S. Menon. 2007. Global Cooling: Effect of Urban Albedo on Global Temperature.
Paper for the Proceedings of the International Seminar on Planetary Emergencies. Erice, Sicily.
42 U.S. EPA. 2003. Beating the Heat: Mitigating Thermal Impacts. Nonpoint Source News-Notes.
72:23-26.
43 James, W 2002. Green Roads: Research into Permeable Pavers. Stormwater. Retrieved
May 8, 2008 from .
44 U.S. EPA. Reducing Stormwater Costs through Low Impact Development (LID) Strategies and
Practices. EPA 841-F-07-006, December 2007. Retrieved April 2, 2008 from .
45 Booth, D. and J. Leavit. 1999. Field Evaluation of Permeable Pavement Systems for Improved
Stormwater Management. Journal of the American Planning Association. 65(3): 314-325.
46 James, W. 2002. Green Roads: Research into Permeable Pavers. Stormwater. Retrieved
May 8, 2008 from .
47 Pomerantz, M., H. Akbari, and J. Harvey. 2000. Durability and Visibility Benefits of Cooler Re-
flective Pavements. Paper LBNL-43443. Lawrence Berkeley National Laboratory, Berkeley, CA.
48 Bijen, Jan. 1996. Benefits of slag and fly ash. Construction and Building Materials 10.5: 309-314.
See also the Federal Highway Administration's summary of slag cement at .
49 U.S. Department of Transportation, Federal Highway Administration. European Road Lighting
Technologies. International Technology Exchange Program: September 2001. Retrieved June 16,
2008, from . See also: Interna-
tional Commission on Illumination. 2007. Road Transport Lighting for Developing Countries.
CIE 180:2007.
34 REDUCING URBAN HEAT ISLANDS - DRAFT
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50 Kinouchi, T., T. Yoshinaka, N. Fukae, and M. Kanda. 2004. Development of Cool Pavement
with Dark Colored High Albedo Coating. Paper for 5th Conference for the Urban Environment.
Vancouver, Canada. Retrieved November 15, 2007, from .
51 Glazier, G. and S. Samuels. 1991. Effects of Road Surface Texture on Traffic and Vehicle Noise.
Transportation Research Record. 1312: 141-144.
52 Pipien, G. 1995. Pervious Cement Concrete Wearing Course Offering Less than 75 dB(A) Noise
Level. Revue Generale des Routes et Aerodromes. 735: 33-36.
53 National Center of Excellence on SMART Innovations at Arizona State University. 2007.
Alternative Paving—Recycling Crumb Rubber. Case Study, 1(3).
54 U.S. Department of Transportation, Federal Highway Transportation Administration. 2005. Tech-
nical Advisory: Surface Texture for Asphalt and Concrete Pavements. Retrieved September 17,
2008, from . Michigan Depart-
ment of Environmental Quality. 1992. Porous Asphalt Pavement. Retrieved 16 Sep 2008 from
.
55 U.S. Department of Transportation, Federal Highway Administration. Stormwater Best Manage-
ment Practices in an Ultra-Urban Setting: Selection and Monitoring. Fact Sheet - Porous Pave-
ments. Retrieved April 2, 2008, from .
56 Figures are taken from multiples sources and express the maximum range of the values: 1)
Cambridge Systematics. 2005. Cool Pavement Draft Report. Prepared for U.S. EPA. 2) ASU's draft
of the Phoenix Energy and Climate Guidebook. 3) Center for Watershed Protection. 2007. Rede-
velopment Projects. New York State Stormwater Management Design Manual. Prepared for New
York State Department of Environmental Conservation. Retrieved June 13, 2008, from . 4) Bean, E.Z.,WF. Hunt, D.A. Bidelspach, and
J.T. Smith. 2004. Study on the Surface Infiltration Rate of Permeable Pavements. Prepared for
Interlocking Concrete Pavement Institute. 5) Interlocking Concrete Pavement Institute. 2008.
Permeable Interlocking Concrete Pavements: A Comparison Guide to Porous Asphalt and Pervi-
ous Concrete. 6) Pratt, CJ. 2004. Sustainable Drainage: A Review of Published Material on the
Performance of Various SUDS Components. Prepared for The Environment Agency. Retrieved
June 13, 2008, from . 7) NDS, Inc. Technical
Specifications for Grass Pavers. Retrieved June 13, 2008, from . 8) Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak.
2008. Strategies for Design and Construction of High-Reflectance Asphalt Pavements. Under
review for the 2009 Transportation Research Board Annual Meeting.
57 See the Building for Environmental and Economic Sustainability (BEES) software at
.
58 U.S. EPA. 2007. Reducing Stormwater Costs through Low Impact Development (LID) Strategies
and Practices. EPA 841-F-07-006. Retrieved April 2, 2008, from .
59 National Center of Excellence on SMART Innovations at Arizona State University
.
COOL PAVEMENTS - DRAFT 35
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60 The National Asphalt Pavement Association conducts training and professional development
(see ) and the National Ready Mixed Concrete Association has a research
lab near College Park, Maryland, and conducts training and professional development (see
for details). For the Interlocking Concrete Pavement Institute seminars, see
. See also recent sponsored research efforts, such as:
Kevern, J., V.R. Schaefer, and K. Wong. 2008. Temperature Behavior of a Pervious Concrete
System. Under review for the 2009 Transportation Research Board Annual Meeting.
Tran, N., B. Powell, H. Marks, R. West, and A. Kvasnak. 2008. Strategies for Design and Con-
struction of High-Reflectance Asphalt Pavements. Under review for the 2009 Transportation
Research Board Annual Meeting.
61 For the design guidelines, see .
62 City of Chicago. Chicago Green Alley Handbook. Retrieved May 15, 2008, from .
63 See:
Claudio, L. 2008. Synthetic Turf: Health Debate Takes Root. Environmental Health Perspec-
tives 116.3. Retrieved September 16, 2008, from .
Aubrey, A. 2008. High Temps On Turf Fields Spark Safety Concerns. NPR Morning Edi-
tion, 7 Aug. Retrieved September 16, 2008, from .
36 REDUCING URBAN HEAT ISLANDS - DRAFT
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