United States EPA-600 /R-93-218
Environmental Protection
Agencv November 1993
<&EF¥V Research and
Development
CHARACTERISTICS
OF SCHOOL BUILDINGS
IN THE II, S.
Prepared for
Office of Radiation and Indoor Air
I I
Prepared by
Air and Energy Engineering Research
Laboratory
Research Triangle Park NC 27711
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EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
reflect the views and policy of the Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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urn mum in
PB94-121704
EPA-600 ?R-93~2l8
November 1993
CHARACTERISTICS OF SCHOOL BUILDINGS
IN THE U.S.
Prepared by:
Harry I. Chmelynski
S. Cohen & Associates, Inc.
1355 Beverly Road
McLean, VA 22101
EPA Contract No. 68-D0-0097
Work Assignment No. 3-2
Project Officer: Kelly W. Leovic
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Prepared for:
U.S. Environmental Protection Agency
Office of Research & Development
Washington, D. C. 20460
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ABSTRACT
A subsample of 100 schools from the Environmental Protection Agency's (EPA's)
National School Radon Survey were visited to obtain information on building structure,
location of utility lines, and the type of heating, ventilating, and air-conditioning system.
Information from each school was entered into a database to determine the relative
proportions of physical characteristics of the U.S. school building population. Results
indicate that most school structures are of slab-on-grade construction, gravel was used as
subslab fill material in approximately half of the structures, approximately 80 percent of the
schools have wither central HVAC or unit ventilators capable of delivering conditional
outdoor air to the classrooms, and almost one quarter of the schools have subslab footings
extending both beneath the classroom walls and along the corridors, thus complicating the
installation of effective subslab depressurization systems. The results obtained in this study
will be used by EPA to guide future mitigation research in schools.
This report has been reviewed in accordance with EPA's peer and administrative
review policies and approved for presentation and publication.
ii
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TABLE OF CONTENTS
ABSTRACT ii
1. INTRODUCTION 1
2. SAMPLE SELECTION PROCEDURES 2
3. DESCRIPTION OF PROFILE SHEETS AND DATA ENTRY 6
4. RESULTS OF SCHOOL BUILDING PROFILE . 11
4.1 Structural Characteristics 11
4.2 HVAC System Characteristics 18
5. DETAILED SCHOOL PROFILE DATA TABLES 25
6. STATISTICAL LIMITATIONS 37
7. CONCLUSIONS 41
REFERENCES 42
APPENDIX A. SCHOOL BUILDING PROFILE FORMS USED IN STUDY . A-l
iii
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TABLES
Table
1. ASSIGNMENT OF RADON POTENTIAL CATEGORIES FOR
RESIDENTIAL SURVEY 4
2. LOCATION AND CHARACTERISTICS OF PARTICIPATING SCHOOLS
IN THE SCHOOL PROFILE SAMPLE 5
3. SCHOOL PROFILE STUDY DATABASE VARIABLE LIST 8
4. DISTRIBUTION OF TYPES OF HVAC SYSTEMS BY SCHOOL 23
5. TYPE OF HVAC EQUIPMENT BY NUMBER OF SCHOOLS,
NUMBER OF STRUCTURES, AND STRUCTURAL AREA 24
6. DETAILED RESPONSES TO SELECTED ITEMS 30
7. APPROXIMATE 95% CONFIDENCE INTERVALS FOR ESTIMATE ...... 40
8. REGIONS OF SIGNIFICANT DIFFERENCE BETWEEN TWO
POPULATION PERCENTAGE ESTIMATES, A AND B 40
iv
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FIGURES
Figure
1. DISTRIBUTION OF STRUCTURES BY YEAR CONSTRUCTED 12
2. DISTRIBUTION OF GENERAL BUILDING DESIGNS 14
3. DISTRIBUTION OF STRUCTURES BY AREA 15
4. DISTRIBUTION OF NUMBER OF FLOORS 16
5. DISTRIBUTION OF STRUCTURE TYPES 17
6. DISTRIBUTION OF SUBSLAB MATERIALS 19
7. DISTRIBUTION OF SUBSLAB WALL LOCATIONS 20
8. DISTRIBUTION OF UTILITY LINE LOCATIONS 21
9. DISTRIBUTION OF AIR SUPPLY DUCT LOCATIONS 26
10. DISTRIBUTION OF AIR RETURN LOCATIONS 27
11. DISTRIBUTION OF TYPICAL LOCATIONS OF UNIT
VENTILATORS AND FAN COILS 28
v
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1. INTRODUCTION
The Environmental Protection Agency's (EPA's) Radon Mitigation Branch (RMB)
within the Office of Research and Development conducts research and development on
reduction of indoor radon levels. To help guide future radon research in schools and
better focus technical guidance documents, RMB conducted a literature search to find
information that quantifies the physical characteristics of U.S. school buildings.
Information on school characteristics specific to radon mitigation research in schools was
not found in any existing reports or databases. In fact, according to a 1989 publication by
the Education Writers Association (1), "Nationally, not even a marginally adequate data
base about school facilities exists.... Several national groups have conducted surveys of
school facilities, but these tend to be either outdated or incomplete." A questionnaire on
school building characteristics was included in the National School Radon Survey (NSRS)
conducted by the EPA Office of Radiation and Indoor Air (ORIA). The questionnaires
were completed by designated school contact personnel while radon tests were conducted.
In many cases, the school radon contacts were unable to provide complete information on
the building characteristics addressed in the NSRS. As a result, RMS chose to collect
more detailed structural information through on-site inspection of a nationally
representative sub-sample of 100 of the NSRS schools tested by ORIA. To record the
necessary information, a building characteristic profile sheet was completed for each of
the sub-sample schools by RMB staff engineers and selected contractors during 1991 and
1992.
This report discusses the random sample selection procedures, describes the
information collected on the building characteristic profile sheets, summarizes some of the
results recorded on the school profile database produced by this project, compares the
results with those observed in RMB's research schools, and presents the statistical
limitations of this study.
1
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2. SAMPLE SELECTION PROCEDURES
The NSRS consists of two independent samples: (1) a large sample of
approximately 1,000 schools where all ground-contact rooms were measured with charcoal
canisters, and (2) a smaller sample of 101 schools where all occupied rooms were
measured with both alpha track detectors (ATDs) and charcoal canisters. This smaller
sample was selected independently of the larger sample. The schools were drawn
randomly from lists of schools in 25 geographical areas called Primary Sampling Units
(PSUs). These 25 PSUs were randomly selected for the NSRS from the 125 PSUs used
previously by EPA for the National Residential Radon Survey. ORIA's use of these
residential PSUs in selection of schools for the NSRS is intended to permit comparison of
residential and school building radon concentrations in these PSUs.
The 125 PSUs used for the Residential Survey were selected from a list of counties
or county-equivalents covering the entire U, S., except for portions of Alaska and all
territories and possessions. This list was partitioned in 22 strata, developed to guarantee
proportioned sample sizes in each of the 10 EPA regions. Within each region, counties
were assigned to one of three radon potential categories: High, Medium, or Low. The
assignment of states and substate areas to radon potential categories is summarized for
each region in Table 1. The number of residential PSUs selected for the Residential
Survey is shown in the far right column.
Within each of the 25 NSRS PSUs selected randomly from Table 1, approximately
5 public schools were randomly selected for inclusion in the NSRS ATD/canister sample,
resulting in a total of 125 schools. This small sample of schools represents a random
sample of the 78,715 U. S. public school population in 1988 (2).
For the NSRS, radon was measured (using both ATDs and charcoal canisters) in
101 of the 125 schools in the sample. The remaining schools either declined to participate
2
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or were unable to decide to participate within the time frame allotted for placement of the
ATDs, One of the 101 schools did not participate in the building characteristic profile
described here, resulting in a sample of 100 schools for our study. The locations of the
100 participating schools are shown in Table 2.
3
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TABLE 1. ASSIGNMENT OF RADON POTENTIAL CATEGORIES
FOR RESIDENTIAL SURVEY
EPA
Region
Radon
Potential
Category
State/Substate Area
No. of
PSUs
Selected
1
High
Medium
Low
ME, NH, VT
MA, CT, RI
None
3
5
0
2
High
Medium
Low
Northern NJ
NY
Southern NJ
4
8
2
3
High
Medium
Low
PA, Western MD, WV, Western VA
None
DE, Central and Eastern VA, Eastern
MD, DC
15
0
2
4
High
Medium
Low
Western NC, Western SC, Northern GA,
Northern AL, Eastern TN
KY, Western and Central TN
Central and Eastern NC, Eastern SC,
Southern GA, Southern AL, MS, FL
7
3
7
5
High
Medium
Low
MN, WI, IL, IN, OH
None
MI
30
0
2
6
High
Medium
Low
NM
OK, Western and Central TX, Northern
AR
LA, Southern AR, Southeastern TX
2
5
3
7
High
Medium
Low
NE, IA
KS, MO
None
4
3
0
8
High
Medium
Low
MT, WY, UT, CO, ND, SD
None
None
6
0
0
9
High
Medium
Low
NV
None
CA, AZ, HI
2
0
8
10
High
Medium
Low
AK, ID
None
WA, OR
2
0
2
Total
125
4
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TABLE 2. LOCATION AND CHARACTERISTICS OF PARTICIPATING SCHOOLS
IN THE SCHOOL PROFILE SAMPLE
EPA Region
State
No. of
Schools
Type of Schools"
1
Massachusetts
3
K-6, K-6, K-6
2
New Jersey
New York
5
7
K-6, 7-12, K-6, K-6, K-8
7-9, K-6, K-6, P-3, K-6, K-6,
K-6
3
Virginia
West Virginia
5
5
6-8, 6-8, K-6, K-6, K-6
K-6, K-6, 7-12, K-6, 7-12
4
Mississippi
Tennessee
7
5
6-8, P-K, 10-12, 6-8,
K-6, K-6, K-6
6-8, K-8, K-6, K-6, SP-ED
5
Illinois
Ohio
4
4
K-8, K-8, K-6, 9-12
SP-ED, 6-8, 7-9, K-6
6
New Mexico
Oklahoma
Texas
4
5
11
K-6, K-6, K-6, 6-8
K-6, 7-12, K-6, 6-8, 9-12
9-12, K-6, 6-8, K-6, K-6, 6-8,
K-6, K-6, K-8, 9-12, K-6
7
Kansas
Nebraska
5
4
9-12, 7-12, K-6, 7-12, K-6
7-12, 6-8, K-6, K-6
8
Utah
5
K-6, K-6, 6-8, K-6, 9-12
9
Arizona
California
4
13
9-12, K-6, K-6, 6-8
K-6, K-6, K-6, 7-9, K-6, K-6,
P-K, K-6, 6-8, K-6, 9-12, K-6,
K-6
10
Washington
4
K-6, K-6, K-6, 6-8
Total
100
* K = Kindergarten
P = Primary
SP-ED = Special Education
5
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3. DESCRIPTION OF PROFILE SHEETS AND DATA ENTRY
A three-page profile sheet was developed for this project for on-site
characterization of the structure, utility penetrations, types of heating, ventilating, and air-
conditioning (HVAC) equipment, and other building features pertinent to radon
diagnostics and mitigation. Because many schools have several contiguous structures
often constructed at different times and each with its own unique characteristics, the
profile sheet was completed separately for each structure. In a few cases, where the
structures are not contiguous but are campus-style school complexes, profile sheets were
completed for each distinct structure in the school, unless all were of the same vintage and
construction type. A listing of the variables contained on the school profile sheets is
included as Table 3. A copy of the school profile sheet is included in Appendix A. A
second copy of the profile sheet annotated with the variable names used in the database
files is also included in Appendix A to facilitate identification of the proper variable name
for each item.
Where available, building plans were examined to determine structure and HVAC
system information that is not always available through on-site observation. Following
inspection of the building plans, the school was visited to verify information on the plans
and to collect any additional profile sheet information that was not on the plans.
Complete sets of construction plans were available for only 40% of the structures. When
the plans were not available, the profile sheet was completed based on discussions with
school personnel and the judgement of the researchers. However, some entries were left
blank if it was impossible to judge (e.g. the type of sub-slab fill material).
Distribution of the profile sheet responses into the categories used for data analysis
required reducing detailed responses to shorter, categorical responses for many of the
profile sheet questions. The original responses for each school were entered into a dBase
IV file along with the shorter categorical responses used for the statistical analyses.
6
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Because many of the schools have a number of distinct structures, it is difficult to
generally describe the entire school for a given characteristic, except rarely when all
structures have the same characteristic. For example, in a school with two additions to
the original building, two of the three buildings might be slab-on-grade and the third
building a basement. Each of the individual buildings would be treated separately on the
profile sheet. Therefore, no attempt is made to calculate percentage distributions based on
the number of schools in each category. Instead, distributions are calculated both in terms
of the number of sample structures and in terms of structure area.
The main results of the study are discussed in the following section of the report.
Detailed listings of survey results for selected items of the profile sheet are then
presented. Statistical limitations of the study are contained in the final section of the
report.
7
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TABLE 3. SCHOOL PROFILE STUDY DATABASE VARIABLE LIST
PART 1.
BASIC SCHOOL-LEVEL INFORMATION
SCHCODE
1)
PROFILE STUDY SCHOOL CODE
SCHNAME
2)
SCHOOL NAME
DISTRT
3)
SCHOOL DISTRICT
STREET
4)
STREET
CITY
5)
CITY
STATE
6)
STATE
ZIP
7)
ZIP
NSRSCOD
8)
NSRS SCHOOL CODE
COCOUNT
9)
COUNTY
CODATE
10)
DATE PROFILE COMPLETED
CONAME
11)
SCHOOL CONTACT PERSON
COPOST
12)
POSITION
COPHONE
13)
PHONE
SANAME
14)
NAME OF PERSON COMPLETING PROFILE SHEET
SAPOST
15)
POSITION
SAPHONE
16)
PHONE
PART 2. QUESTIONNAIRE ITEMS WITH DETAIL BY STRUCTURE (See note at end of table.)
A. STRUCTURAL
CHARACTERISTICS OF THE SCHOOL
OSYRBD
1)
YEAR CONSTRUCTED
OSSUB
2)
SUBSTRUCTURE TYPE: BSMT/SLAB/CRAWL
OSLWD
3)
IF CRAWL SPACE, IS FIRST FLOOR: SLAB/HOOD
OSTSFT
4)
TOTAL SQ. FT. OF BUILDING
OSSQGD
5)
SQ. FT. OF GROUND CONTACT
OSFFCL
6)
# 1st FL CLASSROOMS
OSFLCLO
7)
# OTHER 1st FL OCCUPIED ROOMS
OSNUMFL
8)
• OF FLOORS (INCL. BSMT)
OSBDOC
9)
APPROX # OF BUILDING OCCUPANTS
OSGDSQ
10)
DESCRIBE GENERAL BUILDING DESIGN: CONVENTIONAL/OPEN CLASSROOMS/OTHER
OSA3LAB
11)
ARE SUBSLAB HALLS BLOCK OR POURED: BLOCK/POURED
OSSWSP
12)
DO SUBSLAB HALLS SEPARATE EACH CLASSROOM: YES/NO/UNK
OSSLW
13)
ARE SUBSLAB HALLS UNDER THE CORRIDOR HALLS: YES/NO/UNK
OSSLOP
14)
SUBSLAB MATERIAL ON PLANS: NA/GRAVEL/SAND/EARTH/OTHER
OSSLVER
15)
SUBSLAB MATERIAL VERIFIED: NA/GRAVEL/SAND/EARTH/OTHER
OSLUTIL
16)
LOCATION(S) OF UTILITY LINES: TUNNEL/SUBSLAB(NO TUNNEL)/OVERHEAD/BSMT/CRAHL/OTHER
OSTUNNEL
17)
IF TUNNEL: WIDTH t HEIGHT
OSTUNLT
18)
TUNNEL LOCATION: OUTSIDE WALL/CORRIDOR/OTHER
OSTUNHL
19)
TUNNEL WALL: POURED/BLOCK
(Continued)
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TABLE 3. (Continued)
OSTUFL
20) TUNNEL FLOOR: DIRT/SLAB
B. COMPLETE
IF
ANY PART OF THE BUILDING HAS A CENTRAL HVAC SYSTEM
OCAHDL
1) * OF AIR HANDLING UNITS
OCSCL
2) SERVICES CLASSROOMS: YES/NO
OCSMUL
3) SERVICES MULTIPURPOSE: YES/NO
OCSOFF
4) SERVICES OFFICES: YES/NO
OCSROT
5) SERVICES OTHER AREA: YES/NO
OCLABD
6) LOCATION(S) OF AIR HANDLER(S): MECH ROOM/DROPPED CEILING/ROOF/BSMT/CRAWL/OTHER
OCSFRT
7) SEPARATE RETURN FAN: YES/NO
OCMIOUT
8) MINIMUM « OUTDOOR AIR
OCMAOUT
9) MAXIMUM % OUTDOOR AIR
OCADCT
10) AIR SUPPLY DUCTS LOCATION: CEILING/SUBSLAB(NO TUNNEL)/TUNNEL/BSMT/CRAWL/OTHER
OCLART
11) LOCATION OF AIR RETURN: CEILING/SUBSLAB(NO TUNNEL)/HALL/TUNNEL/BSMT/CRAHL/OTHER
OCARDUC
12) IS AIR RETURN DUCTED? YES/NO
OCSPRF
13) DOES SYSTEM HAVE A PRESSURE RELIEF? YES/NO
OCBDAHD
14) BRIEFLY DESCRIBE ANY OTHER DETAILS ABOUT THE AIR HANDLING SYSTEM
C. COMPLETE
IF
ANY PART OF THE BUILDING HAS UNIT VENTILATORS/FAN COILS
OUSCL
1) SERVICES CLASSROOMS: YES/NO
OUSMUL
2) SERVICES MULTIPURPOSE: YES/NO
OUSOFF
3) SERVICES OFFICES: YES/NO
OUSOTH
4) SERVICES OTHER AREA: YES/NO
OUTLUN
5) TYPICAL LOCATION OF UNITS: OUTSIDE HALL/INSIDE HALL/CEILING/TUNNEL/CRAHL/OTHER
OUMIOUT
6) MINIMUM % OUTDOOR AIR
OUMROUT
7) MAXIMUM % OUTDOOR AIR
D. COMPLETE
IF
ANY PART OF THE BUILDING HAS RADIANT HEAT
ORRHT
1) TYPE: BASEBOARD/RADIATORS/INTRA-SLAB PIPING/OTHER
ORSCL
2) SERVICES CLASSROOMS: YES/NO
OR3MUL
3) SERVICES MULTIPURPOSE: YES/NO
ORSOFF
4) SERVICES OFFICES: YES/NO
ORSOTH
5) SERVICES OTHER AREAS: YES/NO
E. BUILDING
EXHAUSTS (IF KNOWN SPECIFY TOTAL CFM FOR FANS)
OECLAS
1) CLASSROOMS: NONE/GRAVITY/FAN
OECORR
2) CORRIDOR: NONE/GRAVITY/FAN
OEMUL
3) MULTIPURPOSE: NONE/GRAVITY/FAN
OEKIT
4) KITCHEN: NONE/GRAVITY/FAN
OECAF
5) CAFETERIA: NONE/GRAVITY/FAN
(Continued)
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TABLE 3. (Continued)
OERES 6) RESTROGMS: NONE/GRAVITY/FAN
OELAB 7) LABS: NONE/GRAVITY/FAN
OEOTH 8) OTHER: SPECIFY/GRAVITY/FAN
F. GENERAL QUESTIONS ABOUT THE BUILDING
OGWIN 1) DOES BUILDING HAVE WINDOW AC UNITS? YES/NO/PARTIALLY
OGHVAC 2) HVAC SYSTEM CONTROL ENERGY: MGT/ROOM CONTROLS/OTHER/ELECTRONIC OR PNEUMATIC
OGPLAN 3) WERE BUILDING CONSTRUCTION PLANS AVAILABLE TO COMPLETE PROFILE SHEET? YES/NO
OGENER 4) HAVE "ENERGY CONSERVATION" MEASURES BEEN MADE? SPECIFY
OGWATER 5) IS THE BUILDING WATER SUPPLY: WELL/PUBLIC
G. ADDITIONAL COMMENTS ABOUT THE BUILDING
ADDCOM ADDITIONAL COMMENTS
For Part 2 variables in sections A through F of the profile sheet:
a. The first letter of variable name denotes the structure:
O — Original Structure; S «* Second Structure; T « Third Structure; F "¦ Fourth Structure.
b. The second letter denotes the portion of the questionnaire, underlined in the title of each part
S ™ Structural; C — Central HVAC; U = Unit ventilators; R = Radiant heat; E — Exhausts;
G ¦ General building information.
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4. RESULTS OF SCHOOL BUILDING PROFILE
The sample of schools selected for this profile are nationally representative.
However, due to the small sample size, extrapolation of estimates based on the sample
statistics to the national population of schools involves some degree of sampling error.
The standard deviations due to sampling errors for reported percentages range from 2.5 to
5.5 percentage points for population estimates of 5% and 50%, respectively. The 95%
confidence intervals for these estimated population percentages thus range from +1-5%
points to +/- 11 %. Due to the large confidence intervals, small differences (less than 10
percentage points) in reported population percentages may not be significant at the
commonly used 95% level of significance. These statistical limitations are discussed in
detail in the next section.
The results presented in this report are the actual proportions of the school
characteristics for the nationally representative sample of 100 schools. For most of the
characteristics, the results are presented both in terms of the percentage of the number of
structures and in terms of area. Where information on a given characteristic was
available only for a fraction of the 100 schools, the percentage figures are calculated as a
percent of the responses. The discussion is grouped into structural characteristics and
HVAC system characteristics.
Where available, comparisons from RMB's 47 research schools are presented.
Although the RMB research schools do represent a biased sample in that they are located
in radon prone areas, comparisons of these two samples are helpful in observing trends.
4.1 Structural Characteristics
The schools used for this study typically contain two or three unique structures.
The distribution of structures by year of construction is shown in Figure 1. Nearly half
11
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YEAR CONSTRUCTED
Interval Count Percent
1900-09
1
0. 4%
1910-19
5
2 . 1%
1920-29
9
3 . 7%
19 3 0 — 3 9
32
13.3%
1940-49
8
3,3%
1950-59
56
23 . 2%
1960-69
56
23.2%
1970-79
46
19.1%
1980-89
28
11.6%
Note: Unknown years are not included in analysis.
Figure 1. Distribution of Structures by Year Constructed
12
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of the school structures for which the year of construction could be determined were built
between 1950 and 1969, with about 20% built before and 30% built after. This
distribution is consistent with the survey conducted by the Education Writers Association
that found that more than 50% of the schools in use today were constructed during the
1950s and 1960s (1). By comparison, 46% of the schools in our profile were constructed
during this period.
As shown in Figure 2, over 85% of these school structures have a conventional
classroom design, with a corridor that has classrooms on either side. Approximately 7%
have a campus-type design, with a number of individual buildings.
The distribution of school structures in terms of total area is shown in Figure 3.
Approximately 45% of these structures are less than 10,000 square feet*, probably because
many of the older buildings have had additions to the original building. Approximately
one out of eight structures (12.3%) have more than 50,000 square feet, ranging to over
600,000 square feet in one school structure.
The distribution of the number of floors in these structures is shown in Figure 4,
Over two-thirds of the structures have only one floor, while over 20% have two floors.
For radon reduction research, the substructure of a school is of interest. As seen
in Figure 5, slab-on-grade substructures are most prevalent, accounting for 72.6% by
structure and 51.6% by area. Crawl spaces and basements account for 10.3% and 6.7%
of the structures, respectively. These results are consistent with RMB's research schools
which are 70% slab-on-grade (3). Figure 5 also shows that about 10% are combination
substructures, such as slab-on-grade and crawl space in the same structure. Comparing
the percentage by number of structures with the percentage by area, there is a tendency
for a crawl space to be constructed in conjunction with either a slab-on-grade or a
* 1 square foot = 0.093 square meter
13
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GENERAL BUILDING DESIGN
Type
Count
Percent Total Sq.Ft
Sq.Ft %
conv
182
85.4%
5585780
91.2%
open-clsrm
1
0.5%
13072
0.2%
modular
4
1.9%
28596
0.5%
campus
16
7.5%
325497
5.3%
sngl-purp
2
0.9%
5400
0.1%
podium
3
1.4%
137250
2.2%
clsrnt
3
1.4%
23900
0.4%
office
1
0.5%
450
0.0%
link
1
0. 5%
5906
0.1%
Note: Unknown designs are not included in analysis.
(conv = conventional, clsrnt = classroom, sngl-purp
purpose)
Pereeftl by type
single
100%
90*
&o%
70%
SQ%
40%
00%
20%
10%
0%
100%
SO%
80%
70%
60%
50%
65.4%
7.5%
Q£%
14%
14%
ei*»v operr-cJvrm modular campo« vugf-pup pe&mn
Percent In S^JFt
cbrrr
0.5%
5
office
0.5%
"
40%
30%
20%
tax
5.3%
0-2%
1
05%
—!
0.1%
!
2-2%
conv opotvebem m«Mluhr caynrtpu* mt&rpmp pedum
0.4%
t"1
ctom
ao%
affice
0,1%
-•—I—
Mi
Figure 2. Distribution of General Building Designs
(top, % by number of structures; bottom, % by area)
14
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TOTAL SQUARE FEET OF BUILDING
1000 Sq. Ft.
Count
Percent
0-10
99
45.0%
10-20
45
20. 5%
20-30
20
9.1%
30-40
14
6.4%
40-50
15
6.8%
50-60
8
3 . 6%
60-70
7
3 . 2%
70-80
1
0.5%
80-90
2
0.9%
90-100
2
0.9%
100-200
4
1.8%
200-600
2
0.9%
600 +
1
0.5%
Note: Unknown square feet are not included in analysis.
AREA. 1000 aq ft
Figure 3. Distribution of Structures by Area
15
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NUMBER OF FLOORS (INCLUDING BASEMENT)
Floor Count Percent Total Sq.Ft Sq.Ft %
1
14 3
68.8%
2320781
48.2%
2
45
21.6%
1473620
30.6%
3
16
7 . 7%
394890
8 . 2%
4
2
1.0%
499200
10. 4%
5
2
1.0%
130800
2.7%
Note: Unknown number of floors not included in analysis.
100%
BOX
BOX
70%
eo%
50%
40%
3Q%
20%
lO%
o%
100%
90%
©0%
70%
60%
50%
40%
30%
20%
10%
0%
Percent by rwrnbm of floora
68.3%
10%
LO%
Pwwmt b S«|FI
Figure 4. Distribution of Number of Floors
(top, % by number of structures; bottom, % by area)
16
-------
SUBSTRUCTURE TYPE
Type
Count Percent Total Sq.Ft
Sq.Ft %
slab
162
72.6%
3174758
51.6%
crawl
23
10, 3%
269551
4.4%
bsmt
15
6.7%
412568
6.7%
slab/crawl
13
5.8%
1268594
20.6%
bsmt/crawl
6
2 .7%
860692
14 . 0%
slab/piers
1
0.4%
52000
0.8%
slab/bsmt
1
0.4%
46300
0.8%
bsmt/slab
2
0.9%
63702
1.0%
Notes: Unknown
types are not
included
in analys
is.
(bsmt = basement)
SUBSTRUCTURE TYPE
Figure 5. Distribution of Structure Types
(top, % by number of structures; bottom, % by area)
17
-------
basement. These two categories account for approximately %% of the number of
structures, but almost 35% of the area.
Location of subslab footings and the presence of subslab aggregate are very
important in designing a subslab depressurization (SSD) system for radon mitigation. As
seen in Figure 6, gravel (which improves the SSD system effectiveness) was indicated on
the plans for about 45 % of the structures with information available. Many of the
structures did not indicate the subslab material on the plans or the plans were not
available. The remaining structures indicated fine-grained material (such as sand or earth)
under the slab. The location and number of subslab footings is also important in
determining subslab barriers for SSD systems. Figure 7 shows that over half of the
structures have no internal footings (typically post-and- beam construction, facilitating
SSD). However, 24% have footings between classrooms gnd along the corridor,
complicating a SSD system installation.
Location of utility lines is also important since utility lines located under the slab
or in a subslab tunnel can serve as a major radon entry route. The data in Figure 8 show
that about a third of the structures (and area) have overhead utility lines. However, a
third (a quarter by area) also have utility lines in either a tunnel or subslab. Utility
tunnels were present in one-third of RMB's research schools (3), and tended to be more
prevalent in certain school districts than others.
4,2 HVAC System Characteristics
Research on the use of HVAC systems for radon reduction includes a large portion
of both RMB's and ORIA's radon research in schools. As a result, it is important to
quantify the various types of HVAC systems found in existing U.S. school buildings.
18
-------
SUBSLAB MATERIAL ON PLANS
Type
Count
Percent Total Sq.Ft
Sq.Ft %
sand
12
8.1%
158251
4.3%
earth
45
30.2%
796683
21.5%
gravel
66
44 . 3%
2156939
58 .2%
grvl-sand
8
5,4%
49631
1.3%
dirt-fil
5
3.4%
102004
2.8%
grvl-fil
4
2.7%
245718
6.6%
sndy-soi1
5
3.4%
104500
2.8%
cinder-fil
1
0.7%
43581
1.2%
pea grvl
1
0.7%
45700
1.2%
fil-sand
2
1.3%
6200
0.2%
Notes: Unknown types are not included in analysis,
(grvl = gravel, fil - fill, sndy = sandy)
100
90
ao
TO
60
50
40
30
20
10
O
too
90 -
80 -
TO -
60 -
50 -
40 -
30 -
20 -
10 -
0 J
Figure 6. Distribution of Subslab Materials
{top, % by number of structures; bottom, % by area)
19
sa.2%
•and eatlh g«a«l .ndy-.oJ cMor-H pea grvl H-sand
SUBSLAB MATERIAL
-------
LOCATION OF SUBSLAB WALL
Location
Count
Percent
clsrin + corr
i TO
corridor
none
all structures
56
9
42
126
233
24 . 0%
3 . 9%
18 . 0%
54 . 1%
Notes; Unknown locations are not.included in analysis,
(clsrm = classroom, corr = corridor)
<
O
o
o*
O
a.
CisffTi ~ COff
cfatrm corridor
SUBSLAB WA11 LOCATION
Figure 7. Distribution of Subslab Wall Locations
20
-------
LOCATION OF UTILITY LINES
Location
Count
Percent Total Sq.Ft
Sq.Ft %
crawl
12
5.7%
221293
3.7%
ovrhd
81
38.2%
1829219
30.3%
bsmt
8
3.8%
6B4390
11.3%
subs lab
52
24.5%
987682
16.4%
ceiling
A
1.9%
54513
0.9%
tunnel
25
11.8%
514330
8.5%
mech rm
5
2.4%
1272000
21.1%
os wall
2
0.9%
62000
1.0%
slb-cr1
1
0.5%
12000
0.2%
ovhd-cr1
2
0.9%
87581
1.5%
mech rm
1
0.5%
46300
0.8%
buried
19
9.0%
268617
4.4%
Notes; Unknown locations are not included in analysis.
(ovrhd = overhead, bsmt - basement, mech rm = mechanical room, crl
space, os wall = outside wall, slb-crl = combination of subslab and
crawl space, ovh~-£f"l = combination of overhead and crawl space)
100
90
BO
TO
60
SO
40
30
20
10
0
100
90
B0
70
60
SO
40
30
20
10
0
aa 2%
24.5%
ILS%
9.0%
5.7% .
L9% 2.4% 0.9% g tunrudl mech rm m wal slab erwdvrhd diviil mech ritouried
UimiTY LWE LOCATION
Figure 8. Distribution of Utility Line Locations
(top, % by number of structures; bottom, % by area)
21
-------
The distribution of types of HVAC equipment used in the classrooms in the sample
schools is shown in Table 4. The categories in this table are mutually exclusive. Over
one-third of all schools have a single type of equipment in all classrooms. Most often,
this is a central HVAC system. Radiant heat only (7%) or fan coils only (10%) or both
(4%) are present in the classrooms of 21 % of the surveyed schools, indicating that die
other 79% of schools have either central HVAC or unit ventilators capable of delivering
conditioned outdoor air to the classrooms. The remainder of the schools have various
combinations of central HVAC, unit ventilators (UVs), Ian coils (FCs), and radiant heat
(RAD). In some schools, other radiant heat systems have been abandoned (RAD-NTJ) for
heating, but their presence must be considered from a radon perspective.
In Table 5, the distribution of the four basic types of HVAC systems used in the
sample schools is tabulated by number of schools, count of structures, and structural area.
These categories are not mutually exclusive, due to the occurrence of combinations of
HVAC systems within a school structure. Central HVAC is the predominant system,
occurring in 71% of the schools and 52% of the structures, either alone or in combination
with other equipment. Radiant heat, including abandoned systems, is the second most
common system, when counted by schools (56%) or by structures (44%). In terms of
structural area, radiant heat systems are as prevalent as central HVAC systems. Unit
ventilators and fen coil systems (with no ventilation capability) are less common than
central HVAC and radiant heat systems, each occurring in approximately 30% of all
structures and 40% of all schools.
Considering the combinations of HVAC systems within a given school, 45% of
RMB's research schools have central air handling systems; 43% have unit ventilators;
30% have radiant heat; and 11 % have fen-coil units (3). Only radiant heat (11 %) or only
fan-coil units (6%) are present in 17% of the research schools, indicating that the other
83 % have some type of installed HVAC system that can deliver conditioned outdoor air.
22
-------
TABLE 4. DISTRIBUTION OF TYPES OF CLASSROOM HVAC SYSTEMS BY
SCHOOL
Type of System: Mo. Schools
Central HVAC only (SVAC) 12
Unit ventilators only (UV) 9
Fan coils only (FC) 10
Radiant heat only (RAD) 7
UV/RAD-NU* 2
HVAC/UV/RAD-NU 1
SVAC/UV/FC/RAD 4
HVAC/UV/RAD 8
HV&C/FC 5
ntfaf* /pan i s.
mm ~ JEVJTULr JU "¦
HVAC/FC/RAD 4
HVAC/UV 8
IVAC/FC/RAD-HO 2
UV/FC 1
FC/RAD 4
UV/RAD 9
Total Number of Schools 10 CJ
* KU = not used
23
-------
TABLE 5.
TYPE OF HVAC EQUIPMENT BY NUMBER OF SCHOOLS, NUMBER
OF STRUCTURES, AND STRUCTURAL AREA
Type of System
Central HVAC
Radiant heat
Unit ventilators
Fan coils
Number
of Schools
73
57
43
38
Percent
of Schools
—7T73
56.4
42.6
37.6
Number of
Structures
ISS
103
70
61
Percent of
Structures
5T75
44.2
30.0
26.2
Area
(sguare feet)
—^<543(504
3659727
1734323
1883987
Percent
of Area
57TT-
67.4
31.9
34.7
Note: * Unknown types are not included in analysis.
" Percents add to more than 100% due to the possibility
or more than one system for a structure.
CO
-------
The school profile sheets contain more detailed information concerning the location of
air supply and return ducts, the location of unit ventilators and fan coils, and the types of
radiant heating systems. As shown in Figures 9 and 10, the most common location of air
supply and return ducts in structures with central HVAC systems is in the ceiling or suspended
overhead. However, ducts located in corridors, basements, or tunnels occur more often in
larger structures.
Figure 11 shows that the most common location of unit ventilators and fen coils is along
the outside wall. Radiators are used in most structures, but baseboard systems amount for
more structural area.
5. DETAILED SCHOOL PROFILE DATA TABLES
The dBase IV data files were create by SC&A as a mean to put the profile sheets of
structural characteristics of the 100 schools into electronic form for data retrieval and analysis.
There were two versions of dBase file; SCHLG.DBF and SCHST.DBF.
SCHLG.DBF
The data was entered into this dBase file as it appeared on the profile sheets. The file
contained of about 280 data fields. Each field name is an abbreviation of the related question
on the school profile sheets. The first letter of each field was used to distinguish original and
additional structures. For example, the original structure of each school has the data fields
staring with the letter O. Likewise the letter S is for the second structure, T for the third, and
F for the fourth, if needed. In addition, several fields contain data related to school name,
school district, street, city, state, ZIP code, NSRS code, county, date of contact, name of
contacted person, position of contacted person, phone number of contacted person, name of
contact person, position of contact person and phone number of contact person. Also, a
comment field was used to store comments for each school. The variable names used
25
-------
AIR SUPPLY DUCTS LOCATION
Location
Count
Percent Total Sq-Ft
Sq.Ft %
crawl
2
1.7%
24800
0.5%
subslab
5
4.3%
61227
1.3%
overhd
24
20.7%
490462
10.5%
tunnel
2
1.7%
287995
6.2%
corr
2
1.7%
971660
20.9%
clsm
5
4 . 3%
51528
1.1%
bsmt
6
5 . 2%
671628
14.4%
ceiling
67
57 .8%
2005678
43.0%.
os wall
2
1-7%
59000
1.3%
multi
1
0.9%
35400
0.8%
Note: Unknown locations are not included in analysis.
(overhd = overhead, corr = corridor, clsm = classroom,
bsmt = basement, os wall = outside wall, multi = multiple
locations)
Percent by typo
Figure 9. Distribution of Air Supply Duct Locations
(top, % by number of structures; bottom, % by area)
26
-------
location of air return
Locat ion
crawl
subs lab
overhd
tunnel
corr
floor
bsrat
ceiling
os wall
mix
Count
Percent
Total Sq.Ft
Sq. Ft %
I
1.0%
5600
0.1%
9
8 . 8%
247980
5.5%
10
9,8%
124700
2.8%
3
2.9%
1426000
31,7%
7
6.9%
227516
5.1%
4
3 . 9%
115608
2.6%
5
4.9%
222428
4.9%
57
55.9%
1933411
42.9%
4
3.9%
180860
4.0%
2
2.0%
20361
0.5%
Note:
Unknown locations are not included in analysis,
(overhd = overhead, corr = corridor, bsmt = basement,
os wall = outside wall, mix = multiple locations)
Percent by type
100%
so as
80%
70%
60%
SOX
40%
30%
20%
10%
Q%
crawl fjbtlab overhd tunrw) corr floor
In S«^Fl
b*mt eeing a* wal mi*
42J3%
&5%
0.1%
I-
«f«wi «ub«te overhd
floor
c4^Br«g
Figure 10. Distribution of Air Return Locations
(top, % by number of structures; bottom, % by area)
27
-------
TYPICAL LOCATION OF UNITS (VENT/FAN COILS)
Location
Count
Percent Total Sq.Ft
Sq.Ft %
ceiling
27
21. 8%
768124
23.1%
overhd
15
12. 1%
181300
5.5%
os wall
56
45.2%
1348149
40.6%
is wall
12
9 . 7%
237283
7.1%
corr
1
0.8%
449200
13.5%
roof
10
8. 1%
80614
2.4%
tunnel
1
0.8%
248000
7.5%
space
2
1. 6%
8901
0.3%
Note: Unknown
locations
are
not included in analysis.
(overhd = overhead, os wall = outside wall,
is wall = inside wall, corr = corridor)
Percent by type
tOQ% -1
90% -
80% -
70% -
60* -
ctirfl overhd o* w«f t* wal cofi roof iunrxHI »p*c«
Percent in S^Ft
Figure 11. Distribution of Typical Locations of Unit Ventilators and Fan Coils
(top, % by number of structures; bottom, % by area)
28
-------
for each survey item are annotated on the second copy of the Profile Sheets contained in
Appendix A.
SCHST.DBF
This file is identical to the file SCHLG.DBF except that data in each data field was
abbreviated for the purpose of statistical analysis. The statistics and graphs reported in this
report were constructed based on the data in this file. Variable names are the same as for the
original file and are shown in Appendix A. Selected items of interest to radon researchers
were tabulated during the course of the study. These data are provided in Table 6, which
shows the distribution of structures for the short-form answers to the profile items contained in
this database. Distributions are reported both by the number of structures and by area of
structure for most of the 17 items covered in Table 6.
To enter and to view school characteristics in row and column format, a format file
SCHFORM.FMT was created. Because the length of profile sheets and screen limitation, the
user must scroll the screen several times to see all profile items for each school. There are
many dBase programs in "programs" subdirectory on the diskette which contains the datafiles.
These programs were written to enter, view and analyze the school characteristic data. Budget
limitations did not allow these programs to be integrated into a menu-driven interface.
29
-------
TABLE 6. DETAILED RESPONSES TO SELECTED ITEMS
Interval of Total
year constructed
1900-1909 1
1910-1919 5
1920-1929 9
1930-1939 32
1940-1949 8
1950-1959 56
1960-1969 56
1970-1979 46
1980-1989 28
unknown 6
Al. YEAR CONSTRUCTED
A2, SUBSTRUCTURE TYPE
Tm
Total
Percent Total SO.
ft sa
slab:
162
69.8%
3174758
51.2%
crawl:
23
9.9%
269551
4.3%
basement:
15
6.5%
412568
6.6%
slab/crawl:
13
5.6%
1268594
20.4%
basement/crawl:
6
2.6%
860692
13.9%
slab/piers:
1
0.4%
52000
0.8%
slab/basement:
1
0.4%
46300
0.7%
basement/slab:
2
0.9%
63702
1.0%
unknown:
6
2.6%
50381
0.8%
n/a:
3
1.3%
5906
0.1%
(Continual)
30
-------
Tvpe
slab:
wood:
dirt:
sand:
crawl/wood:
slab/wood:
slab/crawl:
Single Purpose:
unknown:
na:
TABLE 6. (Continued)
A3. IF CRAWL SPACE IS FIRST FLOOR:
Total Percent in total
24 13.6%
19 10.8%
2 1.1%
1 0.6%
1 0.6%
1 0.6%
2 1.1%
1 0.6%
4 2.27%
121 68.75%
A4. TOTAL SQ. FT OF BUILDING
Interval Total
of SO. FT
0-10000 99
10000-20000 45
20000-30000 20
30000-40000 14
40000-50000 15
50000-60000 8
60000-70000 7
70000-80000 1
80000-90000 2
90000-100000 2
100000-200000 4
200000-600000 2
> 600000 1
(Continued)
31
-------
TABLE 6. (Continued)
A8. # OF FLOOR(INCL. BSMT)
Number
Total
Percent
Total SO.
FT SO. FT Percent
1 fl:
143
64.7%
2320781
37.1%
2 fl:
45
20.4%
1473620
23.6%
3 fl:
16
7.2%
394890
6.3%
4 fl:
2
0.9%
499200
8.0%
5 fl:
2
0.9%
130800
2.1%
unknown:
13
5.9%
1434241
22.9%
A10. GENERAL BUILDING DESIGN
Type Total Percent Tptal $Q. FT SQ, FT Percent
convention:
182 85.4%
5585780
91.2%
open-classroom.
1 0.5%
13072
0.2%
modular:
4 1.9%
28596
0.47%
campus:
16 7.5%
325497
5.3%
single purpose:
2 0.9%
5400
0.1%
podium:
3 1.4%
137250
2.2%
classroom:
3 1.4%
23900
0.4%
office:
1 0.5%
450
0.01%
link:
1 0.5%
5906
0.1%
All. SUBSLAB WALLS BLOCK OR POURED
Type
Total
Percent
Total SO. FT
SO. FT Percent
block:
33
14.0%
823682
13.1%
poured:
173
73.6%
4985385
79.4%
wood:
1
0.4%
11000
0.2%
na:
10
4.3%
118822
1.9%
unk:
9
3.8%
177991
2.8%
pier block:
1
0.4%
1800
0.03%
fill block:
2
0.9%
63040
1.0%
poured block: 6
2.6%
97537
1.6%
(Continued)
32
-------
TABLE 6. (Continual)
A12. DO SUBSLAB WALLS SEPARATE EACH CLASSROOM
Type Total Percent Total SO. FT SO. FT Percent
yes: 65 27.9% 1547070 24.6%
no: 118 50.6% 2754883 43.9%
unk: 33 14.2% 1852959 29.5%
na: 16 6.9% 72345 1.2%
mix: 1 0.4% 52000 0.8%
A13. ARE SUBSLAB WALLS UNDER THE CORRIDOR WALLS
Type
Total
Percent
Total SO.
FT
SO. FT Percent
yes:
98
42.1%
2521778
40.2%
no:
88
37.8%
1841746
29.3%
unk;
28
12.0%
1783347
28.4%
na:
19
8.2%
132386
2.1%
A14. SUBSLAB MATERIAL ON PLAN
Tvpe
Total
Percent
Total SO.
FT
SO. FT Percent
sand:
12
5.3%
158251
2.6%
earth:
45
19.7%
796683
12.9%
gravel:
66
28.9%
2156939
34.9%
gravel sand:
8
3.5%
49631
0,8%
dirt fill:
5
2.2%
102004
1.7%
gravel fill:
4
1.8%
245718
4.0%
sandy soil:
5
2.2%
104500
1.7%
cinder fill:
1
0.4%
43581
0.7%
pea gravel:
1
0.4%
45700
0.7%
unk:
35
15.4%
1755960
28.4%
na:
44
19.3%
656402
10.6%
filled sand:
2
0.9%
62000
1.0%
(Continued)
33
-------
TABLE 6. (Continued)
A15. SUBSLAB MATERIAL VERIFIED
Type
Total
Percent
Total SQ. FT SQ. FT Percent
sand:
5
2.3%
74313
1.3%
earth:
16
7.2%
200828
3.6%
gravel:
7
3.2%
444580
8.0%
fill ed sand *
2
0.9%
62000
1.1%
unk:
27
12.2%
345197
6.2%
na:
165
74.3%
4423897
79.7%
A16. LOCATION(S) OF UTILITY LINES
Location Total Percent Total SO. FT SO. FT Percent
crawl:
12
5.4%
221293
3.6%
overhead:
81
36.7%
1829219
29.7%
basement:
8
3.6%
684390
11.1%
subslab:
52
23.5%
987682
16.0%
ceiling:
4
1.8%
54513
0.9%
tunnel:
25
11.3%
514330
8.3%
mechanical room:
5
2.3%
1272000
20.6%
outside wall:
2
0.9%
62000
1.0%
slab crawl:
1
0.5%
12000
0.2%
overhead crawl:
2
0.9%
87581
1.4%
basement and
mechanical room:
1
0.5%
46300
0.8%
na:
9
4.1%
126153
2.0%
buried:
19
8.6%
268617
4.4%
(Continued)
34
-------
TABLE 6. (Continued)
BIO. AIR SUPPLY DUCTS LOCATION
Location
Total
Percent
Total SO.
FT SO. FT Percent
crawl:
2
0.9%
24800
0.4%
subslab;
5
2.2%
61227
1.0%
overhead:
24
10.4%
490462
7.9%
tunnel:
2
0.9%
287995
4.6%
corridor:
2
0.9%
971660
15.6%
classroom:
5
2.2%
51528
0.8%
basement:
6
2.6%
671628
10.8%
ceiling:
67
29.1%
2005678
32.2%
outside wall:
2
0.9%
59000
0.9%
multiple area: 1
0.4%
35400
0.6%
unk:
11
4.8%
114485
1.8%
na:
103
44.8%
1462850
23.5%
Bll. LOCATION OF AIR RETURN
Location
Total
Percent
Total SO.
FT SO. FT Percent
crawl:
1
0.4%
5600
0.1%
subslab:
9
4.0%
247980
4.0%
overhead:
10
4.4%
124700
2.0%
tunnel:
3
1.3%
1426000
23.1%
corridor:
7
3.1%
227516
3.7%
floor:
4
1.8%
115608
1.9%
basement:
5
2.2%
222428
3.6%
ceiling:
57
25.3%
1933411
31.4%
outside wall:
4
1.8%
180860
2.9%
mix:
2
0.9%
20361
0.33%
unk:
18
8.0%
182051
3.0%
na:
105
46.7%
1479950
24.0%
35
(Continued)
-------
TABLE 6. (Continued)
C5. TYPICAL LOCATION OF UNITS
Location
Total
Percent
Total SO. FT SO. FT Percent
ceiling;
27
11.7%
768124
12.3%
overhead:
15
6.5%
181300
2.9%
outsid wall:
56
24.3%
1348149
21.7%
inside wall:
12
5.2%
237283
3.8%
corridor:
1
0.4%
449200
7.2%
roof:
10
4.3%
80614
1.3%
tunnel.
1
0.4%
248000
4.0%
space:
2
0.9%
8901
0.1%
unk:
4
1.7%
60276
1.0%
na:
102
44.3%
2840858
45.65%
Dl. RADIANT HEAT TYPE
Type
Total
Percent
Total SO.
K»i c oKao rH *
DuSvPOuTQ *
19
8.2%
1282970
20.7%
radiator:
51
22.1%
1143368
18.4%
fine tube:
20
8.7%
570162
9.2%
baseboard radiator:
3
1.3%
58240
0.9%
intra-slab piping:
3
1.3%
64460
1.0%
abandoned:
5
2.2%
42900
0.7%
unk:
5
2.2%
98787
1.6%
na:
115
49.8%
2877447
46.4%
not used:
10
4.3%
66171
1.1%
SO. FT Percent
F3. BUILDING CONSTRUCTION PLANS AVAILABLE
Answer
Total
Percent
Total SO,
FT SO. FT Percent
yes:
84
35.9%
3764548
60.0%
no:
61
26.1%
819365
13.1%
partial:
21
9.0%
529636
8.4%
unk:
53
22.6%
1015301
16.2%
na:
15
6.4%
148532
2.4%
36
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6. STATISTICAL LIMITATIONS
Because of the random selection of NSRS ATD/eanister schools within the 25
selected residential PSUs, the sample of profiled schools is nationally representative.
However, extrapolation of the survey estimates to the national population of schools must
reflect the magnitude of sampling errors expected for a survey of this size. Sampling
errors should also be considered when the relative proportions of two response categories
are compared.
Clustering of the sample schools within the residential PSUs results in some loss of
sampling efficiency compared to a truly random sample of schools for this survey. An
additional loss of sampling efficiency arises due to non-response adjustments to the
sampling weights, which will be made when the final weights are provided by ORP. At
this time, the radon measurements and sampling weights for the NSRS ATD/canister
sample are not available.
The loss in sampling efficiency can be explained in terms of a design factor (DF)
for the survey, defined as:
DF = —
n
where N represents the actual sample size (100) and n represents the reduced effective
sample size for this design. The effective sample size is defined as the required size for a
truly random sample to generate the same sampling errors. Because of the random
selection of residential PSUs and the random selection of schools within these PSUs, we
estimate that a worst case DF would not exceed 1.25. For this assumption, the effective
sample size is approximately 80.
37
-------
I
The standard error (SE) of an estimated population percentage (P) is given by:
SE = * P { 1 - P F"
n = = effective sample size
DF
Knowledge of the standard errors of the estimated percentages permits
determination of approximate 95% confidence intervals (CIs) for the reported estimates.
An estimated population percentage P has a 95 % CI extending approximately two standard
errors on either side of the estimate. Thus, the approximate 95% CI for a population
percentage estimate P would be the interval (P - 1.96SE, P + 1.96SE).
The estimated 95 % CIs for various estimated population percentages are reported
in Table 7 for the specified effective sample size. The 95% CI for an estimate of 5%
extends approximately from 0 to 10%. For a population percentage of 20%, the 95% CI
extends approximately from 10 to 30%. Similarly, an estimate of 80% has a 95% CI
ranging approximately from 70 to 90%.
The 95 % CIs reported in Table 7 are relatively large, due to the small effective
sample size of approximately 80. The size of these CIs should be considered when
comparisons are made between the reported population proportions for two different
response categories. For example, if outcome "a" is observed in A % of the 100 schools,
and outcome "b" in B% of the schools, then A + B < = 100% with the inequality
applying if more than two outcomes are possible. To determine if A is significantly less
(or greater) than B, the standard error of the difference (A - B) is determined by:
38
-------
To test the hypothesis that A is greater than B (or A is less than B), the difference
between A and B should be significantly greater (less) than 0, Hence, the quantity (A -
B) should be more than two standard errors away from 0, indicating that the difference is
significantly positive (A greater than B) or significantly negative (A less than B).
Regions where A is significantly greater (or less) than B are shown in Table 8. In
this table, the symbol < < denotes that A is significantly less than B, and > > denotes
that A is significantly greater than B (at the 95% significance level) as determined by:
| A - B | > 1.96 SE( A - B )
For example, an estimate of 8% is significantly less than an estimate of 20%, but it is not
significantly less than an estimate of 16% because the SE of the difference between
estimates of 8 and 16% is about 5 percentage points. Thus the difference of 8 percentage
points is less than 1.96 SE, and the difference is not considered significant at the 95%
significance level.
39
-------
TABLE 7, APPROXIMATE 95% CONFIDENCE INTERVALS FOR ESTIMATES
Estimated Expected
Population Percentage 95% Confidence Interval*
P = 5% or P = 95% (P - 4.81, P + 4.8%)
P = 101 or P = 90% (P - 6.61, P + 6.61)
P = 201 or P = 80% (P - 8.81, P + 8,81)
P = 50% (P - 11.2%, P + 11.21)
The actual confidence intervals surrounding the estimates
will not be symmetric except for the case P = 501.
TABLE 8. REGIONS OF SIGNIFICANT DIFFERENCE BETWEEN TWO
POPULATION PERCENTAGE ESTIMATES, A AND B,
PERCENTAGE B
8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 B4 88 92 96
m
15
<
Z
M
U
cc
w
a>
4 T
8 I
12 |
16 |
20 |
24 |
28 |
32 !
36 |
40 |
44 |
48 |
52 |
56 [
60 |
64 |
68 [
72 |
76 i
80 |
64 |
88 |
92 |
96 1
» .
» »
» »
» »
» »
» »
» »
» »
» >>
» »
>> »
» »
» »
» »
» »
» »
» »
» »
» »
» »
»
« << « « « « << « « « « « « « « « « « « « «
<< « « « « << « « « « « « << « « « « « <<
« « « « « « « « « « « « « << « «
« « « « « « « « « « « « « «
« « « « « « « « « « « <<
« « « « « « « « «
« « « « « « «
« « « « «
>>
>> »
» » » .
» » >> .
>> » » »
» » » » »
» » » » » » ,
» » » » » » .
» >> » >> » >> »
» » » » » » »
» » » » » »
» » >> » »
» » » »
» » »
» »
»
« «
NOTE: The symbol "»" denotes that percentage A is significantly greater than
percentage B at the 95% significance level; the symbol "<<" denotes that A is
significantly less than B; and the symbol denotes that A and B are not
significantly different at the 95% significance level.
40
-------
7. CONCLUSIONS
The school profile database contains many significant findings concerning the
distribution of school building characteristics. The profile sheets provide evidence of the
variety of building structures and HVAC equipment found in typical schools. The age of
a school, number and size of different structures, type of substructure, location of utility
lines, and types of HVAC equipment vary widely in the sample schools.
The substructure of a school has important implications for radon diagnostics and
mitigation. Determination of substructure detail depends on locating building plans, which
were available for only half of the structures. Where identified, subslab materials were
almost evenly divided between gravel and fine-grained material such as earth or sand.
Internal footings are found in half of the structures, with footings under both corridor and
classroom walls in one-quarter of the structures. Utility lines may enter the building at a
wide variety of locations, including tunnels, subslab penetrations, and overhead. In a few
schools, older unused radiant heating systems may provide additional radon entry routes.
Commonly encountered structural characteristics include slab-on-grade with a
conventional school building design with a single floor. Central HVAC is common, but
often combined with other HVAC systems within a single school. Where applicable,
central HVAC ductwork is usually located in the ceiling or suspended overhead. Radiant
heat, using baseboard or radiator systems, is the second most common HVAC system.
Unit ventilators and fan coils also present in many of the schools are most often located
along outside walls, but may be in the ceiling, suspended overhead, along an inside wall,
or on the roof.
41
-------
REFERENCES
1. Education Writers Association, Wolves at the Schoolhouse Door. Washington,
DC, 1989.
2. Quality Educational Data (QED), Inc., Denver, CO, 1988.
3. Leo vie, K.W., A.B. Craig, and D.B. Harris, Update on Radon Mitigation
Research in Schools. Presented at the 1991 AARST Conference, Rockville, MD,
October 1991.
42
-------
Appendix A
School Building Profile Forms Used in Study
A-l
-------
RADON MITIOATIOW BRM4CS SCHOOL PROFILE SBEET (7/19/91 REVISION)
- USE ONE PROFILE SHEET FOR EACH BUILDING, USE ADDITIONAL SHEETS IF THERE ARE MORE THAN TWO
SUBSTRUCTURES/ADDITIONS.
- THE ARCHITECTURAL PLANS AND SPECIFICATIONS MAY NEED TO BE EXAMINED TO ANSWER MANY OF THE QUESTIONS,
- GROUND CONTACT ROCKS INCLUDE SLAB-ON-GRADE, BASEMENT, AND ROCKS LOCATED DIRECTLY OVER THE CRAWL SPACE;
- PLEASE ATTACH A FLOOR PLAN OF THE SCHOOL (WITH RADON LEVELS IF AVAILABLE)
- A SECTION FOR CCMMENTS IS PROVIDED ON THE LAST PAGE, PLEASE KEY THE APPROPRIATE LINE WITH EACH CCHM1NT
(i.e., Al).
SCHOOL: DISTRICT:
STREET: CITY: ST: ZIP:
NSRS CODE: COUNTY: DATE:
CONTACT: POSITION: PHONE:
YODR NAME: POSITION: PHONE:
A. THE FOLLOWING TABLE INCLUDES STRUCTURAL. CHARACTER!3TICS OF THE SCHOOL:
STRUCTURAL CHARACTERISTICS
ORIGINAL STRUCTURE
2nd STRUCTURE
3rd STRUCTURE
1! YEAR CONSTRUCTED
2) SUBSTRUCTURE TYPE:
BSMT/SLAB/CRAWL
3) IF CRAWL SPACE, IS FIRST
FLOOR: SLAB/MOOD
4) TOTAL SQ. FT. OF BUILDING
5) SQ. FT. OF GROUND CONTACT
6) # 1st FL CLASSROOMS
7) # OTHER 1st FL OCCUPIED ROOMS
8) # OF FLOORS (INCL. BSMT)
9) APPROX # OF BUILDING OCCUPANTS
10)DESCRIBE GENERAL BUILDING
DESIGN: CONVENTIONAL/OPEN
CLASSROOMS/OTHER
11)ARE SUBSLAB WALLS BLOCK OR
POURED:BLOCK/POURED
12) DO SUBSLAB WALLS SEPARATE
EACH CLASSROOM: YES/NO/UNK
13!ARE SUBSLAB WALLS UNDER THE
CORRIDOR WALLS: YES/NO/UNK
14)SUBSLAB MATERIAL ON PLANS;
NA/GRAVEL/SAND/EARTH/OTHER
15) SUBSLAB MATERIAL VERIFIED:
NA/GRAVEL/SAND/EARTH/OTHER
16)LOCATION(S) OF UTILITY LINES:
TUNNEL/SUBSLAB(NO TUNNEL)/
OVERHEAD/BSMT/CRAKL/OTHER
17)IF TUNNEL: WIDTH S HEIGHT
18)TUNNEL LOCATION: OUTSIDE
WALL/CORR1DOR/OTHER
19)TUNNEL WALL: POURED/BLOCK
20)TUNNEL FLOOR: DIRT/SLAB
A-2
-------
B. CCHPLETE THE FOLLOWING TABLE If AMf PART OF THE BUILDING HAS A CDffilH. HVAC SYSTEM;
rvtJ'iinT nvfcr ffvoTrvi
Va>E>rixrynywi tiv
-------
1) CLASSROOMS: NONE/GRAVITY/FAN
2] CORRIDOR: NONE/GRAVIT Y /FAN
3) MULTIPURPOSE:NONE/GRAVITY/FAN
4! KITCHEN: NONE/GRAVITY/FAN
5} CAFETERIA:NONE/GRAVITY/FAN
6) RESTROCHS :NONE/GRAVITY/FAN
7) LABS:NONE/'GRAVITY/FAN
8) OTHER:SPECIFY/GRAVITY/FAN
g. THE FOLLOWIHa PZRIA1H TO GEKERAX. QUESTIONS ABOUT THE BUI LP I WO:
GENERAL INFORMATION
ORIGINAL STRUCTURE
2nd STRUCTURE
3rd STRUCTURE
1) DOES BUILDING HAVE WINDOW
AC UNITS: YES/NO/ PART I ALLY
2) HVAG SYSTEM CONTROL:ENERGY
KG?/ROOM CONTROLS/OTHER/
ELECTRONIC OR PNEUMATIC
3) WERE BUILDING CONSTRUCTION
PLANS AVAILABLE TO
COMPLETE PROFILE SHEET?
YES/NO
4) HAVE "ENERGY CONSERVATION"
MEASURES BEEN MADE: SPECIFY
5) IS THE BUILDING WATER
SUPPLY: WELL/PUBLIC
G. IH THE SPACE BELOW, PLEASE PROVIDE ANY APDITIOHAL COM-EHTS:
SECTION
COMMENTS
IF YOU HAVE ANY QUESTIONS OR NEED CLARIFICATIONS PLEASE CONTACT: KELLY LEOVIC, RADON MITIGATION BRANCH
-------
BACON MITIGMTIOK BRANCH SCHOOL PROFILE DATABASE: VARIABLE NAMES
- USE ONE PROFILE SHEET FOR EACH BUILDING. USE ADDITIONAL SHEETS IF THERE ARE MORE THAN TWO
SUBSTRUCTURES/ADDITIONS.
- THE ARCHITECTURAL PLANS AND SPECIFICATIONS MAY NEED TO BE EXAMINED TO ANSWER MANY OF THE QUESTIONS.
- GROUND CONTACT ROCKS INCLUDE SLAB-ON-SRADE, BASEMENT, AND ROOMS LOCATED DIRECTLY OVER THE CRAWL SPACEf
- PLEASE ATTACH A FLOOR PLAN OF THE SCHOOL (WITH RADON LEVELS IF AVAILABLE)
- A SECTION FOR COMMENTS IS PROVIDED ON THE LAST PAGE. PLEASE KEY THE APPROPRIATE LINE WITH EACH COMMENT
(i.e., A15.
SCHOOL: I SCHNAME] DISTRICT: (DISTRT)
STREET: [STREET] 1 CITY: [CIT5f J ST:_(STATS]_ZIP: [ZIPJ
NSRS CODE: [NSRSCOD] COUNTY: [COCOUNT] DATE: [ COD ATE ]
CONTACT: [CONAME] POSITION: (COPOST] PHONE: [COPHONE]
YOUR NAME: (SANAME1 POSITION: f SAPOST1 PHONE: f SAPHONEI
A. THE FOLLOWING TABLE INCLUDES STRUCTURAL CHARACTERISTICS OF TBS SCHOOL:
STRUCTURAL CHARACTERISTICS
ORIGINAL STRUCTURE
2nd STRUCTURE
3rd STRUCTURE
1) YEAR CONSTRUCTED
[OSYRBD]
[SS...1
ITS... (4th STRUCT:
FS.. .))
2) SUBSTRUCTURE TYPE:
B SMT / S LAB / C RKWL
[OSSUB]
3) IF CRAWL SPACE, IS FIRST
FLOOR: SLAB/WOOD
[OSLWD]
TOTAL SQ. FT. OF BUILDING
[OSTSFTj
5) SQ. FT. OF GROUND CONTACT
[gssqgd;
-
6! # 1st FL CLASSROOMS
IOSFFCL]
1) # OTHER 1st FL OCCUPIED ROOMS
[OSFLCLO]
8) # OF FLOORS (INCL. BSMT'i
[OSNUMFL]
9) APPROX # OF BUILDING
OCCUPANTS
(OSBDOCj
10)DESCRIBE GENERAL BUILDING
DESIGN:
CONVENTIONAL/OPEN
CLASSROOMS/OTHER
IOSGDSG]
11)ARE SUBSLAB WALLS BLOCK OR
POURED:BLOCK/POURED
[OSASLAB]
12)DO SUBSLAB WALLS SEPARATE
EACH CLASSROOM:
YES/NO/UNK
[OSSWSP]
13)ARE SUBSLAB WALLS UNDER THE
CORRIDOR WALLS: YES/NO/UNK
IOSSLW]
14)SUBSLAB MATERIAL ON PLANS:
NA/GRAVEL/SAND/EARTH/OTHER
JOSSLOP]
15!SUBSLAB MATERIAL VERIFIED:
NA/ GRAVEL/SAND/EARTH/OTHER
IQSSLVER]
16!LOCATION(S) OF UTILITY LINES:
TUNNEL/SUBSLAB(NO TUNNEL)/
OVERHEAD/BSMT/CRAWL/OTHER
JOSLUTIL)
17}IF TUNNEL: WIDTH & HEIGHT
[OSTUNNEL]
13]TUNNEL LOCATION: OUTSIDE
WALL/CORRIDOR/OTHER
1OSTUNLT J
19!TUNNEL WALL: POURED/BLOCK
[CSTUNWL]
20)TUNNEL FLOOR: DIRT/SLAB
[OSTUFL]
A-5
-------
B. COMPLETE THE FOLLOWIHO TABLE IF AMY PART OF SHE BUTUOING HAS A CENTRAL HVAC SYSTEM:
CENTBAL HTOC SYSTEM
ORIGINAL STRUCTURE
2nd STRUCTURE
3rd STRUCTURE
1) # OF AIR HANDLING UNITS:
IOCAHDL]
[SC.
1TC...J
2! SERVICES CLASSROOMS: YES/NO
[OCSCL1
3) SERVICES MULTIPURPOSE:
YES/NO
[OCSMUL]
4) SERVICES OFFICES! YES/NO
(OCSOFFJ
5) SERVICES OTHER AREA: YES/NO
{OCSROT)
6) LOCATION(S) OF AIR
HANDLER(S):
MECH ROOM/DROPPED CEILING/
ROCF/BSMT/CRAKL/OTHER
[OCLAHD]
7) SEPARATE RETURN FAN: YES/NO
[OCSPRT]
8) MINIMUM » OUTDOOR AIR
[OCHIOUT]
9) MAXIMUM % OUTDOOR AIR
[QCMAOUT]
10)AIR SUPPLY DUCTS LOCATION:
CEILING/SUBSLAB(NO
TUNNEL)/
TUHNEL/BSMT/CRAWL/OTHER
(OCADCT]
11)LOCATION OF AIR RETURN:
CEILING/SUBSLAB(NO TUNNEL)/
HALI. / T UNNE L/HSMT/ CRAWL / OTHER
[OCLART]
12) IS AIR RETURN DUCTED:
YES/NO
[OCARDUC]
13)DOES SYSTEM HAVE A PRESSURE
RELIEF: YES/NO
[OCSPRF]
14)BRIEFLY DESCRIBE ANY OTHER
DETAILS ABOUT THE AIR
HANDLING
SYSTEM:
[ OCBDAHD ]
C. COMPLETE THE FOLLOWING TABLE IF ANY PART OF THE BUILDING
HAS UNIT VENTILATORS/FAN C
•OILS:
UNIT VENTILATORS/FAN COILS
ORIGINAL STRUCTURE
2nd STRUCTURE
3rd STRUCTURE
1) SERVICES CLASSROOMS:
YES/NO
[OUSCL]
[SU.
[TO...]
2) SERVICES MULTIPURPOSE:
YES/NO
[OUSMULI
3) SERVICES OFFICES: YES/NO
[OUSOFF]
4) SERVICES OTHER AREA:
YES/NO
IOUSOTH]
5) TYPICAL LOCATION OF UNITS:
OUTSIDE WALL/INSIDE WALL/
CEILING/TUNNEL/CRAWL/OTHER
[OUTLUN1
6) MINIMUM 1 OUTDOOR AIR
[oumiout;
7) MAXIMUM 1 OUTDOOR AIR
[OUMAOUT]
B, COMPLETE THE FOLLOWING TABLE IF AMY PART OF THE BUILDING
HAS RADIANT SEAT:
RADIANT HEAT
ORIGINAL STRUCTURE
2nd STRUCTURE
3rd STRUCTURE
1) TYPE: BASEBOARD/RADIATORS/
INTRA-SLAB PIPING/OTHER
[ORRHTi
[SR...)
(TR...J
2) SERVICES CLASSROCWS:
YES/NO
JORSCLJ
3) SERVICES MULTIPURPOSE:
YES/NO
[ORSMUL]
4) SERVICES OFFICES: YES/NO
[ORSOFF1
A-6
-------
5| SERVICES OTHER AREAS:
[ORSOTH]
YES/NO
E. COMPLETE THE FOLLOWING TABLE FOR BUILDING EXHAUSTS:
EXHAUSTS! IF KNOWN SPECIFY TOTAL
CM FOR FANS
ORIGINAL STRUCTURE
2nd STRUCTURE
3rd STRUCTURE
1) CLASSROOMS: NONE/GRAVITY/FAH
10ECLAS]
[SE.,
(TE...]
2) CORRIDOR; NONE/GRAVITY/FAN
iOECORR]
3) MULT I PURPOSE: NONE/ GRAVITY/ FAN
[OEMUL]
4) KITCHEN: NONE/GRAVITY/FAN
[OEKIT]
5! CAFETERIA: NONE/GRAVITY/FAN
[OECAF]
6! RESTROCMS;NONE/GRAVITY/FAN
(OERES)
7) LABS!NONE/GRAVITY/FAN
[OELAB]
8) OTHER:SPECIFY/GRAVITY/FAN
[OEOTH]
F. THE FOLLOWING PERTAIN TO SEH2RM, QUESTIONS ABOUT THE BUILDING:
GENERAL INFORMATION
ORIGINAL STRUCTURE
2nd STRUCTURE'
3rd STRUCTURE
1) DOES BUILDING HAVE WINDOW
AC UNITS:
YES/NO/PARTIALLY
IOGWINJ
[SG,..]
1TG...]
2} HVAC SYSTEM CONTROL:ENERGY
MGT/ROOM CONTROLS/OTHER/
ELECTRONIC OR PNEUMATIC
IOGHVAC]
3! WERE BUILDING CONSTRUCTION
PLANS AVAILABLE TO
COMPLETE PROFILE
SHEET? YES/NO
IOGPLAN]
4) HAVE "ENERGY CONSERVATION"
MEASURES BEEN MADE:
SPECIFY
[OGENER]
5! IS THE BUILDING WATER
SUPPLY: WELL/PUBLIC
[OGWATER]
G. IH THE SPACE BELOW, PLEASE PROVIDE ANY ADDITIONAL COMMENTS:
SECTION
COMMENTS
IF YOU HAVE ANY QUESTIONS OR NEED CLARIFICATIONS PLEASE CONTACT: KELLY LEOVIC, RADON MITIGATION BRANCH (MD-54),
U.S. EPA, RESEARCH TRIANGLE PARK, NC 27111. PHONE: 919-541-7717; FAX 2157
A-7
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TECHNICAL REPORT DATA ...
(Please read Instructions on the reverse before eomple III III |l II 1||||||| Mill 11
1. REPORT NO. 2,
EFA-60O/R-93-218
3 Hi 1111 II Sill 1IIII1I11J 11111 III
PB94-121704
4, TITLE AND SUBTITLE
Characteristics of School Buildings in the U.S.
S. REPORT DATE
November 1993
S. PERFORMING ORGANIZATION CODE
7, AUTHOfl(S)
Harry Chrnelynski
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
S. Cohen and Associates, Inc.
1355 Beverly Road
McLean, Virginia 22101
10. PROGRAM ELEMENT NO.
It. CONTRACT/GRANT NO.
68-DO-0097, Task 3-2
12, SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 4-9/93
14. SPONSORING AGENCY CODE
EPA/600/13
is. supplementary notes AEERL project officer is Kelly W. Leovic, Mail Drop 54, 919/541-
7717.
16 ABSTRACT
- The report gives results of visitirg a subsample of 100 schools from the En-
vironmental Protection Agency's (EPA's) National School Radon Survey to obtain in-
formation on building structure, location of utility lines, and the type of heating, ven-
tilating, and air-conditioning (HYAC) system. Information from each school was en-
tered into a database to determine the relative proportions of physical characteris-
tics of the U.S. school building population. Results indicate that most school struc-
tures are of slab-on-grade construction, gravel was used as subslab fill material in
approximately half of the structures, approximately 80% of the schools have either
central HVAC or unit ventilators capable of delivering conditioned outdoor air to the
classrooms, and almost 25% of the schools have subslab footings extending both be-
neath the classroom walls and along the corridors, thus complicating the installation
of effective subslab depressurization systems. The results obtained in this study
will be used by EPA to guide future mitigation research in schools.
17. KEY WORDS AND DOCUMENT ANALYSIS
a, DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATl Field/Group
Pollution
School Buildings
Structural Design
Utilities
Air Conditioning Equipment
Radon
Pollution Control
Stationary Sources
13 B
13 M, 051
13 A
07B
18, DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
55
20. SECURITY CLASS (This page)
Unclassified
22, PRICE
EPA Form 2220-1 (9-73)
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