Passive Radon Resistant Construction Performance IN VENTILATED CRAWL SPACE HOMES

8/11/2019 Passive Radon Resistant Construction Performance IN VENTILATED CRAWL SPACE HOMES

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PASSIVE RADON-RESISTANT CONSTRUCTION PERFORMANCE

IN VENTILATED CRAWL SPACE HOMES

FINAL REPORT

Conducted By

NAHB Research Center, Inc.

Upper Marlboro, MD

For

United States Environmental Protection Agency

Washington, D.C.

EPA Assistance ID No. X 819586-01-5

Task 1

May 1996


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TABLE

OF

CONTENTS

INTRODUCTION 1

Background 1

Radon-Resistant Methods 1

Measurement Procedures 2

TESTSITES 4

Nashville, Tennessee

4

Coeur dAlene, Idaho 8

Roanoke, Virginia

10

Indianapolis, Indiana 12

Lake Ariel, Pennsylvania 14

Huntsville, Alabama 16

TESTRESULTS 18

DISCUSSION 20

Nashville, Tennessee 20

Coeur dAlene, Idaho 21

Roanoke, Virginia 22

Indianapolis, Indiana

23

Lake Ariel, Pennsylvania

24

Huntsville,

Alabama

25

CONCLUSIONS

26

REFERENCES 27

APPENDIX A Quality Control Procedures A-1

APPENDIX B Construction Characteristics

B-1

APPENDIX C Test Data C-1

APPENDIX D Climatic Data D-1


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INTRODUCTION

Background

The United States Environmental Protection Agency (EPA) and the NAHB Research Center, Inc.

(Research Center) have been involved in a cooperative program to identify and evaluate cost-

effective methods to construct radon-resistant homes. Recently, the program has been expanded

to include 15 to 5 new single-family crawl space homes. The objective was to evaluate the

effectiveness of radon mitigation methods in the EPAs

Mo del Standards and Techniques fo r

Control of Radon in New Residential Buildings [l].

The Research Center recruited builders of crawl space homes from several areas of the

continental United States. Builders were targeted in counties and cities designated as Zone 1

according to the

EPA Map

of

Radon Zones.

The Research Center worked with the builders to

educate them on radon-resistant construction methods, and periodically observed their operations

to record the degree to which they complied with EPA recommendations. This report presents

and discusses test results from 17 crawl space homes constructed by seven builders in six states.

Four homes were located in Nashville, Tennessee, seven in Coeur dAlene, Idaho, two in

Roanoke, Virginia, one in Indianapolis, Indiana, two in Lake Ariel, Pennsylvania, and one in

Huntsville, Alabama. All of these locales are designated as Zone 1 on the EPA

Map

of

Radon

Zones [2].

Soil radon levels were measured prior to construction of each home as a screening tool to assess

the potential for elevated radon levels at the sites. Indoor tests in the Tennessee, Idaho, Virginia,

and Indiana homes were conducted between January and May 1995. The Pennsylvania homes

were tested during October and November 1995, and the Alabama homes was tested during April

and May 1996.

Radon-Resistant Methods

The

uilders

recruited for the project agreed to construct crawl space homes in accordance with

EPA recommended methods for radon-resistant construction. These methods, listed in EPAs

Mod el Standards and Techniques fo r Control

of

Rad on in New Residential Buildings

(published

in March 1994), define specific construction methods and techniques for preventing radon entry

in new residential buildings. Radon-resistant construction methods for crawl space homes

essentially consist of a vent pipe (stack) installed from the crawl space floor through the roof.

The bottom of the stack terminates in a tee fitting that rests on the crawl space floor, and the

floor is completely covered with a vapor barrier that is sealed at the foundation walls, piers, and

at seams. The sealed vapor barrier and vent stack (sealed under the vapor barrier) is designed

to vent radon to the outdoors before it can enter a house. The EPA recommended radon-resistant

construction methods are as follows:

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The crawl space floor should be covered with 6-mil polyethylene sheeting or equivalent

membrane material. The sheeting should be sealed at joints, pipe openings, around

interior piers, and at the perimeter of foundation walls. The ground cover should be

continuous over the entire floor and lapped a minimum of 12-inches at joints.

A length of 3 or 4-inch diameter perforated pipe or strip of manufactured drainage

matting should be inserted horizontally below the sheeting. The perforated pipe or

matting should extend for the width of the crawl space and be connected to a

3-

or 4-inch

diameter tee fitting with a vertical PVC pipe installed through the sheeting in a central

location. The pipe should extend vertically

through

the building floors and terminate

through the roof.

Crawl spaces should have non-closeable foundation vents.

The top course of concrete masonry walls should be constructed of solid or filled concrete

Ductwork passing through the crawl space should be seamless or sealed.

Penetrations through floors above the crawl space should be caulked or sealed.

Access doors and other openings or penetrations between basements and adjoining crawl

The attic should contain wiring for possible installation of a duct fan for active sub-

masonry units.

spaces should be closed, gasketed, or otherwise sealed.

membrane depressurization.

Measurement Procedures

The Research Center worked with EPA to develop a standard procedure for conducting indoor

radon tests in each home. It was agreed that up to five phases of indoor tests would be

conducted in each home during the colder months of the year. Each test phase was scheduled

to last approximately two weeks, and would permit the evaluation of a different aspect of the

radon-resistant construction. Each test phase was conducted according to the following

procedures:

Phase

1

Tests Radon vent stack and foundation vents were closed.

Phase 2 Tests Radon vent stack closed and foundation vents were open.

Phase 3 Tests Radon vent stack and foundation vents were open.

Phase 4 Tests Radon vent stack open and extra foundation vents were open.

Phase 5 Tests Fan installed and operating in vent stack with foundation vents open.

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Phase 1 tests were designed to indicate the radon levels that would be experienced if the home

did not have a radon vent pipe and foundation vents. This test phase was designed to reveal a

baseline for which to compare radon levels. Phase 2 tests were designed to measure the

effectiveness

of

foundation vents in reducing radon levels, while Phase

3

tests were designed to

measure radon vent stack performance.

Phase

4

and Phase

5

were designed as optional test phases. One of the builders installed extra

foundation vents in one of the homes, and Phase 4 ests were intended to measure the effect of

these extra vents on indoor radon levels. Phase

5

tests called for installation

of

a duct

fan

(active

radon-resistant construction) in the vent stack of homes with Phase

3

levels exceeding

2.0

pCi/1.

Indoor radon levels were measured in each home with Electret Ion Chambers (EICs). Two EICs

were placed side-by-side (duplicates) in each house for each phase of testing. The EICs were

placed in a central location on the lowest lived-in floor of the home in accordance with EPAs

Indoor Radon and Radon Decay Product Measurement Device Protocols.

Measurements were

determined by averaging the measurement obtained from each duplicate EIC. In accordance with

EPA protocols, a retest was conducted if duplicate measurements differed more than

10

percent.

The calibration of the EIC measurement equipment was verified on a regular basis by comparison

against reference EICs and the reference EICs were measured and certified by the manufacturer

on January

24, 1995.

Specific quality control procedures are listed in Appendix A.

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TEST SITES

Seven builders in six states constructed 17 crawl space homes with radon-resistant features

recommended in the EPA's Model Standards and Techniques o r Rad on Resistant Construction

in New Residential Buildings. This section provides a description of each home, including radon-

resistant construction features. Construction characteristics for each location is listed in Appendix

B.


Four homes were constructed in a southern suburb of Nashville, Tennessee. All of the homes

were constructed by the same builder and are located in two developments located approximately

five miles apart.

The Nashville homes presented

a

unique opportunity for indoor tests. Due to the large demand

for new homes in the area, the builder constructed these homes as spec homes (construction

was initiated prior to sale). This allowed indoor tests to be conducted under highly controlled

conditions. Since the homes were unoccupied during testing, closed house conditions could be

maintained at all times, and the possibility of interference with the radon measurement equipment

was minimized.

Homes TNl and TN2

The two homes located in the first development, TN1 and TN2, are both two-story contemporary

homes with similar floor plans. TN1 is located approximately 100 yards from TN2. Figures 1

and 2 are photographs of these homes.

Figure 1

Home TN1

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Figure

2

Home TN2

Except for the garages, both homes are built over ventilated crawl spaces. Crawl space floors

in both homes are covered with 6-mil polyethylene vapor barrier. Foundation walls and piers are

CMU block. Although solid top courses were not used, the top edge of all walls and piers are

sealed with a layer of polyethylene covered with 2 x 8 sill plates. A 3-inch diameter PVC vent

stack is located in the central area of each crawl space. Each vent stack terminates in a tee

fitting on the crawl space floor and extends up through the roof.

The HVAC units of both homes are located outdoors. Both homes are equipped with gas-fired

forced-air furnaces with central air conditioning. Flexible ducts are routed through the crawl

space of both homes, and all ductwork is taped and sealed. Figure 3is a photograph of the

HVAC unit installed in TN2. This figure also shows the crawl space access door in the

foundation wall next to the HVAC unit. Crawl space access doors in the other Tennessee homes

are installed in similar locations.

Foundation vents are evenly interspersed along the perimeters of the foundation walls. The

screened area of each vent measured approximately 8 x 16 , but the actual free area is reduced

by the presence

of

three metal louvers that permit the vents to be closed during the winter

months. Both homes are equipped with the same type of vents; TN1 had 9 vents and TN2 had

10

vents. Figure

4

is a photograph of a foundation vent typical of all the Tennessee homes.

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Figure

3

HVAC Unit and Craw l Space Access

Door

in

TN2

Figure

4

Typical Foundation Vent for all T ennessee Hom es

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Homes

TN3 and TN4

Homes TN3 and TN4 are located in a subdivision approximately five miles west

of

TN1 and

TN2. Both homes are one-story wood-framed contemporary homes with similar floor plans.

Similar to TN1 and TN2, these homes are located relatively close together on the same street.

Figures 5and

6

are photographs

of

these homes.

Figure 5

Home

TN3

Figure

6

Home TN4

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Except for the garages, both homes are built over ventilated crawl spaces. Post-construction

inspections revealed that radon-resistant features in these homes were similar to TN1 and TN2,

with the exception of the radon vent stacks. Instead of terminating in a tee fitting on the crawl

space floor, the pipes in both homes terminated approximately two-feet above the floor. The vent

pipes in both homes were extended below the polyethylene vapor barrier prior to initiating the

indoor radon tests.

Coeur d'Alene, Idaho

Seven homes were constructed by a builder in Coeur d'Alene, Idaho. Five of the homes are

located on the same street, essentially adjacent to each other. Another home is located in the

same development approximately a 1/4-mile to the south of these homes. The final home is

located in a subdivision approximately four miles to the west.

One of the homes is a tri-level (split level), with approximately two-thirds of the house

constructed over a ventilated crawl space. The lowest portion of this house is built on a concrete

slab, the next level is over the crawl space, and the highest level is over the lowest level. The

other homes

are

wood-framed ranchers built entirely over ventilated crawl spaces. All of the

homes are similar in size and have cast concrete foundation walls. Home ID1, shown in Figure

7, is similar in appearance to the other Idaho homes.

Figure 7

Home ID1

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The Idaho homes have unique crawl space layouts. While the other homes in the study have

individual piers interspersed throughout the crawl spaces to support floor joists, the joists in

the

Idaho homes are supported on continuous 2 x 4 wall sections that are supported by concrete

footings on the floors of the crawl spaces. Since these footings run the length of the crawl space

at two or three locations perpendicular to the floor joists, they essentially divide the crawl space

floor. into several ''bays''. Each bay is covered by 6-mil polyethylene vapor barrier. Figure

8

is

a photograph of a bay in the crawl space of home ID1. The concrete footing and

2

x

4

wall

supporting the floor joists is visible on the right, and the cast concrete foundation walls are

visible on the left.

Figure 8

Typical Cast Concrete Footing Supporting Floor Joists in Idaho Homes

Each home, with one exception, was constructed with a 3-inch diameter

PVC

adon vent stack.

The vent stacks terminate in tee fittings on or near the crawl space floors and extend up through

the roofs. One of the homes was inadvertently constructed without a vent stack. However, a

stack was improvised after construction was complete. This improvised vent stack is discussed

in detail in a following section of this report.

All of the homes have gas-fired forced-air furnaces with central air conditioning. The furnaces

in six of the seven homes are located in utility rooms adjacent to the garage. The furnace of the

remaining home (the tri-level) is installed on a concrete slab on the floor of the crawl space. All

ductwork is sealed and routed through the crawl space of each home. Access is provided through

a door installed in the floor above the crawl space in each home.

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During post construction inspections, it was discovered that six of the homes have a non-

closeable combustion air vent connecting the utility room with the crawl space. An additional

vent near the ceiling of each utility room connects the utility room with the rest of the house.

It should be noted that the CABO

One

and Two

Family Dwelling

Code [ 3 ] recognizes this vent

configuration as an acceptable means of providing combustion air to fuel-burning appliances.

However, this vent configuration creates a direct path for air in the crawl space to enter the

habitable area of a home. Since attempts to block or reroute the vents could have created

misfiring or backdrafting of the furnace and water heater, indoor radon tests were conducted with

the combustion air vents open.

Foundation vents are evenly interspersed along the perimeters of the foundation walls. The

screened area of each vent is approximately

8

x 16 , with a free area of 100-in2. Each home

has seven to ten vents. Two plastic covers permit each vent to be closed during the winter

months. Although the floors in each home

are

insulated with fiberglass batts between the floor

joists in the crawl spaces, the builder insisted that the closeable foundation vents reduced

homeowner complaints of cold floors during the winter months.

Roanoke, Virginia

Two homes, with similar designs, were constructed by a builder in Roanoke, Virginia. Both of

these homes are two-story wood-framed modular houses built on ventilated crawl spaces. The

foundation walls and piers are CMU block without a solid top course. Figure 9is a photograph

of home VA1.

Figure

9

Home VA1

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Both homes have a 3-inch diameter PVC vent stack extending from the crawl space through the

roof. The post-construction inspection in VA1 revealed that the vent pipe terminated

approximately 2-feet above the floor of the crawl space. The pipe was extended to the floor prior

to initiating tests. The post-construction inspection in VA2 revealed that the vent pipe terminated

in a tee fitting installed below a 6-mil polyethylene vapor barrier on the floor of the crawl space

per EPA recommendations.

Both homes have electric forced-air furnaces with central air conditioning. The furnaces in both

homes are suspended from the floor joists in the crawl spaces. All ductwork is sealed and routed

through the crawl space of each home. Crawl space access

to

both homes is provided by doors

in the foundation walls.

Different types of foundation vents are installed in the two homes. Home VA1 has six closeable

foundation vents distributed between two of the four foundation walls. Each vent measures

8

x

16

and has a free area of 40-in2. One of these vents is shown in Figure 10.

Figure

10

Found ation Vent in Home VA1

The foundation vents in home VA2 are non-closeable. The front of each vent is covered with

a plastic grille and a wire mesh screen. Ten of these vents are distributed between all four

foundation walls. The vents have the same external dimensions as the vents installed in home

VA1, however, the free area

is

not indicated. One of these vents is shown in Figure

11.

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Figure 11

Foundation Vent in

Home

VA


One home was constructed by a builder in Indianapolis, Indiana. This home is a wood-framed

rancher built over a ventilated crawl space. The crawl space has seven closeable foundation

vents that are identical to those installed in the Tennessee homes. The foundation walls and piers

are constructed of CMU block.

Figure

12

is a photograph of

this

home.

Figure 12

Home

IN1

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The crawl space floor of this home is covered by approximately 4-inches of pea gravel. The

post-construction inspection revealed that

4 mil

polyethylene vapor barrier was installed over the

pea gravel throughout the crawl space. Furthermore, the interior of the foundation walls is

covered with spray polyurethane foam insulation. According to the builder, this technique is less

labor intensive than installing insulation between the floor joists. The builder typically uses a

solid top course, although it was not visible sine the insulation extends from the pea gravel on

the floor up to the sill plates.

A 3-inch diameter PVC adon vent stack extends from a tee fitting, buried in the layer of pea

gravel, up through the roof. The house has a gas-fired furnace located in a utility room above

the crawl space with central air conditioning. Uninsulated sheet metal ductwork is routed through

the crawl space. Figure

13

is a photograph of the crawl space.

Figure 13

Crawl Space of Home

IN1

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Two homes were constructed on the same street by two different builders in Lake Ariel,

Pennsylvania. PA1 is a log home built on CMU block foundation walls with 10 closeable

foundation vents. PA2 is a contemporary wood-framed home built on CMU block foundation

walls with four temperature controlled foundation vents. Figure 14is a photograph of home

PA1, and Figure

15

is a photograph of home PA2.

Figure 14

Home PA1

Figure 15

Home PA2

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Unlike the other homes in the study, the Pennsylvania builders decided to cover the crawl space

floor in both homes with a skim coat

of

concrete.

This

feature was requested

by

both of the

homeowners, who wished to use their crawl spaces as storage areas. Prior to pouring the

concrete, the floors were covered with 6-mil polyethylene vapor barrier and a 3-inch diameter

PVC radon vent stack was stubbed up from a tee fitting buried below the floor of each crawl

space. Vent stacks were eventually routed through the roof of each home. The builders did not

seal or caulk pipe penetrations through the slabs or at joints between slabs and foundation walls.

Both homes are heated by hot-water baseboard radiators supplied by gas-fired boilers located in

the crawl spaces. Since the homes do not have forced-air ductwork, neither home has central air

conditioning. Crawl space access is provided by a door through the floor of each home.

Different types of foundation vents are installed in the two homes. Home PA1 has 10 closeable

foundation vents that are identical to the vents installed in home VA1. Each vent measured 8

x

16 and has a free area of 40-in2. Home PA2 has four closeable foundation vents that are

automatically controlled by temperature. Although these vents appear similar to those installed

in the Tennessee and Indiana homes, they are designed to close when the outdoor temperature

falls below freezing. One of these vents is shown in Figure 16.

Figure

16

Foundation Vent in Home PA2

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Huntsville, A labama

One home was constructed by a builder in Huntsville, Alabama.

This

home is a wood-framed

rancher built over a ventilated crawl space. The crawl space has eight closeable foundation vents

that are identical to those installed in the Tennessee and Indiana homes. The foundation walls

and piers are constructed of

CMU

block. Figure 17is a photograph of this home.

Figure

17

Home AL1

The crawl space floor was thoroughly covered with 6-mil polyethylene vapor barrier that was

tightly sealed at seams and foundation walls by contact cement.

A

3-inch diameter

PVC

radon

vent stack was routed from a tee fitting resting

on

thesoil below the vapor barrier up through

the roof.

The crawl space was accessible through a door in the foundation wall. Figure 18

shows the vapor barrier sealed to the foundation wall, with the radon vent stack in the

foreground.

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Figure

18

Sealed Vapor Barrier and Radon Vent

Stack in

Home

AL1

Although the builder constructed the foundation and framed this home, the owners were finishing

construction by themselves. Although construction of the home was essentially complete at the

time indoor tests were conducted, the owners still had not installed a heating

system.

Consequently, the crawl space did not have ductwork.

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TEST RESULTS

Indoor radon tests in

all

of the homes were conducted during 1995 and 1996. Tests in the

Tennessee, Idaho, Virginia, and Indiana homes were conducted between January and May 1995.

The Pennsylvania homes were tested during October and November 1995, and the Alabama home

was tested during April and May 1996. HVAC systems in all homes, except for the Alabama

home, were operated under normal living conditions during the tests. Closed-house conditions

were maintained as much as possible during the tests.

Three sets of tests, or phases , were conducted in most of the homes. Home VA1 was subjected

to a fourth phase of tests conducted with extra foundation vents opened. Each test phase lasted

approximately two weeks and was conducted as follows:

Phase

1

Radon vent stack and foundation vents closed.

Phase 2 Radon vent stack closed and foundation vents open.

Phase

3

Radon vent stack and foundation vents open.

Phase 4 Radon vent stack and extra foundation vents open.

Phase

5

tests (with activated radon-resistant construction) were not required in any of the homes

since all Phase 3 and 4 est results were below-2 pCi/1. Test results are presented in Figure 19

and listed in Table 1. Detailed test results are listed in Appendix C, and climatic data are listed

in Appendix D.

Figure 19

Summary of Test Results

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Table

1

Summary

of

Test

Results

'Phase

1

Tests: Radon vent stack and foundation vents closed.

'Phase 2 Tests: Radon vent stack closed and foundation vents open.

3Phase3 Tests: Radon vent stack and foundation vents open.

4Averages do not include ID7,VA2,

IN1,

and PA2 due to incomplete Phase 2 or

3

results.

Phase 1 tests in ID2 and PA2 were conducted with the vent stack open and the foundation vents

closed. The occupants of these homes were concerned about possible adverse health effects

caused by sealing the vent stack. However, the owners agreed to allow testing with the

foundation vents closed while the vent stack remained open.

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DISCUSSION

Baseline radon levels (Phase 1 levels) were reduced in 15 of the 17 homes when the foundation

vents were opened during Phase 2 tests. Phase 2 tests were not conducted in VA2 and PA2 due

to scheduling difficulties with the homeowners. Only three of the homes, TN2, TN4, and ID4,

had baseline measurements exceeding the EPA action level of

4

pCi/1. Opening the foundation

vents reduced these indoor measurements below the action level in each of these homes. Smaller

reductions were observed when the radon vent stacks were opened during Phase

3

tests. Four

homes had Phase 3 radon levels that were equal to or slightly greater than the corresponding

Phase 2 radon levels. Standard t-tests conducted on the paired data (Phase 1 and 2; Phase 2 and

3) indicated that these reductions are statistically significant at the 95% confidence level [4].


Tests in the Nashville homes were conducted between March and May 1995. Passive stacks and

foundation vents were closed during Phase

1

tests. Foundation vents were opened during Phase

2 tests, and passive stacks were opened during Phase 3 tests. Average measurements from the

lowest habitable level of each home are shown in Figure

20.

Figure 20

Radon Levels in Tennessee Homes

Opening the foundation vents during Phase 2 tests reduced the baseline radon levels (Phase 1

levels) in all of the Tennessee homes. TN2 and TN4 were reduced below the EPA action level

of 4-pCi/1. Opening the radon vent stacks during Phase 3 tests (foundation vents remained open)

provided additional reductions in all homes except TN1. The average Phase 2 radon level in

TN1 was 1.0-pCi/1,while the average Phase 3 level was 1.2-pCi/1. Phase 3 measurements may

have been affected by interior painting that was performed during the tests.

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Coeur d'Alene, Idaho

Tests in the Idaho homes were conducted between January and May 1995. Passive stacks and

foundation vents were closed during Phase 1 tests. Foundation vents were opened during Phase

2 tests, and passive stacks were opened during Phase

3

tests.

Average measurements from the

lowest habitable level of each home are shown in Figure 21.

Figure 21

Radon Levels' in Idaho Homes

Opening the foundation vents during Phase 2 tests reduced baseline radon levels (Phase 1 levels)

in all of the Idaho homes. ID4 was the only home with baseline radon levels above the EPA

action level, and these levels were reduced below the action level when the foundation vents were

opened. Opening the radon vent stacks during Phase 3 tests provided additional reductions in

all homes except ID3 and ID7. Since the builder did not install a vent stack in ID3, this home

was fitted with an improvised vent stack consisting of a length of 4-inch diameter drain tile

routed from under the vapor barrier to a foundation vent. Test results indicate that this

improvised stack had no measurable effect on radon levels. Phase 3 tests were not conducted

in ID7.

All of the Idaho homes, except ID6, were built with a non-closeable combustion air vent in the

utility room floor above the crawl space. Although the CABO

One nd

Two Family Dwelling

ode

recognizes this vent configuration as an approved method of supplying combustion air to

fuel-burning appliances, these vents provide a direct path for radon to enter the living areas of

a home. However, these vents do not appear to adversely affect the performance of the radon-

resistant features in the Idaho homes.

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Roanoke,

Virginia

Tests in the Virginia homes were conducted between March and May 1995. Passive stacks and


2 tests, and passive stacks were opened during Phase 3 tests. Extra foundation vents were opened

in VA1 during Phase 4 ests. Average measurements from the lowest habitable level of each

home are shown in Figure 22.

Figure

22

Radon

Levels

in Virginia Homes

Baseline radon levels (Phase 1 levels) in VA1 were reduced when the foundation vents were

opened during Phase 2 tests. Opening the vent stack during Phase 3 tests appeared to provide

little or no additional reductions. However, additional reductions were measured during Phase

4 ests where extra foundation vents were opened (vent stack and original foundation vents

remained open). Indoor radon levels during all tests in VA1 remained below the EPA action

level.

Phase 1 and 3 tests were conducted in VA2.

Since this home had non-closeable foundation

vents, Phase 3 tests were conducted first to permit the fabrication of vent covers for Phase 1 and

2 tests. Due to scheduling difficulties with the homeowners and impending warm weather, Phase

2 tests were skipped in order to measure baseline radon levels. Although Phase

3

radon levels

were lower than baseline levels, measurements during all tests were below 1-pCi/1.

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Tests in the Indiana home were conducted during April

and

May 1995. The passive stack and


2

tests, and the passive stack was opened during Phase

3

tests. Average measurements from the

lowest habitable level are shown in Figure

23 .

Figure

23

Radon

Levels

in Indiana Home

Radon levels in the Indiana home were extremely low. The average baseline radon level (Phase

1 level) of 0.4-pCi/1 ell to 0.1-pCi/1 fter the foundation vents were opened during Phase

2

tests.

Phase 3 tests were not conducted.

The soil radon level for this home was similar to several of the Tennessee homes that exhibited

higher indoor radon levels (see Table 1). However, the Indiana home had several unique

construction features including a gas-permeable aggregate layer under the vapor barrier and

foundation walls insulated with spray polyurethane foam. Furthermore, the builder did not

insulate or seal the sheet metal ductwork since the crawl space was insulated. The effect of these

construction features cannot be determined from the test results.

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Tests in the Pennsylvania homes were conducted during October and November

1995.

Passive

stacks and foundation vents were closed during Phase 1 tests. Foundation vents were opened

during Phase

2

tests, and passive stacks were opened during Phase

3

tests. Average

measurements from the lowest habitable level of each home are shown in Figure 24.

Figure 4

Radon L evels in Pennsylvania Homes

Radon levels in both of the Pennsylvania homes were very low. Average Phase 2 and 3 radon

levels in PA1 were slightly higher than the average baseline level (Phase

1

level). Furthermore,

opening the radon vent stack during Phase 3 tests provided no measurable reductions from Phase

2 levels. Despite these inconclusive results, average radon levels in PA1 never exceeded 0.6

pCi/1.

Opening the foundation vents and the radon vent stack provided small reductions in PA2,

although average radon levels never exceeded 1.0-pCi/1. Phase 2 tests were not conducted due

to scheduling difficulties with the homeowners.

The builders used a unique method of sealing the vapor barrier. Since the crawl space floors

were flat, the builders poured a skim coat of concrete (approximately 2-inches thick) over the

barrier. This concrete layer covered the entire floor, and effectively sealed the barrier at seams,

foundation walls, and piers. Although the effect of the concrete layer on indoor radon levels

cannot be determined from the test results, it should be noted that the crawl spaces resembled

ventilated basements instead of typical crawl spaces.

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Huntsville, A labama

Tests in the Alabama home were conducted during April and May 1995. The passive stack and


2 tests, and the passive stack was opened during Phase 3 tests. Average measurements from the

lowest habitable level are shown in Figure 25 .

Figure

25

Radon Levels

in

Alabama Home

Radon levels in the Alabama home were extremely low. However, average baseline radon levels

(Phase

1

levels) were reduced when the foundation vents were opened during Phase

2

tests.

Opening the vent stack during Phase 3 tests had little or no measurable effect on indoor radon

levels.

Although the Alabama home had the highest soil radon measurement in this study (see Table l),

indoor radon levels remained below 1.0-pCi/1during all tests. It should be noted that this was

the only home

in

the study where the builder tightly sealed the vapor barrier at seams, piers, and

foundation walls. Furthermore, since this home did not have central heating and air conditioning,

penetrations between the crawl space and the living area were minimized. Although the effect

of these construction features cannot be determined from the test results, it is possible that they

contributed to the low baseline radon levels.

25


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CONCLUSIONS

Only three of the 17 homes had average baseline radon levels (Phase 1 levels) greater than or

equal to the EPA action level of 4.0-pCi/1. Radon levels in all three homes fell below the action

level when the foundation vents were opened during Phase 2 tests.

Phase 2 and Phase

3

radon levels

in

all homes

were

below the EPA action level. The highest

average Phase 2 radon level was 2.4-pCi/1. Phase 2 radon levels were consistently lower than

baseline radon levels. Test results from most of the homes indicate that foundation vents appear

to have a measurable effect on indoor radon levels. The (geometric) average baseline radon level

of 2.2-pCi/1 ell to 0.7-pCi/1when the foundation vents were opened during Phase 2 tests. The

highest average Phase

3

radon level was 1.6-pCi/1. Average Phase

3

radon levels in all but two

of the remaining homes were below 1.0-pCi/1. The (geometric) average Phase 2 radon level of

0.7-pCi/1 ell to 0.5-pCi/1when the vent stacks were opened during Phase 3 tests.

One home was subjected to an additional set of tests intended to measure the effect of extra

foundation vents on indoor radon levels (Phase 4 tests). Although the average radon level was

only 1.6-pCi/1with the vent stack and (original) foundation vents open, the extra foundation vents

reduced the average level to 1.3-pCi/1.

The effect of the vent stacks on indoor radon levels is difficult to determine. Since opening the

foundation vents during Phase 2 tests generally reduced baseline radon levels below 1 0-pCi/1 n

most of the homes, there was little opportunity for additional reductions during Phase 3 tests

when the vent stacks were opened. However, in the three homes with baseline radon levels

above the EPA action level, opening the vent stacks resulted in reductions from Phase 2 levels.

Since indoor radon levels in all of the homes were below 2.0-pCi/1with the vent stacks and

foundation vents open, none of the homes required active radon-resistant construction.

In summary, measurements in the homes in this study indicate that passive foundation vents may

be an effective stand-alone mitigation system in crawl space homes, especially where adequate

vent area is provided. This method should be investigated further in homes with higher baseline

radon levels. It should also be noted that many local practices can be in conflict with the EPA

recommendation (for example, most of the homes in this study had closeable foundation vents.

Solutions to these issues should be investigated to provide greater flexibility in using the Model

Standards Code.

26


29/48

REFERENCES

[ l]

U.S. EPA. Mode l Standards and Techniques fo r Control of Radon in New Residential

Buildings.

Published

by

the United States Environmental Protection Agency, Washington, D.C..

EPA. 402-R-94-009.

March

1994.

[2]

U.S. EPA.

EPA s Map of Radon Zones.

Published by the United States Environmental

Protection Agency, Washington, D.C..

EPA 402-R-93. September 1993.

[3] CABO.

1995 CABO One and Two Family Dwelling Code.

Published by the Council

of'

American Building Officials, Falls Church, Virginia. 1995.

[4] Gidra, I.N.

Pro babil ity and Statistical Inferencefor Scientists and Engineers.

Prentice-Hall,

Inc. 1973. pp. 265-269.

27


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Appendix A

Quality

Control Procedures

A - 1


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Soil Tests

Soil radon measurements were obtained by connecting the scintillation cell of a

continuous radon monitor (a Pylon AB-5) to a hollow steel probe driven into soil.

A

small pump drew an air sample from the probe into the radon monitor.

The accuracy of these measurements was maintained using the following quality

assurance procedures:

Scintillation cells were flushed before each test. Each cell was flushed for at least

10

minutes before each use and for approximately an hour at the end of each day

of testing.

Background radon levels were measured before each test. The readings were

subtracted from the soil readings to ensure that they would not skew soil radon

measurements.

The accuracy of the continuous radon monitor was verified by calibration against

a calibrated test cell.

Indoor

Tests

Electret ion chamber (E-PERM) radon detectors were used to measure all indoor radon

concentrations. All testing was conducted in accordance with EPAs Indoor Radon and

Radon Decay Product Measurement Protocols (1992). Several specific quality assurance

procedures were employed to ensure the accuracy of these indoor measurements.

Test Procedures

E-PERMS were deployed in accordance with EPAs

Protocol fo r Radon and Radon Deca y

Product Measurement in Homes

(1993) and

Indoor Radon and Radon Decay Product

Measurement Protocol

(1992). E-PERMS were deployed in accordance with the

following procedure:

E-PERMS were located in areas least susceptible to drafts, away from exterior

walls, vents, doors, fireplaces, and excessive heat sources.

E-PERMS were placed in areas where they would not be disturbed during

deployment.

E-PERMS were placed at least 30-inches above the floor.

A - 2


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Procedure Documentation

A database was maintained during the project to record key construction characteristics

and radon measurements for each home. A travel log was also kept to record activities

accomplished during each visit to each home.

The construction characteristics log contains the following information:

Location of test devices

Duration of tests

Type of tests

Topography

Other unusual conditions

Type of heating and cooling system

Description of the home, including foundation type, number of stories, and

construction materials

Details of radon reduction/prevention techniques

The E-PERM log contains the following information for each home:

E-PERM serial numbers

Indoor test locations

Duration of each test phase (date and time of E-PERM installation and retrieval)

Measured indoor radon concentration (pCi/1)

The travel log contains the following information for each home:

Date of each visit

Activities conducted during each visit

Duplicate Tests

Duplicate E-PERMS were installed side-by-side in the lowest occupied level of each

home. Although EPA protocol only requires 10-percent of all homes to be tested with

duplicate E-PERMS, all 17 homes in the study were tested with duplicates to maximize

measurement reliability. According to EPA protocol, duplicate measurements must not

vary by more than 10-percent for measurements exceeding 4.0-pCi/1.

If

the readings vary

by a greater value, the home must be retested and the measurement equipment checked

for proper operation.

A - 3


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Accuracy

of

Recorded Data and Analytical Procedures

Radon measurements obtained from each tested home were screened by the Research

Center for accuracy. The screening process involved comparing readings obtained from

different phases of testing. Readings obtained from tests conducted with the radon vent

pipe open (Phase 2 tests) were compared to readings obtained with the vent pipe closed

(Phase

1

tests).

If

readings obtained with the vent pipe open were higher than readings

obtained with the vent pipe closed, a retest was ordered. Extremely high or low readings

were also subject to scrutiny.

The Research Center compiled a database consisting of E-PERM test results for

all

the

tested homes. The error associated with all E-PERM results is calculated in accordance

with procedures dictated by Rad-Elec, Inc., the E-PERM manufacturer. These errors are

listed with the test results presented in Appendix C.

E-PER M Measurement and C alibration

The E-PERM voltage reader, used to obtain the measured radon concentrations, was

calibrated with two reference cells every two months. The readings obtained from these

reference cells were compared against their certified values and are entered in a logbook.

If the reference cell readings differed by more than a specified amount, test protocol

required the voltage reader to be returned to the manufacturer for calibration.

Measurements indicated that calibration cell readings were within specified tolerances

throughout the project. Both reference cells were certified by Rad Elec, Inc. in January,

1995.

The Research Centers measurement capabilities are also verified by the EPAs National

Radon Measurement Proficiency (RMP) Program. RMP laboratories periodically test the

Research Centers measuring capabilities by exposing E-PERMS submitted by the

Research Center to a known radon concentration in an EPA radon chamber. Without

knowledge of this radon concentration, the E-PERMS are returned to the Research Center

for measurement. The readings are then submitted to the RMP laboratory for comparison

against the known values. The values measured by the Research Center must fall within

25-percent of the known values to meet the RMPs performance requirement. The

Research Center is currently listed by the RMP for performance of radon tests using

short-term (SST) E-PERMS.

A - 4


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Appendix B Construction Characteristics

B - 1


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CONSTRUCTION CHARACTERISTICS DATA SHEET

Sites:

Location: Nashville, Tennessee

Description

Two-story wood-framed homes built over ventilated crawl space foundations with 7 to

10 (closeable) foundation vents. Each vent has exterior dimensions of 8 x 16 with

unspecified free area. Foundation walls and piers are CMU block.

Crawl space

access doors are located in foundation walls (exterior).

HVAC Systems

Gas-fired forced-hot air furnaces with central air conditioning.

HVAC units are

located outdoors and ductwork is routed through foundation walls through the crawl

spaces. Ductwork is insulated and taped.

Radon-Resistant Construction

Crawl space floors are covered with 6-mil polyethylene vapor barrier. Barrier is

sealed at foundation walls, piers, utility penetrations, and seams in TN2 and TN4 with

a general construction adhesive (caulk). Barrier is sealed along seams in the vicinity

of the radon vent stack in TNl and TN3. 3-inch diameter PVC vent pipes extend

from tee fittings on crawl space floors through the roof of each home. Tee fittings on

the bottom of all vent pipes are sealed underneath the vapor barrier. Top courses of

block walls are not solid, but are covered with polyethylene vapor barrier and 2x8 sill

plates. There are no visible openings between crawl spaces and living areas above

the crawl spaces.

TN1, TN2, TN3, and TN4

B - 2


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Sites:

Location: Coeur d'Alene, Idaho

Description

Wood-framed ranch-style (single level) homes built over ventilated crawl space

foundations with

7

to 10 (closeable) foundation vents. Exterior dimensions of each

vent is

8

x 16 with 100-square inches of free area. Foundation walls are cast

concrete. Crawl space floors are divided into three or four individual sections by

concrete footers that support floor joists (instead of piers). Crawl space access doors

are located in bedroom closets (indoors).

HVAC

Systems

Gas-fired forced-hot air furnaces with central air conditioning. Furnaces are located in

utility rooms adjacent to garages. One noncloseable combustion air duct (4 x 12 ) is

located in the floor of each utility room, and

an

identical vent is located in the

partition wall between the utility room and living area. Ductwork is insulated, taped,

and routed through crawl spaces.



sealed at foundation walls, piers, utility penetrations, and seams in ID1 and ID4 with a

general construction adhesive (caulk). Vapor barrier in the other homes is pulled

tightly against foundation walls and piers but is not sealed. 3-inch diameter PVC vent

pipes extend from tee fittings on crawl space floors through the roof of each home.

Tee fittings on the bottom of all vent pipes are sealed underneath the vapor barrier.

Each individual section of the crawl space floor in each home is connected to the vent

pipe by pipes routed between each floor section. Foundation walls are cast concrete.

ID1, ID2, ID3, ID4, ID5, and

ID7

B - 3


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Site: ID6

Location: Coeur d'Alene, Idaho

Description

Wood-framed tri-level home. The second level is built over a ventilated crawl space

(approximately two-thirds of the foundation footprint) and the first and third levels are

built slab-on-grade. The crawl space has 7 closeable foundation vents with exterior

dimensions of 8 x 16 and 100-square inches free area. Foundation walls are cast

concrete. Crawl space floor is divided into three individual sections by concrete

footers that support floor joists (instead of piers). Crawl space access door is located

under stairwell between first and second levels (indoors).

HVAC System

Gas-fired forced-hot air furnace with central air conditioning. Furnace is installed on

a slab in the crawl space. Ductwork is insulated, taped, and routed through the crawl

space.


Crawl space floor (except for furnace slab) is covered with 6-mil polyethylene vapor

barrier. Vapor barrier is pulled tightly against foundation walls and piers but is not

sealed. A 3-inch diameter PVC vent pipe extends from a tee fitting on the crawl

space floor through the roof. The tee fitting on the bottom of vent stack is sealed

underneath the vapor barrier. Foundation walls are cast concrete. There are no visible

openings between crawl space and living area above the crawl space.

B - 4


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Sites:

VA1 and VA2

Location:

Roanoke, Virginia

Description

Two-story wood-framed homes built over ventilated crawl spaces. VA1 has 6

closeable foundation vents with exterior dimensions of 8 x 16 and free area of

40-

square inches. VA2 has 10 noncloseable foundation vents with exterior dimensions of

8'' x 16 with unspecified free area. Foundation walls and piers are CMU block.

Crawl space access doors are located in foundation walls (exterior).

HVAC Systems

Electric forced-hot air furnaces with central air conditioning. Furnaces are suspended

from crawl space ceilings (floor joists). Ductwork is insulated, taped, and routed

through crawl spaces.



sealed at foundation walls, piers, utility penetrations, and seams with a general

construction adhesive (caulk). 3-inch diameter PVC vent pipes extend from tee

fittings on crawl space floors through the roof of each home. Tee fittings

on

the

bottom of all vent pipes were sealed underneath the vapor barrier. Top course of

block walls in VA2 is solid, while top course in VA1 is not solid. There were no

visible openings between crawl spaces and living areas above the crawl spaces.

B - 5


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Site:

IN

Location: Indianapolis, Indiana

Description

Wood-framed rancher-style (single level) home built over a ventilated crawl space

with

7

closeable foundation vents with exterior dimensions of 8 x 16 and

unspecified free area. Foundation walls and piers are cast concrete. Interior side of

foundation walls is covered with foam insulation; unable to determine if solid top

course was used. Crawl space access door is located in bedroom closet (indoors).

HVAC System

Gas-fired forced-hot air furnace with central

r

conditioning. HVAC unit is located

outdoors and ducts are routed through the crawl space. Sheet-metal ductwork in crawl

space

is

not insulated or taped.


Crawl space floor is covered with a 4-inch layer of course aggregate (pea gravel) and

a 4-mil polyethylene vapor barrier. Vapor barrier is pulled tightly against foundation

walls and piers but is not sealed.

A

3-inch diameter PVC vent pipe extends from a tee

fitting buried in the aggregate layer through the roof. The tee fitting on the bottom of

the vent stack is sealed underneath the vapor barrier. There are no visible openings

between crawl space and living area above the crawl space.

B 6


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Site:

PA1

Location:


Description

Two-story log home built over a ventilated crawl space with

10

closeable foundation

vents with exterior dimensions of

8

x

16

and 40-square inches of free area.

Foundation walls and piers are CMU block. Interior side of foundation walls is

insulated with -inch polystyrene board. Crawl space access door is located under the

stairwell (indoors).

HVAC System

Hot water baseboard radiators supplied by a gas-fired boiler in the crawl space. No

central air conditioning and no ductwork.


Crawl space floor is covered with 6-mil polyethylene vapor barrier that is covered by

a skim coat (approximately 2-inches) of concrete.

A

3-inch diameter PVC vent pipe

extends from

a

tee fitting buried under the slab through the roof. Foundation walls

have solid top course.

area above the crawl space.

There are

no

visible openings between crawl space and living

B - 7


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Site: PA2

Location: Lake Ariel, Pennsylvania

Description

Two-story wood-framed home built over a ventilated crawl space with 4 loseable

foundation vents with exterior dimensions of 8 x 16 and unspecified free area.

Vents are designed to close when outdoor temperature falls below freezing.

Foundation walls and piers are CMU block. Interior side of foundation walls is

insulated with -inch polystyrene board. Crawl space access door is located under the

stairwell (indoors).

HVAC System

Hot water baseboard radiators supplied by a gas-fired boiler in the crawl space. No

central air conditioning and no ductwork.


Crawl space floor is covered with 6-mil polyethylene vapor barrier that is covered by

a skim coat (approximately 2-inches) of concrete. A 3-inch diameter PVC vent pipe

extends from a tee fitting buried under the slab through the roof. Foundation walls

have solid top course. There are no visible openings between crawl space and living

area above the crawl space.

B - 8


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Site: AL1

Location:

Huntsville, Alabama

Description

Rancher-style (single level) home built over a ventilated crawl space with 7 closeable

foundation vents with exterior dimensions of

8

x 16 and unspecified free area.

Foundation wallsand piers are CMU block. Crawl space access door is located in the

foundation wall (outdoors).

HVAC System

This home was not equipped with an HVAC system or ductwork during indoor radon

tests.


Crawl space floor is covered with 6-mil polyethylene vapor barrier that is sealed at

foundation walls, piers, and

seams

with a construction adhesive.

A

3-inch diameter

PVC vent pipe extends from a tee fitting sealed under the vapor barrier through the

roof. Foundation walls do not have a solid top course. There are no visible openings

between crawl space and living area above the crawl space.

B - 9


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AppendixC Test Data

C 1


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Tennessee Homes

Home

ID 1

ID2

3.73 0.62 0.84 0.1 1

TN3 2.26 0.55 1.48 0.43 0.89 0.1 1 14.1 7.2 7.8

2.58 0.54 1.38

0.40

0.82 0.1 1

TN4 5.48 0.62 2.42 0.45 1.41 0.13 7.6 1.1 7.2

5.09 0.61 2.44

0 46

1.51 0.13

I Phase 1 Phase 2 Phase 3 Duplicate Variation ( )

Radon Error Radon Error Radon Error Phase Phase Phase

(pCi/1)

(pCi/1) (pCi/1) (pCi/1)

(pCi/1) (pCi/1) 1 2 3

3.27 0.19 0.32 0.10 0.20

0.10 0.9 11.9

3.30

0.19 0.28 0.10 0.08 0.10

2.79

0.17 0.7 1 0.11 0.30 0.10 13.0 11.8 9.2

Idaho Homes

ID5

ID6

ID7

2.22 0.35 0.35 0.10 0.25 0.10 6.5 12.3 11.1

2.37 0.39 0.39 0.10 0.23 0.10

1.40 0.27 0.21 0.10 0.30

0.10

8.4 21.4

1.52 0.29

0.25 0.10 0.10 0.10

1.47 0.13 0.12 0.10 17.0 88.0

1.72 0.13 0.22 0.10

C 2


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Virginia, Indiana, Pennsylvania, and Alabama Homes

Home

VA1

VA2

IN1

PA1

PA2

AL1

Phase 1 Phase 2 Phase 3 Duplicate Variation

( )

Radon Error Radon Error Radon Error Phase Phase Phase

2.75 0.39 1.59 0.13 1.60 0.13 2.3 4.4 5.8

2.8 1

0.40

1.66 0.13 1.69 0.13

0.75 0.11 0.37 0.10 7.0 6.0

0.70 0.11 0.39 0.10

(pCi/1) (pCi/1) (pCi/1) (pCi/1) (pCi/1) (pCi/1) 1 2 3

0.50 0.10 0.23 0.10 75.2 124.3

0.28 0.10

0.10 0.10

0.43 0.1 1 0.68 0.12 0.61 0.11 37.2 17.8 5.8

0.3

1

0.10 0.58 0.1 1 0.65 0.12

0.85 0.12

0.59 0.1 1 36.1 10.2

1.16 0.13

0.53 0.1 1

0.58 0.1 1 0.24 0.10 0.34 0.10 6.9 78.4 88.4

0.54 0.1 1 0.43 0.10 0.18 0.10

VA1

C 3

Radon Error Duplicate Variation

(pCi/1) (pCi/1)

( )

1.23 0.12

1.27 0.12

3.1


46/48

Appendix D Climatic

Data

D - 1


47/48

Average

Daily

Outdoor Tem peratures

(F)

Day

1

2

Nashville, TN Coeur d'Alene, ID

Mar.

1995

Mar. Jan Feb.

1995 1995 1995

38 46

6 18

43

29

47

51

35

54 57

18 41 30 44 5

D - 2


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Average Daily Outdoor Temperatures

(F)

Day

1

2

Roanoke,

VA

Indianapolis,

IN

Scranton,

PA

Oct. Nov.

1995 1995 1995

Mar.

47

48

55

40 6

59

52

44

45

50 46

53 66 62

Documents

Passive Radon Resistant Construction Performance IN VENTILATED CRAWL SPACE HOMES