United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-87/027 Sept. 1987
Project Summary
Development and Demonstration
of Indoor Radon Reduction
Measures for 10 Homes in
Clinton, New Jersey
Linda D. Michaels
In the spring of 1986, the New Jersey
Department of Environmental Protec-
tion (DEP) found a cluster of houses
with extremely high radon levels in the
town of Clinton, New Jersey. Research
Triangle Institute was contracted to
develop and demonstrate radon reduc-
tion techniques in 10 of these houses.
The work was to be completed before
the 1986-87 winter heating season
began.
The demonstration homes were se-
lected from 56 houses in the subdivision
of Clinton Knolls. All of these houses
had shown radon concentrations in
excess of 64 pCi/l when monitored in
the spring of 1986. Each of the houses
was inspected, and 10 representative
houses were selected for the radon
reduction demonstration project.
Following intensive diagnostic work
and monitoring in each of the houses, a
radon reduction plan was developed.
With the agreement of the homeowners,
radon reduction systems were installed
during the summer of 1986. All 10
houses had radon concentrations signi-
ficantly reduced by the fall of 1986.
The average cost of radon reduction
was $3,127.
This Project Summary wat developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).
Introduction
The discovery of high indoor concen-
trations of radon gas in the Reading Prong
area of New Jersey, New York, and
Pennsylvania, and in other locations in
the United States, has raised serious
concerns about a large number of people
being exposed to the radioactive gas. In
response, the U.S. Environmental Protec-
tion Agency (EPA) issued guidelines re-
commending corrective action in houses
with radon concentrations in excess of 4
picocuries per liter (pCi/l), or 148
Becquerels per cubic meter, of air. At
radon concentrations of 200 pCi/l,
temporary relocation is recommended.
In the early spring of 1986, more than
50 of the houses with indoor radon con-
centrations greater than 100 pCi/l were
identified in the subdivision of Clinton
Knolls. Many of these houses had radon
concentrations of 600 pCi/l or higher.
The primary purpose of the work de-
scribed in this report was to develop and
demonstrate cost-effective radon reduc-
tion techniques in 10 representative
Clinton Knolls houses. Radon reduction
was to be completed before the beginning
of the 1986-87 heating season to keep
the exposure of residents to a minimum.
Additional data were collected to add to
the general body of information on radon
transport and its control in houses; how-
ever, this data collection was secondary
to the pressing need to demonstrate ef-
fective radon reduction techniques by the
fall of 1986.
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Background
The subdivision of Clinton Knolls is
near the center of the town of Clinton,
New Jersey. The neighborhood is domi-
nated by frame houses with approximately
139 m2 (1500 ft2) of floorspace. This
uniformity is the result of development of
the subdivision by a single builder. Some
custom-built houses, similar in style and
size to the developer-built houses, are
scattered among those built by the prime
contractor. While most of the houses are
approximately 18 years old, many of the
56 volunteer houses that were surveyed
were still occupied by their original
owners, making this neighborhood a
stable one.
The development is built on a dolomitic
limestone hill that rises above Main Street
and ends at the edge of an abandoned
quarry. The hill crests at the interior
streets of the subdivision with bedrock
rising to the surface in the area. Several
homeowners reported that the bedrock
beneath their houses had to be blasted
before basements could be built or before
sewer lines could be put in place.
Residents also reported the appearance
of sinkholes throughout the neighborhood
where the formation of underground
caves had caused the earth to subside.
Selection of Demonstration
Houses
Participants in the DEP radon survey in
March and April of 1986 — 103 home-
owners — were asked to volunteer their
houses for the radon reduction demon-
stration effort. Of the volunteers, 56 were
selected for screening. Table 1 shows the
range of radon concentrations for the
103 houses participating in the DEP radon
survey.
Three basic floorplans were repeated
throughout the subdivision and are re-
produced from the original developer's
promotional brochure in the full report. In
addition, a small number of diverse floor-
plans built by independent contractors
were also investigated.
During a 1 -week period, each of these
houses was investigated by a diagnostic
team of EPA and Research Triangle
Institute (RTI) personnel. The objective of
EPA's house screening effort was to
characterize the pool of houses and select
10 houses as representative of the Clinton
housing stock which could be used to
demonstrate radon reduction measures.
Diagnostic Procedures Used
Prior To Radon Reduction
Diagnostic techniques focused on the
detection and isolation of three main
mechanisms of radon entry and transport
in a structure:
• Simple transfer through substructure
openings. Radon enters a house
through openings connecting the
house substructure to the soil. These
entrances need not be very large to
constitute a significant radon path-
way. Small slab-cracks, hollow pipes,
sump holes, or any other features
that penetrate the foundation of the
house are likely sources.
• Negative-pressure-driven transport.
Negative air pressure over the portion
of the structure with soil contact
results in a pressure-driven transport
of radon and other soil gases into
the house. Negative pressure can be
induced by the use of fans, appli-
ances, and natural ventilation in the
house.
• Thermally driven transport. Differ-
ences in temperature between the
soil-contacting portions of the build-
ing and the rest of the structure due
to normal heating of the house may
cause the thermally driven transport
of radon from the soil into the house.
Although numerous sources have con-
firmed these general mechanisms, little
Tab/0 1. Clinton Radon Levels
Concentration (pCi/ll
>2048
1024-2047
512-1023
266-511
128-255
64-127
32-63
16-31
8-15
4-7
<4
No. of Houses
2
3
13
17
17
12
12
14
5
6
2
103
% of Sample
1.9
2.9
12.6
16.5
16.5
11.7
11.7
13.6
4.9
5.8
1.9
information is available on the effect on
indoor radon levels as the three mecha-
nisms interact with one another in a
house. Also, limited data are available to
describe the interactive effects of other
factors such as the tightness of a house
or the operation of an assortment of
common indoor venting devices such as
a whole house fan.
Consequently, the 10 houses in Clinton
were diagnosed using two approaches.
The first approach was to identify and
characterize all possible sources of in-
leakage, negative pressure, and thermally
induced transport in each house. The
second approach was to simulate, in
isolation, conditions that might enhance
or reduce radon transport and then mea-
sure the actual effect. The second ap-
proach was used in a small number of
houses. Experiments in this latter cate-
gory include:
• Measuring the effect of whole house
fan operation.
• Investigating the negative pressure
induced on the basement by the use
of various household appliances.
• Using a high volume fan to simulate
winter-time stack effect.
• Measuring the effect that furnace
operation has on basement pressure.
• Experimenting with supplied outdoor
makeup air to reduce negative
pressure.
In all cases, the objective of the diag-
nostic procedure was to understand the
mechanism and identify sources of radon
infiltration to develop a low-cost and
effective radon reduction strategy for each
of the demonstration houses.
Radon Grab Sample
Measurements
Radon grab samples, used in the diag
nostic procedures, were obtained using
Pylon scintillation cell in conjunction witl
a Pylon AB-5 fitted with a Lucas ce
adapter. Following EPA recommende
procedures, grab samples were used t
identify suspected soil gas entry route:
In all houses with sump holes, gra
samples were taken in the stream of a
exiting the footer drain pipe.
Qualitative Measurements of So
Gas Entry
In all cases, the floors, joints, ar
undergrade walls of each house wei
visually examined to identify potent!
entry points. A simple smoke tube te
was then made at any potential site
entry to determine the direction of airflow
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Characterization of Subslab
Aggregate
Because of the high radon concentra-
tions encountered in the 10 demonstra-
tion houses, it seemed likely that soil
depressurization would be necessary.
Consequently, all houses were inspected
to determine the composition of the sub-
slab aggregate.
Measurement of House
"Tightness"
House tightness is used, in the context
of this report, to indicate relative leakage
area in a house. Air exchange rates were
measured for each of the 10 homes in
Clinton using a standard blower door test
(ASTM Method E779-81). The objective
was to determine the extent of leakage
into the house. If the leakage was ex-
tensive, structural rebuilding might have
been necessary for the radon reduction
efforts to be effective. If tightness showed
a good correlation with high radon levels,
radon reduction measures might con-
centrate on compensating for the low
volume of available dilution air in a house.
Data from blower door measurements
were fitted using various models for the
prediction of air exchange rates.
Infiltration rates predicted by the
models range from 0.4 to 1.1 air changes
per hour (ACH) with an average of 0.62
ACH (excluding results from the Shaw
combined model). Correlation between
predicted air exchange rates and radon
concentrations in the 10 houses was
low, with a coefficient of correlation of
0.60.
On the basis of these results, it was
concluded that the extremely high radon
concentrations encountered in the Clinton
homes were not due to the tightness of
the structures, but were more likely due
to the unusually high source strength.
Whole House Fan Test
A test was made to gain some insight
into the potentially competing effects of
increased soil gas entry versus added
dilution air when a whole house fan was
used for ventilation. The results are shown
in Figure 1. Although the fan dramatically
increased ventilation (in the neighborhood
of 2,000 cfm), the large negative pressure
differential (=28 Pa) increased the rate of
soil gas entry sufficiently to overwhelm
the diluting effect. Since this test was
made in only one house, the results may
depend on factors that are peculiar to the
individual building, soil gas, and soil
characteristics.
140
120
100
80
^ 60 1
\
-S 40
c
20-
*/vA
(fan on)
*M*t
0 y*-~i i I I I I I I « •!< M M ) M M II < I I I M I I I I I I I I I I I I nil I
5.30 7:30 9:30 11.30 1:30 3:30 5:30 7:30 9.30 11:30 1:30 3.30
P.M. A.M. P.M.
Time
Figure 1. Effect on radon concentration of whole house fan use with all windows open
Investigations of Negative
Pressure Induced on Basements
In the majority of houses, differential
air pressure between basement air and
outside air was measured. Temperature-
driven stack effects and mechanical
equipment effects were isolated, and the
induced pressure differences were
measured.
Simulation of Winter Conditions
Data from a variety of sources have
confirmed that winter indoor air concen-
trations of radon are even higher than
those measured under closed-house
conditions in other seasons. Work in
Clinton took place in the summer. As a
result, a variety of means were attempted
to simulate winter conditions. These ap-
proaches were largely unable to produce
summer radon concentrations that were
similar to those that had been recorded
the previous spring.
Increasing Makeup Air
Additional negative pressure in base-
ment areas produced by the normat
operation of furnaces can result in in-
creased indoor radon levels. One approach
to controlling this effect is the introduction
of makeup air to the basement or the
furnace itself. Several methods of pro-
viding makeup air were tested in one of
the houses in Clinton. Results of these
tests are reported.
Radon Monitoring
Two radon monitoring techniques were
used during this program: continuous
radon monitoring using a Pylon AB-5
monitor together with a passive radon
scintillation cell detector (PRO), and an
integrating short-term technique using
charcoal canisters. Protocols for the use
of these techniques are detailed in the
project Quality Assurance Project Plan
(QAPP).
To differentiate between random fluc-
tuations in concentration levels and any
real reductions due to the radon reduction
efforts, control houses were selected for
simultaneous monitoring with radon re-
duction demonstration houses to be
mitigated. Control houses were chosen
on the basis of proximity and similarity in
floorplan to the radon reduction demon-
stration houses.
Installation of Radon
Reduction Equipment
The report describes in detail both the
radon reduction equipment installed in
each house and a rationale based on
diagnostic measurements and house
structure for the methods used. Materials
employed are also detailed. Summary
cost estimates for the installations are
presented in the report.
Results and Discussion
Table 2 shows the estimated radon
reductions achieved for each of the
houses in Clinton. Since pre-installation
radon measurements were made in the
summer when radon concentrations are
lower than in any other season, two
estimates are shown. The first shows the
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Table 2. Approximate Reduction In Radon Concentrations Using Charcoal Canister Data Following Application of Radon Reduction
Techniques (pd/1)
House
No.
A30
A39
A8
A46
B10
B31
B48
C33
D32
E24
Before
Radon Reduction
(Early Spring)
(DEPr
2,254
1.500
791
635
418
691
936
1.190
1,357
426
Before
Radon Reduction
(Summer)
(Closed House)
1.450
10.4
(1.250 w/Py/onl
409
772
15.8
(70 w/ Pylon)
89.0
771
304
29.0
(130 w/ Pylon)
91.0
(210 w/ Pylon)
After
Radon Reduction**
(Late Fall)
(Closed House)
4.1
4.3
2.9
9.0
16.0
5.8
11.1
4.7
11.3
12.3
Minimum
Percent
Reduction
99.7
58.7
99.3
98.8
0
93.5
98.6
98.5
61.0
86.5
Maximum
Percent
Reduction
99.8
99.7
99.6
99.2
97.6
99.2
98.8
99.7
99.2
97.2
DEP screening study charcoal canister measurements taken in March and April of 1986.
Highest post-radon reduction charcoal canister measurements taken in August 1985 through
January 1986.
difference before and after installation of
the radon reduction systems using pre-
installation summer radon concentra-
tions. The second relies on data collected
in the spring by the New Jersey DEP to
calculate the difference between pre- and
post-installation levels of radon gas.
Recommendations
• A database of houses receiving the
application of radon reduction tech-
niques in Clinton Knolls should be
maintained and analyzed. The data-
base should contain pre- and post-
radon reduction radon levels. A
summary of the radon reduction
method used, the house floorplan,
and any unusual features of the
house or the property on which it is
built should be included.
• Long-term followup monitoring
should be carried out in each of the
mitigated houses to determine the
average annual radon levels. This
monitoring should be carried out for
a period of at least 2 years and
should include continuous monitor-
ing for 1 week in each season in an
effort to identify seasonal effects on
the radon concentrations in the
houses and peak exposures.
• In future radon reduction projects,
at least 1 control house for each 10
demonstration houses should be
monitored continuously during the
entire period that radon reduction
work and monitoring is being done.
The control house should not be
subjected to radon reduction
methods during this time.
The mechanisms controlling the
strong diurnal variation in radon
concentration in indoor air should
be investigated. If periods of high
radon levels during the day can be
reliably predicted, radon reduction
techniques could be directed toward
reducing or eliminating those peaks.
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Linda D. Michaels is with Research Triangle Institute. Research Triangle Park.
NC 27709.
Michael C. Osborne is the EPA Project Officer (see below)
The complete report, entitled "Development and Demonstration of Indoor Radon
Reduction Measures for 10 Homes in Clinton. New Jersey," (Order No. PB
87-215 356/AS; Cost: $18.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S8-87/027
OOQU329 PS
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