United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-95/170 April 1996
EPA Project Summary
New House Evaluation of
Potential Building Design and
Construction for the Control of
Radon in Marion and Alachua
Counties, Florida
Fazil T. Najafi, David E. Hintenlang, C. E. Roessler, A. J. Shanker, and
Jim Tyson
The report describes the approach,
methods, and detailed data used to
evaluate the effectiveness of different
radon entry controls into new houses.
The main objective focused on finding
engineering solutions to controlling ra-
don entry into houses. The overall re-
sistance of the building to radon soil
gas entry and the dynamic forces that
influence building performance were
examined.
The New House Evaluation Project is
directed toward developing standards
for radon-resistant new home construc-
tion. Once adopted, these standards will
become part of the building construc-
tion codes of Florida counties and mu-
nicipalities.
The analysis was based on 14 new
houses built in accordance with the
Draft Florida Standard for Radon-Re-
sistant Building Construction. There are
three approaches to reducing radon lev-
els in the construction of new houses:
1) preventing radon entry by using
barrier methods;
2) reducing the radon entry driving
forces; and
3) diverting the radon from entering
the houses by sub-slab depres-
surization.
Approaches 1 and 2 are passive. The
passive approaches used in construc-
tion include placement of a vapor bar-
rier, sealing of plumbing penetrations,
mixing of floor slab concrete with
superplasticizers, reinforcing of slab at
reentrant corners, and proper slab cur-
ing and loading.
Approach 3 is active. A fan was used
to depressurize the sub-slab, making
sub-slab pressure lower than the in-
door pressure.
Research measurements focused on
soil conditions at each building site, as
well as the physical conditions of the
building and dynamic forces after con-
struction completion. Soil measure-
ments included radium content, soil
permeability, moisture content, and
physical characteristics. Building mea-
surements included air leakage rate,
soil gas entry rate, radon concentra-
tions, and floor slab crack dimensions.
The building dynamics tests included
pressure effects of the heating and air-
conditioning systems and the active
sub-slab depressurization fan on the
indoor and sub-slab environment. Af-
ter construction completion, houses
were evaluated using short-term indoor
radon tests. All houses were tested;
the indoor radon levels in all houses
were found to be under the limit of 4
pCi/L prescribed by the Florida Depart-
ment of Community Affairs.
This project summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The New House Evaluation Project of
the Florida Radon Research Program is a
continuation of major studies directed to-
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ward developing standards for radon-
resistant new home construction. Once
adopted, these standards will become part
of the building construction codes of Florida
counties and municipalities.
The project objectives are accomplished
at several stages: 1) preconstruction; 2)
during construction, and 3) postconstruction.
At the preconstruction stage, selections
were based on soil with high radon levels.
When the potential sites were identified, a
contract was drawn between the Univer-
sity of Florida (UF) and the home build-
ers.
During the house construction process,
the UF researchers conducted various ac-
tivities including the placement of a vapor
barrier, sub-slab depressurization (SSD)
system, concrete slab crack measure-
ments and radon tests through cracks,
etc.
House dynamic tests were performed
during post construction.
In general, UF researchers found that
use of ventilation matting and proper seal-
ing of radon entry points will maintain the
indoor radon level below the EPA level.
1.At the preconstruction stage the fol-
lowing tasks were performed:
a) selection of potential residential
sites with native soil gas radon level
equal to or greater than 1,000 pCi/
L;
b) site characterization consisting of
a series of insitu measurements
and collection of soil and fill
samples for laboratory analysis of
moisture content, soil permeability
profile, soil gas radon, radon ema-
nation coefficient, etc.
2. During construction, UF research in-
volved the following activities:
a) design and installation of sub-slab
depressurization system composed
of ventilation matting and radon gas
suction points with a piece of 3-in
(7.6-cm) polyvinyl chloride (PVC)
inserted into a toilet flange by at-
taching it to the mat. Testing points
were selected and small Enkavent
pads were placed and connected
to 3/16-in (0.48-cm) plastic radon
gas testing tubes beneath each pad
that were run under the slab to the
outside construction foundation
walls for taking radon gas mea-
surements.
b) pressure field mapping produced
by measuring radon gas from the
3/16-in plastic testing tubes.
3. During postconstruction, the following
tasks were performed:
a) house dynamics tests using the
blower door test to assess the tight-
ness of the house envelope, and
locate and quantify leaks in the air
distribution system. The houses
were pressurized to about 15 Pa
by the blower door, with the air
handler turned off, and smoke (ti-
tanium tetrachloride) from a smoke
stick was placed in front of each
supply and return register to ob-
serve the speed with which it en-
tered each register. If the smoke
entered slowly or not at all, then
little or no duct lead existed nearby
in the ducts. If, on the other hand,
smoke entered the register rapidly,
then a large duct leak was nearby.
b) sub-slab radon sampling at each
site under a number of different
house conditions (e.g., vent
capped, vent uncapped, and ac-
tive fan). These tests were per-
formed at various stages of con-
struction (e.g., after slab was
poured and framing of the house
had begun).
c) indoor radon sampling tests under
different conditions: vent capped,
vent uncapped, and with active fan.
In addition, a number of different
methods were used for the indoor
testing.
The data collected under these sam-
pling methods were used in the analysis
of indoor radon levels. Each technique
provided discussion on the evaluation and
effectiveness of various construction mea-
sures. The data were used in various mod-
els which provided details that allow appli-
cations ranging from statistical treatment
of house parameters to detailed house-
specific models that require a large amount
of input data.
Conclusions
This research resulted in several con-
clusions.
1)A screening technique consisting of
"sniff sampling of radon soil gas mea-
surements with a selection criterion
of 1,000 pCi/ was effective in finding
sites with an elevated radon source
potential.
2)The correlation between preconstruc-
tion site characterization soil gas radon
measurements and postconstruction sub-
slab radon measurements was weak.
3)The indoor radon concentration ratio
between an uncapped ventilation sys-
tem and a capped ventilation system
can be examined as possible evi-
dence of a passive ventilation effect.
4)The passive barrier was sufficient to
maintain indoor concentrations below
the 4 pCi/L action level when sub-
slab concentration was less than
3,000 pCi/L.
5)The very limited data from this study
support the role of active SSD as an
effective radon control technique.
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F. Najafi, A. Shanker, C. Roessler, and D. Hintenlang are with The University of
Florida, Dept. of Civil Engineering, Gainesville, FL 32611; andJ. Tyson is with the
Florida Solar Energy Center, Cape Canaveral, FL 32920.
David C. Sanchez is the EPA Project Officer (see below).
The complete report, entitled "New House Evaluation of Potential Building Design
and Construction for the Control of Radon in Marion and Alachua Counties,
Florida," (Order No. PB96-168299; Cost: $47.00, 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 Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-95/170
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