United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-92/010 March 1992
Project Summary
Recommended HVAC
Standard of the! Florida
Radon Research Program
James B. Cummings
The report contains the recomi-
mended language for the heating, ven-
tilation, and air-conditioning (HVAC)
section of the "Florida Code for Rai-
don-Resistant Construction and Mitiga-
tion." It deals with elements of con-
struction that relate to the HVAC of
houses. Its primary intent is to prevent
pressure differentials in houses that
can increase the transport of radon into
houses. Three pathways of compli-
ance are available to meet the require-
ments of the HVAC portion of the stan-
dard. The first is purely prescriptive;.
The second is a performance and pre-
scriptive approach. The third is a mar-
ketplace approach.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri;-
angle Park, NC, to announce key find-
ings 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 report contains the recommended
language for the heating, ventilation, and
air-conditioning (HVAC) section of tho
"Florida Code for Radon-Resistant Coni-
struction and Mitigation" from the HVAG
Specifications Committee of the Florida
Radon Research Program. \
This section of the Florida Code for
Radon-Resistant Construction and Mitiga-
tion deals with elements of construction
that relate to the HVAC of houses. Th«
primary intent of the recommended meaj-
sures is to prevent pressure differentials
in houses that can increase the transport
of radon into houses.
Three pathways of compliance are avail-
able to meet the requirements of the HVAC
portion of the standards. The first path is
purely prescriptive. Builders need only
comply with all the measures listed in
Section 307.
The second path is a performance and
prescriptive approach. Builders would
comply with a reduced number of pre-
scriptive measures and pass a perfor-
mance test. The performance test would
have two parts: the first would determine
the airtightness of the air distribution sys-
tem, and the second would determine pres-
sure differentials with various house con-
figurations and various mechanical sys-
tems operating.
A third path is a marketplace approach
in which the state requires builders to
provide a radon information sheet (which
the buyer to conduct periodic radon infor-
mation sheet (which the buyer and builder
sign at closing) which encourages the
buyer to conduct periodic radon tests. The
builder agrees to take care of the problem
if elevated radon levels are found within
the normal construction warranty period.
No performance test or prescriptive mea-
sures are required.
Approach
Radon is an invisible, odorless, radio-
active gas which can enter houses and
increase the risk of lung cancer. It origi-
nates from the decay of radium in the soil.
Since it is a gas, it can migrate through
the soil and enter buildings.
Printed on Recycled Paper
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Several variables influence the amount
of radon to enter a building. First, there
must be radon in the soil. Certain soils
have higher radon levels. The higher the
level in the soil, the greater is the poten-
tial radon level in the building.
Second, there must be pathways for
radon to travel between the soil and the
building space. An air-impermeable bar-
rier can prevent radon passage. Con-
crete is an effective barrier to radon. While
radon can pass through concrete, its
progress is so slow that most of the radon
decays en route, rendering it essentially
harmless. In the real world, however, the
effectiveness of the concrete slab and a
plastic sheet below the slab is comprised
substantially by penetrations and cracks
created during construction.
Third, there must be a driving force to
transport the radon from the source
through the pathway into the building.
When pressure differences occur across
the air barrier, much larger quantities of
radon can be transported into the build-
ing. Therefore, control of pressures within
buildings is a very important variable in
the reduction of radon intrusion. In order
to better understand the extent and causes
of pressure differentials in Florida houses,
a study has been undertaken. The objec-
tives of the study are to:
1. Discover what pressure differentials
exist in a sample of 70 or more new
(age 5 years or less) houses.
2. Discover the causes
sure differences.
of the pres-
3. Recommend how pressure differen-
tials can be controlled in order to
reduce radon intrusion.
4. Provide pressure differential data to
groups designing subslab ventilation
systems.
In each house, pressure differences across
the house envelope to the outdoors and
to the subslab were measured:
1. When no air-moving systems in the
house were turned on.
2. When the central AC system was
turned on.
3. When various items of exhaust
equipment were turned on; e.g.,
kitchen exhaust fans, bathroom ex"
haust fans, dryers, and attic exhaust
fans.
4. When interior doors were closed and
the air handler was operating.
A total of 70 houses have been tested.
The findings of this project show that me-
chanical systems in the house produce
greater pressure differentials across the
slab than the natural forces of wind and
temperature. Duct leaks, closed interior
doors, and exhaust fans frequently create
pressures greater than 4pCi/L (0.016 in.
WG), while naturally produced pressures
are generally less than 2 pCi/L In some
cases, depressurization across the slab
is as high as 20 pCi/L (0.080 in. WG) or
more.
The findings from this research on 70
houses are documented in the report, "Ra-
don Pressure Differential Project, Phase
I."
To reduce pressure-driven radon intru-
sion in Florida buildings, an HVAC related
building code has been developed. This
code is contained in "Recommended
Changes to the Florida Code for Radon-
Resistant Construction and Mitigation" as
well as in this report. The remainder of
this report supports, explains, and justifies
the recommended changes and additions
to the Florida Radon Code.
Conclusions
It is the opinion of the HVAC Specifica-
tions Committee that the state of knowl-
edge concerning the correlation of me-
chanically induced pressure differentials
and radon intrusion is not sufficient at this
stage of research to guarantee that com-
pliance with these recommended code
measures or multiple pathways will en-
sure that elevated radon levels will not
occur in Florida houses. Also, it should
be noted that resolution of mechanically
induced pressure differentials in houses is
only part of the solution.
•&U.S. GOVERNMENT PRINTING OFFICE: I99Z - 648-080/40217
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FJ. Cummings 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 "Recommended HVAC Standard of the FLorida
Radon Research Program,"(OrderNo. PB92-147909/AS; Cost: $17.00; 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 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
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/SR-92/010
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