[Federal Register Volume 59, Number 54 (Monday, March 21, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-6551]
[[Page Unknown]]
[Federal Register: March 21, 1994]
_______________________________________________________________________
Part IV
Environmental Protection Agency
_______________________________________________________________________
Model Standards and Techniques for Control of Radon in New Residential
Buildings; Notice
ENVIRONMENTAL PROTECTION AGENCY
[AD-FRL-4795-3]
Model Standards and Techniques For Control of Radon in New
Residential Buildings
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of publication of final EPA Model Standards.
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SUMMARY: The Environmental Protection Agency is today publishing final
``Model Standards and Techniques For Control of Radon in New
Residential Buildings,'' hereinafter referred to as ``EPA Model
Standards,'' as required by section 304 of title III of the Toxic
Substances Control Act. These model standards and techniques are
designed to prevent or reduce the potential for elevated levels of
indoor radon in newly constructed residential buildings and are
provided for use by national code development organizations, states,
and local jurisdictions as they develop and enforce building codes for
radon control specifically applicable to their regional and local
requirements. This publication reflects changes and additions resulting
from comments received during the public review period on the proposed
EPA Model Standards.
EFFECTIVE DATE: These EPA Model Standards are effective on March 21,
1994.
FOR FURTHER INFORMATION CONTACT: David M. Murane, Radon Division
(6604J), 401 M St., SW., Washington, DC 20460, Telephone: 202/233-9442.
Requests for copies of this notice and supporting Cost-Benefit Analysis
should also be directed to this contact.
SUPPLEMENTARY INFORMATION:
I. Introduction
EPA today publishes its ``Model Standards and Techniques for
Control of Radon in New Residential Buildings.'' These final EPA Model
Standards have been modified after consideration of public comments
received on the proposed EPA Model Standards during the period April
12, 1993 through June 11, 1993. Title III of the Toxic Substances
Control Act (TSCA) (15 U.S.C. 2661 et seq.) (also known as the Indoor
Radon Abatement Act of 1988) was enacted on October 28, 1988. Section
304 of TSCA requires the Administrator of the Environmental Protection
Agency to develop model construction standards and techniques for
controlling radon levels within new buildings. To the maximum extent
possible, these model standards and techniques were to be developed
with the assistance of organizations involved in establishing national
building construction standards and techniques and be made available in
draft for public review and comment. Section 304 also requires the
Administrator to work to ensure that organizations responsible for
developing national model building codes and authorities which regulate
building construction within states or political subdivisions within
states, adopt the Agency's model standards and techniques.
II. Background
A. Radon Occurrence and Health Risks
Radon was first recognized as a cause of lung cancer in underground
miners in the 1930's. In 1955, the International Commission on
Radiological Protection established the first occupational health
standard for radon exposure in mines. In 1970, homes in the United
States were found to have elevated levels of radon when uranium mill
tailings were used as fill dirt or when built on reclaimed phosphate
mining land. Starting in 1984, it became increasingly evident that
homes could have elevated indoor radon levels caused by naturally
occurring radium in the underlying soil and rock. In the past 6 years,
homes with elevated radon levels have been found throughout the United
States. Surveys indicate that up to 6 million homes may have radon
levels above the EPA action level guideline established in 1986 of 4
pico Curies per liter of air (4 pCi/L). Based on studies by the
National Academy of Sciences and other scientific organizations, EPA
believes that from 7,000 to 30,000 lung cancer deaths per year can be
attributed to exposure to elevated levels of indoor radon. There are
also data that indicate a synergistic effect between radon exposure and
smoking which places smokers at a higher risk. Several studies are
underway that could provide new information and insights on the
magnitude of the radon health risks. Information from these studies
will be considered and, if appropriate, incorporated by EPA in any
future revisions of the radon health risk estimates.
B. Initial Steps by EPA To Develop New Construction Guidance
EPA's initial efforts to reduce public exposure to radon were
focused on educating the public on the health risk and identifying
methods for reducing radon levels in existing homes. ``A Citizen's
Guide to Radon,'' (OPA-86-004, 1986) and ``Radon Reduction Methods, A
Homeowner's Guide,'' (OPA-86-005, August 1986) were published by EPA in
1986 to meet those needs. It was also recognized that long-term risk
reduction would be facilitated if new homes built each year were
constructed with radon-resistant features. In 1987, EPA and the
National Association of Homebuilders jointly published ``Radon
Reduction in New Construction, An Interim Guide,'' (OPA-87-009, August
1987) to provide initial guidance for builders. At the same time, a
number of research projects were initiated to validate the interim
guidance and to identify additional construction techniques that would
be effective in reducing radon levels in new residential buildings. In
1988, EPA published its first technical guide on ``Radon-Resistant
Residential New Construction,'' (EPA/600/8-88/087, July 1988) and, in
early 1991, published an updated version of this technical guidance
titled, ``Radon-resistant Construction Techniques for New Residential
Construction. Technical Guidance,'' (EPA/625/2-91/032, February 1991).
C. EPA's Goals in Preparing a Model Standard
EPA believes that the ultimate success of the EPA Model Standards
will be determined by reaching six basic goals:
1. The Model Standards should meet the requirements established by
Congress in the 1988 Indoor Radon Abatement Act (Title III of TSCA (15
U.S.C. 2661 et seq.)).
2. The Model Standards should result in significant radon risk
reduction in newly constructed homes in areas of highest radon
potential and not induce other significant indoor air problems.
3. The recommended construction techniques should be
technologically achievable, and readily implementable by the nation's
builders.
4. The provisions of the Model Standards should be cost-effective
for both homebuilders and homebuyers. A significant aspect of all cost
considerations is the underlying fact that steps taken to reduce radon
entry during construction are less costly than retrofitting mitigation
systems into homes after they are built.
5. The provisions of the Model Standards should be readily
adoptable and/or adaptable by the national Model Code Organizations and
by officials who administer building codes at the state and local
level.
6. The Model Standards should be targeted for adoption in areas of
highest radon risk potential.
D. Summary of Public Participation
On February 1, 1989, EPA convened a Standards and Codes Work Group
consisting of over 45 representatives of governmental and building
industry organizations. This Work Group developed the outline and
essential features for a first draft of the proposed Model Standards.
EPA then established a cooperative agreement with the National
Institute of Building Sciences (NIBS) to provide broadly based
technical assistance in the development and review of the specific
building standards and techniques. The NIBS Radon Project Committee
ultimately involved over 90 representatives of Federal Agencies
(Department of Energy, Department of Housing and Urban Development,
Department of Defense), building code organizations, state and local
governmental agencies, and private sector companies. This Committee met
five times to review and modify the draft document and provided a
summary report titled, ``Methods and Techniques for Reducing Radon
Levels within New Buildings,'' April 1990, which was used by EPA as one
of the sources in developing the model building standards and
techniques outlined in section 9.0. The NIBS Report is available by
submitting a request to: The National Institute of Building Sciences,
1201 L Street, NW., suite 400, Washington, DC 20005, telephone 202/289-
7800. Other support documents, including the ``Analysis of Options For
EPA's Model Standards For Controlling Radon in New Homes,'' July, 1992,
(hereinafter referred to as the Cost-Benefit Analysis (CBA)) are
available through EPA. On April 12, 1993, the proposed EPA Model
Standards were published for public review and comment as a Notice in
the Federal Register (58FR, 19097, April 12, 1993). A total of 173
comments were received from 23 commenters. This Notice responds to the
comments and contains the final EPA Model Standards.
III. Overview of Technical Analysis
A. Radon Reduction Technology
The three methods for controlling radon levels in new residential
buildings involve the use of (1) passive systems, (2) active systems,
and (3) stack effect reduction systems.
1. A passive system includes use of all the construction techniques
that create physical barriers to radon entry, reduce the forces that
draw radon into a building, and facilitate post-construction radon
removal if the barrier techniques prove to be inadequate. A ``passive
system,'' as used in the Model Standards, includes an open vent pipe
stack that carries radon from the area beneath the slab or from under
the plastic sheeting covering the crawl space floor to an exit point
above the roof. It also includes roughed-in electrical wiring to
facilitate future installation of both a fan in the vent stack and a
system failure warning device, if radon tests indicate that further
radon reduction is necessary. The natural convective flow of air upward
in the vent pipe draws soil gas containing radon from beneath the slab
and vents it to the outside. Limited research has demonstrated that
passive systems are effective in reducing indoor radon concentrations
below the current EPA action level in the large majority of homes where
post-construction radon levels would otherwise have been slightly
elevated. EPA believes that radon reductions of about 50 percent are
achievable using a passive system approach alone (CBA, chapter 4).
Under certain climatic conditions and in cases where the radon source
strength in the underlying soil is greatly elevated, the performance of
the passive stack may not be sufficient to lower indoor radon levels
below EPA's current action level, but performance can easily be
improved by adding a fan in the vent stack. The cost to builders of
installing a passive system, as described above, is in the range of
$350 to $500 per house depending on its design and size (CBA, chapter
6). In cases where builders already use passive barrier techniques for
controlling moisture entry and for energy conservation, the costs to
install passive radon control systems will be lower.
2. An active system involves use of all the passive control
techniques described above plus installation of an electric fan in the
vent pipe stack and a system failure warning device. The active system
creates a strong suction on the area beneath the slab or under the
plastic sheeting covering the crawlspace floor. This results in the
pressure of soil gas containing radon beneath the slab to be lower than
the air pressure in the home, creating a pressure barrier to radon
entry. Because of the active mechanical ventilation of the sub-slab
space, an active system can reduce indoor radon concentrations to their
lowest achievable levels and is effective even in the presence of very
high radon concentrations in the underlying soils. Based on limited
Agency and independent research, active radon control systems have
reduced radon levels to below 2 pCi/L in over 90 percent of new homes.
Levels below 4 pCi/L are achieved in nearly all new homes (CBA,
appendix B). The cost of installing the additional components of an
active radon control system (the electric fan and system failure
warning device) is about $250. The total cost of an active system is
therefore in the range of $600 to $750. These costs will also vary
depending on the design and size of the house (CBA, chapter 6). As in
the passive system, costs applied to radon control may be lower in
areas where builders are already using barrier techniques and stack
effect reduction techniques for moisture control and energy
conservation. There are additional annual costs to homeowners for
operating and maintaining active radon control systems. EPA estimates
these costs to be in the range of $40 to $75 (CBA, chapter 6).
3. Stack Effect Reduction involves installation of features that
prevent or reduce the flow of warm conditioned air upward and out of
the building superstructure. This upward movement of air actually can
draw soil gas containing radon into the lower levels of a building. The
recommended stack effect reduction techniques include common
construction practices such as providing adequate makeup air for
combustion appliances, weather stripping exterior doors and windows,
sealing openings around attic access doors, and using sealable recessed
ceiling lights. In some areas, these energy conserving techniques are
already required by code. Although these techniques, when used alone,
may not be effective in achieving significant reduction in indoor radon
levels, when combined with the barrier techniques and a passive or
active vent stack installation, the stack effect reduction techniques
can contribute to reducing radon entry through below ground openings in
the foundation. It is recognized that use of these techniques can also
reduce the infiltration of dilution air through above ground openings
in the superstructure of the home. This can lead to some reduction in
the air change rate. EPA is not aware, however, of any evidence that
use of the recommended stack effect reduction techniques reduces air
change rates to a level below the current ASHRAE standard of .35 air
changes per hour (ACH), or that use of these techniques exacerbates
problems with other indoor air pollutants. Use of these techniques does
contribute to the fire resistance of a building, and reduces heating
and cooling costs. As previously noted, the recommended stack effect
reduction techniques are already requirements in the Model Building and
Energy Codes used throughout the U.S. The application of these features
to the control of radon does not impose additional changes in current
construction practices.
B. Map of Radon Zones
With the assistance of the U.S. Geological Survey (USGS) and State
geologists, the Agency has developed a ``Map of Radon Zones'' designed
to help state and local governments target certain data collection and
outreach programs. It is also designed to help building code officials
determine areas where adoption of radon-resistant construction codes
may be advisable. The methodology for developing the Agency's ``Map of
Radon Zones'' involved categorization of distinct geologic provinces
based on indoor radon measurements, geology, aerial radioactivity, soil
parameters, and house foundation types. These geologic provinces were
then overlayed on county maps, and each county was assigned to a Zone
based on the geologic province that is predominant in that county.
Counties located within a geologic province that had predicted average
indoor radon screening levels greater than 4 pCi/L were assigned to
Zone 1. Counties with predicted average screening levels between 2 and
4 pCi/L were assigned to Zone 2, and counties below an average of 2
pCi/L were assigned to Zone 3.
While EPA believes that the Map of Radon Zones and its accompanying
documentation is useful for setting general boundaries of areas of
concern, EPA recommends that state and local jurisdictions collect and
analyze local indoor radon measurements, and assess geology, soil
parameters and housing characteristics--in conjunction with referring
to the EPA Map of Radon Zones--to determine specific areas within their
jurisdictions that should be classified as Zone 1.
EPA published the ``Map of Radon Zones,'' along with accompanying
state-specific documentation, in December 1993. Copies of the national
map and state-specific booklets are available from state radon program
offices, EPA headquarters, and EPA regional offices.
C. Cost-Benefit Considerations
The Agency considered a number of approaches for applying the Model
Standards in the different radon potential zones. The basic approaches
examined included: Application of active systems nationwide or only in
Zone 1, application of passive systems nationwide or only in Zone 1,
and application of some mixture of passive and active systems in Zones
1 and 2.
Each of the approaches for applying the Model Standards was
analyzed in the CBA. The CBA compared costs of installing and operating
the recommended radon control systems with the benefits in risk
reduction and energy conservation. This evaluation was done for each of
the alternative approaches described above.
Consistent with common EPA practices for estimating annual risk
reductions from cancer-causing pollutants, EPA estimated the total
number of lives saved in the population that will occupy new radon-
resistant homes built over the time of the analysis (74 years) and
converted that total estimate into an average of lives saved per year.
Such an approach to the analysis allows consistent comparison of cost-
effectiveness of the EPA Model Standards with EPA's pollution control
decisions in other programs.
It should be noted that many of the construction standards and
techniques recommended in this document are included in current model
building codes, such as The Council of American Building Officials
(CABO) ``One and Two Family Dwelling Code'' and the CABO ``Model Energy
Code,'' or in the American Society of Heating, Refrigerating and Air-
Conditioning Engineers (ASHRAE) Standards, as techniques for reducing
water infiltration or energy loss, or for maintaining acceptable indoor
air quality. Applying these standard techniques as a means to control
the levels of indoor radon simply adds a complementary function that
does not conflict with the objectives of other indoor air quality
programs within EPA. In addition, applying the recommended radon
barrier and stack effect reduction techniques will result in
significant long-term energy savings.
The provision of radon control systems involves cost considerations
for both homebuilders and homebuyers. In the passive approach to radon
control, there are no homeowner costs associated with operation and
maintenance of a vent fan. The result is long-term radon risk reduction
at a small initial cost which later results in savings due to improved
energy efficiency.
IV. Summary of the EPA Model Standards and the Implementation
Approach
A. Summary of the Model Standards
The EPA Model Standards include a codified presentation of
construction methods and recommended procedures for their application.
The EPA Model Standards also include scope and limitations sections, a
listing of pertinent reference documents and terminology, a discussion
of the principles for radon-resistant construction, and a summary of
the construction techniques as applied to basement, slab-on-grade, and
crawlspace foundations. The recommended construction method and
recommended procedures for its application are contained in sections
7.0 and 8.0, and the specific construction techniques are listed in
section 9.0. Model Code Organizations, states, and local jurisdictions
are encouraged to adopt those portions of the EPA Model Standards that
are appropriate for their building code needs.
B. Implementation Approach
EPA considered five approaches for implementing the EPA Model
Standards. These include: (1) Active systems in Zones 1 and 2, (2)
active systems in Zone 1 only, (3) passive systems in Zones 1 and 2,
(4) passive systems in Zone 1 only, and (5) a combination of active
systems in Zone 1 and passive systems in Zone 2, plus a requirement to
test and fix homes above the action level in Zone 2. Based on its
analysis, EPA selected option (4). EPA believes that the use of passive
radon control systems in areas of high radon potential (Zone 1), and
the activation of those systems if necessitated by follow-up testing,
is the best approach to achieving both significant radon risk reduction
and cost-effectiveness in construction of new homes. EPA believes that
this approach best accomplishes the goals identified by the Agency in
Section II.C. Other approaches and their associated costs and benefits
are explained in detail in the CBA.
The EPA Model Standards meet the requirements established by
Congress in the Indoor Radon Abatement Act. EPA worked to develop the
Standards in cooperation with the National Institute of Building
Sciences (NIBS), a Standards and Codes Workgroup, individual home
builders, and the National Association of Home Builders (NAHB), and
will work to have the Standards adopted by the Model Code
Organizations, states, and local jurisdictions.
EPA believes that the implementation approach selected will result
in significant risk reduction to the buyers of newly constructed homes
since about 145,000 of the one million new homes built each year are in
Zone 1. By applying the selected approach, it is estimated that
ultimately from 10 to 41 lung cancer deaths could be averted annually.
In addition, as the EPA Model Standards are adopted across the United
States, the growing number of new houses equipped with radon-resistant
features will result in a cumulative increase in the number of lives
saved each year. For example, after the first five-year period of fully
implementing the Standards, the Agency estimates that, statistically,
over 200 lives ultimately will be saved (CBA, Chapter 5).
These estimates are based only on the risk reduction achieved by
use of passive radon control systems in Zone 1. If all new homes built
in Zone 1 with passive radon-resistant features are tested for radon,
and passive systems activated when elevated radon levels are still
present, an estimated 3 to 4 additional lives would be saved annually.
To achieve maximum risk reduction, all new homes should be tested, and
passive systems activated when necessary.
The construction techniques are technologically feasible and can be
readily implemented by builders in the field. Agency research has
demonstrated the effectiveness of the techniques, and they involve the
use of standard construction practices and materials readily available
to builders in all geographical areas.
The provisions of the EPA Model Standards and the recommended
implementation program are cost-effective to both homebuilders and
homebuyers. EPA believes this approach to controlling radon in new
construction provides a balance between radon risk reduction and the
cost to both homebuilders and homebuyers. The cost to builders to
install a passive system is $350 to $500 per house. If applied to all
new homes in Zone 1 areas, the annual installation cost would range
from $50 to $70 million (CBA, chapter 6). Even at the higher end of
this range, a very favorable cost-benefit relationship results when
these costs are compared to lung cancer deaths that may ultimately be
averted. Due to the long-term energy savings achieved by using the
recommended radon reduction techniques, the 10 to 41 lung cancer deaths
ultimately averted yearly would be at a savings of about $440,000 per
life saved, using a 3 percent discount rate. At a 7 percent discount
rate, the savings would be $281,000 per life saved. In a sensitivity
analysis of this option, in which no credit was taken for energy
savings, the cost was calculated to be $149,000 per life saved at the 3
percent discount rate, and $309,000 at the 7 percent discount rate.
With passive systems, there are no system operation costs to the
homebuyer. However, if a home is tested, and elevated levels of radon
are found, the passive system can be made significantly more effective
in reducing radon levels by the addition of a fan. The installation of
the fan and a system failure warning device would cost approximately
$250 and the yearly operation costs of the system to the homebuyer
would be about $40 to $75 (CBA, chapter 6).
Building radon-resistant features into a new home during
construction is extremely cost effective. It should be noted that the
cost of reducing high radon levels in existing homes that do not
contain these construction features can range from $800 to $2,500
(EPA's ``Consumer's Guide to Radon Reduction,'' 402-K92-003, August
1992).
Finally, EPA believes the Model Standards can be readily adopted by
the Model Code Organizations, states, and local jurisdictions that want
to address the radon problem. The Agency has developed the Model
Standards with a format and content that will assist in their adoption
by the Model Code Organizations. The Agency anticipates increasing
support for this adoption from the building industry. Indeed, the
National Association of Home Builders passed a resolution (NAHB Radon
Policy Update, January 22, 1992) that is supportive of the targeted
approach taken in the EPA Model Standards. The expected acceptance and
use of the Standards by builders will also contribute to timely
adoption by the Model Code Organizations and in the building codes and
regulations of state and local jurisdictions.
Each of the other implementation options addressed in the CBA
offers certain advantages and disadvantages. Active radon control
systems applied in both Zones 1 and 2 would result in greater risk
reduction. However, these systems would provide limited benefits in the
large number of new homes that would be below 4 pCi/L without any
radon-resistant features installed. If targeted only to Zone 1, active
systems would still be unnecessary in a large percentage of new homes.
At this time, the Agency believes that the installation, operation, and
maintenance costs of active systems outweigh the benefit of the greater
risk reduction achieved by these systems. Similarly, the costs of
installing passive radon control systems throughout Zones 1 and 2 are
considered by the Agency to be too great because of the large number of
homes that would receive no benefit in terms of radon risk reduction.
EPA also concludes that a ``mixed approach'' (active systems in Zone 1;
passive systems in Zone 2) would also not be as cost effective as the
recommended approach. Further explanation of the data leading to these
conclusions is contained in the CBA. The CBA is available through the
EPA contact listed at the beginning of this Notice.
V. Response to Comments
A. Comment Review Process and General Responses
1. Comments were reviewed and similar or related comments were
grouped within one of the following 7 topical categories:
(1) Syntax, Language, General Editorial.
(2) Radon Measurement and Risk Assessment.
(3) Training, Certification, Proficiency Rating.
(4) Referencing Existing Standards and Requirements.
(5) Technical Standards and Requirements.
(6) Cost-Effectiveness of Proposed Standards.
(7) Comments Pertaining to EPA's ``Significant Issues.''
2. The following general responses address each of these 7
categories of comments. Specific responses to individual comments are
contained in section B below.
(1) In general, a review of the 22 comments recommending editorial,
syntax, or modified language changes resulted in improvements in the
text of the Model Standards. These changes were adopted and no further
response was considered necessary.
(2) The 14 comments relating to radon measurement and risk
assessment reflected a broad spectrum of divergent views, ranging from
total rejection of the Model Standards (due to an alleged failure to
substantiate the risk), to recommendations that the 4 pCi/L Action
Level be lowered to achieve greater risk reduction. Specific responses
to comments in this category are included in section B, below.
(3) There were 6 comments that focused on the need to clarify
provisions in the Model Standards relating to Training, Certification,
and Proficiency Rating. Appropriate editorial changes were made to
clarify those provisions. More detailed responses to the 6 comments in
this category were not considered necessary.
(4) There were 21 comments citing a need to include additional
references to Existing Codes or ASTM Standards, or to include more
detailed specifications on construction techniques. The majority of
these comments were accommodated by adding appropriate building code or
ASTM references to sections 9.1.3, 9.1.6, 9.1.7, 9.1.12, 9.1.14, 9.2.1,
9.2.4, and 9.2.5 of the Model Standards. Specific responses to several
of the comments in this category are included in section B, below.
(5) Many of the comments (69 out of 173) were categorized as
addressing Technical Standards and Requirements. As in the previous
category, the majority of these comments were accommodated since they
enhanced the clarity and completeness of the Model Standards. Specific
responses to suggested changes that were rejected are included in
section B, below.
(6) There were 14 comments categorized as addressing Cost-
Effectiveness of the Proposed Standards. All of these comments were
directed toward the introductory material contained in the preamble to
the Model Standards and did not recommend specific changes in the body
of the Standards. However, specific responses to this category of
comments have been included in Section B, below.
(7) There were 17 responses to EPA's request for comments on the 7
``Significant Issues'' listed in the preamble to the Proposed EPA Model
Standards. Responses to these comments are included in Section C,
below.
B. Responses to Specific Comments
The following responses are related to comments on the radon
measurement and risk assessment aspects of the Model Standards.
(1) One commenter questioned the need for Model Standards for
radon-resistant new construction by stating that ``without conclusive
evidence that radon increases the risk of lung cancer, is such
protective action warranted?'' EPA believes that there is clear
evidence to support the radon risk assessment that resulted in a
Congressional mandate to develop the Model Standards. The
carcinogenicity of radon has been well established by the scientific
community, including the World Health Organization's International
Agency for Research on Cancer (IARC 1988), the Biological Effects of
Ionizing Radiation (BIER IV) Committee of the National Academy of
Sciences (NAS 1988), the International Commission of Radiological
Protection (ICRP 1987), and the National Council on Radiation
Protection and Measurement (NCRP 1984). These concerns were also
affirmed in the ``Comparative Dosimetry of Radon in Mines and Homes''
(NAS 1991), by the National Academy of Sciences. EPA's discussion of
the aforementioned findings and other data is contained in the
``Technical Support Document for the 1992 Citizen's Guide to Radon''
(USEPA 1992).
(2) One commenter requested that EPA's Map of Radon Zones be
included as an appendix to the Model Standards. EPA believes that the
Map of Radon Zones and the more detailed state-specific booklets that
accompany the map should be published separately from the Model
Standards. The lack of precise definition of zone boundaries on a
single page map of the U.S. would limit its usefulness to home builders
or to state and local building officials as they make decisions
regarding the specific application of the Model Standards to their
local requirements. The state-specific booklets are considered an
essential element in interpreting the Map of Radon Zones, and it would
not be feasible to also include the booklets in an appendix to the
Model Standards. EPA recommends that parties interested in the Map of
Radon Zones consult with their state radon office to obtain information
specific to their locality or area of interest.
(3) One commenter stated that EPA has not substantiated its action
level with any studies showing that radon poses a risk at that level.
The Agency disagrees with this statement. EPA's estimates of lung
cancer risks to the general population due to radon are based on human
exposure-response data from epidemiologic studies of underground
miners. These studies show excess cancer risk in miners whose
cumulative exposure overlaps those exposures expected in residential
settings at 4 pCi/L. The Agency has provided a detailed discussion of
the exposure, risk, and uncertainty issues in the ``Technical Support
Document for the 1992 Citizen's Guide to Radon,'' (EPA 400-R-92-011,
May, 1992).
(4) The same commenter suggested that ``even if one accepts EPA's
radon action level, the standards are not cost-effective. It is more
cost-effective to retrofit only those homes testing above the EPA
action level, than to install passive systems in all homes in Zone 1.''
This assumption is incorrect on several counts. EPA estimates that
144,808 new homes are constructed in the 12 Zone 1 states each year
(CBA, chapter 6). If passive radon control systems, at a cost of $500
each, were installed in each of these homes, the total installation
cost would be $72,400,000. However, the costs of post-construction
mitigation of homes in Zone 1 that would be expected to test above 4
pCi/L would be almost double that amount. Based on federal and state
radon surveys, the Agency estimates that 55,585 of the 144,808 new
homes built annually in Zone 1 would have radon levels above 4 pCi/L.
If those homes were mitigated, at a cost of $2,500 per home, the total
costs of mitigation would be $139,000,000. Actually, the difference
between these two approaches is even greater due to the energy savings
that result when passive radon control systems are installed during
construction. Over the typical 74 year life of the 144,808 homes, the
installation of passive systems will result in energy savings to
homeowners of $7,045,000. On the cost issue, another factor must also
be considered. In its evaluation of rates of voluntary radon testing by
owners of existing homes across the country, EPA has found that
approximately 9 percent of the homes have been tested. The rate of
radon testing by owners of new homes is not expected to be any higher.
Therefore, the approach suggested by the commenter would result in very
little risk reduction, when compared to installation of passive systems
by builders during construction.
(5) The same commenter also stated that ``given the uncertain basis
for EPA's action level, EPA must consider the full social cost of the
standards before acting.'' The Agency's CBA contains an extensive
analysis of the lives to be saved through implementation of the Model
Standards as well as the costs incurred through this and other
approaches. It is calculated that the installation of passive systems
in new homes in Zone 1 and the associated energy savings derived, will
result in an overall savings of $442,000 per life saved, at a 3 percent
discount rate, or $281,000 at a 7 percent discount rate. As discussed
earlier, if no credit is taken for energy savings, the cost was
calculated to be $149,000 per life saved at a 3 percent discount rate,
or $309,000 at a 7 percent discount rate. These calculations did not
factor in the additional significant savings to society resulting from
not having to treat cancers that have been avoided.
(6) One commenter stated that ``if, according to EPA's
calculations, these measures save only 16 deaths per year, then they
are not worth the cost of installing.'' As stated earlier, if the Model
Standards are fully implemented, it will result in an overall savings
of $442,000 per life saved at a 3 percent discount rate. The cost per
life saved indicates how cost-effective an alternative is in providing
health benefits to the public. It should be compared to the cost the
public is willing to pay to save a ``statistical life,'' i.e., buy risk
reductions. In the past, EPA's 1983 Regulatory Impact Analysis (RIA)
Guidelines indicated that the public appears to value a risk reduction
that saves a life (in statistical terms) for between $600,000 to
$9,900,000. A more recent study titled, ``The Value of Reducing Risks
of Death: A Note on New Evidence,'' by Fisher, et al. 1989, suggests
that the public places the value of saving a statistical life between
$2,000,000 and $10,500,000 in 1991 dollars.
(7) One commenter stated that ``EPA has failed to consider studies
that contradict its linear no-threshold theory for radon-induced lung
cancer.'' The Agency has considered these studies but continues to
believe the evidence available supports the no-threshold approach. In
order for there to be a threshold, all non-lethal genetic damage from
alpha radiation which would lead to cancer would have to be repaired
perfectly. Research has established that even at low doses, only a
fraction of the damage caused by alpha radiation is effectively
repaired. Because of the tendency toward double stranded rather than
single stranded DNA breaks with alpha radiation, there is high
probability of extensive damage and a high probability of ``mis-
repair.'' Any repair that is evident indicates only cell survival, and
may not indicate continued DNA integrity. The findings of the National
Academy of Sciences BEIR IV report (p. 426) suggest that ``carcinogenic
damage induced by high-LET radiation (e.g., alpha radiation) in
mammalian cells is very inefficiently repaired'' and ``the
intracellular effect of exposures to high-LET radiation can be
cumulative.'' Mis-repaired cells can survive, multiply, and reproduce
the mis-repair (i.e., mutation) that may lead to cancer. Although a
threshold cannot be definitively ruled out, there is currently no
scientific evidence of a threshold for cancer induction from exposure
to radon or any other ionizing radiation.
(8) One commenter stated that ``EPA has overlooked a significant
body of scientific literature which suggests that low levels of
radiation are not only harmless, but possibly beneficial.'' The Agency
has considered ``ecologic studies'' which have shown lower lung cancer
rates in some states with a high incidence of radon, and some
experimental evidence in animals. Ecologic studies are preliminary
studies which examine groups of people rather than individuals; the
relationship between individual lung cancer cases and their exposure to
radon or other cancer causative agents such as smoking cannot be
studied. Also the mobility of the individuals cannot be assessed. A
sensitivity analysis of ecological studies by Dr. Jonathan Samet showed
that they had little value. Based on the considerable limitations of
this type of study design, the scientific community, including
participants in a recent international epidemiologist's workshop, has
recommended against further use of ecologic studies for examining
residential radon risk. Some studies conducted in laboratory animals
kept under sub-optimal conditions have shown a stimulatory effect of
low levels of radiation. However, these studies have found no change in
the expected risk of lung cancer induced by radiation exposure. Given
the strong a priori understanding of the carcinogenicity of radon
(National Research Council, BEIR IV, 1988) an inverse association of
radon with lung cancer is not biologically plausible.
(9) One commenter stated that ``EPA's proposed action guideline of
4 pCi/L is not safe,'' and indicated that ``the Standard should be
based on 2 pCi/L instead.'' Another commenter inquired as to ``why EPA
does not go As Low As Reasonably Achievable, ALARA?'' Average levels of
radon outdoors are about 0.4 pCi/L. The Agency believes that there is
some risk associated with human exposure to any level of radon. In
assessing residential radon risk, EPA assumes that the exposure-
response relationship is linear at low exposures and exposure rates.
This assumption is consistent with the evidence for linearity at a wide
range of cumulative exposures in the radon epidemiologic studies of
underground miners. There is no evidence of a threshold for lung cancer
response from radon exposure, that is, a level of radon exposure below
which no increased risk of lung cancer would exist. EPA's action level
of 4 pCi/L is based on the mitigation capabilities of existing
technology. This technology reduces radon levels to below 4 pCi/L in
almost 95 percent of the existing homes mitigated, and below 2 pCi/L in
75 to 80 percent of these homes (CBA, Appendix B). The Agency believes
a construction standard for builders should target builders to the more
readily achievable 4 pCi/L, while also acknowledging that as builders
follow the techniques of the Model Standards they will in fact be
achieving levels below 4 pCi/L in 75 to 80 percent of the cases. The 4
pCi/L level is also consistent with EPA's action level for existing
homes, as stated in the Citizen's Guide To Radon.
The following responses are related to comments on specific
sections of the EPA Model Standards.
Section 1.0.1 Two commenters recommended amending this section to
more clearly restrict the scope of the Model Standards to specific
kinds of residential dwellings and to avoid including buildings such as
high rise apartment buildings and others. EPA concurs with this
amendment. Restricting the Model Standards to one- and two-family
dwellings and other residential buildings three stories or less in
height has been the intent throughout development of the Standards.
This intent was already reflected in the Limitations section 2.0.1 and
in the Summary section 6.0, and is now specifically stated in section
1.0.1.
Section 1.0.2 Two commenters questioned the need to apply the
Model Standards when modifying the foundations or central air handling
systems of existing buildings. This provision was not considered
appropriate for inclusion in standards for new construction. It was
believed to be more appropriately covered in EPA's Radon Mitigation
Standards. EPA concurs with deleting the provision related to
modification of central air handling systems. This section has also
been modified to more clearly define applicability of the Model
Standards when additions to the foundations of existing one- and two-
family dwellings result in extension of the building footprint.
Section 2.0 One commenter recommended including a statement in
this section that ``all homes should be tested in order for the
Standard to accomplish its goal of reducing the risks from radon.'' EPA
has consistently recommended that all homes, including new homes, be
tested for radon. However, in developing the recommended passive
approach to radon reduction in new homes as set forth in section 7.1 of
the Model Standards, it was determined that the recommendation for
post-construction testing should be applied only to those new homes in
which passive radon control systems were installed. This approach would
identify homes where activation of the passive system is needed to
achieve radon levels below the locally prescribed action level. In new
homes, where builders install active radon control systems during
construction, research has shown that radon concentrations below the
EPA Action Level of 4 pCi/L are achieved in almost all cases (CBA,
appendix B). While EPA continues to recommend testing of all new homes,
inclusion of that recommendation as a specific provision of the Model
Standards was not considered appropriate.
Section 7.2 One commenter disagreed with the recommendation that
EPA Protocols be used for any radon testing referenced in the Model
Standards and expressed a preference for ``use of prescriptive
Standards.'' It was suggested that prescriptive standards ``allow less
latitude in interpretation and less variance in test results
obtained.'' EPA believes that the rigorous requirements for gaining
approval of all types of radon test devices (under the Radon
Measurement Proficiency (RMP) Program), combined with the demonstrated
and proven effectiveness of the procedures for use of those test
devices in homes (as prescribed in EPA's ``Indoor Radon and Radon Decay
Product Measurement Device Protocols'' and ``Protocols For Radon and
Radon Decay Product Measurements In Homes''), results in consistent,
easily interpreted, and accurate radon testing.
Section 7.3 There were 6 comments on this section recommending
changes or additions to improve clarity in describing the individuals
and qualifications needed to design and install radon control systems.
Additions were made in this section to include registered design
professionals (architects or engineers) and contractors listed in EPA's
Radon Contractor Proficiency (RCP) Program as being qualified to
perform or supervise radon control system installations in new homes.
Section 8.2.3 This section states that radon-resistant features
may not be needed, or that limited use of selected techniques may be
sufficient in areas identified as having a low potential for indoor
radon (Zone 3). One commenter recommended that in Zone 3, the Model
Standards ``should specify instead that radon protection measures would
not be needed unless analysis indicated otherwise.'' The difference in
these two approaches appears to be largely semantic. EPA believes that
by establishing a Zone of low radon potential (Zone 3), an analysis has
already been made which provides state and local jurisdictions with an
adequate basis for deciding what, if any, radon-resistant features may
be appropriate for inclusion in their building codes. The original
wording has been retained.
Section 8.3.1 This section was designed to provide an example of
how states or local jurisdictions might approach the development of
rules, regulations, or ordinances for implementing provisions of the
Model Standards. It also suggested the related training that might be
appropriate for local building inspectors and officials. One commenter
stated that, ``Given no criteria for training or resources specified,
it is inappropriate to recommend such training.'' EPA believes that it
is appropriate and desireable to provide an Agency assessment of the
general type of training that may be necessary in jurisdictions where
the Model Standards are adopted in building codes. EPA has agreed to
work with the National Association of Home Builders and with the Model
Code Organizations to develop appropriate training programs and
materials. Funding for this type of activity is expected to be
available through grants to states, as authorized by current
legislation.
Section 9.1.1 Two commenters recommended changes in this section
to more clearly define the alternatives and specifications for creating
a gas permeable layer under slab floors. EPA concurs with this
recommendation and modified the language to include more detailed
specifications for alternative sub-slab materials.
Section 9.1.2 Three commenters recommended changes in this section
to more clearly define specifications and placement requirements for
sub-slab soil-gas-retarder membranes. EPA believes that the current
specifications for membrane type (polyethylene) and thickness (6-mil or
3-mil cross laminated), provides sufficient definition to ensure that
effective soil-gas-retarders are installed by builders nationwide. At
the local level, jurisdictions may decide to add more detailed, locally
approved membrane specifications when they adopt provisions of the
Model Standards in their building codes. This would facilitate
enforcement of the requirement by local building inspectors. On the
question of membrane placement, EPA concurs with the need for more
specific guidance and revised this section accordingly.
Section 9.1.3 This section provides guidance for construction of
concrete floor slabs and makes reference to several guides and manuals
published by the American Concrete Institute (ACI). One commenter
recommended that the Model Standards refer instead to existing Model
Building Code standards for construction of concrete floors. EPA
concurs with this recommendation but has also retained the ACI
publications as ``references that provide additional information on
construction of concrete floor slabs.''
Section 9.1.5 Three commenters recommended changes in this section
to establish a performance standard for sealing large openings through
floors that are in contact with the soil. EPA concurs. The section has
been revised to require the use of sealant materials that ``provide a
permanent air-tight seal.'' Examples of materials that may be used to
achieve that performance standard are also included in this section.
Sections 9.1.6, 9.1.7, 9.1.8, 9.1.13, 9.1.15, 9.1.17, and 9.1.18.
Four commenters recommended changes in one or more of these sections to
more clearly define the characteristics and specifications of sealants
used to retard soil gas entry. EPA concurs with the need to provide
more specific guidance on use of sealants and has made appropriate
changes in each of these sections. The changes have either established
a performance standard (such as air-tight sealing), or have referenced
an ASTM Standard, or have included both a performance standard and
samples of ASTM approved sealant materials.
Section 9.1.9 This section includes specific procedures for
routing the discharge from floor drains and air conditioning condensate
drains so as to prevent radon entry through those openings. One
commenter indicated a preference for applying the procedures for floor
drain discharge that are contained in current model building codes. EPA
concurs with using existing building or plumbing codes as references
when they provide guidance that is also applicable to radon control
techniques. This section was changed to reference local plumbing codes.
Sections 9.1.8, 9.1.11, 9.1.12, and 9.1.14. Each of these sections
contained references to one or more publications of the National
Concrete Masonry Association, the National Forest Products Association,
or the American Concrete Institute. One commenter suggested that if
these publications are included in the Model Standards, they would not
be enforceable since they are not consensus documents and are not
referenced in Model Building Codes. As in the previous comment, EPA
concurs with use of existing, applicable building codes whenever
possible and has either deleted references to the Trade publications or
listed them as additional sources of valuable information to builders.
Section 9.1.15 This section covers the placement of air handling
ducts beneath slabs or in other areas exposed to earth. Two commenters
recommended elimination or prohibition of sub-slab ducting,
particularly in homes where passive or active sub-slab depressurization
systems are installed. Because of the common use of sub-slab and
crawlspace ducting in some areas of the United States, it is not
considered feasible to recommend prohibition or elimination of this
type of construction. EPA believes that the current wording of this
section contains sufficient safeguards to ensure that installation of
such ductwork does not result in increased radon entry into homes.
Section 9.1.16 This section includes a recommendation that air
handling units not be placed in crawlspaces. One commenter suggested
that ``it is possible to place air handling units in crawlspaces if the
joints and seams are sealed.'' As in the previous comment, EPA
recognizes that placing air handling units in crawlspaces is a common
construction practice in many areas of the United States. To
accommodate this reality and, at the same time, ensure that such
installations do not contribute to radon entry, this section has been
revised to include a standard for designing and sealing air handling
units in a manner that prevents air surrounding the unit from being
drawn into the unit.
Section 9.1.20 This section introduces the requirements for
installing components of a passive sub-membrane depressurization (SMD)
system in homes with crawlspace foundations. Two commenters identified
cases where such components should not be required due to the
installation of other effective radon control systems. EPA concurs and
has added an ``Exception'' to this section which eliminates the
requirement for SMD components when other effective crawlspace
ventilation systems are installed.
Section 9.1.20.1 This section addresses the installation
requirements for crawlspace membranes. Several commenters recommended
deletion of the requirement to seal the membrane to interior piers and
foundation walls. Based on experience in mitigation of radon in
existing crawlspace homes (and considering that the Model Standards
recommend use of passive radon control systems in areas of high radon
potential), EPA believes that sealing the membrane to piers and walls
should be a standard construction technique in order to maximize the
effectiveness of passive SMD systems. An additional sentence has been
added to this section to further ensure that the integrity of the
membrane is maintained after construction activity is completed.
Sections 9.1.20.2, 9.21.1, 9.21.2, and 9.3.4. Each of these
sections addresses, among other things, the routing and exhaust point
of radon vent pipes. Three commenters recommended revisions in these
sections to clarify limitations on the exhaust point location. These
sections have been revised to more clearly define the limitations.
Section 9.21.1.1 Two commenters questioned the permitted use and
effectiveness of small diameter (2 and 3-inch) radon vent pipes when
installed as part of a passive radon control system. Small vent pipes
down to 2 inches in diameter have been shown to be effective when
installed in active radon control systems, but EPA agrees that there is
insufficient evidence at this time to support a recommendation that 2-
inch pipes be permitted in passive radon vent stacks. That provision
has been deleted from this section.
Section 9.2.1 One commenter recommended revision of this section
to more clearly define the types of air passages that should be closed
or sealed to reduce the stack effect in buildings. EPA concurs and
revised this section accordingly.
Section 9.2.3 Three commenters recommended a more specific
definition of the type of recessed ceiling lights that should be
installed to reduce the loss of conditioned air through these fixtures.
EPA concurs and has revised this section to include the recommended
Type IC light fixture rating.
Section 9.2.4 Four commenters recommended deletion of the
requirement to install outside air ducts to provide combustion and
makeup air for fireplaces and other combustion and vented appliances.
Conflicts were cited between that proposed requirement and existing
building, mechanical, and gas codes. EPA concurs and has revised this
section to require installation of combustion and vented appliances in
accordance with local codes.
Section 9.3 Two commenters suggested the need for more detailed
guidance on the type, location, and specifications of system failure
warning devices to be used when radon control systems are activated.
There are a variety of devices currently available to builders and
homeowners that provide an acceptable level of audible or visual
warning if the active radon control system fails. EPA believes that
establishment of more detailed warning device specifications in the
Model Standards could increase costs and inhibit installation of such
devices. EPA concurs, however, with the need to require, as a minimum,
that warning devices be prominently positioned to ensure that building
occupants are alerted if the radon control system fails. This section
has been revised to include that requirement.
Section 9.3.3 One commenter suggested that establishment of a
specific slope requirement (\1/8\ inch per foot) for horizontal runs of
radon vent pipes is overly restrictive and that any slope would be
effective for handling rain water and condensation flow. The \1/8\ inch
per foot slope specification was based on the more demanding need for
sufficient slope to handle sewage flow in plumbing waste lines. EPA
agrees that such a specification is not applicable to radon vent pipes
and has revised this section to require only that such pipes slope
downward.
Section 9.3.5 One commenter recommended adding a requirement that
radon vent pipes be routed through attics in a location that would
facilitate future installation and maintenance of a fan. EPA concurs
with the recommendation and has inserted this section as an addition to
the Model Standards.
Section 9.3.6 (Formerly 9.3.5) This section addresses the size
and air movement capacity of radon vent pipe fans. One commenter
recommended inclusion of a more definitive prescriptive size for the
fan. EPA believes that a general specification, related to sub-slab or
sub-membrane pressure field extension, permits needed flexibility in
selection of fans for the wide variety of new home sizes and
configurations that exist in the U.S.
C. Response to Comments on Significant Issues
During development of the Model Standards, a number of significant
issues were raised that warranted special consideration. Comments were
specifically solicited on all of these issues.
1. The first issue relates to the effectiveness of passive systems
in achieving average annual indoor radon levels below 4 pCi/L when
applied in areas of high radon potential. For example, passive systems
may be affected by climatic conditions. Although data available to the
Agency indicates that passive systems will result in reductions of
indoor radon levels, respondents were encouraged to provide any
information that would serve to further quantify effectiveness of
passive systems in different house designs and in different
geographical and climatic areas.
Two commenters responded on this issue. One ``did not share EPA's
confidence in effectiveness of passive systems,'' but offered no data
to support that concern. The second commenter indicated that ``passive
systems rarely work'' and expressed ``doubt about the 50% radon
reduction figure given by EPA,'' citing experience in Spokane County
(Washington) where ``new houses with EPA-style passive systems are
testing above 4 pCi/L at a rate of 46 percent.'' EPA is currently
conducting three studies designed to further quantify the effectiveness
of passive radon control systems in new homes throughout the U.S. One
of these studies has just begun in the Spokane area and will not be
completed until the end of 1994. EPA believes that it is premature to
draw any conclusions from any preliminary data coming out of this
study. EPA agrees that in some local areas, where radon source strength
is particularly high, or where climatic conditions reduce the upward
convective flow of soil-gas in the passive radon vent stack, installing
passive radon control systems may not always result in radon levels
under 4 pCi/L in the new homes built in those areas. This could be the
case even though 50 percent reductions in radon levels were achieved in
all of these homes. These limitations are the basis for recommending in
the Model Standards that all new homes in which passive radon control
systems are installed should be tested to determine whether activation
of the system is needed.
2. The second issue relates to questions concerning ``stack
effect'' reduction techniques, the degree to which they contribute to
radon reduction, and their contribution to building safety and energy
conservation. Although widely used by many builders to enhance energy
conservation, it is acknowledged that there are different views on the
effectiveness of these techniques in reducing indoor radon levels. Some
research has been done to quantify the specific impact of individual
stack effect reduction techniques on radon entry. The Agency chose to
include these techniques as a prescriptive requirement in the
recommended construction method because the preliminary research
indicates they do contribute to reducing radon entry, and produce
significant energy savings and increased fire resistance. EPA invited
comment and information on this topic.
Two commenters responded to this issue. Both expressed concern that
further research is needed to validate the effectiveness of stack
effect reduction methods in reducing radon entry, but provided no data
to support their concern. One commenter suggested that the ``stack
effect reduction techniques should be discussed in a non-mandatory
appendix to the Model Standards due to continuing doubt as to their
effectiveness.'' EPA concurs in the need for additional research to
reduce uncertainties on this issue. However, pending receipt of
additional data proving otherwise, EPA continues to believe that stack
effect reduction methods contribute to reducing radon entry (and to
energy conservation) and should be retained as an integral part of the
Model Standards.
3. The third issue relates to the degree that radon measurements
made in a new home prior to occupancy will represent actual exposure of
future occupants to radon. The Agency believes that all new homes
should be tested, but a concern has been raised as to whether a
measurement in a newly constructed unoccupied house can be used to
reliably indicate the potential for elevated post-occupancy radon
levels. For example, can the house be closed and the heating and
cooling systems operated under normal conditions for a minimum of 12
hours prior to and during the radon test period? The Agency
specifically solicited any information or quantitative analyses related
to conditions existing in a newly constructed home versus an existing
home that would influence radon levels.
One commenter responded on this issue by recounting the reasons why
radon measurements should not be made prior to occupancy of a new home,
but offered no quantitative data. In general, EPA agrees that, for a
variety of reasons, radon measurements taken prior to occupancy may not
reflect actual long term exposure to occupants. To begin the process of
quantifying the accuracy of pre-occupancy radon testing, EPA is
currently conducting a study to assess the effect on radon levels
caused by the normal settling and drying of a house during the first
year after occupancy. EPA supports the need for additional studies to
address other aspects of this issue.
4. The fourth issue concerned the need to ensure that new homes are
tested for radon, especially homes with passive radon control systems
in Zone 1, where, if high radon levels are found, greater risk
reduction can be achieved by activation of the system. The Agency
solicited information on methods that have been successful in
increasing testing of new homes for radon.
There were no comments specifically responding to this issue apart
from the related comments on pre-occupancy testing addressed in the
third issue. One commenter did recommend that ``the Standard should
clearly identify the homeowner as the party responsible for radon
testing.'' EPA has consistently encouraged homeowners to test for radon
but has not found a workable method that would guarantee that a new
home built with a passive radon control system will voluntarily be
tested. EPA continues to solicit information on successful approaches
to new home testing.
5. The fifth issue relates to areas of very low radon potential
where jurisdictions may not believe it advisable to adopt any radon-
resistant construction techniques or radon test re- quirements in their
building codes. As a result, a small number of homes in these areas may
have undetected elevated radon levels. EPA solicited suggestions on how
to address this issue.
Related to this issue, one commenter asked why the Model Standards
``address radon only in high radon zones,'' but did not offer any
suggestions for how to deal with isolated cases of high radon levels in
low radon potential zones. EPA believes that use of passive radon
control systems in areas of high radon po- tential (Zone 1), and
activation of those systems if necessitated by follow-up testing, is
the best approach at this time to achieving both significant radon risk
reduction and cost-effectiveness in construction of new homes. Other
options considered in the CBA were not judged to be cost-effective. EPA
will continue to explore ways in which new houses with elevated radon
levels in Zones 2 and 3 can be identified and mitigated. As indicated
in sections 8.2.2 and 8.2.3 of the Model Standards, if jurisdictions in
Zones 2 and 3 have reason to believe that radon ``hot spots'' exist in
their area, the Agency recommends that appropriate radon-resistant
features be built-in to new homes in those areas.
6. A final issue concerned the approaches that may be taken to
achieve early adoption of the Model Standards by Model Code
Organizations and by local jurisdictions. It was noted that in some
jurisdictions, adoption has been facilitated by including language in
the codes or regulations that absolves builders and building officials
from liability if the required new construct- ion standards and
techniques are applied as dictated by such codes or regulations. EPA
indicated a special interest in comments on that approach and in
examples of other successful attempts to have model standards relating
to environmental issues adopted by Model Code Organizations or local
jurisdictions. One commenter reinforced the example cited above,
suggesting that adoption of the Model Standards would be ``best
facilitated by state laws and model codes containing provisions that
absolve builders from liability if new construction standards are
applied as dictated by local laws and codes.'' There were no other
examples of approaches that might facilitate early adoption of the
Model Standards. EPA will continue to work with state and local
building officials and with Model Code Organizations to gain acceptance
and early adoption of the Model Standards.
7. While EPA requested comments on the entire document, the Agency
was particularly interested in comments relating to the foregoing
issues. Respondents were also encouraged to provide comments on the
overall energy impact of applying the Model Standards. There were no
comments specifically addressing the energy impact of the Model
Standards. EPA continues to believe that an important by-product of
building radon-resistance into new homes is the significant energy
savings that also results.
Dated: March 9, 1994.
Carol M. Browner,
Administrator.
Model Standards and Techniques for Control of Radon in New Residential
Buildings
1.0 Scope
1.0.1 This document contains model building standards and
techniques applicable to controlling radon levels in new construction
of one- and two-family dwellings and other residential buildings three
stories or less in height as defined in model codes promulgated by the
respective Model Code Organizations.
1.0.2 The model building standards and techniques are also
applicable when additions are made to the foundations of existing one-
and two-family dwellings that result in extension of the building
footprint.
1.0.3 This document is not intended to be a building code nor is
it required that it be adopted verbatim as a referenced standard.
1.0.4 It is intended that the building standards and techniques
contained in section 9.0 of this document, the construction method in
section 7.0, and the recommended procedures for applying the standards
and construction method in section 8.0, serve as a model for use by the
Model Code Organizations and authorities within states or other
jurisdictions that are responsible for regulating building construction
as they develop and adopt building codes, appendixes to codes, or
standards and implementing regulations specifically applicable to their
unique local or regional radon control requirements.
1.0.5 The preferential grant assistance authorized in section
306(d) of the Indoor Radon Abatement Act of 1988 (title III of the
Toxic Substances Control Act, TSCA, 15 U.S.C. 2666) will be applied for
states where appropriate authorities who regulate building construction
are taking action to adopt radon-resistant standards in their building
codes.
1.0.6 Model building standards and techniques contained in this
document are not intended to supersede any radon-resistant construction
standards, codes or regulations previously adopted by local
jurisdictions and authorities. However, jurisdictions and authorities
are encouraged to review their current building standards, codes, or
regulations and their unique local or regional radon control
requirements, and consider modifications, if necessary.
1.0.7 This document will be updated and revised as ongoing and
future research programs suggest revisions of standards, identify ways
to improve the model construction techniques, or when newly tested
products or techniques prove to be equivalent to or more effective in
radon control. Updates and revisions to the model building standards
and techniques contained in section 9.0 will undergo appropriate peer
review.
1.0.8 EPA is committed to continuing evaluation of the
effectiveness of the standards and techniques contained in section 9.0
and to research programs that may identify other more effective and
efficient methods.
2.0 Limitations
2.0.1 The Indoor Radon Abatement Act of 1988 (title III of TSCA)
establishes a long-term national goal of achieving radon levels inside
buildings that are no higher than those found in ambient air outside of
buildings. While technological, physical, and financial limitations
currently preclude attaining this goal, the underlying objective of
this document is to move toward achieving the lowest technologically
achievable and most cost effective levels of indoor radon in new
residential buildings.
2.0.2 Preliminary research indicates that the building standards
and techniques contained in section 9.0 can be applied successfully in
mitigating radon problems in some existing nonresidential buildings.
However, their effectiveness when applied during construction of new
nonresidential buildings has not yet been fully demonstrated.
Therefore, it is recommended that, pending further research, these
building standards and techniques not be used at this time as a basis
for changing the specific sections of building codes that cover
nonresidential construction.
2.0.3 Although radon levels below 4 pCi/L have been achieved in
all types of residential buildings by using these model building
standards and techniques, specific indoor radon levels for any given
building cannot be predicted due to different site and environmental
conditions, building design, construction practices, and variations in
the operation of buildings.
2.0.4 These model building standards and techniques are not to be
construed as the only acceptable methods for controlling radon levels,
and are not intended to preempt, preclude, or restrict the application
of alternative materials, systems, and construction practices approved
by building officials under procedures prescribed in existing building
codes.
2.0.5 Elevated indoor radon levels caused by emanation of radon
from water is of potential concern, particularly in areas where there
is a history of groundwater with high radon content. This document does
not include model construction standards or techniques for reducing
elevated levels of indoor radon that may be caused by the presence of
high levels of radon in water supplies. EPA has developed a suggested
approach (see paragraph 8.3.2) that state or local jurisdictions should
consider as they develop regulations concerning private wells. EPA is
continuing to evaluate the issue of radon occurrence in private wells
and the economic impacts of testing and remediation of wells with
elevated radon levels.
2.0.6 While it is not currently possible to make a precise
prediction of indoor radon potential for a specific building site, a
general assessment, on a statewide, county, or grouping of counties
basis, can be made by referring to EPA's Map of Radon Zones and other
locally available data. It should be noted that some radon potential
exists in all areas. However, EPA recognizes that based on available
data, there is a lower potential for elevated indoor radon levels in
some states and portions of some states, and that adoption of building
codes for the prevention of radon in new construction may not be
justified in these areas at this time. There is language in paragraph
8.2.3 of this document recommending that jurisdictions in these areas
review all available data on local indoor radon measurements, geology,
soil parameters, and housing characteristics as they consider whether
adoption of new codes is appropriate.
3.0 Reference Documents
References are made to the following publications throughout this
document. Some of the references do not specifically address radon.
They are listed here only as relevant sources of additional information
on building design, construction techniques, and good building
practices that should be considered as part of a general radon
reduction strategy.
``Building Foundation Design Handbook,'' ORNL/SUB/86-72143/1, May
1988.
``Building Radon Resistant Foundations--A Design Handbook,'' NCMA,
1989.
``Council of American Building Officials (CABO) Model Energy Code,
1992.
``Design and Construction of Post-Tensioned Slabs on Ground,'' Post
Tensioning Institute Manual.
``Energy Efficient Design of New Buildings Except Low-Rise
Residential Buildings,'' ASHRAE Standard 90.1-1989.
``Energy Efficient Design of New Low-Rise Residential Buildings,''
Draft ASHRAE Standard 90.2 (Under public review).
``Homebuyer's and Seller's Guide to Radon,'' EPA 402-R-93-003,
March 1993.
``Guide to Residential Cast-in-Place Concrete Construction,'' ACI
332R.
``Indoor Radon and Radon Decay Product Measurement Device
Protocols.'' EPA 402-R-92-004, July, 1992.
``Protocols For Radon and Radon Decay Product Measurements in
Homes.'' EPA 402-R-92-003, June, 1993.
``Permanent Wood Foundation System--Basic Requirements, NFPA
Technical Report No. 7.''
``Radon Control Options for the Design and Construction of New Low-
Rise Residential Buildings,'' ASTM Standard Guide, E1465-92.
``Radon Handbook for the Building Industry,'' NAHB-NRC, 1989.
``USEPA Map of Radon Zones,'' Dec. 1993.
``Radon Reduction in New Construction, An Interim Guide.'' OPA-87-
009, August 1987.
``Radon Reduction in Wood Floor and Wood Foundation Systems.''
NFPA, 1988.
``Radon Resistant Construction Techniques for New Residential
Construction. Technical Guidance.'' EPA/625/2-91/032, February 1991.
``Radon-Resistant Residential New Construction.'' EPA/600/8-88/087,
July 1988.
``Guide for Concrete Floor and Slab Construction,'' ACI 302.1R-89.
``Ventilation for Acceptable Indoor Air Quality,'' ASHRAE 62-1989.
4.0 Description of Terms
For this document, certain terms are defined in this section. Terms
not defined herein should have their ordinary meaning within the
context of their use. Ordinary meaning is as defined in ``Webster's
Ninth New Collegiate Dictionary.''
Action Level: A term used to identify the level of indoor radon at
which remedial action is recommended. (EPA's current action level is 4
pCi/L.)
Air Passages: Openings through or within walls, through floors and
ceilings, and around chimney flues and plumbing chases, that permit air
to move out of the conditioned spaces of the building.
Combination Foundations: Buildings constructed with more than one
foundation type; e.g., basement/crawlspace or basement/slab-on-grade.
Drain Tile Loop: A continuous length of drain tile or perforated
pipe extending around all or part of the internal or external perimeter
of a basement or crawlspace footing.
Governmental: State or local organizations/agencies responsible for
building code enforcement.
Map of Radon Zones: A USEPA publication depicting areas of
differing radon potential in both map form and in state specific
booklets.
Mechanically Ventilated Crawlspace System: A system designed to
increase ventilation within a crawlspace, achieve higher air pressure
in the crawlspace relative to air pressure in the soil beneath the
crawlspace, or achieve lower air pressure in the crawlspace relative to
air pressure in the living spaces, by use of a fan.
Model Building Codes: The building codes published by the 4 Model
Code Organizations and commonly adopted by state or other jurisdictions
to control local construction activity.
Model Code Organizations: Includes the following agencies and the
model building codes they promulgate: Building Officials and Code
Administrators International, Inc. (BOCA National Building Code/1993
and BOCA National Mechanical Code/1993); International Conference of
Building Officials (Uniform Building Code/1991 and Uniform Mechanical
Code/1991); Southern Building Code Congress, International, Inc.
(Standard Building Code/1991 and Standard Mechanical Code/1991);
Council of American Building Officials (CABO One- and Two-Family
Dwelling Code/1992 and CABO Model Energy Code/1993).
pCi/L: The abbreviation for ``picocuries per liter'' which is used
as a radiation unit of measure for radon. The prefix ``pico'' means a
multiplication factor of l trillionth. A Curie is a commonly used
measurement of radioactivity.
Soil Gas: The gas present in soil which may contain radon.
Soil-Gas-Retarder: A continuous membrane or other comparable
material used to retard the flow of soil gases into a building.
Stack Effect: The overall upward movement of air inside a building
that results from heated air rising and escaping through openings in
the building super-structure, thus causing an indoor pressure level
lower than that in the soil gas beneath or surrounding the building
foundation.
Sub-Slab Depressurization System (Active): A system designed to
achieve lower sub-slab air pressure relative to indoor air pressure by
use of a fan-powered vent drawing air from beneath the slab.
Sub-Slab Depressurization System (Passive): A system designed to
achieve lower sub-slab air pressure relative to indoor air pressure by
use of a vent pipe routed through the conditioned space of a building
and connecting the sub-slab area with outdoor air, thereby relying
solely on the convective flow of air upward in the vent to draw air
from beneath the slab.
Sub-Membrane Depressurization System: A system designed to achieve
lower sub-membrane air pressure relative to crawlspace air pressure by
use of a fan-powered vent drawing air from under the soil-gas-retarder
membrane.
5.0 Principles for Construction of Radon-Resistant Residential
Buildings
5.1 The following principles for construction of radon-resistant
residential buildings underlie the specific model standards and
techniques set forth in section 9.0.
5.1.1 Residential buildings should be designed and constructed to
minimize the entrance of soil gas into the living space.
5.1.2 Residential buildings should be designed and constructed
with features that will facilitate post-construction radon removal or
further reduction of radon entry if installed prevention techniques
fail to reduce radon levels below the locally prescribed action level.
5.2 As noted in the limitations section (paragraph 2.0.2),
construction standards and techniques specifically applicable to new
nonresidential buildings (including high-rise residential buildings),
have not yet been fully demonstrated. Accordingly, the specific
standards and techniques set forth in section 9.0 should not, at this
time, be considered applicable to such buildings. There are, however,
several general conclusions that may be drawn from the limited
mitigation experience available on large nonresidential construction.
These conclusions are summarized below to provide some initial factors
for consideration by builders of nonresidential buildings.
5.2.1 HVAC systems should be carefully designed, installed and
operated to avoid depressurization of basements and other areas in
contact with the soil.
5.2.2 As a minimum, use of a coarse gravel or other permeable base
material beneath slabs, and effective sealing of expansion joints and
penetrations in foundations below the ground surface will facilitate
post-construction installation of a sub-slab depressurization system,
if necessary.
5.2.3 Limited mitigation experience has shown that some of the
same radon reduction systems and techniques used in residential
buildings can be scaled up in size, number, or performance to
effectively reduce radon in larger buildings.
6.0 Summary of the Model Building Standards and Techniques
The model building standards and techniques listed in section 9.0
are designed primarily for control of radon in new one- and two-family
dwellings and other residential buildings three stories or less in
height.
6.1 Basement and Slab-on-Grade Foundations
The model building standards and techniques for radon control in
new residential buildings constructed on basement and slab-on-grade
foundations include a layer of permeable sub-slab material, the sealing
of joints, cracks, and other penetrations of slabs, floor assemblies,
and foundation walls below or in contact with the ground surface,
providing a soil-gas-retarder under floors and installing either an
active or passive sub-slab depressurization system (SSD). Additional
radon reduction techniques are prescribed to reduce radon entry caused
by the heat induced ``stack effect.'' These include the closing of air
passages (also called thermal by-passes), providing adequate makeup air
for combustion and exhaust devices, and installing energy conservation
features that reduce nonrequired airflow out of the building
superstructure.
6.2 Crawlspace Foundations
The model building standards and techniques for radon control in
new residential buildings constructed on crawlspace foundations include
those systems that actively or passively vent the crawlspace to outside
air, that divert radon before entry into the crawlspace, and that
reduce radon entry into normally occupied spaces of the building
through floor openings and ductwork.
6.3 Combination Foundations
Radon control in new residential buildings constructed on a
combination of basement, slab-on-grade or crawlspace foundations is
achieved by applying the appropriate construction techniques to the
different foundation segments of the building. While each foundation
type should be constructed using the relevant portions of these model
building standards and techniques, special consideration must be given
to the points at which different foundation types join, since
additional soil-gas entry routes exist in such locations.
7.0 Construction Methods
The model construction standards and techniques described in
section 9.0 have proved to be effective in reducing indoor radon levels
when used to mitigate radon problems in existing homes and when applied
in construction of new homes. In most cases, combinations of two or
more of these standards and techniques have been applied to achieve
desired reductions in radon levels. Because of success achieved in
reducing radon levels by applying these multiple, interdependent
techniques, limited data have been collected on the singular
contribution to radon reduction made by any one of the construction
standards or techniques. Accordingly, there has been no attempt to
classify or prioritize the individual standards and techniques as to
their specific contribution to radon reduction. It is believed that use
of all the standards and techniques (both passive and active) will
produce the lowest achievable levels of indoor radon in new homes
(levels below 2 pCi/L have been achieved in over 90 percent of new
homes). It is also believed that use of only selected (passive)
standards and techniques will produce indoor radon levels below the
current EPA action level of 4 pCi/L in most new homes, even in areas of
high radon potential.
7.1 It is recommended that all the passive standards and
techniques listed in section 9.0 (including a roughed-in passive radon
control system) be used in areas of high radon potential, as defined by
local jurisdictions or in EPA's Map of Radon Zones. Based on more
detailed analysis of locally available data, jurisdictions may choose
to apply more or less restrictive construction requirements within
designated portions of their areas of responsibility. To ensure that
new homes are below the locally prescribed action level, in those cases
where only passive radon control systems have been installed, occupants
should have their homes tested to determine if passive radon control
systems need to be activated. In addition, it is recommended that
periodic retests be conducted to confirm continued effectiveness of the
radon control system.
7.2 Any radon testing referenced in this document should be
conducted in accordance with EPA Radon Testing Protocols or current EPA
guidance for radon testing in real estate transactions as referenced in
paragraph 3.0. It is recommended that all testing be conducted by
companies listed in EPA's Radon Measurement Proficiency Program (RMP)
or comparable State certification programs.
7.3 The design and installation of radon control systems should be
performed or supervised by individuals (i.e., builders, their
representatives, or registered design professionals such as architects
or engineers) who have attended an EPA-approved radon training course,
or by an individual listed in the EPA Radon Contractor Proficiency
Program.
8.0 Recommended Implementation Procedures
The following procedures are recommended as guidelines for applying
the model building standards and techniques and construction methods
contained in this document. These procedures are based on the rationale
that a passive radon control system and features to facilitate any
necessary post-construction radon reduction should be routinely built-
in to new residential buildings in areas having a high radon potential.
8.1 State, county, or local jurisdictions that use these model
building standards and techniques as a basis for developing building
codes for radon resistant construction should classify their area by
reference to the Zones in EPA's Map of Radon Zones or by considering
other locally available data. While EPA believes that the Map of Radon
Zones and accompanying state-specific booklets are useful in setting
general boundaries of areas of concern, EPA recommends that state and
local jurisdictions collect and analyze local indoor radon
measurements, and assess geology, soil parameters and housing
characteristics--in conjunction with referring to the EPA radon maps--
to determine the specific areas within their jurisdictions that should
be classified as Zone 1.
8.2 State, county, or local jurisdictions that use these model
building standards and techniques as a basis for developing building
codes for radon-resistant construction should specify the construction
methods applicable to their jurisdictional area.
8.2.1 In areas classified as Zone 1 in the Map of Radon Zones, or
by local jurisdiction, application of the construction method in
paragraph 7.1 is recommended.
8.2.2 In areas classified as Zone 2, home builders may apply any
of the radon-resistant construction standards and techniques that
contribute to reducing the incidence of elevated radon levels in new
homes and that are appropriate to the unique radon potential that may
exist in their local building area.
8.2.3 In those areas where state and local jurisdictions have
analyzed local indoor radon measurements, geology, soil parameters, and
housing characteristics and determined that there is a low potential
for indoor radon, application of radon-resistant construction
techniques may not be appropriate. In these areas, radon-resistant
construction techniques may not be needed, or limited use of selected
techniques may be sufficient.
8.3 It is recognized that specific rules, regulations, or
ordinances covering implementation of construction standards or codes
are developed and enforced by state or local jurisdictions. While
developing the model construction standards and techniques contained in
this document, EPA also developed several approaches to regulation that
states or local jurisdictions may find useful and appropriate as they
develop rules and regulations that meet their unique requirements. For
example:
8.3.1 In areas where the recommended construction method or
comparable prescriptive methods are mandated by state or local
jurisdictions, regulations would need to include, as part of the
inspection process, a review of the radon-resistant construction
features by inspectors who have received additional training, to ensure
that the radon-resistant construction features are properly installed
during construction. It would also be necessary to establish
requirements for those building officials who review and approve
construction plans and specifications to become proficient in
identifying and approving planned radon-resistant construction
features.
8.3.2 In any area where surveys have shown the existence of high
levels of radon in groundwater, or in areas where elevated levels of
indoor radon have been found in homes already equipped with active
radon control systems, well water may be the source. In such areas,
authorities responsible for water regulation should consider
establishing well water testing requirements that include tests for
radon.
9.0 Model Building Standards and Techniques
9.1 Foundation and Floor Assemblies:
The following construction techniques are intended to resist radon
entry and prepare the building for post-construction radon mitigation,
if necessary. These techniques, when combined with those listed in
paragraph 9.2, meet the requirements of the construction method
outlined in paragraph 7.1. (See also the construction methods listed in
ASTM Standard Guide, E-1465-92.)
9.1.1 A layer of gas permeable material shall be placed under all
concrete slabs and other floor systems that directly contact the ground
and are within the walls of the living spaces of the building, to
facilitate installation of a sub-slab depressurization system, if
needed. Alternatives for creating the gas permeable layer include:
a. A uniform layer of clean aggregate, a minimum of 4 inches thick.
The aggregate shall consist of material that will pass through a 2-inch
sieve and be retained by a \1/4\-inch sieve.
b. A uniform layer of sand, a minimum of 4 inches thick, overlain
by a layer or strips of geotextile drainage matting designed to allow
the lateral flow of soil gases.
c. Other materials, systems, or floor designs with demonstrated
capability to permit depressurization across the entire subfloor area.
9.1.2 A minimum 6-mil (or 3-mil cross laminated) polyethylene or
equivalent flexible sheeting material shall be placed on top of the gas
permeable layer prior to pouring the slab or placing the floor assembly
to serve as a soil-gas-retarder by bridging any cracks that develop in
the slab or floor assembly and to prevent concrete from entering the
void spaces in aggre- gate base material. The sheeting should cover the
entire floor area, and separate sections of sheeting should be
overlapped at least 12 inches. The sheeting shall fit closely around
any pipe, wire or other penetrations of the material. All punctures or
tears in the material shall be sealed or covered with additional
sheeting.
9.1.3 To minimize the formation of cracks, all concrete floor
slabs shall be designed, mixed, placed, reinforced, consolidated,
finished, and cured in accordance with standards set forth in the Model
Building Codes. The American Concrete Institute publications, ``Guide
for Concrete Floor and Slab Construction,'' ACI 302.1R, ``Guide to
Residential Cast-in-Place Concrete Construction,'' ACI 332R, or the
Post Tensioning Institute Manual, ``Design and Construction of Post-
Tensioned Slabs on Ground'' are references that provide additional
information on construction of concrete floor slabs.
9.1.4 Floor assemblies in contact with the soil and constructed of
materials other than concrete shall be sealed to minimize soil gas
transport into the conditioned spaces of the building. A soil-gas-
retarder shall be installed beneath the entire floor assembly in
accordance with paragraph 9.1.2.
9.1.5 To retard soil gas entry, large openings through concrete
slabs, wood, and other floor assemblies in contact with the soil, such
as spaces around bathtub, shower, or toilet drains, shall be filled or
closed with materials that provide a permanent air-tight seal such as
non-shrink mortar, grouts, ex- panding foam, or similar materials
designed for such application.
9.1.6 To retard soil gas entry, smaller gaps around all pipe,
wire, or other objects that penetrate concrete slabs or other floor
assemblies shall be made air tight with an elastomeric joint sealant,
as defined in ASTM C920-87, and applied in accordance with the
manufacturer's recommendations.
9.1.7 To retard soil gas entry, all control joints, isolation
joints, construction joints, and any other joints in concrete slabs or
between slabs and foundation walls shall be sealed. A continuous formed
gap (for example, a ``tooled edge'') which allows the application of a
sealant that will provide a continuous, air-tight seal shall be created
along all joints. When the slab has cured, the gap shall be cleared of
loose material and filled with an elastomeric joint sealant, as defined
in ASTM C920-97, and applied in accordance with the manufacturer's
recommendations.
9.1.8 Channel type (French) drains are not recommended. However,
if used, such drains shall be sealed with backer rods and an
elastomeric joint sealant in a manner that retains the channel feature
and does not interfere with the effectiveness of the drain as a water
control system.
9.1.9 Floor drains and air conditioning condensate drains that
discharge directly into the soil below the slab or into crawlspaces
should be avoided. If installed, these drains shall be routed through
solid pipe to daylight or through a trap approved for use in floor
drains by local plumbing codes.
9.1.10 Sumps open to soil or serving as the termination point for
sub-slab or exterior drain tile loops shall be covered with a gasketed
or otherwise sealed lid to retard soil gas entry. (Note: If the sump is
to be used as the suction point in an active sub-slab depressurization
system, the lid should be designed to accommodate the vent pipe. If
also intended as a floor drain, the lid shall also be equipped with a
trapped inlet to handle any surface water on the slab.)
9.1.11 Concrete masonry foundation walls below the ground surface
shall be constructed to minimize the transport of soil gas from the
soil into the building. Hollow block masonry walls shall be sealed at
the top to prevent passage of air from the interior of the wall into
the living space. At least one continuous course of solid masonry, one
course of masonry grouted solid, or a poured concrete beam at or above
finished ground surface level shall be used for this purpose. Where a
brick veneer or other masonry ledge is installed, the course
immediately below that ledge shall also be sealed.
9.1.12 Pressure treated wood foundations shall be constructed and
installed as described in the National Forest Products Association
(NFPA) Manual, ``Permanent Wood Foundation System--Basic Requirements,
Technical Report No. 7.'' In addition, NFPA publication, ``Radon
Reduction in Wood Floor and Wood Foundation Systems'' provides more
detailed information on construction of radon-resistant wood floors and
foundations.
9.1.13 Joints, cracks, or other openings around all penetrations
of both exterior and interior surfaces of masonry block or wood
foundation walls below the ground surface shall be sealed with an
elastomeric sealant that provides an air-tight seal. Penetrations of
poured concrete walls should also be sealed on the exterior surface.
This includes sealing of wall tie penetrations.
9.1.14 To resist soil gas entry, the exterior surfaces of portions
of poured concrete and masonry block walls below the ground surface
shall be constructed in accordance with water proofing procedures
outlined in the Model Building Codes.
9.1.15 Placing air handling ducts in or beneath a concrete slab
floor or in other areas below grade and exposed to earth is not
recommended unless the air handling system is designed to maintain
continuous positive pressure within such ducting. If ductwork does pass
through a crawlspace or beneath a slab, it should be of seamless
material. Where joints in such ductwork are unavoidable, they shall be
sealed with materials that prevent air leakage.
9.1.16 Placing air handling units in crawlspaces, or in other
areas below grade and exposed to soil-gas, is not recommended. However,
if such units are installed in crawlspaces or in other areas below
grade and exposed to soil gas, they shall be designed or otherwise
sealed in a durable manner that prevents air surrounding the unit from
being drawn into the unit.
9.1.17 To retard soil gas entry, openings around all penetrations
through floors above crawlspaces shall be sealed with materials that
prevent air leakage.
9.1.18 To retard soil gas entry, access doors and other openings
or penetrations between basements and adjoining crawlspaces shall be
closed, gasketed or otherwise sealed with materials that prevent air
leakage.
9.1.19 Crawlspaces should be ventilated in conformance with
locally adopted codes. In addition, vents in passively ventilated
crawlspaces shall be open to the exterior and be of noncloseable
design.
9.1.20 In buildings with crawlspace foundations, the following
components of a passive sub-membrane depressurization system shall be
installed during construction: (Exception: Where local codes permit
mechanical crawlspace ventilation or other effective ventilation
systems, and such systems are operated or proven to be effective year
round, the sub- membrane depressurization system components are not
required.)
9.1.20.1 The soil in both vented and nonvented crawlspaces shall
be covered with a continuous layer of minimum 6-mil thick polyethylene
sheeting or equivalent membrane material. The sheeting shall be sealed
at seams and penetrations, around the perimeter of interior piers, and
to the foundation walls. Following installation of underlayment,
flooring, plumbing, wiring, or other construction activity in or over
the crawlspace, the membrane material shall be inspected for holes,
tears, or other damage, and for continued adhesion to walls and piers.
Repairs shall be made as necessary.
9.1.20.2 A length of 3- or 4-inch diameter perforated pipe or a
strip of geotextile drainage matting should be inserted horizontally
beneath the sheeting and connected to a 3- or 4-inch diameter ``T''
fitting with a vertical standpipe installed through the sheeting. The
standpipe shall be extended vertically through the building floors,
terminate at least 12 inches above the surface of the roof, in a
location at least 10 feet away from any window or other opening into
the conditioned spaces of the building that is less than 2 feet below
the exhaust point, and 10 feet from any adjoining or adjacent
buildings.
9.1.20.3 All exposed and visible interior radon vent pipes shall
be identified with at least one label on each floor level. The label
shall read: ``Radon Reduction System.''
9.1.20.4 To facilitate installation of an active sub-membrane
depressurization system, electrical junction boxes shall be installed
during construction in proximity to the anticipated locations of vent
pipe fans and system failure alarms.
9.1.21 In basement or slab-on-grade buildings the following
components of a passive sub-slab depressurization system shall be
installed during construction:
9.1.21.1 A mimimum 3-inch diameter PVC or other gas-tight pipe
shall be embedded vertically into the sub-slab aggregate or other
permeable material before the slab is poured. A ``T'' fitting or other
support on the bottom of the pipe shall be used to ensure that the pipe
opening remains within the sub-slab permeable material. This gas tight
pipe shall be extended vertically through the building floors,
terminate at least 12 inches above the surface of the roof, in a
location at least 10 feet away from any window or other opening into
the conditioned spaces of the building that is less than 2 feet below
the exhaust point, and 10 feet from any adjoining or adjacent
buildings.
Note: Because of the uniform permeability of the sub-slab layer
prescribed in paragraph 9.1.1, the precise positioning of the vent
pipe through the slab is not critical to system performance in most
cases. However, a central location shall be used where feasible.
In buildings designed with interior footings (that is, footings
located inside the overall perimeter footprint of the building) or
other barriers to lateral flow of sub-slab soil gas, radon vent pipes
shall be installed in each isolated, nonconnected floor area. If
multiple suction points are used in nonconnected floor areas, vent
pipes are permitted to be manifolded in the basement or attic into a
single vent that could be activated using a single fan.
9.1.21.2 Internal sub-slab or external footing drain tile loops
that terminate in a covered and sealed sump, or internal drain tile
loops that are stubbed up through the slab are also permitted to
provide a roughed-in passive sub-slab depressurization capability. The
sump or stubbed up pipe shall be connected to a vent pipe that extends
vertically through the building floors, terminates at least 12 inches
above the surface of the roof, in a location at least 10 feet away from
any window or other opening into the conditioned spaces of the building
that is less than 2 feet below the exhaust point, and 10 feet from any
adjoining or adjacent buildings.
9.1.21.3 All exposed and visible interior radon vent pipes shall
be identified with at least one label on each floor level. The label
shall read: ``Radon Reduction System.''
9.1.21.4 To facilitate installation of an active sub-slab
depressurization system, electrical junction boxes shall be installed
during construction in proximity to the anticipated locations of vent
pipe fans and system failure alarms.
9.1.21.5 In combination basement/crawlspace or slab-on-grade/
crawlspace buildings, the sub-membrane vent described in paragraph
9.1.20.2 may be tied into the sub-slab depressurization vent to permit
use of a single fan for suction if activation of the system is
necessary.
9.2 Stack Effect Reduction Techniques.
The following construction techniques are intended to reduce the
stack effect in buildings and thus the driving force that contributes
to radon entry and migration through buildings. As a basic principle,
the driving force decreases as the number and size of air leaks in the
upper surface of the building decrease. It should also be noted that in
most cases, exhaust fans contribute to stack effect.
9.2.1 Openings around chimney flues, plumbing chases, pipes, and
fixtures, ductwork, electrical wires and fixtures, elevator shafts, or
other air passages that penetrate the conditioned envelope of the
building shall be closed or sealed using sealant or fire resistant
materials approved in local codes for such application.
9.2.2 If located in conditioned spaces, attic access stairs and
other openings to the attic from the building shall be closed,
gasketed, or otherwise sealed with materials that prevent air leakage.
9.2.3 Recessed ceiling lights that are designed to be sealed and
that are Type IC rated shall be used when installed on top-floor
ceilings or in other ceilings that connect to air passages.
9.2.4 Fireplaces, wood stoves, and other combustion or vented
appliances, such as furnaces, clothes dryers, and water heaters shall
be installed in compliance with locally adopted codes, or other
provisions made to ensure an adequate supply of combustion and makeup
air.
9.2.5 Windows and exterior doors in the building superstructure
shall be weather stripped or otherwise designed in conformance with the
air leakage criteria of the CABO Model Energy Code.
9.2.6 HVAC systems shall be designed and installed to avoid
depressurization of the building relative to underlying and surrounding
soil. Specifically, joints in air ducts and plenums passing through
unconditioned spaces such as attics, crawlspaces, or garages shall be
sealed.
9.3 Active Sub-Slab/Sub-Membrane Depressurization System. When
necessary, activation of the roughed-in passive sub-membrane or sub-
slab depressurization systems described in paragraphs 9.1.20 and 9.1.21
shall be completed by adding an exhaust fan in the vent pipe and a
prominently positioned visible or audible warning system to alert the
building occupant if there is loss of pressure or air flow in the vent
pipe.
9.3.1 The fan in the vent pipe and all positively pressurized
portions of the vent pipe shall be located outside the habitable space
of the building.
9.3.2 The fan in the vent pipe shall be installed in a vertical
run of the vent pipe.
9.3.3 Radon vent pipes shall be installed in a configuration and
supported in a manner that ensures that any rain water or condensation
accumulating within the pipes drains downward into the ground beneath
the slab or soil-gas-retarder.
9.3.4 To avoid reentry of soil gas into the building, the vent
pipe shall exhaust at least 12 inches above the surface of the roof, in
a location at least 10 feet away from any window or other opening into
the conditioned spaces of the building that is less than 2 feet below
the exhaust point, and 10 feet from any adjoining or adjacent
buildings.
9.3.5 To facilitate future installation of a vent fan, if needed,
the radon vent pipe shall be routed through attics in a location that
will allow sufficient room to install and maintain the fan.
9.3.6 The size and air movement capacity of the vent pipe fan
shall be sufficient to create and maintain a pressure field beneath the
slab or crawlspace membrane that is lower than the ambient pressure
above the slab or membrane.
9.3.7 Under conditions where soil is highly permeable, reversing
the air flow in an active sub-slab depressurization system and forcing
air beneath the slab may be effective in reducing indoor radon levels.
(Note: The long-term effect of active sub-slab depressurization
or pressurization on the soil beneath building foundations has not
been determined. Until ongoing research produces definitive data, in
areas where expansive soils or other unusual soil conditions exist,
the local soils engineer shall be consulted during the design and
installation of sub-slab depressurization or pressurization
systems.)
[FR Doc. 94-6551 Filed 3-18-94; 8:45 am]
BILLING CODE 6560-50-P