Model Standards and Techniques For Control of Radon in New Residential Buildings

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