Standard Practice for Radon Control Options for the Design and Construction of New Low-Rise Residential Buildings
This practice provides the design details and construction methods for two built-in soil depressurization radon control and reduction systems appropriate for use in new low-rise residential buildings. Depending on the configuration of the radon vent stack installed, the radon system's operation may have a pipe route appropriate for a fan-powered radon reduction system, or have a more efficient pipe route appropriate for passively operated radon reduction systems. This practice covers special features for soil depressurization radon reduction systems including (1) slab-on-grade, basement and crawlspace foundation types with cast concrete slab and membrane ground covers, (2) sub-slab and submembrane gas-permeable layers and their drainage, (3) radon system piping, (4) radon discharge separation from openings into occupiable space, (5) radon fan installation, (6) electrical requirements, (7) radon system monitor installation, (8) labeling, (9) radon testing, and (10) system documentation.
Fan-powered radon reduction systems built into new residential buildings according to this practice are likely to reduce elevated indoor radon levels, where soil-gas is the source of radon, to below 2.0 picocuries per litre (pCi/L) (75 becquerels of radon per cubic metre (Bq/m3)) in occupiable spaces. Passive radon reduction systems do not always reduce such indoor radon concentrations to below 2.0 picocuries per litre (pCi/L) (75 becquerels of radon per cubic metre (Bq/m3)) in occupiable spaces. When a passive system, built according to this practice, does not achieve acceptable radon concentrations, that system should be converted to fan-powered operation to significantly improve its performance. Exceptions—New residential buildings built on expansive soil and karst may require additional measures, not included in this practice, to achieve acceptable radon reduction. Consider consulting with a soil/geotechnical specialist, a qualified foundation structural engineer and contacting the state’s radon in air specialist for up-to-date information about construction methods. Names of your state radon specialist are available from the U.S. EPA website (http://www.epa.gov/radon).
Note 1—Residences using private wells can have elevated indoor radon concentrations due to radon that out-gasses from the water used indoors, like water used to shower (7). Consider contacting your state’s radon specialist for up-to-date information on available methods for removing radon from private well water.
All soil depressurization radon reduction methods require a gas-permeable layer which can be depressurized. The gas-permeable layer is positioned under the building’s sealed ground cover. In the case of the active soil depressurization system, a radon fan pulls air up the vent stack to depressurize the gas-permeable layer. In the case of a passive soil depressurization system, when air in the vent stack is warmer than that outdoors, the warmer air rises in the stack causing the gas-permeable layer to be depressurized. The passive system depressurizes the gas-permeable layer intermittently; the fan-powered system depressurizes the gas-permeable layer continuously. The performance of gas-permeable layers depends on their design; see 188.8.131.52. A radon reduction system that operates passively requires the most efficient gas-permeable layer.
U.S. EPA recommended action level concerning indoor radon states that the radon concentration should always be reduced if it is 4 picocuries per litre (pCi/L) (150 becquerels of radon per cubic metre (Bq/m3)) or above in occupiable spaces. According to U.S. EPA there is also reduced risk when radon concentrations in indoor air are lowered to below 2.0 picocuries per litre (pCi/L) (75 becquerels of radon per cubic metre (Bq/m3)) in occupiable spaces (4).
Significant benefit is obtained from reducing indoor radon concentrations to below 4 pCi/L (150 Bq/m3). According to the U.S. EPA’s risk assessment (8), about 62 out of 1000 people who smoke will die from a lifetime’s average radon exposure of 4 pCi/L (150 Bq/m3); for people who never smoked about 7 out of 1000 will people die from the same lifetime exposure. Smokers’ lifetime risk of death from lung cancer is reduced by about half (50 %) when their average radon exposure is reduced from 4 to 2 pCi/L (150 to 75 Bq/m3); their risk is reduced by about two-thirds (67 %) when their exposure is reduced from 4 to 1.3 pCi/L (150 to 75 Bq/m3). Never-smokers’ lifetime risk of death from lung cancer is reduced by about 40 % when their average radon exposure is reduced from 4 to 2 pCi/L (150 to 75 Bq/m3); the risk is reduced by 70 % when their exposure is reduced from 4 to 1.3 pCi/L (150 to 50 Bq/m3). U.S. EPA recommended action level about reducing radon to less that 4 pCi/L (150 Bq/m3) is “Radon levels less than 4 pCi/L (150 Bq/m3) still pose a risk, and in many cases may be reduced” (4). U.S. EPA recommendation is to “Consider fixing between 2 and 4 pCi/L (75 and 150 Bq/m3).” (See radon reduction goals in 1.4 and 6.11.4.)
This practice assumes that the customer is informed about the risks of lung cancer from exposure to radon and able to establish by contract the maximum acceptable indoor radon concentration allowed in the new residential building. Because there are goals and recommended action level but no government mandated maximum indoor radon concentration for new residential construction in the United States customers and their agents should negotiate to establish by contract the maximum acceptable indoor radon concentration. The customer should keep in mind that the building’s indoor radon concentration can never be less than the radon concentration in the outdoor air in the vicinity of the building; that establishing target radon levels below 2 pCi/L (75 Bq/m3) could be more expensive; and that radon concentrations below 2 pCi/L (75 Bq/m3) are difficult to measure using current commercially available technology. (See (4, 7), 1.4, and 6.11.4.)
The negotiated acceptable radon concentration defined by this standard can vary from customer to customer and contract to contract. The owner’s goal for radon reduction should be known and considered before the radon system design is specified. The construction choices for void space in the gas-permeable layer; vent stack pipe diameter and route; radon fan capacity; and building features influence the radon reduction system’s performance. (See 1.4, 3.2.1, 5.3, 5.4, 5.5, and 184.108.40.206.)
This practice offers organized information about radon reduction methods. This practice cannot replace education and experience and should be used in conjunction with trained and certified radon practitioner's judgment. Not all aspects of this practice may be applicable in all circumstances.
This practice is not intended, by itself, to replace the standard of care by which adequacy of a professional service may be judged, nor should this practice alone be applied without consideration of a project's unique aspects.
The word “Standard” in the title of this practice means that the document has been approved through the ASTM consensus process.
Reliable methods for predicting indoor radon concentrations for a particular residential building prior to its construction are not available at this time. If the house is in contact with the ground, it is possible for radon gas to be present. Not all houses will need a radon system; nationally, 1 out of 15, or 7 % of the houses have indoor radon concentrations greater than 4 pCi/L (150 Bq/m3). In the highest state 71 % of the houses have indoor radon greater than 4 pCi/L (150 Bq/m3). In fifteen states less than 10 % of the houses are over 4 pCi/L (150 Bq/m3). In six states 40 % or more of the houses have indoor radon over 4 pCi/L (150 Bq/m3). State and local jurisdictions and individual owners are in the best position to decide where houses with radon reduction features should be built.
1.1 This practice covers the design and construction of two radon control options for use in new low-rise residential buildings. These unobtrusive (built-in) soil depressurization options are installed with a pipe route appropriate for their intended initial mode of operation, that is, fan-powered or passive. One of these pipe routes should be installed during a residential building’s initial construction. Specifications for the critical gas-permeable layer, the radon system’s piping, and radon entry pathway reduction are comprehensive and common to both pipe routes.
1.1.1 The first option has a pipe route appropriate for a fan-powered radon reduction system. The radon fan should be installed after (1) an initial radon test result reveals unacceptable radon concentrations and therefore a need for an operating radon fan, or (2) the owner has specified an operating radon fan, as well as acceptable radon test results before occupancy. Fan operated soil depressurization radon systems reduce indoor radon concentrations up to 99 %.
1.1.2 The second option has a more efficient pipe route appropriate for passively operated radon reduction systems. Passively operated radon reduction systems provide radon reductions of up to 50 %. When the radon test results for a building with an operating passive system are not acceptable, that system should be converted to fan-powered operation. Radon systems with pipe routes installed for passive operation can be converted easily to fan-powered operation; such fan operated systems reduce indoor radon concentrations up to 99 %.
1.2 The options provide different benefits:
1.2.1 The option using the pipe route for fan-powered operation is intended for builders with customers who want maximum unobtrusive built-in radon reduction and documented evidence of an effective radon reduction system before a residential building is occupied. Radon systems with fan-powered type pipe routes allow the greatest architectural freedom for vent stack routing and fan location.
1.2.2 The option using the pipe route for passive operation is intended for builders and their customers who want unobtrusive built-in radon reduction with the lowest possible operating cost, and documented evidence of acceptable radon system performance before occupancy. If a passive system’s radon reduction is unacceptable, its performance can be significantly increased by converting it to fan-powered operation.
1.3 Fan-powered, soil depressurization, radon-reduction techniques, such as those specified in this practice, have been used successfully for slab-on-grade, basement, and crawlspace foundations throughout the world.
1.4 Radon in air testing is used to assure the effectiveness of these soil depressurization radon systems. The U.S. national goal for indoor radon concentration, established by the U.S. Congress in the 1988 Indoor Radon Abatement Act, is to reduce indoor radon as close to the levels of outside air as is practicable. The radon concentration in outside air is assumed to be 0.4 picocuries per litre (pCi/l) (15 Becquerels per cubic metre (Bq/m3)); the U.S.’s average radon concentration in indoor air is 1.3 pCi/L (50 Bq/m3). The goal of this practice is to make available new residential buildings with indoor radon concentrations below 2.0 pCi/L (75 Bq/m3) in occupiable spaces.
1.5 This practice is intended to assist owners, designers, builders, building officials and others who design, manage, and inspect radon systems and their construction for new low-rise residential buildings.
1.6 This practice can be used as a model set of practices, which can be adopted or modified by state and local jurisdictions, to fulfill objectives of their residential building codes and regulations. This practice also can be used as a reference for the federal, state, and local health officials and radiation protection agencies.
1.7 The new dwelling units covered by this practice have never been occupied. Radon reduction for existing low rise residential buildings is covered by Practice E 2121, or by state and local building codes and radiation protection regulations.
1.8 Fan-powered soil depressurization, the principal strategy described in this practice, offers the most effective and most reliable radon reduction of all currently available strategies. Historically, far more fan-powered soil depressurization radon reduction systems have been successfully installed and operated than all other radon reduction methods combined. These methods are not the only methods for reducing indoor radon concentrations (1-3).
1.9 Section 7 is Occupational Radon Exposure and Worker Safety.
1.10 Appendix X1 is Principles of Operation for Fan-Powered Soil Depressurization Radon Reduction.
1.11 Appendix X2 is a Summary of Practice E 1465 Requirements for Installation of Radon Reduction Systems in New Low Rise Residential Building.
1.12 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.13 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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