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Radon Control in New Home Construction:

Developments in State Policy


According to the U.S. Environmental Protection Agency (EPA), indoor radon is the second leading cause of lung cancer in the United States and the leading cause of lung cancer among non-smokers. Indoor radon exposure is responsible for about 21,000 lung cancer deaths in the U.S. each year. See http://www.epa.gov/radon/healthrisks.html.

Radon is a radioactive gas found in soil and rock in all parts of the United States. The concentration of radon in indoor air is affected by the way we design and construct houses and other buildings. EPA has established an “action level” of 4 picoCuries/liter (pCi/L) — the level at which a building owner should take action to reduce radon in the indoor air. Because there is no known safe level of exposure to radon, EPA also recommends that Americans consider fixing their home for radon levels between 2 pCi/L and 4 pCi/L.

The EPA Map of Radon Zones shows the radon potential for each county in the nation. Zone 1 counties have the highest potential radon levels, with predicted average indoor radon screening levels greater than 4 pCi/L, while predicted average radon levels are 2-4 pCi/L in Zone 2 counties, and under 2 pCi/L in Zone 3 counties. Although the map shows predicted average radon levels, elevated radon levels have been found in every state and can be found in any area. The only way to know the radon level in a particular home is to test the home for radon.

When a new home is built, radon control techniques (also referred to as radon-resistant new construction) can be used to help keep radon from entering the home. The EPA has developed a voluntary guidance document on radon control techniques for new residential construction. The guidance recommends and describes the installation of a “passive sub-slab or sub-membrane depressurization system.” See U.S. EPA, Building Radon Out: A Step-by-Step Guide on How to Build Radon-Resistant Homes (2001).

Given the potential limitations of a passive (non fan-powered) system, installing such a system does not ensure radon levels under 4 pCi/L. EPA’s Building Radon Out further recommends that “[t]he home should be tested after occupancy and the passive system should be activated [fan powered] if post-occupancy testing reveals radon levels at or above 4pCi/L.” See Building Radon Out at 30.

EPA also recently developed voluntary guidance addressing radon and many other indoor air quality issues in new home construction. The guidance, known as Indoor airPLUS, calls on builders of new homes in Zone 1 areas to use radon control techniques and to provide home owners in Zones 1 and 2 with radon testing kits and instructions for their use.

Certain non-governmental organizations have developed consensus-based, technical standards for radon control techniques in new home construction. For example, the International Residential Code (IRC), a model building code developed by the International Code Council, contains a radon control standard that calls for a passive (no fan) sub-slab or sub-membrane depressurization system to be installed in homes located in Zone 1 areas. Because the IRC standard is included as an optional appendix (“Appendix F”) jurisdictions that adopt the IRC as part of their building code must explicitly include Appendix F in order to establish the IRC’s radon control standard.

Another third-party standard is ASTM International’s ASTM E-1465 (“Standard Practice for Radon Control Options for the Design and Construction of New Low-Rise Residential Buildings"). An important difference between this model standard and the IRC Appendix F standard is that the ASTM standard requires pre-occupancy radon testing; if the testing indicates unacceptable radon concentrations, a fan (active system) must be installed. In addition, a new RRNC standard ("CCAH—2013"), developed by the American Association of Radon Scientists and Technologists (AARST) and approved by the American National Standards Institute (ANSI), also incorporates pre-occupancy radon testing.

State Policies

State and local governments can play an important role in reducing the risks from radon exposure. In addition to providing education and information to builders and consumers, they can enact policies to help ensure that homes are built with radon control techniques. These policies can reference an existing radon control standard, or they can modify and adapt existing standards and guidance.

One important policy opportunity for protecting public health is to include radon control requirements in residential building codes— both local building codes and statewide building codes that are mandatory at the local level. The following states have incorporated such mandatory radon control requirements for new home construction into their residential building codes. Click on the links below for brief summaries of these policies.

States can also include radon control standards in their model state building codes. For example, the state building codes in Florida and Virginia incorporate radon control standards that must be applied if a local jurisdiction chooses to adopt a radon control standard at all. A 2017 Utah law amending the state residential code established that “when passive radon controls or portions thereof are voluntarily installed, the voluntary installation shall comply with Appendix F of the IRC.” Similarly, the state of Maine has a state-wide building code that adopts the ASTM E-1465 standard; according to the Maine Bureau of Building Codes and Standards, home owners or builders who choose to incorporate radon control techniques into new home construction should do so in accordance with the ASTM standard. In addition, Maine’s Manufactured Housing Board has adopted a  rule requiring state-certified manufactured housing to comply with the board’s radon mitigation preparation standard.

In 2017, Nebraska enacted a law establishing a Radon Resistant New Construction Task Force to develop recommended minimum standards for radon resistant new construction by April 2018, for consideration by the Governor and the legislature.The Task Force issued its recommendations on April 9, 2018.  In May 2019, the state passed additional legislation establishing that the RRNC minimum standards adopted pursuant to the 2017 law will be incorporated into the state building code.

There are many more states that can benefit from policies to control radon in new construction. A number of states have both state-wide residential building codes and a significant number of high and moderate radon potential areas, but do not address radon in their codes. These states include Indiana, Montana, Pennsylvania, New Mexico, New York, Wisconsin, California, and Georgia.

Watch for updates to this page as new policies are established.


Last Updated: June 2019

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