The US Environmental Protection Agency (EPA) is developing a model radon control standard for residential construction, with adoption of the standard expected sometime this winter.

In developing the standard, the EPA considered a variety of alternative requirements for three radon potential zones. Areas with the highest radon levels were assigned to Zone 1, which encompasses counties where research predicts average indoor radon screening levels of greater than 4 picocuries per liter (pCi/l). (Picocuries per liter is a measurement of the concentration of radioactivity in the air. Radon's carcinogenic effect stems not from the gas itself, but from the radioactive radon decay products deposited in the lungs.) Counties with averages between 2 and 4 pCi/l were assigned to Zone 2, and averages of below 2pCi/l to Zone 3.

The EPA considered several approaches for applying standards in the different zones, and opted for what it deemed most cost-effective and practical. The more comprehensive option for passive measures in both Zones 1 and 2 would add costs in many homes at no risk of radon contamination. It was a compromise but...to get the builders to do something, to get NAHB's [National Association of Home Builders] support, we had to go with an option that was reasonable in terms of costs, said Dave Murane, staff scientist with the EPA's radon division. In Zone 1, he said, you know you're going to get some benefit in the majority of homes.

The new standard--to be published in its final version this winter--calls only for passive radon control measures in Zone 1. It recommends, but does not require subsequent testing, and installation of active measures if the passive measures prove inadequate. The passive system required in Zone 1 includes construction techniques which prevent or reduce the entry of radon into the home, and installation of a pipe to vent radon out through the top of the roof, paving the way for conversion to an active system if necessary. The active system adds a fan into the vent pipe to suck radon out from under the house.

The cost of meeting the model standard ranges from $350-$500, according to Murane. If a home is being built the way it should be built, with quality construction, the additional cost of radon-resistant features is very low, he said.

The additional cost of installing an active system--which consists of an electric fan and a system failure warning device--comes to about $250, for a total cost of $600-$750. And the EPA estimates another $40-$75 per year in additional electrical costs for operating and maintaining an active system.

Not everyone agrees with the EPA's methodology. The EPA has led with something that's not very well-grounded scientifically, said Rich Sextro, a staff scientist in the Indoor Air and Environment Program at Lawrence Berkeley Laboratory. There just isn't enough information. Sextro notes that the EPA's data base is very limited, consisting of about 15 houses for the passive tests.

Murane conceded that more research is needed, and that the EPA doesn't have all the answers. But we have a whole body of information on things that have been successful in existing homes (for example, sealing the floor-wall joint). Is it necessary to do more research in new homes to see if they're different, somehow, from existing homes? Murane asked.

However, Sextro countered that most of that data is on active systems, not the passive systems called for in the model standard. Sextro argues that predicted long-term radon concentrations should be the basis for identifying the zones, as opposed to more short-term predicted screening measures. These estimates, currently being used by the State of Florida, would generally give lower but more reliable readings, and the fact that testing is not mandatory in the standard is also problematic, according to Sextro. Most people aren't testing, even in areas where, from my point of view, it ought to be required, said Sextro. It will be difficult to determine whether the proposed passive features are really working.

Radon testing is an issue everywhere. Radon hotspots can occur even in generally low-radon areas and only 9% of the nation's homes have been tested. Murane cites one house in Alabama, a predominantly Zone 3 state, which tested higher than any other house in nationwide tests over the period of a year. Additionally, Ron Burton, director of NAHB's energy and home improvement department, points out the importance of averaging a number of tests over a period of six months to a year to get an accurate picture of exposure risk. New homes need to settle, said Burton. However, Sextro questions how much time is required.

Finally, Sextro is especially concerned about the EPA's adoption of an imperfect standard because legislation is currently being considered to eventually make the standards mandatory for federally funded homes, which could make it more difficult to revise the standards, or to tailor them for specific regional building practices. It's a one-size-fits-alls standard, but how a house in Minnesota behaves is a lot different than how a house in Florida behaves, said Sextro.

Throughout the standard development process, the EPA worked with staff and members of the NAHB to produce a standard that the construction industry could accept. Although there are some technical differences, in general, NAHB approves of the model standard's approach to addressing the issue. Burton said the industry group is pleased with the partnership and its product. It addresses the three issues we were most concerned about, Burton said, which were:

• The standard is voluntary

• The standard applies only to high radon potential areas

• The standard emphasizes passive systems

   

For more information, or to request a copy of the proposed standard, Proposed Model Standards and Techniques for Control of Radon in New Buildings, contact the EPA's Radon Division, 401 M Street, SW, Washington, DC 20460. Tel: (202)233-9442.

-- Abba Anderson

Figure 1. The EPA's draft map of radon potential zones.