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What Home Builders Should Know About Radon
Radon-resistant measures can be installed for very little extra money or effort during home construction
By Glen Salas,
December 2, 2008
HousingZone
Last summer was the granite countertop radon scare, fomented by an article in the New York Times reporting that granite countertops may release dangerous level of radon. Since debunked by EPA, the issue resurfaced in a November study from the Marble Institute of America, which found no radon in a single slab it examined.In all this discussion of granite, what we have missed is an important opportunity to talk about the real radon exposure problem — a problem so serious and so underreported that EPA has declared January National Radon Action Month. Radon is the second leading cause of lung cancer in America and the leading cause of lung cancer among non-smokers, claiming about 20,000 lives in the U.S. annually. For those exposed to radon, smoking increases the chance of lung cancer by more than a factor of five.
And unlike cigarettes — the leading cause of lung cancer — you can't see, smell or taste this natural radioactive gas.
Radon comes from the natural decay of uranium that is found in nearly all soils. It typically moves up into the home through cracks and other holes in the foundation and it can be present in any home. "Most people actually know about radon but don’t know what to do about it," says Tom Neltner of the National Center for Healthy Housing.
Here's where the builder comes in.
Unaware of the dangers, many homebuyers skip the radon test. Few know about radon-resistant measures, which can be installed for very little extra money or effort. With those measures already in place, homeowners can test for radon a month or two after they move in, when elevated radon levels would be detectible. If unsafe levels exist, the radon can be easily and inexpensively remediated.
Attending to radon resistance during construction not only helps protect the health of the occupants, but also demonstrates your commitment to building a quality home.
The Radon Problem
According to EPA, nearly one out of every 15 homes in the U.S. has elevated radon levels. EPA publishes a map at www.epa.gov/radon that shows radon potential by county, Zone 1 having the highest potential and Zone 3 the lowest. Regardless of the potential, elevated levels of radon gas have been found in homes in every state. (Zone Map is shown below).
Testing is the easy part. Inexpensive home testing kits are available at almost any hardware store. Unfortunately, indoor radon levels can only be assessed once the home is built. That is why EPA recommends building new homes with radon-resistant features in all areas with high radon potential (Zone 1).
While these measures can lessen radon infiltration, additional work is occasionally needed to do the whole job. Therefore, even if built radon-resistant, every new home should be tested for radon after occupancy.
Radon concentrations are measured in pico curies per liter (pCi/L). Higher levels mean more exposure. EPA says that indoor radon levels should be kept below 4 pCi/L. With the installation of radon-resistant measures, the radon level in most homes today can be reduced to 2 pCi/L or below.
The Radon Solution
Radon-resistant construction techniques are simple, inexpensive, and usually very effective in preventing radon entry. Even very high levels can be reduced to acceptable levels. Installing these measures at the time of construction makes it easier and less expensive to cut radon further if the passive techniques don't reduce radon levels to below 4 pCi/L. Bob Ward Companies of Edgewood, MD, builds single-family homes and townhomes in the northern Baltimore metropolitan region and southern Pennsylvania — both Zone 1 radon areas. All their homes are built radon-resistant.
"It’s easy enough to build radon resistance into any home," says Joe Gregory, Purchasing Manager for Bob Ward, "and that just adds to the quality that we build into every home. Most customers have heard something about radon but don’t even know it can be a problem. A few bring it up when they’re visiting our models, and they’re glad we’re taking care of it at such a low cost."
Basic radon-resistant construction involves the following elements of a passive (i.e., no electrical power required) soil-gas collection and venting system (Figure 1):
Figure 1. Basic elements of a passive soil-gas collection and venting system.
Image used with permission from the U.S. Environmental Protection Agency.
A. Gas Permeable Layer – Place a drainage bed, usually a 4-inch layer of clean gravel, beneath the slab or flooring system to allow the soil gas to move freely underneath the house.
B. Plastic Sheeting – Place plastic sheeting—(Gregory says his firm uses 4-mil poly)—on top of the gas permeable layer and under the slab to help prevent the soil gas from entering the home. In crawlspaces, place the sheeting over the crawlspace floor.
C. Sealing and Caulking – Seal all openings in the concrete foundation floor to reduce soil gas entry into the home.
D. Vent Pipe – Run a 3- or 4-inch gas-tight line, usually PVC pipe (commonly used for plumbing), from the gas permeable layer through the house to the roof to safely vent radon and other soil gases.
E. Junction Box – Install an electrical junction box in case an electric venting fan is needed later.
This passive venting system usually takes care of any radon gas problems. If, after testing, radon levels exceed 2 pCi/L, the passive system is easily turned into an active system by adding a fan to the vent pipe in the attic. With a junction box, or just an electrical outlet, already installed near the vent pipe, having a contractor add a fan is easy.
Gregory says only one home had high radon levels after his company installed radon-resistant measures. Simply adding a fan solved the problem.
Even if the owners decided not to add the fan, the lower levels of radon from a passive system will reduce the risk of cancer.
Gregory estimates that the total cost of adding the passive venting system during new construction is about $300 per household, but that probably has a lot to do with the fact that Bob Ward Companies does this routinely. Some builders report the cost to be four times that much. Gregory’s estimate includes the price of making the sump pit, a sealable pit that prevents the radon gas from escaping. In the event that the passive system does not control the radon, Gregory says that the fan can be purchased, installed and activated for about $375. Taken together, both costs are far less than the cost of mitigating radon after a home is built, which EPA claims can range from $800 to $2,500 (with an average cost of $1,200).
For more information on radon, including a step-by-step guide on building radon-resistant homes, visit www.epa.gov/radon.
Glen Salas is a mechanical engineer and building scientist who writes about green building practices for D&R International, an environmental consulting firm based in Silver Spring, MD. Send your comments on this story to gsalas@drintl.com.
© 2009, Reed Business Information, a division of Reed Elsevier Inc. All Rights Reserved.
