How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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Can I test vacant land for radon before building a house?
Wednesday, June 20, 2018
Not really. The average radon level of outdoor air is 0.4 pico-curies per liter of air (pCi/L), which is 10% of the level at which the Environmental Protection Agency (EPA) recommends remediation action. Some areas exceed the average, but we don’t know of any that even begin to approach the EPA’s threshold of 4.0 pCi/L. So air testing is impractical.
While it is physically possible to test the soil and get a reading, high radon levels happen inside a home because of the accumulation of radon gas that rises out of the ground under all of the enclosed space. Soil testing requires four to eight tests at different locations around the future footprint of the home, which can get expensive. The test locations could miss a significant pathway and the site prep for the home may change the pathway characteristics under the home. Radon gas comes in through the small cracks in the floor and openings at pipe penetrations that are present in all homes, and the enclosure allows the gas to accumulate.
You can test for radon in a home immediately after it is built. The natural settlement that occurs during the first two years will make small openings in the floor slab that may—or may not—increase the radon level somewhat after the initial settlement.
One thing you can do is determine the odds that a home will have high radon once constructed by checking a Florida Department of Health radon data page at their website at:
They have tabulated the percentage of homes in each zip code that have been radon-tested and exceed the level at which the EPA recommends remediation. So, for example, 33.9% of the homes in zip code 32607 have tested over 4.0 pCi/L, or about 1 in 3 homes. This statistic is not a predictor of whether a particular home will test high, only the overall likelihood. Also, some zip codes have not had enough testing for the Department of Health to publish a statistic.
Another option is to install a “passive” radon system when the home is built, leaving open the possibility of adding a fan to the exhaust piping if testing after construction comes in high, to make it an “active” system. Doing a passive radon mitigation system while the house is under construction also enables all of the piping to be concealed, except where it penetrates the roof.
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