Radon In Your Home

how radon spreads

Most indoor radon enters a building from the soil or rock beneath it. As radon and other gases rise through the ground, they can become trapped beneath the structure, building up pressure. Because air pressure inside homes is typically lower than the pressure in the soil, this difference forces gases through cracks and openings in floors and walls. Once inside, radon can accumulate and become concentrated, especially in poorly ventilated areas.

Common entry points that allow radon into your home:

*Cracks in solid floors and foundations below grade

*Construction joints

*Gaps in suspended floors

*Sump pits and open floor drains

*Cavities in foundations below grading

*Gaps in floor around utility penetrations (plumbing and wiring)

*Crawl spaces that open directly into the building

*The water supply (especially well water, though this is less common than soil gas entry)

Radon can also be present in water, especially well water. When this water is used—for example, from a faucet—some of the radon is released into the air. Typically, about one ten-thousandth of the radon in water escapes into the indoor air. The higher the radon concentration in the water, the more it can contribute to indoor radon levels. Trace amounts of uranium, which produces radon as it decays, may also be found in certain construction materials such as concrete, brick, granite, and drywall. While these materials can emit radon, they are rarely the primary source of elevated indoor levels. In some cases, even outdoor air drawn into a building can slightly contribute to indoor radon concentrations.

The average radon level in outdoor air is about 0.4 picocuries per liter (pCi/L), though it can be higher in certain regions. While some geographic areas are more prone to radon issues, any home—regardless of age, construction type, ventilation, or whether it has a basement—can have elevated radon levels.

Radon levels are often higher in homes that are well-insulated, tightly sealed, or built on soil rich in uranium. Basement and first-floor areas typically have the highest radon concentrations due to their proximity to the ground. Homes located below the third floor in multifamily buildings are also particularly at risk.

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Hi Dave,

I just wanted to write and thank you very much for doing our inspection today. You really took an awful lot of extra time to explain things to us. It was a huge help and by far my favorite part of this whole home-buying process. In addition to drawing our attention to the major projects that need to be undertaken right away or in the near future, I was glad that you were also so thorough as to point out smaller things and provide suggestions for fixes that we'd be able to do ourselves. Thanks again for all your effort. I'm finding your "Know Your Home" book a great source of information along with your report. I'll no doubt have some questions for you at some point and really appreciate your willingness to answer them. Have a great rest of your weekend!

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Sean