What every homeowner should know about radon

Ask the Expert Home Improvement

Radon is a colorless, odorless radioactive gas, the leading cause of lung cancer among non-smokers, according to Environmental Protection Agency estimates — and an enemy that lurks in nearly 1 out of every 15 homes in the United States.

In honor of National Lung Cancer Awareness Month, here’s what you should know about radon:

What is radon?

Radon is a noble gas that is a natural byproduct of the constant breakdown of uranium. The radon in soil and rocks rises, resulting in an average level of 0.4 picocuries per liter of outdoor air.

In many cases, buildings are essentially large boxes placed over holes in the ground, so radon that used to mix with outdoor air builds up in a structure. “Radon is found in homes new or old. It is found in homes with and without basements. It is found in houses built on ledge and houses built on the sands of Cape Cod,” according to an online fact sheet from the state.

The EPA advises homeowners to mitigate if the radon level is above 4 pCi/L (10 times the average outdoor level), although “levels less than 4 pCi/L still pose a risk, and in many cases may be reduced.”  The average indoor radon level is about 1.3 pCi/L.

John Lugo, president of Eagle Environmental, a West Boylston company that installs radon-mitigation systems, said there isn’t universal agreement on what a safe level radon is. “Some countries say you should mitigate any building with 2 pCi/L or higher. Others say 8 pCi/L,” Lugo said. “The World Health Organization says anything over 2.7 pCi/L should be mitigated. We install systems designed to get levels as low as they can be. After 30,000 installations all over New England, our average is below 1 pCi/L.”

How radon enters buildings

The state says the majority of radon exposure in a home comes from the ground, so imagine your foundation is a ship’s hull. Any way that water can get past the hull is a way radon can get inside your home. The state offers a primary list:

  • Floor and wall joints
  • Sump pits and floor drains
  • Penetrations of utility lines
  • Dirt floors
  • Crawl spaces
  • Block wall foundations
  • Cracks and crevices in floors and walls

“In Massachusetts, it is estimated that 650,000 homes have radon levels that exceed the EPA action guideline of 4 pCi/L, and approximately 34,000 homes in Massachusetts have radon levels that exceed 20 pCi/L,” according to the state fact sheet. It also notes that “the secondary pathway for radon to enter a home is through private well water. … When well water is used in the home, radon in the water can become airborne.”


Many homeowners, if they tested their house at all, did so during the home inspection — so that the cost of mitigating can be negotiated with the seller.

To get an accurate test, all of the exterior doors and windows in the house must be kept closed — except for normal entering and exiting the house — for 12 hours before the test and throughout the 48-hour test. It’s difficult and often impossible for home buyers to ensure these conditions have been met throughout.

Residential radon tests are subject to many variables that can affect their accuracy, according to Shawn Price, director of laboratory operations for Spruce Environmental Technologies, which owns AccuStar, a radon-testing firm in Haverhill. “In an ideal world, you’d collect a whole year’s worth of data, even though radon can vary by year due to weather pattern anomalies as well,” Price said. “There are also seasonal variations that change the pressure of the house.”

On a sunny day, the air pressure is higher, which naturally lowers radon levels in homes, Price said. If a low-pressure system is rolling through, the radon levels will be unusually high.

There are two methods of testing for radon: charcoal canisters and electronic monitors.

“Monitors tend to be the most accurate, because they have to be calibrated and operated by a licensed tester,” Lugo said. “The charcoal vials give similar radon levels, but I prefer [to use] the monitors in real estate transactions because testers can read the results and determine that the house was closed up and the test was done properly.”

Test kits can be purchased from labs like AccuStar for under $50 each. Both Lugo and Price said testing before you purchase a home and after you move in ensures the most accurate results.

Having someone come to your house and test costs roughly $100 to $400.


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Mitigation systems can differ, but they essentially involve installing perforated PVC pipes beneath the basement and crawl space floors and connecting them to a solid PVC pipe that extends past the roofline. A fan is installed on the solid pipe to draw soil gases out from under the house and blow them out past the roof. Those systems can help keep the basement drier as well.

Lugo said the average cost of a radon-mitigation system in a home runs from $800 to $2,500. Difficult installations can go as high as $5,000, but one in a typical Colonial built in the past 30 years runs right around $1,100, he said.

“Virtually every house can be brought down to below 4 pCi/L,” Lugo said. “We’ve never been stumped. We’ve had some tough ones, but that’s where we learn. Once on the Cape we had to go back six times, but we figured it out.”

Price said every new home should have radon-mitigation pipes, which are relatively inexpensive and “be required to test below 2 pCi/L.”

“Doing it preconstruction is the best, easiest way to do it. If we keep building buildings with radon problems, it’s great for my job security, but it’s not great for public health.”

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