How To Look At A House
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Will opening the windows reduce the radon level in a house?
Monday, June 25, 2018
Our area is one of several radon hotspots in Florida. Depending on the part of the county you live in, there is a 20% to over 50% chance that the indoor air in your home will be higher than the level at which the Environmental Protection Agency (EPA) recommends hiring a mitigation contractor to fix it.
When the subject of radon comes up with homebuyers during an inspection, a realtor often chimes in with the comment “All you have to do is open the windows once in a while and you won’t have a radon problem. That’s what I do!”
Unfortunately, that’s nonsense. While it is possible to reduce the accumulation of radon gas in a home by opening the windows briefly, once the windows, doors, or vents are closed, the radon concentration returns to the previous level in approximately 12 hours according to EPA studies. And, let's face it, nobody really lives with the widows open. We inhabit a closed-up-and-air-conditioned world nowadays.
Radon is different than other indoor air contaminants like mold, stored paint and chemicals, or formaldehyde gas from new carpets and manufactured wood flooring. They all originate in the home and exhausting indoor air to eliminate them makes sense. But radon rises up into a home from the soil below it when the air pressure inside is less than the pressure in the ground.
Homes have a natural upward suction, called the “stack effect,” which is illustrated by the diagram below. Exterior air pressure difference caused by prevailing winds can also create a pressure-differential stack effect. So most houses naturally pull air from the ground. Opening windows on all sides of the home can equalize pressures between inside and outside, but opening windows on only on one or two sides, or using a exhaust fan, will increase the stack effect.
Open windows also have disadvantages: increased energy cost to heat the house in winter and cool it in summer, and open windows are a security risk when you are away from home or at night. Although Florida residents love to brag about our balmy sub-tropical weather, most people keep their windows closed and air conditioner on year-round.
Natural flow-through ventilation has been proven to be helpful, though, in houses with a basement or crawl space under the floor. Venting those spaces may provide some reduction in the radon concentration in the home above, but the EPA states that “natural ventilation in any type of home should normally be regarded as only a temporary radon reduction approach.”
Also see our blog post Can a radon test result be wrong?
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