Can a whole house attic fan help lower radon levels?
I have a passive radon system installed in my house that is semi blocked. Mitigation brought it down to 5. Will an attic fan help or hurt ??
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From a "dilution is the solution to pollution" point of view, sure, it'll work if you provide a path for the incoming air that isn't via the soil, say, by opening a few windows.
An HRV is a far better dilution approach though- less total power use, and minimal impact on heating/cooling loads.
Gale,
A whole-house attic fan is used to cool a house in summer, generally at night or during the early morning hours. As noted by Dana, you need to open your windows when the whole-house fan is operating.
If you are worried about radon levels, then a whole-house fan won't help you on days that are too hot or too cold to operate a whole-house fan. And if you ever operate the whole-house fan without opening enough windows, it's even possible for the whole-house fan to cause enough depressurization to pull more radon into your house.
Most experts recommend that you consult a radon mitigation contractor if your indoor radon levels are higher than 4 picocuries per liter. That's my advice too.
For more information, see All About Radon.