Hello,
I am following up on a recent inspection we had done. I just have a general question about radon gas testing, something we did not have done during that inspection. Do you think that if a house already has a fan/air system installed under a wooden subfloor basement for molding reduction purposes, that it already significantly reduces/minimizes the chances of having a radon gas problem?? Since the radon gas is developed from the soils beneath the subfloor??
Thanks in advance for answering my question!
Sincerely,
Steven and Josie E
Hi Steven and Josie,
Thank you for the opportunity to inspect you home. We are glad to answer any questions you have. Regarding radon levels in a home that have a structural floor is tricky.
First of all the dehumidification systems for structural wood floor (SWF) spaces are not rated for radon mitigation (RM), however they function in a similar fashion as RM systems. Each system exchanges the air in the space. One typically draws air below the barrier (RM) and the other draws air above the barrier to collect humidity and dry the space (SWF). SWF gets make-up air, RM systems don't. The configuration of the SWF system, exhaust fan and plastic installed for SWF are typically insufficient to put the home under negative pressure as RM systems do. They have different purposes.
Second, RM systems are continuously operating. SWF systems typically operate only when it detects high humidity, if the space is dry the fan is off. As a general statement, operating the SWF system will reduce the radon level. The SWF system is exchanging the air that would normally enter the basement based on the humidity level set by the humidistat. If radon testing is done while the fan on, typically the radon levels are lower.
It has been our experience that testing homes with a properly installed, functional SWF dehumidification system, the radon levels typically test below the EPA action level (4.0 pCi/L). Some technicians will insist to test with the SWF fan off. Obviously you will get a higher radon test result. We test with the home under normal operating conditions. We do not adjust the humidistat, timer or fan for the SWF system. We do this because of the potential for mold to develop in some homes in less than 48 hours with the SWF fan off.
The only way of knowing for sure is testing for radon. If you are planning to finish the basement, it would be a good idea to do a long-term test as the home is normally occupied, to see what the radon level is. That way you can have a better snap shot of your radon exposure and make improvements as necessary.
As I stated above, this is tricky, but I hope this helps.
Best regards,
Doug Low
InspectPro, LLC
303-346-2250
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