I have read that running the attic fan can help with an excess humidity/mold problem in my home. Is that true?

Asked by diane geitner
Connellys Springs, NC

i live in nc and am considering installing a whole-house dehumidifier as well. Are they good investments? If so, what's the greenest?


Sean Lintow Sr

Answered by Sean Lintow Sr

Naperville, IL

SLS Construction & Building Solutions

August 12, 2013

While it is true that running an attic fan can pull moisture from the house, the downside is it is also pulling conditioned air from the space and just masking the issue. The other big downside is that instead of you knowing you have an issue, you are creating a bigger issue elsewhere. 

In order to deal with moisture in your house you need to control the source and exhaust it outside by running your bathroom and kitchen exhausts.

  • Your bathroom exhaust needs to run not only while you are taking a shower, but also after you are completed which is one reason why I specify timers for all those fans.
  • One other big caveat is that it needs to vent outside. If your area is anything like mine, that isn’t always a given and might need to be corrected.

Your AC if sized properly will also reduce your moisture levels by removing the water from the air (latent load) and draining it outside. Now if your AC unit is constantly turning on and off (improper size) or you leave the fan on all the time, this greatly reduces its ability to remove the moisture. 

The best advice I can really give you right now, is just say no to the attic fan and get an experienced energy auditor in there to find out what the issues are, and what you can do to fix them.

Living in a humid area a dehumidifier may be necessary based on your lifestyle and house. While I am not a big fan of band aid fixes, you may consider purchasing an ENERGY STAR rated dehumidifier one and using it till the issues can be solved. Just don’t forget to dump the water outside (on your plants!) instead of down the sink.


For more information:

The Find A Pro directory on GreenHomeGuide lists approximately 2,500 energy auditors and raters across the U.S. Click here to find one near you.

Also read Sean Lintow's blog post "Getting the details right: Bathroom Exhaust Venting."

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