What do you think of using only the house fan at night to circulate air when neither heat nor AC is needed?

Asked by Beckie
Gaithersburg, MD

I always tell my husband to just turn everything off on these spring nights. He likes to have air moving and says it is very inexpensive to run the fan only and sometimes will keep just that on during the day when AC isn't really needed yet. Thoughts?


Answered by Colleen McLean

Marina Del Rey, CA

Colleen McLean, Keller Williams Realty/Marina

March 19, 2012

Whole house fans can be terrific. They are more efficient to run than air conditioners and can cool a house down faster.

In your case, it sounds like it is an adjunct to keeping windows open, which you still want to do even with a whole house fan on. Traditionally it is healthier to circulate air, bringing in fresh clean air from the outside to replace any stale air inside.

  • The Environmental Protection Agency reports that indoor air is often 2-5 times more polluted than outdoor air, so it is good to keep it circulating.
  • This works well in milder climates where conditions outside are preferable to conditions inside.

The best times to run the whole house fan is early mornings and evenings. However, be aware of adverse conditions.

  • For instance, if it is very humid outside, a whole house fan will suck all that humidity indoors.
  • Also If you suffer from allergies, it might not be a good idea to bring all the pollution into the house. The window screens will stop some of it, but whole house fans are very powerful and could make you sneeze more than ever.

Now that being said, on the whole, a whole house fan draws in hot air to the attic and then lets it out of the house, and indoor air is considerably fresher. It helps in removal of odors, and provides excellent ventilation all around the house.


For more information:

Read "Are whole-house fans effective in northern latitudes?" a Q&A answered by Cassandra Adams.

Tagged In: heating cooling

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.