We just moved to the south and our house has a whole house fan in the ceiling of the top floor. I’m in a muggy climate in summer and a cool climate in winter.

We have a single air conditioner for both floors and the top floor obviously gets warmer than downstairs... but can the whole house fan actually do anything about this? I’ve read that you’re supposed to open the windows while using it, but then others say that this brings in pollen, humidity, pollution, etc.


I'm located in Miami and installed a whole house fan two years ago and love it. The best time for it is in the winter and yes, you have to open windows and/or doors. The fans are powerful, probably 5400 +- cfm. If the air is moving out, it's got to come in from somewhere. Winter is great because you get that cooler air flowing through the house, summertime, not so much. You would be able to draw some cooler air from downstairs to the top floors during the summer but be careful you don't draw up too much and cause your AC to over work. For the most part, I don't use the whole house fan during the summer unless the temp drops after a rainstorm. Then I open the windows, turn on the fan and air out the place.

Pollen hasn't been a problem but that would depend on the individual.


A whole house fan cannot be used with the ac on. It's only use was to cool and freshen the inside air at times of the year and day when the outside temp was below inside. It will bring in pollen and pollution from the outside. Modern air conditioners are so efficient that the whole house fan has no use anymore.

Get another ac unit to cool the other floor.

  • attic fans and whole house fans are two different things. Attic fans are installed in the attic to regulate the temp of the attic. they are usually installed in the outside walls of the attic and the intake is from soffits or other vents in the attic. A whole house fan is installed in the ceiling of the unit and vents into the attic with the purpose of airing out the entire unit by opening the windows. the attic is then vented through soffits. The whole house fans are very useful.
    – JACK
    Jul 4 '20 at 19:54
  • Edited my post to remove my claim that whole house fans are sometimes called attic fans. We did call them that in 1950s Dallas, but this may be regional and is certainly outdated. But @JACK exactly how would you use a whole house fan in an airconditioned house? Jul 4 '20 at 22:20
  • 1
    I would run the whole house fan to remove some of the warmer air from the second floor and suck some of the cooler air up from the first floor. The OP stated they have one AC unit for both floors but the second floor gets warmer. Obviously, you wouldn't run it 24/7 but it would help a bit. Stay safe out there.
    – JACK
    Jul 4 '20 at 22:43
  • So would you open 1st floor windows to do this? Jul 5 '20 at 0:00
  • You would crack a few in different rooms just to vent the upstairs.
    – JACK
    Jul 5 '20 at 0:31

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