From: Bill Gill 
Newsgroups: alt.home.repair alt.building.construction misc.consumers.house
Subject: Re: fanpower needed to cool house overnight
Date: Tue, 06 Jun 2006 08:07:25 -0500

Lacustral wrote:
> I'd like to use an exhaust fan (fan from a ceiling grille to outside) to 
> run overnight in the summer, with the windows open, so that my house is cool 
> in the morning.  I'm not sure how much CFM is needed.  I don't want a big
> powerful whole house fan because I'd like it to be quiet.  Just a small 
> fan that keeps running overnight.  
> 
> If you're using a fan for that purpose, can you tell me how much CFM gets 
> your house down to the temperature of the outside air, and how many cubic
> feet of airspace you're ventilating, and how long does it take to cool 
> the house down to the outside temperature?  
> 
> Just trying to get a ballpark idea.  
> 
> (I could calculate the cubic feet of airspace in my house, divide by CFM 
> of a fan, and come up with a guess, but I'm sure it's not that simple - 
> the hot stuff in the house is heating up the air, fans aren't completely 
> efficient about clearing out the inside air, etc.)
> 
> Thanks
> Laura
I have the same message as a lot of other responders. 
Get a whole house fan.  I have a 40+ year old fan that I 
use in the spring and fall.  It works great if the 
temperature over night gets down into the 60s.  If it 
doesn't get that cool then it doesnt' work very good.  I 
wait in the evening until the temperature outside drops 
to about the temperature inside, then open some windows 
and turn on the fan.  When I get up in the morning I 
turn off the fan and close the windows.  By late 
afternoon it is starting to warm up in the house.

When the temperature doesn't cool off enough I just 
close the insulated fan cover and turn on the AC.

I live in Tulsa, Oklahoma.  The temperature here in the 
summer normally runs in the upper 90s to low 100s.

Bill Gill