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

Like some of the other comments regarding exchanging air not affecting
the overall temperature of the house, I would also add that a simple
fresh air exchanger won't do the trick either. We have a very good
system tied into our regular household ductwork (a $2,000 RUUD system
not to control air temp as much as humidity and getting fresh air into
our 'super tight' panelhome). Running the furnace fan 100% and the
fresh air exchanger on high over night with the outside temp in the low
60's doesn't bring the air temp in the home down a degree. The heat
build up in the structure itself does not dissipate easily.

Mike
http://home.earthlink.net/~mikefrand...useRelease.htm

Some other things to consider:

1. The cooler it is outside, the farther the temp will drop overnight.
Even if it doesn't drop much, at least you get fresh air in. In the
fall, I was able to pull in warmer air during the day and raise the
temp in the house by a few degrees.

2. Since you have to leave windows and doors open, consider the
security issue.

3. You'll be pulling in dust from outside.