--
Phil Scott
Ideas are bullet proof.
"Lacustral" wrote in message
...
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.)


One air change an hour would do it... 3 air changes an hour
would do it by midnight.

so if the house is 1500 sq ft with an 8' ceiling the volume is
maybe 12,000 cubic feet...divide by 60 to get CFM for one air
change..thats 200 cfm... a very small fan, you can do a well
by leaving a few windows open... 600 cfm is more like it, most
attic fans will fit that bill. you could mount it on the room
and fit a vent though a hallway ceiling so it pulls the house
air out first, then the attic air cooling both of those
spaces.

Phil Scott


Thanks
Laura