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

Bill Gill wrote:
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
I too, have a "whole house fan," however
it it probably smaller than most.
I have had it for 35 years. It is a
unit that fits in the attic access hole. It
is completely self contained; louvers,
fan, pull chain switch. To access the
attic, you unplug the power cord by
accessing it between the louvers,
remove 4 safety screws and push in 4
tabs, while holding the fan. It's not
real easy, but not that bad. The fan is
probably about 22" and has 2 speed.
It does a pretty good job on a 2400 sq
ft tri-level. It required very little
installation, only mounting a strip on 2
sides of the hole and bringing in power.
BTW, I'm in the Chicago area where
summers can get pretty hot. We use
it, as others have said, when outside
temps are below 70..

We used to have, in addition, attic vent
fans, however, when we put in the
new roof, we put in continuous ridge
venting. I don't think the countinuous
ridge vent keeps the attic as cool as
the powered fan vents, but I have no
actual data.