The fan setting on your HVAC system will just cause the blower to run. This
will balance out the temps in your house and probably make things seem
cooler. It will not bring in fresh air. if you run this with your windows
open I suppose it will help move and mix the air including some outside air,
around. This is not considered a whole house fan. It is cheaper to do this
that to run your AC.

The roof turbines are for venting hot attic air and work by convection.
Someone here may tell you about some temp differential between attic and
outside and living space, etc. I'm not sure what they are off hand. You can
keep your attic cooler, and supposedly, the rest of your house by replacing
the roof turbines with powered ones. The roof turbines need a way for the
air to come into the attic under the eves. If you do not have vents here
then the roof turbines, powered or not, will do nothing.

A whole house fan
First learn to do a google search.
http://www.google.com/search?hl=en&q...e+house+fan%22
The first hit I came up with found this...
http://www.wholehousefan.com/

These fans work best with one open window in the basement or first floor and
an apropriately sized exhaust vent in the attic. These whole house fans move
a lot of air and really make things seem cooler. They WILL pull air
conditioned air from your house so do not use one with AC. My grandmother
had one in her house. It was installed at the top of the stairs. She Kept
all the windows in the house closed except for one per room which was left
open only a couple of inches. There was a really nice breeze in almost every
room of the house! The fan was so string, as I remember, that it would slam
doors closed and pull off you baseball cap when standing under it (Or so it
seemed to a 10 year old kid).

The fan in the link above is equipped with insulated louvers that will close
when not in use. I remember my father would go into my grandmothers attic
and cover up the old fan opening for winter and the open it up again in
summer. With the one on the link above you will not need to do that. Also,
my grandmothers fan had a speed controller on the wall. I would guess you
can get a thermostat for one now.

Good Luck
-B



wrote in message
oups.com...
I'm looking to reduce energy consumption. I was reading up on Attic
fans and Whole house fans. We have a "fan" button on our thermostat
that circulates air in the house. We turn it on when we cook so that we
can have fresh air from outside. Is this considered a whole house fan
or not? How is Whole house fan different from this?

Another question is, we have fans in the roof that rotate mechanically
(no electricity) whenever there's a draft I think. Can we install an
attic fan in its place that's controlled by a thermostat so that when
the attic's temp goes up beyond certain point it's on automatically?

Thanks.