On Oct 6, 10:44*am, millinghill wrote:
Inquiring minds want to know..... *Why does the OP
want to run the attic fan without the attic being hot?

Good question.
I am ~considering~ running the attic fan without the attic being hot
due to a COMPLETELY different subject and thread:http://www.amazon.com/forum/home%20i...d_ttp_ef_tft_t...
which suggests via this report by the Army Corps:http://www.crrel.usace.army.mil/libr.../MP02-5778.pdf
that after you insulate your attic, seal air leaks from conditioned
space below, and install passive ventillation as much as practical,
you may still get an ice dam in the winter simply due to large amount
of snow acting as its own self-insulating blanket (happened to me and
many neighbors last year) and that instead of installing heat wires
etc. on the shingles, the next reasonalbe solution would be to power
ventillate the attic to make sure that the temp stays BELOW freezing
during the time that environmental conditions are favorable for ice
dams to occur (per report).

Like I said, completely different thread and I don't want to hijack
this one. *I respectfully suggest we start new thread if folks want to
comment on this aspect.
-OP

Ya know, if you don't have at least one square foot vent opening
for 300 square feet of vented space, you have no warranty on
most shingles, such as Certainteed and Owens-Corning. Verify
warranty details at 1-800-ROOFING.
But putting that aside, the main aim is to get any BTU's that make
it up to the attic to be removed. Problem with your plan is that
a roof fan will also pull conditioned air from within the wall spaces,
causing a net loss in your efforts to keep warm in, cold out.
Also, I've gotten damn tired of dealing with sites with damage
caused by an overheated fan. A lot is depending on an overtemp
sensor supplied by the lowest bidder in China. Those fans get
forgotten about, at the hottest part of the roof, and all the worst
if you turn on the fan and then forget it. Better to put a timer
switch to shunt the t'stat if you feel you really must.
It would be nice to have a remote-reading temperature sensor
in the eaves area, displayed near the timer switch.