On Tue, 26 Jun 2007 14:06:11 -0400, "bent" wrote:

I am going to install a whole house fan to exhaust hot air out of the rooms
on the top floor , and while I'm at it I'm thinking of installing fan(s),
most likely one (1). in the roof itself to exhaust the air right out from
over the ceiling of those rooms. Get it out of the rooms, into that upper
area; then why not right out of that area, a hot box.

Usually whole house fans are used after 6 pm or after whatever time
the outside has cooled off enough that it won't warm the inside of the
house to suck in the outside air. I guess that could be as late as 9
but I'm not sure.

Usually roof fans go on between 9 and 12 in the morning and off
between 5 and 8, depending on how sunny and hot it was during the day.

I'm a big fan of roof fans, but normally whole house fans have enough
power to get their air into the attic and beyond, unless I guess there
is quite a restriction getting out of the attic. Soffitt vents which
are intake vents when using natural convection and roof fans would
easily function as exit vents when there is a whole house fan, but I
don't know nearly enough to know if your soffits are big enough for
this.

I like roof fans if the attic is conducting it's heat to the second
floor, but regardless, how about buying one fan or the other and
seeing if it is enough. Unless you want one contractor to do it all
at the same time.