I am getting ready to purchase and install a whole house attic fan
form one of the big box home supply stores. Which type is preferable
- belt drive or direct drive ? My roof system uses those pre-made
trusses. Do these fans have a built-in " fire stat" ? Fan selection
and install recommendations are appreciated ? - thanks
Years back I had a one-story ranch with access to the attic in the hallway
to the bathroom and bedrooms. I made this access a little wider and
installed a belt drive fan on hinges with sponge foam insulation to reduce
vibration on the ceiling. On both gable ends I had motor driven louvres. I
had the control set up so that when I pushed a button, the louvres opened,
and then the fan would turn on, if the ceiling attic access was opened. The
fan was two-speed, but we only used the low speed most of the time. With
windows opened, it brought a gentle breeze through the house. With this
method, hot air did not accumulate in the attic. It was blown out the gable
end louvres. On extremely hot days, however, this system did not work well,
and only brought the outside hot air through the house. I remodeled the
control system to open just the louvres and not turn on the fan unless I
wanted it on, and then just used the air conditioning system. I had a
degree spread control system so that the inside air was not more than a few
degrees cooler than the outside air. If you have ever walked into a bank on
a hot day, and felt the extremely cold air in there, and then had to walk
back outside again into a furnace of hot air, you could appreciate just a
few degree differential control system. The air in the house was cooler
than outside, and dryer, and not uncomfortably cold, clammy and damp.
All in all, a rather good plan for a moderate climate. Where I live,
however, more than few degrees between inside and outside are necessary
for my comfort, with 110-115 degree summers and at least 4-6 weeks of
high humidity. If I had to look forward to 100+ temps indoors, I'd
simply have to move.
Big on natural foods?? 82.38% of people die of "natural" causes.
Recommend belt drive and get the biggest one you can afford/or have room to
I had a 2 story, 3000 sf older home. Installed in 2nd floor ceiling at top
of stairs. This was an old home with NO AC. You will have to cut your
attic floor joists and frame in a box to sit the fan on. You cannot install
from the bottom...you WILL need access to the attic and electricity up
The louvers mount to that hole from the bottom/plasterboard side. When you
turn on the fan, the suction automatically opens the louvers under the fan
I found that with this old well shaded house the system worked very well,
except maybe in August when the heat and humidty got to the point where even
moving air wasn't that comfortable. At night though, it was always an
exceelent way to provide low cost cooling.
You MUST have adequate gable/attic ventilation to allow that hot air to
escape from the attic. That is critical!! These fans move a LOT of cubic
feet of air per minute...so little end vents and those rotating attic vents
are not usually big enough to exhaust it.
See if you cannot find venting recommendations on the web or from the fan
manufacturer before you buy and install.
Since you already stated that you have a truss roof, disregard the statement
below about cutting ceiling joists, DO NOT CUT THE BOTTOM CHORD OF THE
TRUSSES, they are under tension to support the roof. You will have to fit
the fan either between the trusses or install it above them and frame a
chase to direct the air to the fan.
Grainger's 5850 cfm 90 watt $73 4TM66 16" window fans might be
a nice alternative, with passive plastic film one-way dampers.
An exhaust fan upstairs and an intake fan downstairs could move
cool air through the house at night, even if the fans were not
Your joking about the fires stat right? Unless you see labeled fire dampers
on the unit, which I have never seen. There is no fire stat as you put it.
Most fire departments have lots of kittens when you mention these to them. A
fire damper 20x20 will cost you a couple of grand and a couple of grand to
install it. Wild ass guess.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.