| |
A WHOLE HOUSE FAN
is a large fan mounted in a venturi housing and is installed
in the attic. They are used to both cool and ventilate
a house.
| A
whole house fan is able to cool your house
in 3 ways: |
- They draw cooler outside air in through
your open windows which lowers the room
temperature by as much as 10 to 20 degrees
F. Your open windows serve as intake “vents”
which allow you to control the air flow
by selecting how many or which windows
you open.
- The moving air blowing through the house
cools the occupants. The cooling breeze
can lower the skin temperature by 5 to
10 degrees F.
- The cooler air, after passing through
the living space, is forced into the attic
which pushes the hot attic air out through
the attic vents. This can lower the attic
air temperature by as much as 40 degrees
F. The attic can reach temperatures in
excess of 150 degrees F. in summer, and
that air, if allowed to remain undisturbed,
will radiate heat down through the insulation
to heat the living space. That is the
main reason that a home, without the use
of a whole house fan, remains uncomfortably
warm in summer evenings, and that the
upper floor of a multi-floor house is
always warmer.
|
|
Whole house fans are rated according to the amount
of air they can move. This is measured in cubic feet
of air per minute, or CFM. In order to be effective,
a whole house fan’s CFM rating should be 2 to
3 times the square footage of the house. For example,
a 1,500 square foot house should have a whole house
fan system capable of 3,000 to 4,500 CFM.
Overall attic venting is the only limiting factor
on how many CFM can be efficiently moved. However,
attic venting can be easily increased. Too many CFM
for the attic venting can cause undue stress on the
whole house fan and pressurizes the attic and walls.
Too little CFM will not provide the desired minimum
of 10 air exchanges per hour as recommended by the
House Ventilation Institute, and may not provide the
cooling draft to lower house, attic, and skin temperatures
in a timely fashion.
See our Ventilation page
explaining why proper ventilation is so important. |
