A whole house fan can be a great way to keep cool in the summer while saving money and energy.  Here are some important things to know about them.

A whole house fan is found on the floor of the attic, sitting on the ceiling below.  When the fan comes on the grille or damper or louvers at the ceiling open up and the fan pulls air out of the house and into the attic, where it escapes to the outside.  So of course air from the outside is pulled into the house through open windows.  Whole house fans are quite powerful, so they move a lot of air very quickly.

The primary use for a whole house fan is to pull in cool outside air when the temperature inside the house is too high but the outside air is low.  This usually happens at the start and end of summer, when it might be very hot outside in the middle of the day but at night the temperature drops.  So you can turn off the air conditioner and turn on the whole house fan and pull in that cool night air.  Depending on where you live, even the night time summer temperatures might be too warm to make a whole house fan useful, or there might be times throughout the entire year when it makes sense.

Running a whole house fan is much less expensive than running your air conditioner so you can save a lot of money and a lot of energy this way.

But here are some things to keep in mind with a whole house fan.

First, as I mentioned before, a whole house fan moves a lot of air.  If you don’t have at least one window open– but hopefully several windows open – then the house will become depressurized and your gas-fired appliances can back draft combustion gases into the house.  This can allow carbon monoxide to spill into your house.  So be sure to have plenty of open window ventilation when you’re running your whole house fan.

One of the potential drawbacks to a whole house fan involves humidity.  One of the primary functions of your air conditioner is to remove humidity from the air, in addition to cooling the air.  If your weather is very humid then you’ll pull that moisture into the house while running the whole house fan and that can make things uncomfortable.  And the next day when you turn on your air conditioner it has to work harder in order to remove that moisture from the air, even before it can do much to cool the air.  So keep the issue of humidity in mind.

A big problem with whole house fans is that the grille at the ceiling of the house probably is very leaky to air.  So in the winter warm air from the house will leak up through the grille and be lost into the attic.  This is a big energy waste.

Some newer whole house fans have an insulated and tight-fitting cover to help prevent this problem.  When the fan is switched on this cover opens also, and then it closes when the fan is off.  There’s little air leakage through this type of fan, but older fans and still many new fans just have a basic grille with slats that open under the force of the air being moved.  These grilles will leak a lot of air during the winter.  So you should buy an insulated cover to install during the winter to stop this air leakage.  You can look here for one good product.  Insulating whole house fan louver shutter cover (batticdoor.com)

 

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