How To Look At A House
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Should I remove an old whole house fan or keep it?
Saturday, July 28, 2018
Today it seems like air conditioning has always been around. But in 1965 only 10% of American homes had an air conditioner and, around Florida and most of the Sunbelt, it was often only a single window-unit in the living room or master bedroom.
A popular way to keep the house comfortable in hot summer months was to open up all the windows and turn on a whole-house fan. It pulled fresh outdoor air into the house from a central location in the home—usually the ceiling of the hallway—and sucked it into the attic, pushing house air out through the attic vents, along with any accumulated attic heat.
They were the original big-ass fans, moved a tremendous volume of air, and created a continuous breeze throughout the house. Although a whole house fan does not cool the air, the constant flow of air around a person has a cooling effect similar to standing under a ceiling fan. One disadvantage compared to air conditioning is that it does not dehumidify. So, on a day with high humidity, the fan also pulls the humid air into the house.
The big plus for a whole house fan, though, is low energy use, and they were a standard feature in many Gainesville homes up until the late 1960s. It may be old technology but, according to the U.S. Department of Energy, whole house fans are also on the leading of edge of energy-efficient solutions for the 21st century. Here’s the DOE’s cost comparison to air conditioning:
Initial Cost Benefit
Equipment cost for whole house fan = $150 to $350
Equipment cost for window AC = $250 to $750
Equipment cost for central AC = $2,000 to $4,000
Economics of Operation
Operating a properly sized 2-ton air conditioner with seasonal energy efficiency of 10 in Atlanta, Georgia, costs over $250 per cooling season (1,250 hours), based on 8.5¢/kWh, or roughly 20¢ per hour of runtime.
A large 18,000 Btu/h window unit air conditioner with energy efficiency (EER) of 8.8 costs more than 17¢ to operate for one hour.
By contrast, a whole house fan has a motor in the 1/4 to 1/2 hp range, uses 120 to 600 watts, and costs around 1¢ to 5¢ per hour of use.
A whole house fan can be used as the only means of cooling or to reduce the need for air conditioning. If both methods of cooling are present, seasonal use of the whole house fan (during the spring and fall) may yield the optimum combination of comfort and cost.
Because of the high humidity in most of Florida and the Southeast U.S. during summer months, use of a whole house fan during spring and fall make the most sense around here. So, if 1) you are buying a home with an old whole house fan that is still functional and, 2) you enjoy opening up the house during cool and moderately warm weather, then definitely keep it and use it until the high humidity days arrive.
But a whole house fan turns from energy-saver to an energy-waster during heating and air conditioning months unless it can be sealed and insulated during those times. The metal louvers close down automatically when the fan is turned off but, because it is similar to having a jalousie window in the ceiling of the house, the lack of insulation and air leakage around the louvers creates an energy-sucking hole into the attic.
If you don’t plan on using the fan, then we recommend removing it, repairing the ceiling and insulating the attic area above it. But, if you want to take advantage of the benefits of a whole house fan, then a cover needs to be constructed to air-seal and insulate around it. The Department of Energy has published an informative whole house fan brochure, that includes instructions and plans for building an off-season cover at the ceiling and insulated box in the attic for your fan. Click on the link below to download it as a pdf document:
One thing you need to be careful about when using a whole house fan is backdrafting of combustion appliances, such as a gas water heater. This is a problem created when the suction created by the fan can causes combustion gases that would ordinarily go up the flue to be pulled back into the home. If your appliances don’t use room air—in other words, they are in a compartment or closet sealed from the rest of the home—it’s not a problem. Otherwise, you should consult a gas appliance professional before using your whole house fan.
If you have a dead fan, a really noisy old one, or are considering installing a whole house fan in your home for the first time, one good resource is www.wholehousefan.com. They can help you determine the right size fan to buy, sell you the fan, and then help you install it right with video instructions.
By the way, if you haven’t seen a whole house fan before, the photos below show what one looks like when turned off, with the louvers closed, and also from the attic (without the off-season cover box).
Also, see our blog post How did homes stay cool in Florida before air conditioning?
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To learn more about heating and air conditioning systems, see these other blog posts:
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