Pros and cons of whole-house fan

As the summer heats up, consider a whole-house fan as an alternative to costly (and energy-hogging) air conditioning.

The fans exhaust warm, stale and possibly contaminated air through louvered shutters, usually on the ceiling at a high point in the house. Fresh air is pulled in through open windows and doors. A wall switch, switch/timer or automatic thermostat controls the fan.

Whole-house fans come in two types: ceiling-mounted or attic-mounted. Ceiling mounts, installed directly above louvers, draw air into the attic, where it is forced out through vents in the eaves, roof or gables. Attic mounts, installed in the roof or exterior wall of the attic, blow air directly out.

Both types are available as direct-drive, with the fan blade attached to the motor, and belt-drive, with the motor mounted to the side to rotate the blade with a pulley and belt. Direct-drives tend to be noisier and less powerful, but less expensive.

Reasons for a whole-house fan:

• If you don't have air conditioning, a whole-house fan creates a cooling indoor breeze.

• If you do have air conditioning, the fan will suffice on all but the hottest days, reducing energy costs. Running a fan before turning on air conditioning also will draw heat out, allowing the home to cool more quickly.

• Regularly replacing house air can reduce airborne hazards and nuisances such as radon, formaldehyde, carbon monoxide, cooking and pet odors.

Reasons against:

• If you live in an extremely humid, dusty or pollen-laden area, a fan brings these problems indoors -- a bad idea for allergy sufferers.

• It's not effective in certain climates. A fan works best when outside night temperatures dip at least five degrees lower than the desired indoor temperature. Ten or more degrees is better.

• It hums while running. Some folks say the droning drives them nuts.

• Ceiling louvers clash with some people's sense of decor.

• It could be redundant. Some central air-conditioning systems have a ventilation mode that accomplishes the same thing as a whole-house fan. But don't confuse this with the fan setting that recirculates air without exhausting it.

Selection:

Noise.

Attic-mounted fans are quieter because they're farther away from the living area.

Speeds and controls.

Two-speed fans allow a high speed for quick cooling or exhausting fumes, and a slower, quieter speed for continuous operation.

Ventilation.

Not all homes have adequate attic ventilation for ceiling-mounted units. Hot air must flow out of the house through screened vents on the roof, at the gable ends, along the eaves or all of the above.

For more information on these fans and how to choose the proper size and install it, see the

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-- Homes & Gardens of the Northwest staff

A very common question we get asked all the time is “do whole house fans really work?” We think whole house fans are one of the best, most effective ways to cool a home, and experts agree with us!

According to the United States Department of Energy (DOE), a whole house fan is the most cost-effective way to cool down your home.

Whole house fans are unique in that they are used when it is cooler outside during the early morning and evening hours. Basically, whenever the outside air cools off. This is opposite to a traditional air conditioning system that runs almost 24/7, regardless of the temperature outside.

In most climate areas, there is a 30 to 50 degree temperature swing every day between the high and low weather forecast each day. This is why whole house fans work so well.

Most people only pay attention to the high temperature forecast of the day during the warmer months of the year. While this is important for figuring out what type of clothes you will wear for the day, it doesn’t tell the whole story when thinking about cooling your home. When looking at the low temperature, you will most likely see it happening in the very early morning hours, but over the course of the night, the temperature is usually at a very comfortable level to where a whole house fan would work very effectively at cooling the home.

When running the whole house fan during the evening and early morning hours, you are effectively pre-cooling the home for the heat of the next day. That way, when it gets to the peak temperature of the day, the home is not as hot as it would be if you didn’t have a whole house fan.

This helps homeowners save up to 90% off their A/C usage, and in some climates it can eliminate A/C usage completely!