Keeping a house cool and well-ventilated is important both for the comfort of its residents and for the health of the house itself. Attics need to stay dry and climate-conditioned to prevent mold and ice dams from developing. Overly heated attics can even ruin shingles. Two products—whole house fans and attic fans—help to mitigate these problems and more.
Whole House Fan vs. Attic Fan: Major Differences
While a whole house fan and an attic fan perform similar functions—both help to ventilate and cool down a house—there is one major difference: the areas that they address. A whole house fan draws out air from the whole house and deposits it in the attic. An attic fan draws out air from just the attic and sends it outside.
Whole House Fan
A whole house fan is an electrically powered fan that pulls fresh air through all of the home’s windows and sends it into the attic. One centrally-located fan in the ceiling of the top-most floor can change out the air in the house three to six times per hour, depending on the size of the house and the fan’s capacity. The ceiling vent’s louvers open and close in response to the fan’s operation.
Because more air is being delivered to the attic, installing a whole house fan usually necessitates creating two to four times the area of attic vents than is normally needed. A good rule of thumb is to provide one square foot of opening for every 750 CFM (cubic feet per minute) of whole house fan capacity.
An attic fan is an electrically powered exhaust fan located either on the roof or on the gable. Sometimes called a power attic ventilator, or PAV, the fan expels hot air from the attic when triggered by a thermostat located within the attic. In order to cycle the air through properly, there must also be an air intake, usually located in the soffit, under eave, or fascia areas of the roof. The fan draws out air from the attic with fresh air from the intake replenishing the attic air.
- Gable Attic Fan: Entirely located in the attic, a gable fan mounts vertically on the home’s existing gable. When signaled by the thermostat, it turns on and pushes built-up attic air out of the gable.
- Roof Attic Fan: A roof attic fan is located partially inside the attic and partially outside of it. The roof attic fan is positioned as high as possible on the roof but no closer than 24 inches to the roof’s ridgeline.
|Whole House Fan||Attic Fan|
|What It Does||Pulls air in the house upward into the attic||Expels air from the attic to the outside|
|How It Cools||Removes built-up hot air and provides a gentle breeze||Cools down space above ceiling; less radiant heat can mean a cooler living area if ceiling is uninsulated|
|How to Use||Manual, controlled by switch or pull cord||Automatic, controlled by thermostat|
|Cost, Materials Only||$200 to $1,600||$75 to $400|
Cooling and Venting Ability
Effective attic insulation reduces the need to use an attic fan to cool the house. The insulation is designed to buffer a cool living space against searing hot attic temperatures or to buffer a warm living space against a cold attic. So, if your home’s attic is well insulated, you may not feel much of a difference by having an attic fan.
If the attic is not insulated, an attic fan can help cool down the living space. An attic fan lowers the heat in the house by lowering the temperature of the attic; it never moves any air within the house. A hot attic radiates heat through the ceiling, much like the heat of a coffee mug on the hand.
Attic fans can keep an attic well-ventilated, preventing the growth of mold and mildew.
Whole House Fan
As long as the outdoor temperature is lower than the indoor temperature, a whole house fan will help to cool down the home. Whole house fans can be used to offset the usage of energy-hungry central air conditioning units. Researchers at Iowa State University estimated that a whole house fan uses about 33-percent as much power as does a central air conditioner. That’s based on a 2-1/2 ton air conditioner and $0.06 kWh cost.
Best for Cooling and Venting Ability: Tied
A whole house fan generally will cool the home better because it actually moves the air within the house. A whole house fan disperses hot air that has collected in the upper regions of your home. Plus, a whole house fan creates gentle air movement. It’s not as pronounced as a room fan, but it can be felt.
Attic fans that mount behind existing gable vents can be installed in little time, as long as there is an existing power source in the attic. Powered roof vents are more difficult to install because a hole must be made in the roof and because the exterior side of the fan must be integrated into the shingles.
Whole House Fan
As long as the attic has electric power, the most difficult part of installing a whole house fan is cutting into the ceiling drywall and attaching the damper box to the ceiling joists. Larger whole house fans that span two joists are more difficult to install because the severed joist must be braced by two side pieces. Venting into the attic is simple: the 9-foot-long, 20-inch vent tube and fan are suspended with two hanger straps from rafters.
Best for Installation: Attic Fan
An attic fan will usually be easier to install than a whole house fan, if anything because installing a whole house fan means enlarging or increasing the attic’s outflow to the exterior.
The most visually obtrusive attic fan installation will be one where several fans are located on a roof. At its least obtrusive, an attic fan will fit within the attic and behind the gable opening’s vent.
Whole House Fan
A whole house fan is located within the attic, but it must open into the home’s ceiling with a vent covering the opening. Whole house fans are the width of your ceiling’s joists and around 36- to 40-inches long.
Best For Appearance: Attic Fan
An attic fan will always be less visually obtrusive than a whole house fan because it has no opening to the living space. If the attic fan is located behind the home’s existing gable vent (rather than a shutter-style fan that replaces the vent), the fan will be nearly invisible from the outside.
Because the attic fan is located either in a gable or on the roof, it is separated from the living area by several feet and by the ceiling. Additionally, the ceiling may be insulated, which provides significant soundproofing.
Whole House Fan
The whole house fan is located in the ceiling of the living space. Some whole house fans have an insulated isolator: a metal bay that fits under the damper box to raise it a foot or two above the ceiling.
Best for Sound: Attic Fan
Individually, an attic fan and a whole house fan each have about the same sound level. But when installed, there is a greater separation between the attic fan and the living space, plus attic insulation may act as soundproofing. This means that an installed attic fan will be quieter than an installed whole house fan.
Ease of Operation
Attic fans turn on and off automatically. A thermostat located in the attic, often with a wide temperature range (from 60- to 120-degrees F, for instance), sends a signal to the fan to turn on when the preset temperature is reached.
Whole House Fan
A whole house fan is turned on and off by the user. Windows and screened doors must first be opened, then the fan turned on. The fan may have a pull cord that drops from the ceiling or it may be operated with a wall switch.
Best for Ease of Operation: Attic Fan
An attic fan operates seamlessly and in the background. It doesn’t need to be adjusted by the user unless the user wants to change the temperature setting. Windows and doors do not need to be opened or closed.
Cost of Product and Installation
Both attic fans and whole house fans require an electrician to route an electric cable into the attic and to hardwire the power to the unit.
Both gable-mount and roof-mount attic fans cost from $75 to $225. Shutter-style attic fans that replace existing gable vents cost $200 to $400.
Whole House Fan
Most whole house fans are rated between 1,500 and 7,000 CFM. Lower-velocity whole house fans that blow directly into the attic and which have no attached vents cost from $200 to $400. Higher velocity fans with attaching vents cost from $800 to $1,600.
Best for Product Cost and Installation: Attic Fan
Attic fans are less expensive to purchase and install than whole house fans.
Which Should You Buy?
You don’t need to choose between either a whole house fan or an attic fan; they are not mutually exclusive. You can install a whole house fan to draw air up through the house and an attic fan to remove that air from the attic.
If you had to choose between a whole house fan and an attic fan to keep the house cooler, a whole house fan is a better bet. As long as the outside is cooler than the inside, you should feel a difference in the interior temperature.
To ventilate the attic, the attic fan is a better choice since it actively moves air out of the attic. In fact, the whole house fan only deposits air from the house into the attic. Unless an attic fan has also been installed, the whole house fan relies on passive methods to remove that air from the attic.
Listed below are some of the most popular and well-respected brands to look out for.
- Active Ventilation
- Air Vent