What is an Attic Exhaust Fan?

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  • Written By: Dana DeCecco
  • Edited By: A. Joseph
  • Last Modified Date: 19 September 2019
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An attic exhaust fan typically is an electrical-powered fan mounted in such a way as to remove hot air from attic spaces. Most units come equipped with an electronic or mechanical thermostat that automatically turns the power on when attic temperatures reach a specified level. Various styles are available from different manufacturers. Installation methods are similar.

There are many benefits associated with the ventilation provided by an attic exhaust fan. Ideally, the air temperature inside the attic should be the same as the outdoor temperature. This will eliminate moisture on interior surfaces of the attic and underneath roofing materials. Asphalt roofing products will last much longer with a well-ventilated attic.

Excessive summer heat in the attic can hinder the performance of an air conditioning system. The installation of an attic exhaust fan can alleviate this problem. The money saved on air conditioning bills in one season can pay for the cost of the fan and the installation fees. In some cases, air conditioning might not be necessary after an attic exhaust fan is in use.

Attic exhaust fans come in basically two styles. One style mounts in the gable end, drawing air through the attic, usually through a stationary vent in the other gable end. The fan is mounted behind a set of louvers that prevent rain and extreme weather from damaging the unit.


The other style of attic exhaust fan is mounted on the roof, normally near the top ridge of the roof. Air is drawn through vents in the overhang of the roof. Various combinations of air supply vents are common. The installer should be sure that these air supply vents are not blocked with insulation. Insulation should be placed on the ceiling of the home without blocking the overhangs.

Both types of units normally come with automatic thermostats. The thermostat is wired to a hot electric line. A switch is not necessary, but the circuit can be switched. The thermostat should be manually set at about 105 degrees Fahrenheit (40.6 degrees Celsius). The fan will turn on at the set temperature and turn off below the set temperature. The exact setting might differ in various climates.

If the attic exhaust fan motor ever wears out, the fan motor can usually be replaced without a complete installation of a new unit. This procedure is easily accomplished from inside the attic rather than from on the roof. Thermostats are also easily replaced. One should be sure that the power is turned off at the main breaker box before attempting these repairs.

Installing an attic exhaust fan is a home improvement that quickly pays for itself. Savings in air conditioning costs far outweigh the cost of electricity for running the fan. The elimination of moisture and excessive heat extends the life of asphalt roof products.


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