How an Attic Gable Fan Works

The corner of an attic with windows on the near wall.

An attic gable fan is one way to help with the circulation of air in the attic. Because heat rises, it tends to make attics the hottest part of the house. Additionally, an improperly ventilated attic can lead to a buildup of moisture, which can wreak havoc on drywall, insulation, and even structural components like joists, studs, and rafters.

There are numerous ways to ventilate an attic, providing for both inflow and outflow of air. If your home has a gabled roof, consider an attic gable fan to aerate the space.

Attic Ventilation Types

Fans, vents, windows, and opening skylights are all options for ventilating your attic. If an attic is large enough, chances are it has windows that, when open, provide circulation. Skylights that open can help move air as well, keeping heat and moisture at bay.

If you attic is just a crawl space, however, your options are limited to vents and fans. Examples include ridge vents, box and dome vents, soffit vents, and gable vents.

Gable Roofs and Fans

Gable roofs are those that consist of two straight, sloping surfaces meeting at the apex of the roof. They extend from the ridge to the eaves of the roof, creating a triangle. The siding of the home extends to the roof rafters and apex on either side. Depending on where the door sits, a home can have a front- or side-gabled roof. Homes with cross-gabled roofs have two perpendicular sections with gables on both ends.

The area known as the gable is vertical and extends up to the roof. This is where gable vents and fans are installed. Whereas gable vents simply provide an opening for air to enter or exit, gable fans are electrically powered and forcibly move air out of the attic. They are essentially small appliances designed to reduce moisture buildup and to help keep and attic space moderately cool during the summertime.

Installation of Gable Fans

To install a gable fan, a small hole is cut into the gable at the level of the attic space. Into this hole goes the gable fan. The edges around it are sealed outside and inside so no water or air can leak in. From the outside, the fan prevents water from entering the attic while allowing for the proper flow of air.

Gable fans can be plugged into an outlet or wired to a circuit. They are designed to ventilate a specific amount of square footage. In general, proper attic ventilation calls for 1 square foot of ventilating ability for every 150 square feet of space. One gable fan for residential use typically provides 1 square foot of ventilating space.