Installing Gable Vents in an Attic

What You'll Need
Gable vents
Measuring tape
Circular saw
Extension ladder
Safety glasses
Dust mask
Work gloves
Plastic roof cement
Utility knife
Building paper
Metal flashing cap
Wooden 2x4

Gable vents are triangular shaped openings in an attic wall that originate from the roof peak. They are considered to be less effective than other ventilators because they only provide airflow over a limited portion of the roof surface. However, gable vents are easy to install and require little or no maintenance. In older construction they may be used alone; however the most effective designs will use gable vents in conjunction with other types of ventilators.

Step 1 – Calculate Ventilation Needs and Obtain Materials

Proper attic ventilation will save energy and protect building materials. If warm, moist air is trapped in a cold attic during the winter, condensation will occur. This will cause insulation to pack together, reducing its effectiveness. The moisture could also lead to mold, rot, or corrosion of the building’s frame. Likewise, hot air trapped in the attic during the summer forces the building’s cooling system to work harder. Ideal ventilation will allow the air in the attic to be completely exchanged every 6 minutes. This requires both intake vents and exhaust vents. Gable vents are intake vents. Attic vents are rated by free vent area (FVA), which depends on both vent size and the presence of louvers or mesh screens. You will need to calculate both the area of your attic and the slope of your building’s roof to determine the volume of the attic. It is important to provide airflow across the entire surface area of the roof; gable vents unfortunately only allow air to enter near the peak. Design a system which provides adequate airflow using a combination of ventilators.

Step 2 – Follow Safety Procedures

Only work in dry conditions and avoid loose or slippery shingles. The distance from the base of the extension ladder and the wall should be at least 1/4 of the height of the ladder, plus the width of the soffit.

Step 3 – Remove Old Installation

Older homes may have gable vents already, but these are often not large enough. Unscrew and slide out the old vent if one is present. Scrape off any caulk left around the opening with a putty knife.

Step 4 – Prepare Opening

Expand the vent opening if necessary. Mark off the outline of the new gable vent and cut through the siding and sheathing with a circular saw. Nail down a 2x4 between the studs and the gable end to act as a frame. Smear caulk on the bottom of building paper and staple it around the opening. Place the metal flashing cap on the peaked top of the opening.

Step 5 – Install Vent

Caulk the flanges of the new gable vent and slide it into place. Fasten it with screws or nails.