How to Install a Solar Attic Fan for Better Airflow All Year Long

When it’s up and running, your fan will move hot air out of your attic, replacing it with cool air from outside. For this to work, you must have adequate ventilation in your attic—specifically, about 1 square foot of ventilation per 300 square feet of attic space.

If your attic doesn’t meet this recommendation, there are several ways to increase its ventilation, such as inserting roof and gable vents.

There are a few factors to consider when deciding where to install your solar attic fan. For starters, because these fans run on sunlight, you’ll want to position yours on the part of your roof that receives the most sunshine. (If you live in the United States, the ideal spot is on the south-facing side of your roof.)

Then, head into your attic to pick a specific location. Generally speaking, you’ll want to choose a place between two rafters and a couple of feet (or more) beneath your roof ridge. However, every fan model is different, so it’s best to check your manufacturer’s installation instructions for specific guidelines on where to place your fan.

Use a tape measure to find the distance between the two rafters where you’ll install the fan, then mark the center point with a marker. With a hammer or drill, drive a nail or screw through that center point so that you can easily see it when you’re on the roof.

If your solar attic fan came with a circular template, grab it and head outside. If not, take a large piece of cardboard and set the fan on top of it. Trace the outline of the fan’s base with a marker, then cut out the template.

After inspecting your ladder (and following all other important ladder safety tips), climb up to your roof and find the spot you marked. Place the template on top (with the nail or screw in the middle of the circle), and use chalk to outline the diameter over your shingles.

With a reciprocating saw, cut along the chalk line to create a hole in the roof. Be careful not to cut through the rafters or any other structural elements.

Before attaching the fan to your roof, you’ll need to lift the shingles around the hole so there’s room for the flashing to slide underneath the shingles. The method for this will depend on the type of shingles you have, but you may need to gently loosen the shingles with a pry bar or pull out any nails or staples to remove individual shingles.

Test the fit by sliding the fan over the hole, making sure that the flashing goes between the shingles and roof sheathing. Remove the fan and apply weatherproof roofing sealant to the bottom side of the base (near the outer edge). Put the fan back into place over the hole, taking care not to get any sealant on the roof.

Secure your fan to the roof using the nails or screws that came with it. (If you aren’t sure where they go, consult your installation guide.) Add another layer of sealant around the flashing and nails or screws.

If you removed any shingles around the opening, put them back in place using a hammer and roofing nails.