Start by hammering a nail through the underside of the roof to mark the location of the fan. The nail should be halfway between two rafters and close to the top of the roof.
A. Make a compass out of a wood strip with a screw in each end, and etch a circular template on the shingles where the fan will go.
B. Cut through the shingles and underlayment to reveal roof sheathing. Mark a second, smaller circle and make the fan cutout using a reciprocating saw. Remove shingles around the cutout so that the fan’s flashing will overlay the roof sheathing.
C. Caulk around the cutout with a tri-polymer roof sealant.
D. Position the fan, and secure it with screws. Follow with a bead of caulk along fan's flashing. Reinstall the shingles.