How to Install Gable Vents. Install gable vents in your attic to keep your home cooler in the warm months. Without vents, the attic temperature can rise 60 degrees F or more above the outside temperature. Vents are helpful in the winter because it eliminates water vapor that rises from the living area. Water vapor can cause your insulation to become wet and rot your rafters and top plates.
Buy two gable vents with flanges for easy installation. Put one vent in each peak of the house for best ventilation results.
Choose copolymer vents for the greatest durability but expect fewer color choices. Prime and paint a durable metal vent any color or choose a wood one.
Plan where the vent will be located in the gable of the house. Follow the manufacturer's template to know what size to cut the hole to install vents.
Framing and Opening
Use 2 by 4 wood boards to build the frame in the gable ends and between the existing studs (see Resources). Check that the new framing is square and has a 1/8-inch clearance around it.
Mark corners of the vent by drilling holes from the inside through to the outside of the house. Use a 3/8-inch drill with a long bit or bit extension.
Go outside and use chalk or pencil to make straight lines that connect the holes that you drilled. Attach the bimetal blade to the reciprocating saw and cut the vent's rough opening using the outline you made.
Place the vent plumb in the rough opening and draw the flange outline with a pencil.
Attach the correct blade on your circular saw for the type of siding you will cut, and adjust the depth so you only cut through the siding. Cut the outline with the saw.
Remove any remaining siding from the opening. Put the vent in the opening to make sure the flange is flat against the sheeting.
Staple building paper under the siding around the opening to serve as flashing. Place a bead of caulking on the outside of the paper so there is a seal when you put the vent in place.
Mount the Vent
Slip the metal cap flashing under the siding and building paper at the top of the vent opening.
Squeeze lots of caulking under the flange and install the gable vent plumb in the opening. It will take some manipulation to get the top of the flange to move under the cap flashing.
Secure the vent with nails or screws in the nailing flange when you install gable vents.