Creating proper attic ventilation can help with heating and cooling and prolong the life of your roof. Maintaining a proper flow from eaves vents through the ridge or gable vents is essential. Rafter vent baffles prevent insulation and other debris from building up over eaves vent grilles. You can create your own version from 1/4-inch luan plywood. Do this project on a cool day since attics get extremely hot.
Cutting the Vent Chutes
Measure the distance between roof rafters in your attic. The dimension you need is the outside to outside width of your rafters, typically 17.5 inches. Mark out and cut pieces from full sheets of 4-by-8-foot, 1/4-inch-thick luan plywood. Cut your pieces across the 4-foot width of the sheet and as wide as the distance between the outsides of the rafters. Cut one piece for each vent grille. Mark out the pieces with chalk. Make your cuts with a fine-tooth plywood blade on a circular saw.
Installing the Vent Chutes
Cut two pieces of 3/4-inch plywood 24 inches square to use as seat boards for crawling out on the rafters in the attic. Wear long sleeves and trousers, goggles, gloves and a dust mask.
Crawl out to the ends of the rafters and uncover each eaves vent grille in turn. Pull any insulation and debris from the area of the grille. Position and screw one piece of luan against the rafters so it touches the eaves above each vent grille. Use at least one 1.25-inch treated deck screw every 6 to 8 inches along each 4-foot edge of the plywood. This will create a vent channel that extends from the eaves grille up above the insulation, securing an airway.
Finishing the Job
Roll any insulation back against the base of the plywood. The plywood will prevent the insulation from covering the vent grille. Staple a piece of window screen over the top opening between the roof and the plywood in attics with blown-in insulation to prevent your homemade rafter vent chute from filling with loose insulation, blocking the eaves vent.