How to Build a Baffle Around an Attic Fan

Measure the size of your ventilation fan's height, length and width and write down these measurements. The baffle needs to be about 2 to 3 inches larger on each side than the fan’s dimensions.

Put on goggles and work gloves. Cut out five pieces of plywood with a circular saw. The two sides of the baffle should to 2 to 3 inches wider and taller than the fan is. The bottom of the baffle should be 2 to 3 inches wider than the fan. The two wings on the baffle should be 2 to 3 inches wide and as long as the two sides of the baffle. Use plywood that is about 1/4- to 1/2-inch in thickness.

Stand the two baffle sides up and place the bottom of the baffle on top of them. The edges of the baffle should meet up to form a box with open ends. Use a hammer to nail the bottom of the baffle to the sides. Space the nails 1 inch apart.

Turn the baffle over so the bottom is flat on the work surface. Place the baffle wing over the edge of the side of the baffle. The wing should stick out and away from the baffle. Mount the wing in place with nails spaced 2 inches apart. Repeat with the other wing on the other side of the baffle.

Fit the baffle over the attic fan and use the hammer and nails to secure it to the roof with the baffle’s wings. Space the nails about 1 inch apart.

Apply caulk around each nail in the baffle’s wings.

Fit insulation around the baffle.