Routing a dryer exhaust through a roof is a sensible option if the dryer is in an interior room in the home, with no access to an exterior wall. Using a specially designed vent for roof installation will allow the air to discharge, but also prevent rain from entering the pipe. Having a properly installed exhaust system for your dryer will allow it to operate at its highest efficiency, and give you dryer clothes.
Locate an area on the ceiling that is directly inline with the rear of the dryer and its vent. Drill a 4-inch hole through the ceiling and into the attic.
Position yourself in the attic, directly over the hole in the ceiling. Line up the carpenter's square over the hole and follow the end to the roof. Mark this spot. This will give you a direct point to drill a matching 4-inch hole in the roof so it lines up perfectly with hole in the ceiling. Drill a 4-inch hole through the roof.
Insert the end of the roof vent down through the hole in the roof and into the attic, until the flashing is touching the roof. Slide the flashing on the top side (side closest to the pitch in the roof) under the shingles. Let the lower side of the flashing lay onto the shingles. This will prevent water from getting under the shingles and into the roof, causing water damage. Attach the roof vent in place by hammering roofing nails through each corner of the flashing and into the roof.
Slide a section of duct up through the hole in the ceiling. Have an assistant hold the duct in place while you attach the end to the bottom of the roof vent. Slide the end of the duct into the end of the roof vent. Wrap a duct clamp around the joint. Tighten the clamp down onto the connection to hold the two aluminium ducts together.
Slide one end of the 90-degree elbow onto the exhaust duct on the rear of the dryer, by insert the end of the elbow over the dryer vent duct. Wrap a duct clamp around the connection and tighten it in place with the screwdriver. Attach the 90-degree elbow bend so that the remaining end is pointing straight up to the ceiling.
Measure the distance between the open end of the elbow and the end of the duct that is extending out of the ceiling. Cut a piece of aluminium duct to fit this distance, using the tin snips. Insert one end of the duct over the end of the elbow and the other end inside the end of the piece of duct in the ceiling. Wrap a clamp around each connection and tighten it down.
Apply roofing tar to the area where the new roof vent flashing is touching the shingles. Use the putty knife to spread the tar all around the area to help seal it from rain.
Turn the dryer on and test the duct work for air flow and proper operation.
Schedule a regular cleaning of your dryer lint trap as well as the duct work, to prevent lint build up and keep your dryer running at peak performance.
Never use any type of rubber hose as a dryer connection because it could overheat and become a fire hazard.