Bathrooms that are not properly vented can become a breeding ground for mould, mildew and other bacteria due to the high moisture content in the air. A bathroom should be maintained with a properly installed exhaust vent that is designed to remove the moisture from the bathroom. Exhaust vents are required to be vented outside through a system of vents or ducts. For many homes, the most logical direction to vent a bathroom exhaust fan is up and through the roof.
Drill a hole in the bathroom ceiling were you would like to install the exhaust vent. If there is an existing lighting fixture in the ceiling, it can easily be replaced with a combination exhaust fan and ceiling light. Turn off the power circuits and remove the existing light to access the space in the ceiling. Insert a long screwdriver, rigid wire or yardstick through the hole in the ceiling so it pokes through to the attic or crawlspace above.
Access the attic or crawl space and use a flashlight to locate the wire or yardstick protruding from the bathroom ceiling. Determine whether the desired spot for the exhaust vent is properly positioned. Most exhaust fans are designed to fit in between ceiling joists. You may have to reposition the location of the fan to fit in between the joists.
Place the exhaust fan in position between the joists and cut out the ceiling around the exhaust housing to allow installation through to the bathroom. Mount the exhaust housing to the joists with screws.
Use the power drill to create a hole in the attic or crawlspace ceiling through the roof of the house, and insert a wire through the hole so it protrudes out the roof. Access the roof with a ladder and locate the position of the hole made in the attic. Trim away any shingles or other roofing materials with a utility knife, and cut a hole on the exterior side of the roof with a saw or oversized drill bit. The hole should be big enough to accommodate the roof vent fixture chosen for your project. Install the roof vent according to the manufacturer directions and replace the roof shingles with screws.
Install the duct to run between the roof vent and the bathroom exhaust fan. Rigid metal is the best material, but flexible plastic or aluminium ducts are available to fit into tight spaces. Some ducts can be screwed into the roof vent and exhaust fan housing, and others will need to be secured with foil duct tape. For added protection, insulate the duct work with metal foil insulation which can be wrapped around the duct and secured with tape to seal in moisture and heat. Install the fan faceplate cover on the bathroom ceiling and restore the power.