The Best Method to Exhaust a Bathroom

Updated March 23, 2017

The best method to exhaust a bathroom is to install a bathroom exhaust fan. While bathroom fans remove unwanted odours, their primary task is to remove excessive moisture from the bathroom. In the past, windows were the main method for providing bathroom ventilation.


Go to the building department and find out what the local codes are for bathroom exhaust fans.

Calculate the correct fan size to install in your bathroom. Simply measure the width and length of the floor to get the square footage and multiply the figure by 1.1. You will need an exhaust fan that is equal to or exceeds this number. A 110 square-foot bathroom would require an exhaust fan with 121 CFM or more. CFM stands for cubic feet per minute, which is the fan's capacity to pull air from the bathroom.

If peace and quiet is a must, purchase a fan with a lower sone. A sone measures the perceived loudness of an object. The average television volume is about three sones. Try to purchase an exhaust fan with 1.2 sones or less if your budget allows it.

Install a Bathroom Fan

Follow the owner's manual and local codes for installing the exhaust fan. The project is one that can be handled by a do-it-yourselfer with good skills. You should also be comfortable doing some basic electrical wiring or able to find a relative or friend who is versed in electrical wiring.

Locate the fan between the toilet and the shower. Position the fan between two joists. If the fan has a heater, make sure that is not too close to objects, such as shower rods or towel bars.

Always use the recommended size piping as specified in the instructions. Keep the pipe run as straight as you can. Each elbow in the system is equivalent to an additional 10 feet of pipe. Some products will allow you to use flexible duct, but you can get better results with rigid stainless steel duct. Not only is it stronger, but the smooth surface optimises the system's air flow.

You can vent the pipe up through the roof or out of an outside wall. Always vent to the outside. Before you cut the opening make sure that the location is free of obstacles and that the water vapours will not harm anything. Locate the opening between two rafters or studs. Drill a test hole and stick an object through so that you can spot the location on the outside.

Duct connections should be secured with three screws. Cover the joints with metal foil tape. Whether you exhaust through the roof or an outside wall, make the opening water tight. When installing a roof cap, pry up the shingles around the top and sides of the opening. Slide the flashing under the shingles and align it with the opening.

Put some roofing mastic under the flashing and the shingles and nail it into place. Apply some sealant on the nail heads. For wall installation, the basic process is the same except you will be installing a wall cap.The cap should have a damper to prevent back drafts and keep birds out of the vent. You may be required to make repairs to the shingles or siding.

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About the Author

John Landers has a bachelor's degree in business administration. He worked several years as a senior manager in the housing industry before pursuing his passion to become a writer. He has researched and written articles on a wide variety of interesting subjects for an array of clients. He loves penning pieces on subjects related to business, health, law and technology.