Using Your Bathroom Exhaust Fans

Bathroom exhaust fans provide a valuable role in keeping your home’s air healthy and temperatures comfortable. Bathrooms in the typical home have the highest humidity and chemical levels, with the least amount of fresh air ventilation.

Some bathrooms have operable windows, but they’re seldom large enough to move the same amount of air out of the room, and it’s so easy to forget to open them. Pulling out bad air from bathrooms removes:

  • Excess humidity that contributes to mold, bacterial and viral growth. The hot, steamy air after bathing will make your home less comfortable during the summer because humidity makes the air feel warmer.
  • Volatile organic compounds (VOCs) from cleaning products, shower curtains, makeup, deodorants and air fresheners. Prolonged exposure to VOCs can have detrimental health effects. In small spaces, like a bathroom, VOCs become highly concentrated.
  • Odors.

If your bathroom doesn’t have a fan or it isn’t working, it’s a good idea to install a new one. Bathroom exhaust fans are sized by how much air they can move within one minute.

Each square foot of space in the bathroom requires one cubic foot per minute (CFM) of capacity. Rooms with high ceilings require a larger fan. If your bathroom is larger than 100 square feet, add 50 CFM per occurrence of a separate shower, tub, toilet, and sink. If sound is an issue, select one whose rating is 1.0 sones and lower.

Besides the fans, your bathroom should have:

  • Clearance under the bathroom door of at least ¾ inch to allow replacement air to enter the room while the fan is running.
  • A separate fan for a toilet in an enclosed space.
  • Moisture-rated fans placed as close to the tub or shower as possible.

Homeowners should rely on a licensed electrician or HVAC contractor to install the fans, since they involve wiring and venting for proper operation.

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