What Size Should My Bathroom Ventilation Fan Be?

Everyday tasks like showering, bathing and shaving can put home-destructive humidity into the air in your Delray Beach home. There’s good news however—a simple bathroom ventilation fan can save you from deformed wood, mold growth, damaged drywall and other trouble associated with a humid bathroom.

Even if you have ventilation fans in your bathrooms, do you know if they’re the proper size? Are they as soft and energy efficient as they could be? Kilbourne Heating & AC is here to answer your questions.

Today’s bathroom ventilation fans are small and modern and they run more quietly and effectively than ever before. You’ll find a great range of selections, from average fans that will get the job done to fans with integrated heat lamps, motion sensors and heat-exchanger ventilation that helps prevent warmed air from escaping through your ventilation. While there are a lot of bells and whistles to select from, the most important feature of your fan is whether or not it’s big enough to do its job.

Rated by the cubic feet per minute (CFM) of air they transfer, a bathroom ventilation fan should be able to exchange the air in a bathroom at least eight times an hour. With a standard 8-foot ceiling, your ventilation fan should have a CFM rating about the number of square feet in your bathroom. Therefore, if your bathroom is 5 feet by 8 feet, a CFM rating of 40 would be satisfactory.

If you have a larger ceiling, the equation gets a little more difficult. You’ll want to multiply the width of the room by its height and length, divide it by 60 and multiply by 8. Or, to keep it easy, you can heed HGTV’s guidance for bathrooms larger than 100 square feet – determine your CFM requirements by increasing 50 CFM for every toilet; 50 CFM for each shower, bath and combo; and 100 CFM for each whirlpool.

If you’re not sure if your bathroom ventilation fan is the correct size, or you know it’s time for a new one, give the experts at Kilbourne Heating & AC at call at 561-287-7071. We’re here to help you make sure you have a ventilation fan that will drive hard to care for your home and keep it comfortable. 

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