24/7 Emergency Support

What Size Should My Bathroom Ventilation Fan Be?

July 28, 2017

Ordinary tasks like showering, bathing and shaving can put home-damaging humidity into the air in your Portland home. There’s good news still—a modest bathroom ventilation fan can protect you from deformed wood, mold growth, broken 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 right size? Are they as quiet and energy efficient as they could be? Three Rivers Heating & Cooling is here to answer your questions.

Today’s bathroom ventilation fans are small and smooth and they run more quietly and effectively than ever before. You’ll find a hefty range of choices, from simple 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 getting out through your ventilation. While there are a lot of bells and whistles to pick from, the most important characteristic of your fan is whether or not it’s large enough to do its job.

Graded by the cubic feet per minute (CFM) of air they push, a bathroom ventilation fan should be able to replace the air in a bathroom at least eight times an hour. With a typical 8-foot ceiling, your ventilation fan should have a CFM rating at least as high as 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 adequate.

If you have a larger ceiling, the equation gets a little more complex. 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 follow HGTV’s tips for bathrooms larger than 100 square feet – establish 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 unclear if your bathroom ventilation fan is the proper size, or you know it’s time for a new one, give the experts at Three Rivers Heating & Cooling at call at 503-213-4433. We’re here to help you ensure you have a ventilation fan that will work hard to guard your home and keep it comfortable.