subject: Choosing the Right Bathroom Ventilation Fan [print this page] Choosing the Right Bathroom Ventilation Fan
The importance of bathroom exhaust fans should never be underestimated. They provide ventilation to help clear the room of steam and odors while preventing the growth of mold and mildew by removing potential problems before they invite themselves into your home.
So which bath fan is right for you?
Bath fans are rated in terms of Cubic Feet Per Minute (CFM), the measurement of air volume that's moved within one minute. The higher the CFM, the more powerful the exhaust fan.
The Home Ventilation Institute (HVI) recommends an Air Changes Per Hour (ACH) value of 8 for the bathroom. Bathrooms vary in size, so to know how many CFM your bath fan needs to have, try this:
First, determine the size of your bathroom. Measure its dimensions (length, width, height) and calculate its air volume in cubic feet. If you've inexplicably forgotten how to find the volume of a cube, simply multiply the three numbers. For example, if your bathroom's dimensions are 7 x 9 x 8, its air volume is 504 cubic feet. This means the fan should ventilate 504 cubic feet of air in order to achieve 1 ACH.
Since the recommended ACH value for bathrooms is 8, the fanwill need to ventilate 504 cubic feet x 8 (or 4,032 cubic feet) in one hour. Finally, since bath fan ratings are determined by the minute, divide 4,032 by 60 (for minutes in an hour) for the desired CFM rating for the bath fan, which in this case rounds up to 68.
Another method assumes you have standard eight-foot ceilings. Multiply your bathroom's length by its width to determine its square footage then multiply it by 1.1.
The bathroom in the above example measures 63 sq. feet. Multiply that number by 1.1, to get 69.3 and you'll need abath fan with 70 CFM.
But, if your bathroom is 100 sq. ft. or more, determining CFM is different. Instead of depending on square footage, you'll have to chime in with the fixtures to determine the fan's CFM rating. HVI recommends the following CFM for different bathroom fixtures: shower, toilet and bathtub, 50 CFM; and whirlpool tub, 100 CFM.
So, if your bathroom exceeds 100 sq. ft. and has a shower and a toilet, you'll need a bath fanwith at least a 100 CFM rating. A bathtub bumps the CFM rating up to 150. You get the idea.
Exhaust fans are pretty much a fixture in contemporary bathrooms. But if you have an older home or need to replace a fan, it's an easy project to start and finish.
