Browse

Browse Bath Fans by CFM rating

Bathroom exhaust fans are rated for their capacity to move air in cubic feet per minute (CFM).  In simplest terms, the higher the CFM rating, the more powerful the fan.  To quickly estimate the minimum amount of CFM needed, we recommend 1 CFM of air for every square foot of floor space.  A 100 sq ft bathroom would therefore require a fan which can move at least 100 CFM. 

Other factors like high humidity and long lengths of ducting will require higher CFM fans. Think you're ready to start browsing fans?  Choose a category below.  Need to read more?  Continue on to the extended Sizing Guidelines below.

Shop by CFM Categories

Sizing Guidelines

In order to ventilate your bathroom properly, it’s important to choose the right size fan. As with any home improvement project, you’ll want to familiarize yourself with a few concepts first.

·         There are two different types of ventilation: intermittent (or spot) and continuous. Intermittent ventilation is designed for bathrooms, kitchens and other rooms, while continuous ventilation refers to whole house fans. For this article, we’ll be concerned with intermittent ventilation.

·         Air Changes per Hour (ACH) refers to the number of times the air in any room should be fully changed in the span of an hour. For the bathroom, the Home Ventilation Institute(HVI)recommends an 8 ACH. In other words, the bath fan should have the capacity to completely change the air in the bathroom at least 8 times per hour.

·         All exhaust fans (like a bath fan) are rated in cubic feet per minute (CFM). This is the measure of air volume moved by the fan blower. 

Bathrooms sizes and needs can differ from house to house, so to ascertain how large a fan you need, try this simple method: 

First, determine the size of your bathroom. Measure the room’s dimensions (length, width, height) and calculate its volume of air. For those who inexplicably forgot how to determine a room’s volume, simply multiply the three numbers. For example, if your bathroom’s dimensions are 7 x 8 x 9, your bathroom’s air volume is 504 cubic feet. This means the exhaust fan needs to ventilate 504 cubic feet of air in order to achieve 1 ACH. 

Then, recalling the recommended ACH for bathrooms is 8, the fan will effectively need to ventilate 504 x 8 cubic feet, which equals 4,032 cubic feet in one hour. Remember, fan ratings are determined per minute. So, when you divide 4,032 by 60, you can achieve the desired CFM rating for the fan, which in this case is rounded up to 68.

Another method assumes you have eight-foot ceilings. In this case, multiply your bathroom’s length by its width to determine its square footage, then multiply that by 1.1. If, for instance, your bathroom is 10 feet long and 10 feet wide, it is 100 sq. feet. Take that 100 sq. ft, multiply it by 1.1 to get 110. As a result, you’ll need an exhaust fan with 110 CFM to properly ventilate your bathroom. Ceiling heights that exceed eight feet with require additional CFM.

But, if your bathroom is 100 sq. ft. or more in size (lucky you), the equation is different. Instead of depending on square footage, you’ll have to chime in with the different fixtures your bathroom holds to determine the fan’s proper CFM rating. HVI recommends the following CFM for different bathroom fixtures:

·         Shower – 50 CFM

·         Toilet – 50 CFM

·         Bathtub – 50 CFM

·         Whirlpool tub – 100 CFM

So, if your bathroom is more than 100 sq. ft. and has both a shower and a toilet, you will need an exhaust fan with at least a 100 CFM rating. Have a bathtub, as well? The CFM rating gets bumped to 150. You get the picture.

Reasons To Shop at BathFans.com