Measuring A Bath Exhaust Fan


Sizing a Bathroom Exhaust Fan

When buying a bathroom fan, there are two major factors you need to consider which include the strength of the fan measured in CFM.

When sizing a bathroom exhaust fan, the rule of thumb is the following:

  1. You need at least 1 CFM per square foot of the room area. To determine the square footage of your bathroom, multiply the length times the width. For example, if your bathroom is 6 feet wide and 9 feet long, its square footage is 54.
  2. Bathroom air fans are rated by the cubic feet per minute (CFM) of air they move and should be sized to replace the air in the room at least eight times an hour. If your bathroom has an 8′ ceiling, the CFM rating for your fan should be as least as high as the number of square feet (5′ x 7′ = 35 sq. ft.) in the room.
  3. CFM ( Cubic Feet per Minute ) — is a measurement that’s used to rate the strength of a fan. On average, most fans have a CFM rating that ranges from 50 all the way to 1,000. For those who don’t have an idea on which type of fan to buy, always check one with a CFM rating of less than 200 to avoid spending much on power.

Next, we have a noise meter. Measured in sones, the noise meter ranges from 0.5 all the way to 4.0 depending on the type of fan you’ve installed. Most people may prefer installing silent motors with a noise rating of 0.5 to 2.0. However, there are some homeowners who may prefer noisier alternatives (ranging from 3.0 to 4.0 sones) as a way of providing privacy against toilet noises.

Finally, when purchasing a bathroom fan, it’s important to understand that CFM and sones are related at some point. You see, a powerful fan with a higher CFM will obviously be expected to produce more sound while a weaker fan with a lower CFM will produce less noise due to the low suction power.

Stanley 25-Feet FatMax Tape Measure

by Stanley
sizing a bathroom exhaust fan
Stanley 25-Feet FatMax Tape Measure


Which Is The Best Location To Install A Bathroom Fan?

Now, having said that, let’s answer this question of whether a bathroom fan can be installed in the shower. To answer this question, let me say that bathroom fans are intended to be installed in the ceiling to allow precise suction of moisture from the bathroom.

When choosing the best location to install a fan, you need to consider the perfect location where the fan will accomplish its mission easily and a location where the ductwork will run efficiently.

The primary objective of a bathroom fan is to suck out as much moisture from the room as possible. Therefore, a fan should be located in an area where the most moisture, steam, and odor are likely to accumulate.

In this case, areas above the shower or the bathtub will be perfect. If your bathroom only has a shower, then the fan should be installed in an area over the shower.

On the other hand, if your bathroom has a shower and a bathtub or a whirlpool tub, then the fan should be installed in between the two to allow perfect suction of moisture and steam from the bathroom.

Something Else You Should Be Keen On

when installing a bathroom fan is the location of any available intake air source. In this case, we’re talking about the windows and the doors. To allow fresh air movement throughout the room, ensure that the bath fan is located away (at least five to eight inches) from the window or the door.

If you have multiple bathrooms in the house, then you should consider installing independent fans in each room to allow precise air circulation.

In the case of a toilet, it would be better to install a noisier fan to maintain privacy due to toilet noises. With that being said, I believe that you’re now fully informed of the best location to place a bathroom fan and which type of fan is the best to consider.

What Is The Best Tape Measure?

So here is my list of The 10 Best Tape Measures.

  • Stanley 33-725 25-Feet FatMax Tape Measure
  • eTape16 ET16.75-db-RP Digital Tape Measure, 16 Feet
  • Lufkin L1025B Black Widow 25′ Tape Measure Low Glare Matte Finish Hi-Visibility Blade
  • Swanson Tool SVPS25M1 25-Feet Magnetic Savage