If you are remodeling your bathroom or simply looking to replace an old bathroom fan in a powder room, it’s important to select an appropriate ventilation fan that will not only look good (an important factor for us designers), but also function properly.

Before we dive into calculating the size of the bathroom fan you should get, many homeowners ask us why they need a bathroom exhaust fan or sometimes why they need 2, especially if they have a window in the bathroom.  Well, let me give you a few reasons:

• Bathrooms with tubs and showers create a lot of moisture.  Though its nice to wake up to a hot and steamy shower during a cold Chicago winter season, all of that moisture will build up and start to be absorbed by the drywall, plaster, and any wood.  This can not only lead to nasty mildew growing on your walls and ceilings, but it can also lead to the wood in your bathroom starting to rot.
• Bathrooms can also become stinky places for obvious reasons, so it’s nice to get the funk out.

Now that we know why we need an exhaust fan, picking the proper one requires you to look at 5 main features:

• Size – If remodeling, you will want a replacement fan that is the same size and shape
• Fan Speed – measured in CFM
• Noise Level – measured in “sones”
• Features
• Style

Fan Size

If you are remodeling you bathroom or replacing an old or outdated bathroom exhaust fan, it’s best if you try to pick a new fan that is the same size and shape.  If you remove the vanity cover of the fan, you can gather the dimensions of the fan housing.  It is possible to go with a larger or smaller fan, but this will require additional carpentry and drywall work.

Determining the Proper Fan Speed for the Bathroom Fan

When you hop on over to the local home improvement store or go online, there can sometimes be hundreds of fans to choose from.  The first thing you should focus on is the speed at which your fan runs.  This is measured in CFM or Cubic Feet per Minute.  The larger the bathroom you have, the higher CFM number you will need to look for.  Now, before you go all Tim Allen on us and look for “More Power”, there is a little math that you can do to make sure you don’t pay for more than you need.  Here is how you calculate the size fan you will need.

(Bathroom Width X Depth X Height) x 0.13 = Minimum CFM Rating

For example, if you bathroom is: 6 X 8 X 8.5, you would need a fan with a ~53 CFM rating.  To speed things up a bit for you, here is a table with a few common bathroom sizes.

Bathroom Width	Bathroom Depth	Bathroom Height	Minimum CFM
6	8	8.5	53
8	8	10	83
8	8	8.5	71
8	10	10	104
10	12	10	156

If you have an incredibly large bathroom, one with an enclosed toilet, or if you have a steam room in your bathroom, you may opt for 2 bathroom exhaust fans instead of one.  Or, favor a fan with a higher CFM rating.

Bathroom Exhaust Fan Noise

The next important feature to think about with your bathroom exhaust is fan noise.  When looking at fan noise, manufacturers of higher end fans will typically promote how quite the fans are.  Personally, I like a bathroom fan with a bit of noise to it.  For me, the noise allows a bit of privacy, which is critical in bathrooms that are in a public space like a powder room on your main floor.  For a master bathroom suite, a quieter fan may be more important so you don’t wake up your significant other in the morning after you take your shower.

Once you determine how “noisy” you want your fan to be, now its time to decipher the coding on the side of the fan box.  When you read the box, it should have a number on the side of it such as 2 sones.  “Sones” are the measurement of fan noise. One sone is equivalent to the sound of quiet refrigerator. The lower the sone rating, the quieter the fan will be. Most fans range anywhere from 1.5 sones to 5 sones.

 Features

Exhaust fans have a variety of features. The most common are:

• Built in light – great for basic bathrooms.
• Night-light – a nice feature for a kids bathroom, may require wiring a new switch if your bathroom doesn’t already have a switch for a night light.
• Heat lamp – We like to avoid this because they are unsightly and use a lot of electricity to run.

Style

Selecting a stylish fan is important to us at Design Inside.  After all, we are interior designers.  We typically go for a white fan that has a clean look.  This is the least distracting to the eye.

Conclusion

When shopping for a replacement bathroom exhaust fan, remember to keep an eye on size, fan speed, fan noise, features, and style.  If you keep those 5 factors in mind, you should have no problems selecting the appropriate fan for your bathroom.

 

Fan image courtesy of Brian Matis