Bathroom Exhaust Fans 101

One of the most important–yet often neglected–parts of your bathroom is the exhaust fan. Unfortunately, because it’s usually out of sight, out of mind, it’s hard to know whether your exhaust fan is really doing its job. We have a few tips to share so you can know that yours is the right one for your home.

What is an exhaust fan?

While this may seem like a silly question, most people don’t know how their fan actually works. This isn’t a surprise since most of its parts are invisible. However, you should be informed of at least its basic functions. This will allow you to choose the correct fan for your bathroom.

The fan ventilates the hot, humid air out of your bathroom through a duct that typically runs through the ceiling and releases air to the outside. It’s also useful for removing odors, dust, and allergens. But its most important job is making sure that mold and mildew don’t grow. An unventilated bathroom is the perfect breeding ground for mold spores to spread. Too much moisture can also damage your walls and ceiling, which is why exhaust fans are so important.

Do I have the right fan for my bathroom?

Exhaust fans are rated by their airflow capacity, is measured in cubic feet per minute, or CFM. A good rule of thumb for proper CFM for your room is at least one per square foot. We say at least because you want to make sure that you have more than you need. For example, if you have a bathroom with 66 square feet, you want a CFM rating of 70 to ensure proper ventilation.

For larger bathrooms, you may need more specific measurements, though. If your bathroom is larger than 100 sq. ft., you should measure by the number and type of fixtures you have:

  • Toilets need 50 CFM
  • Showers need 50 CFM
  • Jetted tubs need 100 CFM
  • Bathtubs need 50 CFM

So if you have a bathtub, a shower, and a toilet (in the same room), you need a fan with at least 150 CFM. Additionally, if you have a separate room for your shower or toilet, a 50 CFM fan should suffice for that area.

For bathrooms with ceilings higher than eight feet, you should take the ceiling’s height into consideration. The standard way to determine what CFM you need for high ceilings is as follows: Multiply the room’s square footage by the ceiling height. Divide that number by 6o (since the rate is per minute), then multiply by 8, which is the recommended number of air exchanges per hour. Round up for the correct CFM. Here’s an example of a room that measures 110 sq. ft. with a 9-foot ceiling:

  • 110 X 9 = 990
  • 990 / 60 = 16.5
  • 16.5 X 8 = 132
  • Rounded up = 140 CFM needed

How do I know mine is working properly?

There are a few signs that let you know if you need to repair or replace your current exhaust fan. If you hear vibrating noises that keep getting louder, that a good sign that you need some repairs. If the fan randomly stops running when you don’t turn it off or it doesn’t turn on at all, you may need to replace it.

Do I need an electrician to install or replace my exhaust fan?

Generally, you need at least an HVAC specialist to ensure the fan will ventilate properly and not cause more moisture problems. However, hiring an electrician is a good idea, especially if you’re installing a brand new fan where there wasn’t one before. The reason is that you will need additional wiring to separate your light wiring from the wiring you need for the fan. It’s not recommended that you tackle this yourself, so give us a call and we’ll make sure your wiring is up to code. For assistance with your exhaust fan in Fort Collins or Windsor, contact us today.

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