Poor ventilation in a bathroom can lead to unpleasant odors and even mold. Exhaust fans help with this problem. But how do you find out if your fan is powerful enough? Let's find out.

Determine Required Fan Power

First of all, you need to determine your exhaust fan’s power. It is measured in CFM (Cubic Feet per Minute) and is usually written on the back of the fan or in the fan manual.

If your bathroom is 100 sq. ft. or smaller, the general rule is that you need 1 CFM per square foot of floor area. This means 80 CFM for an 8′×10′ room, 60 CFM for a 6′×10′ room, etc. The minimum is 50 CFM for any room.

If your bathroom has over 100 sq. ft., the math differs. Now, instead of floor area, we count the fixtures that produce moisture. You need to add 50 CFM for fixtures such as toilet, shower, or bathtub. For example, for a bathroom over 100 sq. ft. with a toilet (50 CFM), shower (another 50 CFM), and a bathtub (another 50 CFM), the bathroom would require 50+50+50=150 CFM in total.

If your bathroom has high ceilings (over 8 feet), use the following formula:

CFM = (Room Volume in cubic feet) x (ACH) / 60

ACH here stands for air changes per hour. 8 is a standard for a bathroom.

You can use online calculators, but it’s better to back up the results with your own calculations. For example, not every calculator considers the ACH for bathrooms to be 8. Some of them use a multiplier of 6 or 7, which is not enough for the bathroom.

It’s even better to contact the Golzar Home support team and have a professional plumbing and ventilation expert check your exact ventilation system.

Test Your Fan

Turn on the fan. Is it running quietly? If you hear screeching or rattling sounds this means your fan isn't working properly, and is probably clogged or malfunctioning.

Also, you need to do a so-called "tissue test". In a closed bathroom, turn your exhaust fan on and hold a lightweight tissue or a piece of toilet paper against the fan. If it stays there - the test is passed. If not, this means your fan isn't working properly. You need to clean it, fix the motor, or replace it entirely.

Important Tip: Turn the power off at the electrical circuit before cleaning your exhaust fan.

HVI Certification

The Home Ventilating Institute (HVI) is a testing facility that certifies fans for power, noise levels, energy efficiency, etc. It is important to choose an HVI-certified fan to avoid unnecessary surprises.

Sones

Sones are the noise measurement unit for fans. Unlike the more common decibels, sones are linear. That means a 4.0-sone fan is twice as loud as a 2.0-sone fan. Check the different fans in the store to see which ones are right for you.

Less than 1 sone is barely audible, like light rain behind a closed window. 1 sone is still quiet, like a weak refrigerator sound. 2 sones is a slightly stronger refrigerator. 4 sones equals the noise level of a normal conversation between two people. 5–6 sones is roughly as loud as a TV running.

Can an exhaust fan be too powerful?

Actually, yes. If your fan is too powerful, it will produce more noise than a properly sized fan and pull heat out of the house. Increased energy use is another disadvantage, causing higher electricity bills.