Bathroom Fans Buying Guides

Install a ventilation fan in your bathroom ceiling for improved air quality

Bathroom fans vent moist air quickly outside, eliminating problems associated with high humidity like mold and mildew growth, steamy mirrors and peeling wallpaper and paint.

This guide will help you understand how to choose the right size and type of bathroom fan.

Bath Fans Performance

A fan’s ability to move air is measured in cubic feet per minute (CFM). The bigger your bathroom, the higher the CFM rating you’ll need.

Tip: A fan should have a CFM rating high enough to replace the air in your bathroom at a rate 8 times per hour.

Most fans are rated from 50 to 110 CFM. For bathrooms 50 square feet and smaller, get a 50 CFM fan. For bathrooms that are larger, you need to select a fan that can move at least 1 CFM per square foot of room. So, for an 80 square foot bathroom, select a fan with at least an 80 CFM rating.

Determine the size of your bathroom with this formula:
Length x Width x Height x 0.13 = Minimum CFM rating

Bath Fans Sound, Light & Ducting

The best bath fans have a sone rating less than 1.5. Before installation, check to see if you can use existing wiring and ducting.

• The industry standard for measuring the amount of sound a fan makes when it’s in use is called sones.
• The lower the sone rating, the quieter the fan will be.
• One sone is equivalent to the sound of a quiet refrigerator. A quiet bathroom fan will be rated at about 1.5 sones or less.
• If you are installing a fan in the bathroom for the first time, consider a model with the light, and place it where your light fixture currently is. This will allow you to use the existing wiring and switch.
• Otherwise, you’ll need to wire the light and fan separately to control them independently, so get a combination switch that has 2 or 3 controls.
• Fans in top story bathrooms are ducted through the attic to the outside through the roof or wall. Fans in bathrooms in the first story of a multi-story home are vented through the side of the house.
• If you are replacing or upgrading a fan, the diameter of the duct connector on the new housing may be larger than the size of your existing duct. To maximize performance, try to match your duct diameter to the new fan.

Tip: Regardless of location, the moist air needs to be exhausted outside. Never vent a fan directly into an attic.