Homeowner Guide to Bathroom Exhaust Fans
December 15, 2021
If you’re renovating your bathroom, consider upgrading your bathroom exhaust fan. A vent fan will ensure that excess moisture is removed, keeping your bathroom mold free. And many current models include bonus features like heat lamps and lighting. The variety of fans can seem overwhelming, so we’ve compiled a Homeowner Guide to Bathroom Exhaust Fans to help you choose the right one.
Why You Need an Exhaust Fan in Your Bathroom
The main reason to install a vent fan in your bathroom is to remove excess moisture. Hot showers and baths produce humidity, and this moisture causes the growth of mold and mildew. Mold can damage your wallboards, molding, and other organic finishes. It’s also unhealthy for people and pets.
Your bathroom exhaust removes unpleasant odors, along with volatile organic compounds (VOCs) from cleaning and grooming products
What Are the Code Requirements for Bathroom Exhaust Fans?
Bathroom exhaust fans are sized by their CFM (cubic feet per minute), which is the volume of air the fan moves. While building codes aren’t specific about placement, they do require a minimum CFM.
For residential bathrooms, IRC building codes require a minimum of 50 CFM intermittent or 20 CFM continuous. That means that if the fan is on a timer, you’ll need a 50-CFM fan. For fans that run as long as the lights are on, you’ll need a 20-CFM fan.
How to calculate optimal fan size
However, HVAC experts recommend going above the minimum if possible. For small half-baths, they recommend a 60 to 80 CFM fan. For large spa/suite type baths, we recommend 200 to 300 cfm.
Starting with a minimum of 50 CFM for a small bathroom, calculate 1 CFM per square foot up to 100 square feet.
If your bathroom is over 100 square feet, add 50 CFM for each standard feature (toilet, shower, tub), and 100 CFM for a jetted tub. You’ll need a separate fan for an enclosed toilet, as well.
The length of the vent duct to the outdoors and the number of bends in the duct can also increase the cfm requirement. While not governed by code, experts recommend increasing the duct diameter and/or fan speed for duct runs over 50 feet. We also recommend using no more than three (3) bends per duct run.
Bonus Features
Now that you know the size of fan you’ll need, consider some popular modern features that will add functionality and pizazz to your bathroom.
Moisture sensors for humidity-based operation
Motion sensors for automatic operation
Build-in heaters (some with thermostats)
Bluetooth speakers for a spa experience
Overhead lights for additional lighting
Overhead night light for safety
ENERGY STAR ratings for energy efficiency