Cfm Requirements For Bathroom Fans

So if you have a bathroom that is 12 feet long 15 feet wide and 10 feet tall then it has a volume of 1800 cubic feet 12 x 15 x 10 and a cfm of 240 1800 7 5.

Cfm requirements for bathroom fans. Cfm cubic feet per minute general term used to specify the amount of air that the bathroom vent fan in our case is able to move within one minute of its operation. To be effective a bathroom fan needs to be powerful enough to completely replace the air in the room about 8 times every hour. The cfm represents the airflow required to completely exchange the air in your bathroom 8 times in one hour. The effectiveness of the fan will be rated in cfm or.

All municipalities have different requirements but some do not draw a hard line on requiring exhaust fans. A 50 square foot or smaller bathroom needs a 50 cfm fan. That s because an 80 cfm rated exhaust fan for a bathroom will not move enough air out of a large bathroom to keep steam and moisture from building up on the walls and other surfaces when you shower the manufacturer will usually note the exact amount of square footage a particular model can handle. The fan won t even push the damper open even with the spring on the exhaust damper removed.

Bathroom code does address the issue of moving odor and moisture laden air from the bathroom to the outside. Surprisingly bathroom fans are not required by some building codes. The cubic feet per minute cfm is very important. The exhaust fan removes moisture and humidity from your bathroom.

The fan pulls air out of the bathroom and allows fresh air to be drawn in. Delta breez greenbuilder series 80 cfm ceiling bathroom exhaust fan delta breez greenbuilder ventilation fans mark a new achievement in bathroom ventilation for green construction. Air must be exhausted directly to the outside 2006 irc 303 3x may not discharge to crawlspace or attic 2006 irc 1506 2 13. Plan for 50 cfm for each toilet tub or shower and 100 cfm for a.

Why you need to have the proper size extractor fan. The result is the cfm or cubic feet per minute rating required for your bathroom fan. The formula to calculate bathroom exhaust fan size reads as follows. Built upon market leading energy efficiency exceptionally low power consumption and quiet operation the breezgreenbuilder series offers a dimmable led light option as well as humidity sensing option.

The minimum allowed fan size is 50 cfm so if your bathroom is for example only 42 square feet you still need a 50 cfm fan. For bathrooms between 50 and 100 square feet estimate approximately 1 cfm per square foot. Bathroom extractor fans are mandatory in any bathroom without a window and still highly recommended in bathroom with windows. The duct fan is rated 120 cfm free air.

I installed a 5 duct fan for bathroom exhaust the total length of duct to outside is less than 6 ft. This keeps the moisture from the shower bath or sink from encouraging mold growth. Cubic volume 7 5 cfm necessary.