Standard Duct Size For Bathroom Exhaust Fan

The fan pulls air out of the bathroom and allows fresh air to be drawn in.

Standard duct size for bathroom exhaust fan.

A bathroom fan is an essential piece of hardware in any indoor bathroom without a window. This keeps the moisture from the shower bath or sink from encouraging mold growth. Ft in the room. Bathroom fan exhaust size calculator.

The minimum duct sizes and recommended duct sizes based on a hood fan s cfm rating are as follows. Standard fan sizing applies to bathrooms that are 100 square feet or less. A bath vent fan duct that is too long may restrict air flow such that the fan is not functional. A bath vent fan duct that is too short may violate the manufacturer s installation instructions may not work properly or may be drafty.

The formula to calculate bathroom exhaust fan size reads as follows. I installed a 5 duct fan for bathroom exhaust the total length of duct to outside is less than 6 ft. If your bathroom has an 8 ceiling the cfm rating for your fan should be as least as high as the number of square feet 5 x 7 35 sq. For a standard 10ft by 10 ft bathroom with an 8 ft ceiling you will need an exhaust fan capable of 106 67 cfm.

Cubic volume 7 5 cfm necessary. A large bathroom with a jetted tub a toilet and a shower a common configuration in new homes would need a 200 cfm ventilation fan such as the broan l200 ventilation fan available from. Here we provide specifications for recommended minimum maximum duct lengths for bathroom vent fans. Here s how we get this number.

Check the size of the exhaust port on the fan to make sure it fits your ductwork if applicable. The duct fan is rated 120 cfm free air. Bathroom vent fans are rated for the amount of air they can move measured in cubic feet per minute or cfm. 10ft 10ft 8ft 7 5 106 67 cfm.

The rule of thumb is that you need at least 1 cfm per square foot of room area. A 0 to 400 cfm fan requires a 4 inch minimum duct size but a 6 inch duct is recommended. A diameter of 4 inches is common for exhaust ducts but some high cfm fans fit a 6 inch diameter duct. Standard fan sizing.