What Size Vent Pipe For Bathroom Exhaust Fan

This article series explains why bathroom vent fans are needed and describes good bath vent fan choices necessary fan capacity and good bath vent fan and vent duct installation details.

What size vent pipe for bathroom exhaust fan.

We explain how to install bathroom exhaust fans or vents the vent ducting. Avoid venting through a soffit vent or ridge vent. If you have access to the attic the fan can vent either through a gable wall or roof. 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.

Here we provide specifications for recommended minimum maximum duct lengths for bathroom vent fans. The master bath pipe is about 30 long and the 2nd bath pipe is about 10 long. The bathroom exhaust ventilation fan disperses air through an opening in the fan housing which is usually 3 inches in diameter and ideally faces in the direction of the ventilation system outlet. A bath vent fan duct that is too long may restrict air flow such that the fan is not functional.

Cubic volume 7 5 cfm necessary. 10ft 10ft 8ft 7 5 106 67 cfm. For a standard 10ft by 10 ft bathroom with an 8 ft ceiling you will need an exhaust fan capable of 106 67 cfm. A bath vent fan duct that is too short may violate the manufacturer s installation instructions may not work properly or may be drafty.

Thank you for this forum. How to install a bathroom vent fan. Bathroom vent fans are rated by the cubic feet per minute cfm of air they move and should be sized to replace the air in the room at least eight times an hour. The formula to calculate bathroom exhaust fan size reads as follows.

Sizing for large bathrooms for bathrooms over 100 square feet exhaust fans can be sized according to the number of fixtures in the room. Surprisingly bathroom fans are not required by some building codes. 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. All municipalities have different requirements but some do not draw a hard line on requiring exhaust fans.

Ft in the room. So there s one timer to activate the fan but it has 2 openings one in each area of the bathroom. When venting a bathroom exhaust fan make sure to vent the air to the outside rather than into your attic where it can cause mold and mildew to form. Regarding the tee i want the fan to exhaust from 2 rooms one s the main area of the bath with shower the other has the toilet behind a separate door.

The warm air will exhaust out the duct and enter back into the attic through the soffit vent or ridge vent. Bathroom exhaust fan duct length specifications. Here s how we get this number. Maybe splitter is the right word to use rather than tee.

Bath vent fan installation building codes bath vent fan troubleshooting bath vent fan repair. Bathroom code does address the issue of moving odor and moisture laden air from the bathroom to the outside. Bathroom fan exhaust size calculator. Letting the fan exhaust into an open attic will cause moisture buildup on the underside of the roof.