Exhaust Fan Vent Size

This page is designed to be a general guide for selecting an exhaust fan based on the size of the room and the type of application the fan will be used for.

Exhaust fan vent size.

3 x 320 cfm 960 cfm to be vented. For example a 10 wide by 15 long bathroom with a 10 ceiling would need. 1500 60 25. You multiply length times width times height.

The exhaust fan drawing below illustrates how static pressures are measured in ductwork with a manometer. All you need to do is select the application from the dropdown enter the size of the room and we will provide you with a general capacity range m3 hr that you should be looking to achieve from the extraction fan. The basics of venting a bathroom exhaust fan 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. Stephen paul many stoves come with their own hoods and the hood is usually the right size for the stove.

The minimum requirements say that this air should be changed 15 times an hour. Attic vent fans are commonly rated from 800 to 1 600 cfm making one fans suitable for attics of up to around 2 200 square feet. However you don t want the hood to be too low or it will get in the way so 24 inches above the cooking surface is the recommended distance. If your bathroom has a higher ceiling multiply the width x length x height of the room divide by 60 minutes in an hour then multiply by 8 number of air exchanges per hour.

The floor to ceiling walls prevent air from circulating to an enclosed shower or a toilet no matter the size of the fan in the main part of the bathroom so it s best to install an additional small. At 1200 cfm and. A 901 to 1200 cfm fan requires an 8 inch minimum and a 10 to 12 inch duct is recommended. For that air volume 8 diameter vent ducts are close to their limit and 10 is indeed preferable.

Attic x 0 7 700 cfm minimum fan rating. A 601 to 900 cfm fan requires a 7 inch minimum but an 8 to 10 inch duct is recommended. Add an additional 20 cfm x 1 20 if you have a steep roof and 15 cfm x 1 15 for a dark roof. A pressure differential between the duct and the atmosphere will cause the water level in the manometer legs to rest at different levels.

This difference is the static pressure measured in inches of water gauge. 10 feet x 12 feet x 8 feet that computes to 960 cubic feet of air in the room. Vent hoods should be close to 24 inches above the cooking surface.