Exhaust Fan Size Chart

The tables below are basic references to help guide you to the exhaust pipe size needed to balance the prevention of excessive back pressure while maintaining adequate exhaust gas velocity.

Exhaust fan size chart.

The effectiveness of the fan will be rated in cfm or cubic feet per minute of air moved. Sizing an exhaust fan use this table to calculate the cubic feet per minute cfm capacity needed for an exhaust fan in a specific room. Learning how to calculate cfm for a bathroom fan will help you purchase the right size fan for your space. If you ask us we will say.

To be effective a bathroom fan needs to be powerful enough to completely replace the air in the room about 8 times every hour. Before you install bathroom kitchen or garage exhaust fans start here to determine what you need to proceed for. 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. Ignore the size charts and buy the biggest fan with the highest wind speed that will fit reasonably in the space.

Higher ceilings would require a larger fan. Tam asks what size exhaust fan should we use in our small bathroom if your bathroom has an 8 ceiling the cubic feet per minute cfm rating for your fan should be as high or higher than the number of square feet in the room. A ventilation fan should meet at least the minimum standard cfm to provide proper exhaust. The exhaust fan drawing below illustrates how static pressures are measured in ductwork with a manometer.

Whether exhausting air or bringing fresh air into a structure the calculation produced should help to figure out the size of fan s required to accomplish the air exchanges needed. This fan calculator is typically used to calculate the cfm or cubic feet per minute of air exchange that may be desired in a building. A ventilation fan should meet at least the minimum size. Bathroom fan exhaust size calculator.

Bathroom extractor fans are mandatory in any bathroom without a window and still highly recommended in bathroom with windows. A pressure differential between the duct and the. One pound per square inch is equivalent to 27 7 sp. Fan static pressure is measured in inches of water gauge.

Sizing for large bathrooms for bathrooms over 100 square feet exhaust fans can be sized according to the number of fixtures in the room. Cubic volume 7 5 cfm necessary. Static pressure in fan systems is typically less than 2 sp or 0 072 psi. Why you need to have the proper size extractor fan.

Read on to find out more. Use this table to calculate the cubic feet per minute cfm capacity needed for an exhaust fan in a specific room.