Standard Bathroom Vent Duct Size

The minimum duct sizes and recommended duct sizes based on a hood fan s cfm rating are as follows.

Standard bathroom vent duct size.

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. Simply enter the dimensions of your bathroom in the calculator below to determine the minimum size vent fan you need for the bathroom in your home. A bath vent fan duct that is too short may violate the manufacturer s installation instructions may not work properly or may be drafty. Never vent a bathroom fan directly into an attic it must always vent outside.

A 0 to 400 cfm fan requires a 4 inch minimum duct size but a 6 inch duct is recommended. 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. Bathroom exhaust fan duct length specifications. When installing a vent fan make sure there s at least a 1 2 gap under the bathroom door to allow fresh air to enter the room when the fan is running.

Duct sizing is pretty much what the size of the fan exhaust fitting is. This guide will help you understand how to choose the right size and type of bathroom fan. They are very. For a fan size i like the largest ones available 150 cfm such as panasonic brand with squirrel cage fans.

Here we provide specifications for recommended minimum maximum duct lengths for bathroom vent fans. All exhaust fan companies have a chart or equations to calculate the minimum exhaust fan sizing per room size width x length x height for cubic feet.