How To Size An Attic Fan

A whole house fan sucks warm house.

How to size an attic fan.

A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. Cfm cubic feet per minute is a measure of the amount of air the fan moves in a minute. Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge.

Simultaneously cool fresh air will be pulled through the open windows and circulated through every room effectively replacing all of the air in your home and minimizing your dependence on air conditioning. By sizing and implementing a whole house fan you can pull the warm stale air from your entire home into the attic where it s vented outside. Attic fan size cfm 0 7 x sq ft area of the attic formula 1 the size of an attic fan is calculated in terms of cfm. Whole house fans work on the principle of removing the hot and humid air out of the house.

This attic ventilation calculator computes the size and number of solar powered attic fans to achieve the proper ventilation for your attic. The warm air escapes through the attic and to the attic vents allowing the circulation of chilly air from the windows. An attic fan works by exchanging the hot air in your attic space for fresh air pulled through the vents. This will help to avoid premature damage to the shingles or mold building up in moist hot.

The whole house fan is installed inside the attic between the living space and ceiling. How to size solar attic exhaust vent fans so we developed our solar powered attic fan sizer calculator. The formula above gives an approximate value of the cfm needed for an attic fan. It s also important to have plenty of soffit or gable vents for the fan to draw air into the attic.

To find out if you have enough vent space divide the cubic feet of air per minute that the fan is rated for by 300 to come up with the minimum number of square feet of intake vent space needed for that size fan. How to size a whole house attic fan.