How Much Air Flow Does My Attic Need

Attic for example has an area of 1 200 sq.

How much air flow does my attic need. Ft divided by 150 equals 10 sq. The picture below courtesy of the epa indoor airplus program which we provide builder verification services for helps show how the system works. So now comes issue of air intake. 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.

How many vents do you need. Calculate the total vent area needed. 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. The soffit vents allow convective air movement from the soffits of the residence to the ridge vent.

First determine your attic area by multiplying the length by the width. However with only two 1 ft x 2 ft gable roof vents i ll need an additional 7 sq ft of exhaust vents. I need additional exhaust ventilation in my roof with the planned installation of a whole house fan in the attic of my home located in sf bay area. Then aim for about 1 sq.

Length x width of attic in feet 150 total sq. A 50 x 30 attic would have a total area of 1 500 sq. Generally speaking you need a ratio of 1 300 where for every 300 square feet of ceiling space you need 1 square foot of attic ventilation. Multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find the total square feet of vent space needed.

This results in a constant upward air movement due to the buoyancy of warmer air. In addition insulation baffles must be installed at the point where the attic floor meets the roofline to prevent the attic insulation from migrating into the cavities and restricting the airflow from the soffit vents. Of vent for every 300 sq. In of vent opening per 150 sq.

A 30 x 40 ft. Placing exhaust vents in the roof the gables or at the ridge of the roof and providing adequate air intake vents in the soffits best accomplishes this. An attic baffle is simply an item to regulate the flow of air aka required roof venting and impede it the insulation from interfering with each other. By my calc pxr squared says area of exhaust vent is 165 square inches.

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. That said air resistance and interference such as vent grates reduces the area of true ventilation. You mention exhaust vents shouldn t exceed intake vents in the roof for proper circulation.