How Much Air Flow Does My Attic Need

Then aim for about 1 sq.

How much air flow does my attic need.

This characteristic of air may be used to help create a flow of air ventilating the attic. The soffit vents allow convective air movement from the soffits of the residence to the ridge vent. By my calc pxr squared says area of exhaust vent is 165 square inches. 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.

So now comes issue of air intake. How many vents do you need. You mention exhaust vents shouldn t exceed intake vents in the roof for proper circulation. However with only two 1 ft x 2 ft gable roof vents i ll need an additional 7 sq ft of exhaust vents.

Ft divided by 150 equals 10 sq. Of total vent space needed. That said air resistance and interference such as vent grates reduces the area of true ventilation. A 50 x 30 attic would have a total area of 1 500 sq.

The picture below courtesy of the epa indoor airplus program which we provide builder verification services for helps show how the system works. Length x width of attic in feet 150 total sq. 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. 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.

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. In of vent opening per 150 sq. 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. Of vent for every 300 sq.

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. 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. Attic for example has an area of 1 200 sq. 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.

This results in a constant upward air movement due to the buoyancy of warmer air. Calculate the total vent area needed. 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.