How Much Air Flow Does My Attic Need

First determine your attic area by multiplying the length by the width.

How much air flow does my attic need. 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. 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. In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Exhaust fan is 14 5 inches in diameter so i figure given this is going to be a tight box i gotta put some intake vent on it and want air intake starting at the bottom and distributed around so all sides of generator get cooling and air flow.

However with only two 1 ft x 2 ft gable roof vents i ll need an additional 7 sq ft of exhaust vents. Length x width of attic in feet 150 total sq. A 50 x 30 attic would have a total area of 1 500 sq. Attic for example has an area of 1 200 sq.

This characteristic of air may be used to help create a flow of air ventilating the attic. 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. Then aim for about 1 sq. 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.

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. You mention exhaust vents shouldn t exceed intake vents in the roof for proper circulation. The picture below courtesy of the epa indoor airplus program which we provide builder verification services for helps show how the system works. By my calc pxr squared says area of exhaust vent is 165 square inches.

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. 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. Of vent for every 300 sq. The soffit vents allow convective air movement from the soffits of the residence to the ridge vent.

So now comes issue of air intake. That said air resistance and interference such as vent grates reduces the area of true ventilation. How many vents do you need. Calculate the total vent area needed.

Ft divided by 150 equals 10 sq. This results in a constant upward air movement due to the buoyancy of warmer air. Of total vent space needed.