Eave Vent Area To Floor Square Ft Ratio

These methods dictate that one 1 square foot of ventilation is provided for every 150 or 300 square feet of attic floor space.

Eave vent area to floor square ft ratio.

Most local building codes require compliance with either the 1 150 method or the 1 300 method exception refer to local code. That determines the total amount of net free area needed to properly ventilate the attic. Remember the minimum area requirement when using a continuous system is a ratio of 1 300. L x w in inches 144 area of vent in sq.

Now let s figure out how much ventilation space we need. 1 square foot of nfva per 300 square feet of attic floor if a vapor barrier is installed on the ceiling below. So in our example we will divide the 1 500 square feet by 300. Once attic square footage is known divide by 150 for the 1 150 ratio.

1 500 square feet 300 5 square feet. See how simple that was. 30 feet x 50 feet 1 500 square feet. Divide the square footage by 150 to calculate the area of ventilation needed since you need 1 square foot of vent space for each 150 square feet of attic space.

Ok so now we know the square footage of the attic area to be ventilated. Determine the total net free area required. For square or rectangular vents muliply the length times width of the vent space in inches then divide by 144 to convert into sq. 150 6 6 square feet of total net free area 3.

If you have 3 000 square feet of attic space this equates to 20 square feet of ventilation needed. This ratio is required for modern insulated homes. A 6 x 12 vent would equal 72 sq.