Eave Input Vent Area To Floor Square Ft Ratio

Once attic square footage is known divide by 150 for the 1 150 ratio.

Eave input vent area to floor square ft ratio. 30 lineal feet required. Always have a balanced ventilation system. Say the contractor is standing in front of a house that has an attic with 2 200 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.

For round vents multiply the radius of the vent half the diameter times itself squared then multiply the total by 3 14 pi and divide by 144 to find the number of square feet r in inches x 3 14 144 sq. 1 100 square inches of intake net free area needed. 30 feet x 50 feet 1 500 square feet. Determine the total net free area required.

So in our example we will divide the 1 500 square feet by 300. Ok so now we know the square footage of the attic area to be ventilated. 1 square foot of nfva per 300 square feet of attic floor if a vapor barrier is installed on the ceiling below. This ratio is required for modern insulated homes.

The next step is to select a suitable exhaust vent and intake vent that fits the roof design for best performance and best aesthetics. 1 500 square feet. 2 200 2 1 100 square inches of exhaust net free area needed. This is distributed between under eave net free vent area and the ridge in a ratio of 60 under eave and 40 in the ridge.

That determines the total amount of net free area needed to properly ventilate the attic. 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. 40 x 25 1 000 square feet of attic area 2. Calculate or enter the square footage of the attic or area to be vented.

Remember the minimum area requirement when using a continuous system is a ratio of 1 300. And this guideline you ll need a minimum of. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation. A 6 x 12 vent would equal 72 sq.

In divided by 144 equals an area of 0 5 sq. Based on your 1100 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.

Now let s figure out how much ventilation space we need.