Attic Ventilation 1 300 Rule

With the amount of needed attic ventilation.

Attic ventilation 1 300 rule.

Here are the answers to the five most frequent questions pertaining to calculating attic ventilation. For every 150 square feet sq. I m putting in continuous soffit vents on friday hopefully and it s looking like we re going to use the standard 2 wide variety which has about 9 nfa per foot. Based on your 1100 sq.

But when i do the math that only gives me. According to the 2018 irc code on attic ventilation the minimum net free ventilating area nfva shall be 1 150 of the area of the vented space. Now let s figure out how much ventilation space we need. Nrca guidelines regarding attic ventilation nrca recommends designers provide at least 1 square foot of nfva for every 150 square feet of attic space 1 150 ventilation.

Mostly i ve seen the 1 300 rule specified for attic ventilation but i ve also seen 1 150 mentioned. 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. So in our example we will divide the 1 500 square feet by 300. 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.

In order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq. Ok so now we know the square footage of the attic area to be ventilated. Local building codes when stricter take precedence. The 1 300 rule is a general rule and does not apply to all situations.

Of vent for every 300 sq. Always consult a design professional for cathedral ceilings insulated roof decks etc. Roof ventilation 1 which states in part 1 square foot of net free area for every 150 square feet of attic floor. Also when using a vapor retarder in an attic space irc 2012 limits the net free ventilation reduction from 1 150 to 1 300 for buildings in climate zones 6 7 and 8.

1 500 square feet 300 5 square feet. Remember the minimum area requirement when using a continuous system is a ratio of 1 300. Building codes vary. See how simple.

Most codes use the 1 300 rule for minimum residential attic ventilation recommendations. And this guideline you ll need a. Owens corning recommends a balanced ventilation system based on the u s. Here s a rule of thumb to follow.

In no case should the amount of exhaust ventilation exceed the amount of intake ventilation. Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator.