Attic Ventilation 1 300 Rule

But when i do the math that only gives me.

Attic ventilation 1 300 rule.

For every 150 square feet sq. The 1 300 rule is a general rule and does not apply to all situations. Mostly i ve seen the 1 300 rule specified for attic ventilation but i ve also seen 1 150 mentioned. Ft of attic space 1 square foot of ventilation is recommended.

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. 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. Here are the answers to the five most frequent questions pertaining to calculating attic ventilation. 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.

Owens corning recommends a balanced ventilation system based on the u s. Remember the minimum area requirement when using a continuous system is a ratio of 1 300. Roof ventilation 1 which states in part 1 square foot of net free area for every 150 square feet of attic floor. 1 500 square feet 300 5 square feet.

Building codes vary. Local building codes when stricter take precedence. Of vent for every 300 sq. Always consult a design professional for cathedral ceilings insulated roof decks etc.

Hvi says to use 150 when there s no vapor barrier and 300 when there is. And this guideline you ll need a. Now let s figure out how much ventilation space we need. Based on your 1100 sq.

So in our example we will divide the 1 500 square feet by 300. Here s a rule of thumb to follow. This means that for every 300 square feet of enclosed attic space 1 square foot of ventilation is required with half at the upper portion exhaust vents and half in the lower portion intake vents. Ok so now we know the square footage of the attic area to be ventilated.

Most codes use the 1 300 rule for minimum residential attic ventilation recommendations. 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. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation. See how simple.

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 order to facilitate this exchange of warm and cool air the general rule of thumb suggests installing at least 1 sq.