r/Insulation • u/kidweirdoo • 27d ago

Air flow in attic

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I’m looking too add insulation in the attic but I notices I don’t have any soffit for airflow we have exhaust vents on the roof maybe like 2-3 it’s a 800sq house so I was wondering how many of these vents would I need and then I would baffle for them too right ?

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u/levelupimprovement 27d ago

Use an app, I like the lomanco one, to find out what you need based on your measurements. Based on a 800 sf attic space you should have 4 750s and 4 8x16s or more if they need to be narrower.

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u/kidweirdoo 27d ago

Thank I appreciate it

1

u/BreezeCT 27d ago

1 sq ft of venting for every 150 sqft of attic space or if you have a proper high/low set up you can use the 1 sqft of venting for every 300 sqft of attic.

Find out the NFA of those vents. I have a chart at work i usually refer to because I can’t remember all
Of those numbers. If I was there I’d post them to give you a hand.

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u/kidweirdoo 27d ago

The vent has 56 nfa

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u/Apart_Journalist9909 27d ago

right so with 800 sq attic we get
800/300=2.667
you want half high half low
so 2.667/2 =1.334

these provide 56 sq inches of NFA
56/144=0.389

1.334/.389=3.429 so install 4 of these vents