1 in 150 Rule Calculation
Shake, Shake XD, Villa, Shingle Plus, Shingle
panel vents
"1 in 150" rule: For no vapor retarder type of attic insulation – no paper, plastic or aluminum layer between the attic floor and insulation layer. Recommends 1 sq. foot of ventilation for every 150 sq. feet of attic space divided 50 / 50 between the inlets and outlets.
1 in 300 Rule Calculation
Shake, Shake XD, Villa, Shingle Plus, Shingle
panel vents
"1 in 300" rule: For vapor retarder equipped attic insulation (for example fiberglass blankets/bats with paper facing), Recommends 1 sq. foot of ventilation for every 300 sq. feet of attic space divided 50 / 50 between the inlets and outlets.
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