Attic Ventilation Worksheet
Roof report → NFVA → ridge vent · ratio 1/300
NC
SC
Attic Ventilation Worksheet
Calculated from the roof measurement report · ratio 1/300 · field verification required
Roof measurement report
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Zone 1 of 1
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Zone name
Roof area, sq. ft.
Ridges, lf (ridges only)
Hips, lf (excluded)
Attic footprint method
B — per pitch (Areas per Pitch table)
C — simplified, predominant pitch
A — reported attic floor area
Product and split
Ridge vent
NFVA, sq. in. / lf
Section length, ft
Take NFVA from the data sheet for the specific product. 18 sq. in./lf is not a universal figure.
Exhaust share of total NFVA
Class I or II vapor retarder confirmed on the warm-in-winter side of the ceiling (NC alternate path to 1/300)
This zone also has box vents, turbines, or a powered attic fan
Intake and existing ventilation
Intake type
not entered / unverified
individual soffit vents (count × NFVA)
continuous soffit vent (lf × NFVA/lf)
Existing ridge vent already installed, lf
Checks
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A roof-report calculation is preliminary. Usable ridge length, actual ventilation zones, and existing intake NFVA are confirmed by field inspection.
