Ventilation Calculator Based on U.S. VA/FHA Guidelines

This Calculator will help you to determine the proper amount of ventilation based on the VA/FHA Guidelines. To use simply enter the dimension or square footage of your attic and click 'Update.' The calculations are done for you. The products listed are GAF Master Flow® products and the quantity numbers are rounded up or down for your convenience.

Please note that the 1/300 or the 1/150 rule are general rules and do not apply to all situations. Local building codes, when stricter, take precedence. Always consult a design professional for cathedral ceilings, insulated decks, etc.

Length OR Total Attic Floor Space
Width

Using the FHA 1/300 rule
384.00 net free vent needed at ridge
384.00 net free vent needed at soffit

Cobra® Plastic Vents
ft. Cobra RidgeRunner®
ft. Cobra® Rigid Vent 3™
ft. Cobra® Snow Country™
ft. Cobra® Snow Country Advanced™


Cobra® Mesh Vents
ft. Cobra® Exhaust Vent-Hand Nail
ft. Cobra® Exhaust Vent-Nail Gun


TruSlate® Ridge Vent
ft. TruSlate® Ridge Vent


Master Flow® Power Roof Ventilators
PR1 (1000CFM)
PR2 (1250CFM)
PR3 (1600CFM)


Note: Gable vents are normally installed in pairs
Metal Gable Louvers
DA 12x12
DA 12x18
DA 14x24
DA 18x24
DA 24x30


Metal Soffit Vents
EAC 16x4 Soffit Vents
EAC 16x8 Soffit Vents


Plastic Soffit Vents
EAP 412 Series Soffit Vents


Plastic Circular Louvers
RLSC 2 (2") Series Soffit Vents
RLSC 3 (3") Series Soffit Vents
RLSC 4 (4") Series Soffit Vents
Static Vents/Roof Louvers
RT 65 Static Vents
IR 61 Static Vents
R 50A Static Vents
IR 65 Static Vents
SSB 960 Static Vents


Turbines
12" Turbines
14" Turbines


Master Flow® Aluminum Ridge Vent
ft. Aluminum Ridge Vent


Master Flow® SOLAR Ventilators
Roof Solar & Dual-Power
Gable Solar & Dual-Power
Intake Booster™ Vent


Plastic Gable Louvers
SL 8x8
SL 12x12
SL 12x18
SL 14x24
SL 18x24


MasterFlow® Power Gable Ventilators
PG2 (1540CFM)
PG3 (1600CFM)


Continuous Metal Soffit Vents
LSV8 Series Soffit Vents


Cobra® Fascia Vents
ft. Cobra® Fascia Vent 1"
ft. Cobra® Fascia Vent 1.5"
ft. Cobra FasciaFlow®

Using the FHA 1/150 rule
(vents placed at or near the ridge only)
1536.00 net free vent area needed

Rigid Cobra® Vents
ft. Cobra® RidgeRunner™
ft. Cobra® Rigid Vent 3™
ft. Cobra® Snow Country™
ft. Cobra® Snow Country Advanced™


Mesh Cobra® Vents
ft. Cobra® Exhaust Vent Hand Nail
ft. Cobra® Exhaust Vent Nail Gun


Master Flow® Aluminum Ridge Vent
ft. Aluminum Ridge Vent
Static Vents/Louvers
RT 65 Static Vents
IR 61 Static Vents
R 50A Static Vents
IR 65 Static Vents
SSB 960 Static Vents


TruSlate® Ridge Vents
TruSlate® Ridge Vent

Professional Installation

GAF Roof Wizard
Virtual Home Remodeler


Product Pricing and Where to Buy