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 Cobra® and 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 ventilation needed at eave (at or near ridge)
384.00 net free ventilation needed at eave (at or near soffit)

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


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


TruSlate® Ridge Vent
ft. TruSlate® Ridge Vent


Master Flow® Power Attic Vent - Roof Mount
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
RT65 Static Vents
IR61 Static Vents
R50/RV50 Static Vents
IR65 Static Vents
SSB960 Static Vents


Turbines
12" Turbines
14" Turbines


Master Flow® Aluminum Ridge Vent
ft. Aluminum Ridge Vent


Master Flow® SOLAR Ventilators
Roof Solar & Dual-Power (PRSOLAR1/PRHYBRID1)
Gable Solar (PGSOLAR1)
High-Power Roof Solar & Dual-Power (PRSOLAR2/PRHYBRID2)
Intake Booster™ Vent


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


MasterFlow® Power Attic Vent - Gable Mount
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

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


Cobra® Mesh Roll 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
RT65 Static Vents
IR61 Static Vents
R50/RV50 Static Vents
IR65 Static Vents
SSB960 Static Vents


TruSlate® Ridge Vents
TruSlate® Ridge Vent

Professional Installation

GAF Roof Wizard
Virtual Home Remodeler


Product Pricing and Where to Buy