GAF Attic Ventilation Calculator

Use this calculator to help determine the proper amount of attic ventilation based on U.S. FHA 1/300 guidelines.

  • Proper attic ventilation consists of a balance between air intake (at your eaves, soffits or fascias) and air exhaust (at or near your roof ridge).
  • The U.S. Federal Housing authority recommends a minimum of at least 1 square foot of attic ventilation (evenly split between intake and exhaust) for every 300 square feet of attic floor space.
  • Always have a balanced ventilation system. In no case should the amount of exhaust ventilation exceed the amount of intake ventilation.

NOTE: The 1/300 rule is a general rule and does not apply to all situations. Local building codes, when stricter, take precedence. Always consult a design professional for cathedral ceilings, insulated roof decks, etc.


Get Started!

Step 1: Enter the length and width of the attic floor -OR- the total square footage of the attic floor.
Step 2: Hit the "Calculate" button for the recommended amount of exhaust and intake ventilation.
Step 3: See quantities below for each GAF Ventilation Product (typically rounded up).

Length (ft.) OR Total Attic Floor Square Footage
Width (ft.)

Ridge & Static Attic Vents

384.00 Minimum Sq. In. of Net Free Area of exhaust needed at or near the ridge.
384.00 Minimum Sq. In. of Net Free Area of intake needed at or near the soffit.

Helpful Hint! For the 1/150 attic ventilation requirement, simply double the amount of exhaust and intake calculated.
* N/R = not recommended

Exhaust Ventilation

Cobra® & TruSlate® Plastic Vents (Lineal Feet)
Cobra Ridge Runner®
Cobra® Rigid Vent 3™
Cobra® Snow Country™
Cobra® Snow Country Advanced™
Cobra® Hip Vent
TruSlate® Ridge Vent


Cobra® Exhaust Vent - Mesh Rolls (Lineal Feet)
Cobra® Exhaust Vent - Hand Nail
Cobra® Exhaust Vent - Nail Gun


Master Flow® Aluminum Ridge Vent (Lineal Feet)
AR10


Master Flow® Roof Louvers (# of Vents)
RT65 Plastic Square - Top
IR61 Plastic Low - Profile
R50/RV50 Metal Utility
IR65 Plastic Slant - Back
SSB960 Metal Slant - Back
HCD144 High-Capacity Dome Vent


Master Flow® Wind Turbines (# of Vents)
12"
14"

Intake Ventilation

Cobra® Intake Vents (Lineal Feet)
Cobra® IntakePro™
Cobra® Fascia Vent (Mesh Roll) 1"
Cobra® Fascia Vent (Mesh Roll) 1.5"


Master Flow® Soffit/Undereave Vents (# of Vents, except for LSV8)
LSV8 Metal Continuous Soffit Vents (Lineal Feet)
EAP 4x12 Plastic Soffit Vents
EAC 16x4 Metal Soffit Vents
EAC 16x8 Metal Soffit Vents
EmberShield® Closeable Soffit Vents


Master Flow® Solar-Powered Intake Vent (# of Vents)
Solar-Powered Intake Booster™


Intake or Exhaust Ventilation

Master Flow® Metal Gable Louvers (# of Vents)
DA 12x12
DA 12x18
DA 14x24
DA 18x24
DA 24x30


MasterFlow® Plastic Gable Louvers (# of Vents)
SL 8x8
SL 12x12
SL 12x18
SL 14x24
SL 18x24
Note: Gable louvers are typically installed in pairs.


MasterFlow® Plastic Circular Louvers (# of Vents)
RLSC 2"
RLSC 3"
RLSC 4"

Power Attic Vents

Exhaust Ventilation

Master Flow® Power Attic Vents - Roof Mount (# of Vents)
ERV4
ERV5
ERV6


Master Flow® Power Attic Vents - Gable Mount (# of Vents)

EGV5
EGV6


Master Flow® Green Machine™ Solar Vents (# of Vents)
Solar & Dual-Powered Roof (PRSOLAR1 / PRHYBRID1)
Solar-Powered Gable (PGSOLAR1)
High-Power Solar & Dual Powered Roof (PRSOLAR2 / PRHYBRID2)
Solar-Powered Ridge Vent (SRV1)

Intake Ventilation

Cobra® IntakePro™ (Lineal Feet)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent


Cobra® Fascia Vent (Mesh Roll) 1" (Lineal Feet)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent


Cobra® Fascia Vent (Mesh Roll) 1.5" (Lineal Feet)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent


LSV8 Metal Continuous Soffit Vents (Lineal Feet)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent


EAP 4x12 Plastic Soffit Vents (# Of Vents)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent


EAC 16x4 Metal Soffit Vents (# Of Vents)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent


EAC 16x8 Metal Soffit Vents (# Of Vents)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent


EmberShield® Closeable Soffit Vents (# Of Vents)
with ERV4
with ERV5
with ERV6
with EGV5
with EGV6
with Solar & Dual-Powered Roof
with Solar-Powered Gable
with High-Power Solar & Dual Powered Roof
with Solar-Powered Ridge Vent



Professional Installation
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