Roof & Attic Ventilation
Roof ventilation controls how heat, moisture, and exhaust air leave a building through the roof. This category includes louvers for attic ventilation, plus roof vents and roof jacks that terminate bathroom and kitchen exhaust ducts at the roof surface and seal the penetration against water.
Balanced roof and attic ventilation removes summer heat and winter moisture from the attic, which protects roof decking, insulation, and shingles. Exhaust terminations carry duct air outdoors instead of releasing it into the attic, where it can condense on framing. These roof ventilation products are built for residential and light commercial work, with steel and aluminum construction, dampers and screens on select roof vents, and tapered roof jacks sized for specific roof pitches. Louvers and other attic ventilation products are rated by net free area. Use the groups below to match each product to the duct size, roof pitch, and application.
Roof & Attic Ventilation
Product Group Explanation
This category covers two groups. Louvers vent the attic itself. Roof vents and roof jacks terminate exhaust ducts from bathroom fans, kitchen hoods, and other exhaust fans at the roof.
Louvers
Louvers are fixed, slatted vents that exhaust moist, heated air from the attic without moving parts or power. Mounted near the ridge or on gable walls, roof louvers provide static exhaust on roofs with limited ridge length. Each louver carries a rated net free area (NFA), which sets how many units an attic requires.
Roof Vents with Damper and Screen
M&M steel roof vents come in 4, 7, 8, and 10 in. diameters with a built-in damper and screen, plus a 6 in. version with a sleeve. A roof vent with a damper closes when the fan stops, which limits cold-air backdraft. The screen keeps birds and insects out of the duct.
Low-Profile Roof Vents
The 4 in. aluminum low-profile roof vent with sleeve sits closer to the roof surface than a standard hood, which reduces its visible height on the roofline. The sleeve connects the vent to the duct below the roof deck. Aluminum resists corrosion and keeps the unit light for installation on finished roofs.
Tapered Roof Jacks with Vent Cap
Tapered roof jacks with an integrated vent cap are built for specific roof pitches, 0/12, 4/12, 5/12, and 9/12, in 4 in. and 6 in. sizes. Matching the jack to the pitch keeps the roof vent cap plumb and the flashing flat on the deck, so the base seals the penetration against water.
Bath Fan Roof Jacks
Bath fan roof jacks terminate bathroom exhaust ducts through the roof and carry humid air outdoors instead of into the attic. The M&M bath fan roof jack is built for a 9/12 roof pitch. Seal the duct joints, and use insulated duct where the run crosses unconditioned attic space.
How It Works / Where to Use
Attic Intake and Exhaust Balance
Attic ventilation systems work on balance. Intake vents low on the roof, usually at the soffits, draw in outside air, and exhaust vents near the ridge release warm, moist air. Keep exhaust area equal to or less than intake area. Avoid mixing exhaust types, such as louvers and a ridge vent, in one attic. Never use an exhaust vent as intake.
Duct Terminations for Bath Fans and Exhaust Fans
Roof jacks and roof vents connect to the end of an exhaust duct and discharge the air above the roof. Pair each termination with the correct vent pipe and fittings for the duct run, and size it to the full duct diameter to avoid restricting airflow. Dryer exhaust has separate code rules, including no screens.
Residential, Commercial, and Retrofit Work
In new construction, roof penetrations are set and flashed before shingles go on. In reroof and retrofit work, installers replace aging vents and jacks while the roof is open. Commercial buildings with multiple exhaust fans use the same products at each roof penetration.
Key Specifications and Planning Steps
Duct Diameter, Material, and Gauge
Match the termination to the duct: a 4 in. duct takes a 4 in. roof vent or jack, and a 6 in. duct takes a 6 in. termination. Steel offers higher strength. Aluminum weighs less and resists corrosion in humid or coastal areas.
Roof Pitch and Flashing
Measure pitch as inches of rise per 12 in. of run, then select the jack built for that pitch. Slide the flashing under upslope shingles and over downslope shingles. Use roof flashings and accessories for nonstandard penetrations.
Net Free Area and the 1:300 Rule
Size roof ventilation in net free area. The International Residential Code (Section R806) sets a 1:150 baseline and allows 1:300 under specific conditions. At 1:300, a 1,500 sq. ft. attic needs 720 sq. in. of NFA, split 360 intake and 360 exhaust.
Choosing the Right Roof Ventilation Product
Start with the application. For attic exhaust on a roof with a short or broken ridge, choose louvers sized by NFA against the available intake. For a bathroom or kitchen exhaust fan, choose a roof jack or roof vent that matches the duct diameter and roof pitch. Where backdraft or pests are a concern, select a steel roof vent with damper and screen. On flat roofs, use a jack built for 0/12. Add roof ventilation accessories such as flashing, sealant, foil tape, and duct connectors to complete the installation. In wildland-urban interface areas, check whether local code requires ember-resistant vent screens.
Frequently Asked Questions
Where can I buy roof ventilation products for bath fan and exhaust terminations?
This category lists roof ventilation products for exhaust terminations and attic airflow. It includes M&M steel roof vents with damper and screen, tapered roof jacks with vent cap, bath fan roof jacks, low-profile roof vents, and louvers.
What should I order for a 6 in. duct on a 5/12 pitch roof?
Order a 6 in. steel tapered roof jack with vent cap built for a 5/12 pitch. Confirm the duct is 6 in. in diameter. Then flash the jack under the upslope shingles and over the downslope shingles.
What is the difference between a roof jack and a roof vent for a bathroom exhaust fan?
A roof jack combines a flashing base, a pipe, and a vent cap, and it is sized for a specific roof pitch. A roof vent is a hooded termination, often with a damper and screen, set over a roof opening. Both terminate bath fan ducts. Choose between them by pitch, duct size, and the backdraft control you need.
Are roof louvers or ridge vents better on a hip roof with a short ridge?
Roof louvers are often used on hip roofs with a short ridge because they install near the ridge without needing a continuous ridge line. Use one exhaust type per attic, and size the louvers by NFA against the intake area.
Should I use a steel or aluminum roof vent for a bath fan or dryer duct?
Steel offers higher strength, and aluminum weighs less and resists corrosion. Either works for a bath fan when sized to the duct. For dryer exhaust, do not use a termination with a screen, because screens collect lint. Check the dryer manufacturer's instructions and local code.
How do I calculate attic ventilation with the 1:300 rule?
Divide the attic floor area by 300 to get square feet of net free area, and multiply by 144 for square inches. Then split the total evenly between intake and exhaust. A 1,500 sq. ft. attic needs 720 sq. in., which is 360 sq. in. of intake and 360 sq. in. of exhaust. The 1:300 ratio applies only where code conditions allow; the baseline is 1:150.
Why is cold air coming back through my bathroom fan's roof vent?
Backdraft usually means the termination has no damper or the damper is stuck open. Install a roof vent with damper sized to the duct. Check that the fan's own backdraft flap closes, and seal and insulate the duct in the attic.
What kind of vent cap keeps birds and insects out of a roof exhaust vent?
Use a roof vent cap with an integrated screen, such as a steel roof vent with damper and screen. The screen blocks birds and insects, and the damper limits drafts. Do not use screened caps on dryer exhaust.
How do I pick a roof jack for a flat roof versus a steep roof?
Match the jack to the measured pitch. Tapered roof jacks are built for set pitches: 0/12 for flat roofs, 4/12 and 5/12 for common residential slopes, and 9/12 for steep roofs. A matched jack keeps the cap plumb and the flashing flat.
Is it bad to mix roof louvers with a ridge vent or power fan in the same attic?
Yes. A ridge vent or power fan can pull air in through nearby louvers instead of through the soffit intake, which short-circuits airflow. Use one exhaust type per attic space and balance it with intake.
What roof ventilation accessories do I need to vent a bath fan through a shingle roof?
You need a roof jack or roof vent matched to the duct diameter and pitch, plus duct connectors or clamps, foil tape, roof sealant, and insulated duct for the attic run. These ventilation accessories complete a sealed termination.
What size roof vent do I need for a 4 in. or 6 in. exhaust duct?
Match the termination to the duct diameter. A 4 in. duct takes a 4 in. roof vent or jack, and a 6 in. duct takes a 6 in. termination. Reducing the size restricts airflow and lowers fan performance.
How does a balanced attic ventilation system work?
Intake vents low on the roof, usually at the soffits, bring outside air in. Exhaust vents near the ridge, such as louvers, let warm, moist air out. Air moves across the attic from intake to exhaust. In balanced attic ventilation, exhaust area does not exceed intake area.
Can a roof louver work as an intake vent if the house has no soffits?
No. Louvers are exhaust vents, and exhaust vents installed near the eave do not work as intake. Where soffits are not available, use a product designed for intake, such as a roof-mounted intake vent.
What does a low-profile roof vent with a sleeve do?
It is a short-hood aluminum termination with a sleeve that connects to the duct below the roof deck. Contractors choose it for 4 in. exhaust ducts where a lower roofline profile is wanted, such as on visible roof planes.