How To Improve Attic Ventilation For Your Home

Attic vents are one of the unsung heroes in a home, quietly maintaining proper air circulation in your attic 365 days a year.

While most of us try to seal our homes from the elements with insulation, siding and high-efficiency windows and doors, attic vents are one place where it’s good to let outside air in. Here, we’ll discuss ways to improve attic ventilation with pro tips and advice from two industry experts: Reuben Saltzman from Structure Tech and Matt Fabry from Roots Construction.

Attic Ventilation Explained

Attic ventilation promotes air circulation to regulate temperatures and humidity levels in an attic. “You want your attic temperature the same as the outside temperature,” Fabry says.

Without attic vents, hot air has nowhere to go and builds up in the summer, raising cooling costs and reducing shingle life. In the winter, warm, moist air that seeps into the attic from the living space below gets trapped, causing moisture issues, mold and ice dams.

Good attic ventilation is key to preventing these issues.

How Does Attic Ventilation Work?

Strategically placed intake and exhaust vents create a constant flow of air through the attic. “Air enters the attic at the lower vents and leaves at the uppermost vents due to the stack effect [that] warm air rises,” Saltzman says. To improve attic ventilation, place exhaust vents near the roof’s peak and intake vents in the eaves.

Types of Attic Ventilation

There are several types of exhaust and intake vents available.

Roof exhaust vents

Exhaust vents are located near the top of the roof.

• Ridge vents: Ridge vents are integrated into the roof ridge, providing even ventilation along the entire roof length. To improve attic ventilation, use ridge vents along with baffles installed in the attic to allow air to flow past the insulation (Photo 9).
• Gable vents: Located near the top of gable walls. These vents work as intake and exhaust points for attic ventilation.
• Box or louver vents: Square roof vents installed between roof rafters, box vents are a popular choice on today’s roofs. Easy to install due to their smaller size (typically 18×18 inches), you will need numerous box vents to provide adequate attic ventilation.
• Turbine vents: These wind-powered exhaust vents use lightweight aluminum blades to catch passing breezes. When wind speeds reach 5 to 6 miles per hour, the turbine vent spins, exhausting air from the attic.

Roof intake vents

Intake vents are usually located in the eaves or soffits.

• Soffit vents: Often rectangular or square, individual soffit vents are evenly spaced along the soffit length. Continuous soffit vents are long, narrow strips of perforated panels that interconnect to form a continuous run along the soffit.
• Drip edge vents: These roof vents are installed in place of a typical drip edge as they have perforated holes to provide ventilation.
• Circular Vents: Available in 2-, 3- and 4-inch diameters, circular vents are ideal if you don’t have soffits. These are installed into the blocking between exposed rafter tails.
• Flash Filter Vent: This vent is a raised channel installed in the roof where it meets a vertical wall.

Attic Venting Requirements

Most building codes require 1 sq. ft. of venting (technically, “net free vent area,” or NFVA) for each 150 sq. ft. of attic. In some circumstances, you can have less, but we recommend the 1:150 ratio. So in a house with a 1,500-sq.-ft. the attic will need 10 sq. ft. of venting.

How To Improve Attic Ventilation

It is not difficult to install more vents to improve attic ventilation.

Split your attic’s total square feet of required venting between the intake and exhaust vents. Plan to place an equal number of intake vents on both sides of the house, evenly spaced along the soffits or roofline.

Space exhaust vents evenly across the roof as well. From the attic, drive a nail through the shingles to mark their location (Photo 1). Place all roof vents on the same side of the roof.

Ridge vents are more complex, so consider hiring a pro or having one installed during a roof replacement.

Attic Fans

Solar or electric attic fans can be used to exhaust attic air.

What are attic fans?

Attic fans are powered exhaust fans located on a roof or gable wall of a home. Installed like a box vent, these are more powerful than passive exhaust methods.

How do attic fans help with ventilation?

In theory, attic fans help expel air from the attic, increasing the intake air from lower vents. However, Saltzman does not recommend using attic fans to help vent your attic. “If the attic lid is not perfectly air-sealed (most aren’t), an attic fan will pull conditioned household air into the attic space,” he says. “This can lead to increased heating and cooling loads for the house and increased frost accumulation in the attic during the winter.”

Frequently Asked Questions

What’s the best ventilation for an attic?

“Every roof should have vents to allow air to enter at the lowest part of the attic, and vents at the top as well,” Saltzman says. The best type of vents for your home will vary. Fabry finds ridge vents to be the most effective exhaust vent solution.

What happens if an attic isn’t vented?

An unvented attic acts like a solar oven in the summer, raising your cooling bills and cooking the shingles. In the winter, snow melts on the roof and the water refreezes on the cold eaves, creating ice dams.

In addition, warm air that escapes the living space will condense on rafters or roof sheathing in an unvented attic. “Frost accumulation can lead to mold in the attic, water stains on the finished ceilings, wet insulation and deteriorated roof sheathing,” Saltzman says.

Can you have too much venting in an attic?

You can have too much exhaust ventilation but not air intake. Powered exhaust vents, in particular, can expel more air than can be replaced via intake vents and can begin to draw air from the living space.

Fabry also cautions against combining too many types of venting. “You should not have gable vents with ridge vents and soffit vents,” he says, “It defeats the purpose.” The ridge vents will pull air from the gable vents instead of the soffit vents and reduce their effectiveness.

Should you block attic vents in winter?

No. Attic vents prevent ice dams and trap moisture during the winter. “Most of the reason you have roof vents is because of the stuff that happens during the winter,” Saltzman says.

Can water or animals get into roof vents?

Yes. Cracked or damaged vents can allow water into the attic and should be replaced. Keep animals out with roof vent covers made of metal mesh.

About the Experts

• Matthew Fabry is the owner of Roots Construction in Easthampton, Massachusetts. He is a licensed general contractor in the state.
• Reuben Saltzman is the owner and CEO of Structure Tech, a home inspection company in St. Louis Park, Minnesota.