Proper attic ventilation ensures the lifespan of your roof system, the longevity of your roofing materials, and the efficiency of your heating and cooling system. How well-ventilated your attic is depends on the type of roof vents you have and their correct placement.
"You want to flush hot air out of the attic and make sure it's properly insulated," says Mike O'Brien, owner of Custom Exteriors, LLC in Colorado. In this article, we'll learn what proper roof ventilation looks like and the various types of vents to make that happen.
Types of roof vents
An attic ventilation system requires two types of vents: intake and exhaust. However, some vents, like the turbine or gable vent, can pull double duty. Here is a list of the most common types of roof vents and the pros and cons of each.
Intake vents
Simply put, intake vents are the vents that allow air to enter into the attic space of your home. Here are a few examples.
Soffit vent
The average cost to install a soffit vent is $35 to $64 each.
Soffit vent pros and cons
Pros
- + Allows cooler air to enter the attic
- + Allows more air to enter the attic than other options
- + Doesn't penetrate the roof deck
Cons
- - Easily blocked inside with insulation or stored items
- - Works best when paired with a ridge vent
A soffit vent is a perforated section of soffit installed every couple of feet the length of the house's eaves. When paired with exhaust vents like ridge or gable vents, outside air enters the soffit vent and pushes the hot air in the attic out of the exhaust vent.
Drip edge vent
Installing a drip edge costs from $2 to $4 per linear foot.
Drip edge vent pros and cons
Pros
- + Alternative to soffit vents on homes without eaves
- + Doesn't penetrate the roof deck
Cons
- - Not as effective as soffit vents
A drip edge is part of the roofing system that diverts rainwater into the gutters. It's placed under the first row of shingles at the roof's edge and is made of metal. A drip edge with holes in it pulls double duty by acting as an intake vent as well. Its placement allows for air intake right where the wind hits the roof.
Exhaust vents
An exhaust vent allows hot air to escape the home. Here are the most common exhaust vents used in residential construction.
Ridge vent
The average cost of installing a ridge vent is $7 to $13 per linear foot.
Ridge vent pros and cons
Pros
- + Barely visible
- + Static vent doesn't require power
- + Rarely leaks
Cons
- - Difficult to retrofit
- - Retrofit requires a shingle match
- - Must be paired with adequate intake vent, preferably soffit vents
Ridge vents come in 4-foot-long rigid panels or 20-foot-long rolls and are installed under asphalt shingles along the roof's ridgeline. Their low profile makes them a popular choice for homeowners. However, they're not suitable for a hip roof, according to O'Brien.
Off-ridge vent
The average cost of installing an off-ridge vent is $113 to $206 each.
Off-ridge vent pros and cons
Pros
- + Suitable for homes with complex roof design
- + Available in various colors
Cons
- - Penetrates the roof deck
- - Not as efficient as other options
Not a very popular style, off-ridge vents are used chiefly with homes that don't have a long ridge line. Typically made of galvanized metal, roofing installers cut a hole through the roof deck to install the vent about a foot below the ridge. Off-ridge vents come in 4-foot sections.
Gable vent
The average cost to install a gable vent is $45 to $320 each, depending on the size and type of material.
Gable vent pros and cons
Pros
- + Can act as intake or exhaust, depending on the other vents in the roof
- + Typically paired with an attic fan
Cons
- - Not suitable for non-gable rooflines
Gable vents are louvered vents installed at the peak of the gable end of the roof. They come in vinyl, wood, or metal to match the siding of your home. They're also available in different colors and styles.
Box vent (louver, static, turtle)
The average cost to install a box vent is $41 to $87, depending on the type and material.
Box vent pros and cons
Pros
- + Perfect for complicated roof lines
- + Easier to retrofit to an existing roof
- + Can be placed anywhere
Cons
- - Penetrates the roof deck
- - The average roof needs eight vents
- - Not aesthetically pleasing
Box vents come in various styles and shapes but are typically square-shaped. Depending on the size of the roof, you'll have multiple box vents strategically located so hot air and moisture escape the attic space. Box vents are also known as static vents, turtle vents, and louver vents and are the best option for complicated roof lines.
Turbine vent
The average cost to install a turbine vent is $95 to $201.
Turbine vent pros and cons
Pros
- + Easier to retrofit to an existing roof
- + Acts as intake and exhaust
- + Wind-powered
- + Need a fewer number than box vents
Cons
- - Penetrates the roof deck
- - Not aesthetically pleasing
- - Can be noisy if not lubricated
- - Need more than one
Turbine vents, also called wind turbines or whirlybirds, are losing popularity because they lack curb appeal. However, they are powerful vents that act as both an intake and exhaust vent when the wind is blowing. Also, being wind-powered makes them a dual vent–both active and passive.
Active ventilation vs. passive
Most roof vents work with airflow naturally and are, therefore, called passive vents. Other vents are powered either by electricity or small solar panels. Powered vents are referred to as active vents.
The advantages of powered vents include the ability to regulate operation automatically. By connecting a thermostat and or humidistat to the vent, you can set it to turn on when the attic reaches a specific temperature or humidity level.
One outlier to this active versus passive classification is the roof turbine. Powered by the wind, turbine vents draw air out of the attic more efficiently than when the air is still. However, even on non-windy days, they still act as passive exhaust vents.
How attic ventilation works
As the illustration shows, hot air rises to the peak of the attic space and escapes through an exhaust vent. As it rises, it draws cooler, fresh air from the outside through the intake vents. The continuous airflow reduces attic temperatures and drives out any damage-causing moisture.
A roofing contractor analyzes the size and design of a roof to create the best roof ventilation system for the home. They'll use measurements to calculate the correct number, types, and strategic placements of vents needed.
Signs you have poor roof ventilation
Ice dams are a sure sign your attic lacks adequate ventilation in the winter.
Houses with inadequate or out-of-balance attic ventilation will exhibit warning signs that are hard to ignore. "You can tell when the attic is under-ventilated," says O'Brien, "because granules start popping off the shingles. We call this blistering." He also cautions against combining two types of systems. "For instance, you don't want to combine a ridge vent and turbines," he says. "Otherwise, you just circulate the air out of the peak without drawing in from the bottom."
Here are some of the most common signs you need to improve your attic ventilation.
Ice dams form on the roof's edge in the winter.
The roof begins to sag or look wavy.
Cracked, curling, blistering, or loose asphalt shingles.
In the attic, you'll find:
Moisture or frost on the trusses or underside of the roof decking in the winter.
Excess moisture leads to mold, mildew, or rust.
Excessively hot summertime temperatures.
Extreme heat in the second story in the summer.
High energy bills.
Can I DIY roof vent installation?
Any homeowner with a saw can cut a hole in their roof and install a vent. The question is, do you want to? Since an effective roof ventilation system involves calculations based on the size and air capacity of the attic, this is a job best left to the professionals. "When I come across a bad system, I have to assume it was done by someone who doesn't understand what the system does," says O'Brien.
Roofing contractors know how to analyze the design of a roof, measure it, and determine how the air flows through it. "You have to take it on a roof-by-roof basis," says O'Brien. They can calculate not only the number and type of vents needed but also the perfect placement of them for the best performance.
Though cautioned against it, homeowners who want to tackle a roof vent installation can use a vent calculator to help them source the correct number and style of vents.
Additional considerations
When choosing and installing the roof vents for your home, there are a few additional things to consider.
Some vents, like box and turbine vents, penetrate the roof decking, which increases the risk of leaks.
You could save money on labor costs by replacing or installing new vents in conjunction with a new roof.
Damage to a roof due to inadequate ventilation could void the warranty on your roof materials.
Learn to inspect your roof and perform routine roof maintenance to prevent little problems from turning into big ones.
Frequently asked questions
In addition to intake vents and exhaust vents, roof vents are also categorized as powered vents and passive vents. Powered vents are powered to operate via electricity or solar when the attic space reaches a set temperature. They have moving parts, much like a fan. Passive vents are basically openings strategically placed to facilitate airflow from the cooler parts of the roof–the eaves–up and out the hotter areas–the ridge.
Vents under the roofline (or the eaves) of your home are there to allow cool air to be drawn into the attic space. They help to keep the space cooler and drive out moisture that could damage your roof sheathing and insulation.
Roof vents have three primary purposes. Supply vents simply ensure the attic space has fresh air. Intake vents allow cooler air to be drawn into the space. Exhaust vents allow hot air to be expelled as the cooler air is drawn in.
The best type of vent depends on the size and configuration of your home. Homes without long ridge lines are not best suited for ridge vents. Box vents penetrate the roof decking, potentially compromising the structure and allowing for points of possible leaks. To choose the best venting options for your home, consult with a professional roofing contractor.
When you consider the possibility of damage to your roof from inadequate ventilation and the higher heating/cooling costs, yes, adding roof vents will save you money.
While, technically, soffit vents are not in the roof, they play an integral role in attic and roof ventilation.
Carol J Alexander is a home remodeling industry expert for Fixr.com. For more than 15 years as a journalist and content marketer, her in-depth research, interviewing skills, and technical insight have ensured she provides the most accurate and current information on a given topic. Before joining the Fixr team, her personal clients included leaders in the building materials market like Behr Paint Company, CertainTeed, and Chicago Faucet, and national publications like This Old House and Real Homes.