House interiors build up heat and moisture, especially in the attic. Keeping the attic dry and well-ventilated is important for preventing mold and for preserving the lifespan of your shingles. A ridge vent and an attic fan are additions that can ventilate and cool down attics.
Ridge Vent vs. Attic Fan: Major Differences
Roof ridge vents and attic fans both promote airflow in attics. Unlike attic fans, ridge vents are passive, not mechanical, ventilation devices. Also, ridge vents move air both in and out of an attic; attic fans mostly move air outward, from the attic's interior to the outdoors.
A ridge vent is a plastic or metal vent that runs the entire ridge of a roof to allow airflow.
After a slot is cut on both sides of the ridge, the ridge vent is installed over the top of the slot to protect the attic from debris, rain, and snow. Next, cap shingles are often installed over the ridge vent for better appearance. Some ridge vents do not need cap shingles.
Since heat rises, ridge vents let attic heat escape where it matters the most: the very top. Though the ridge vent's profile is low, its venting capacity is great because it runs the length of the house. Wind reaching the house from either direction can flow into the attic, though to a limited degree.
Ridge vents are passive cooling systems; that is, they do not require electricity or any other power to move the air.
An attic fan can be located either vertically on the home's gable or on the roof. When the fan is on the gable, the fan mechanism is entirely in the attic. When it's on the roof, it's located high on the roof, less than 24 inches from the ridge. Part of the fan is on the roof and part is located inside the attic.
In automatic models, when a thermostat in the attic senses that the temperature has reached a set point, it triggers the electrically operated attic fan to turn on and move the hot air from the attic.
Since fresh air must replenish the removed air, any attic fan installation must also have a passive air intake in the eaves, soffit, or fascia.
|Ridge Vent vs. Attic Fan|
|Ridge Vent||Attic Fan|
|What It Is||A long vent on the ridge or peak of the roof||An electric fan on the house gable or roof|
|How It Works||Lets hot air escape from the inside peak of the attic and allows some wind to enter.||Moves hot air out of the attic when it reaches a certain temperature.|
|How to Use||Ridge vents operate on their own; there is nothing for the homeowner to do.||Attic fans are first manually turned on with a switch or cord. After being turned on, they automatically operate when triggered by the thermostat.|
|Cost||$300 to $600||$400 to $1,000|
A ridge vent is easier to install when the roof shingles are first installed, but ridge vents can be installed retroactively, too. Roof installers cut through the shingles and the wood roof deck but stop short of the roof rafters, creating a 2-inch wide continuous slot.
Ridge vent material comes in coils that are unrolled along the length of the slot. Ridge vents are often finished off with cap shingles that match the roof shingles. Cap shingles are left open on the side to keep the vents exposed.
An attic fan can be installed relatively easily in a house's gable. If the fan is roof-mounted, it is a bit more difficult to integrate the fan with the existing shingles and protect against leaks.
Ridge vents blend in well with the roofline. Even with added shingles, ridge vents are barely more than 1 inch high. Since they follow the roof ridge, they are not usually visible.
Roof-mounted attic fans are visible and can be obtrusive, especially if more than one is installed. Gable-mounted attic fans are less visible, except when you happen to be looking at the roof from the direction of that gable.
Cost to Operate
Being passive venting devices, ridge vents are openings in your roof; they do not move. No motors are needed for operation. While ridge vents do occasionally need to be cleared of debris, there is no cost to operate them and little cost to maintain them.
Attic fans have motors and are electrically powered. The cost of operation depends on the climate, size of the house, and the number of attic fans installed. Most attic fans run off of 120V power. A 2,860 cubic foot per minute (CFM) attic fan can draw as little as 157 watts.
So, while attic fans do require electricity, the power draw is low and operation is only intermittent.
Which Should You Buy?
Attic ventilation of some type is required by most building codes. Ridge vents and attic fans can work in conjunction with each other. In this scenario, the ridge vent passively handles ventilation and cooling duties until it reaches its full capacity. Then, the attic fan takes over.
If you had to choose just one—and your attic has a great need for ventilation—an attic fan is your best bet. Attic fans in the $300 to $400 range can move upwards of 5,000 CFM.
For lower capacity ventilation at a steep cost savings, a ridge vent might be your best choice. Sixty feet of plastic ridge vent costs $100 to $200.
Roof Ventilation. 2018 International Residential Code (IRC).