Types of Attic Vents, Maintenance & More
Attic ventilation is probably not something you pay attention to on a regular basis. But insufficient airflow through your roof can cause a variety of problems including ice dams, moisture accumulation and unwanted heat retention.
Since you're probably not an attic ventilation expert, work with someone who is. ImproveNet can connect you with up to four vent contractors in your area for free! They'll be able to maintain and repair your existing vents or recommend and install the ventilation you need. If you're curious about how it all works, read on.
While the type and number of vents will vary depending on the specific house design, location, and amount of direct sun, a minimum attic venting system should have one square foot of vent area for every 300 square feet of attic area. When it comes to vents, more is better, and every vent mounted high on a roof needs a counterpart on the lower roof, usually under the eaves. With this arrangement, hot air rising through the upper vents will pull cooler air into the attic.
Ideally, air circulates in the attic by being drawn up through a continuous soffit vent, through the attic space, and then out the ridge through a continuous ridge vent. This is the smoothest and most efficient system. However, few houses have continuous soffit and ridge vents. Most houses, however, do have some type of vent in the roof or an opening at gable ends. Houses with no rafter overhang, or a very short one, may not have soffits. Older houses may not have vents between the rafters leading into the attic space. Venting was not a major problem in older houses because they leaked air everywhere. With the advent of better roofs and tighter house construction though, moisture became a more significant issue.
Calculating the number and size of attic vents is not an exact science but instead is influenced by the climate, the roof pitch, available locations for vents, and the house's orientation to prevailing winds. The Asphalt Roofing Manufacturers Association states:
"In most cases, a minimum free-flow ventilation area equal to one square foot per 150 square feet of attic floor area must be designed and properly installed to provide proper ventilation. Where a properly designed and installed eave and ridge ventilation system is employed, a free-flow ventilation area equal to at least one square foot per 300 square feet of attic floor area is often sufficient. Combination eave and ridge venting is generally recognized as a superior venting technique."
Vent screens should be cleaned regularly because accumulated dust and grime can significantly restrict air movement. Fans connected to thermostats can be placed at gable end openings to draw hot air out of the attic space when temperatures reach a preset level.
Attic Vent Types
Types of vents to consider installing for your attic include:
- Soffit vents: These vents are installed in the soffit (the enclosed portion under the roof overhang) and permit air to flow up under the roof and into the attic. They range in style from 6-inch round stainless steel vent covers that are placed in the soffit between each rafter to continuous vents that run the entire length of the soffit.
- Continuous ridge vents: These vents run the length of the ridge and replace the ridge shingles or tiles. They are designed with interior baffles that permit air to flow out but prevent rain from blowing in.
- Turbine vents: Common on many roofs, the vent top spins on ball bearings. The slightest wind turns the vent, which in turn draws air from the attic.
- Eyebrow vents: Also called turtle vents, they provide curved openings on roof slopes. They should be used in pairs with one on each side of the roof to facilitate air movement.
Whole house fans or wind turbines are also an idea for efficient cooling. When whole-house fans are used in conjunction with roof wind turbines a temperature drop of three to eight degrees can be achieved within minutes. Wind turbines work by drawing in the cool outside air, flushing all the hot air out of your home and attic in minutes.
Ventilation requirements may vary greatly, depending on which state your home is located, as well as the structure's conditions. Proper attic ventilation will help prevent structural damage caused by moisture, increase roofing material life, reduce energy consumption and enhance the comfort level of the rooms below the attic.
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