Original Article by: GAF

Ventilation is defined by the U.S. Department of Energy as "the exchange of indoor and outdoor air." This sounds simple enough, but if your home's attic is not properly ventilated, excess heat and moisture cannot escape and can lead to a plethora of concerns for your home, your roof, and your wallet.

Proper circulation of outside air through your attic space is possible with the right attic ventilation system, which is a specific combination of intake and exhaust vents that work together to allow fresh air from outside to get in while expelling heat and moisture-laden air from your home. A good way to help ensure your home has the most suitable system is to follow the building code ventilation requirements that apply to its particular structure.

Understanding Roof Styles

Not all roof styles are created equal, and neither are attic ventilation systems. Different roof styles often require particular types of attic intake and exhaust vents, and it's important that they're able to balance the amount of air they take in against the amount they expel. Attic ventilation systems fall into two broad categories: static (also known as "passive") and mechanical. In a static system, outside air enters into the attic through soffit/eave vents and exits through vents positioned at or near the top of the space. In order for static ventilation to work, approximately equal amounts of ventilation must be placed at both the entry and exit points. Mechanical systems use engines that are able to force air to ventilate, though it is still important to provide for adequate intake air to make this possible. Mechanical systems are most often used with hip roofs, where the ridge length is shorter.

Gable Roof Ventilation

This is one of the most common roof styles. The two broad sides of the "triangle" that make up the roof rise to meet at the ridge line running along the top. Gable roofs make soffit ventilation (also known as undereave vents) ideal as the intake for fresh air. Soffits are located under the eaves—which is where your roof meets the exterior walls of your home.

Ridge vents are installed at the highest point—the roof ridge where the two sides of the roof meet— and exhaust hot, moist air. One of the most common attic ventilation systems, this is a passive system that performs naturally and without requiring electricity or solar power to operate. Gable-mount power attic vents offer another option for exhausting heat and moisture from this style of roof, but they will require a power source (and therefore careful consideration before installing) to run.

Hip Roof Ventilation

This roof style typically consists of four sides that slope up to meet at a smallish (relative to gable roofs) ridge line at the top. Hip roofs are similar to gable roofs in that they typically have a soffit or undereave vent for the air intake.