An effective roof ventilation system is essential in equalizing temperatures on both sides of a roof. It keeps your house cooler in the summer and prevents ice dams in the winter (if you live in a cold climate). If ventilation is insufficient, condensation can develop causing insulation and wood deterioration. Determining how much ventilation is needed requires measuring your attic floor. Generally, one square foot intake and outtake ventilation is required for every 300 square feet of unheated attic floor space.
Basic Roof Vents
When you need increased outtake ventilation, roof vents are a good choice to add near the ridge line. These covered fixed vents, which prevent rain from seeping in, are easy to install. They should be placed two feet apart for the best results. Because they have no mechanical parts, you don't have to worry about a malfunction.
Continuous Ridge Vents
This screened, water-shielded ventilation opening is available in 10-foot lengths and creates an even outtake airflow. It spans the entire gable roof ridge and is recommended for new construction. Unlike other vents requiring placement in several locations, a continuous ridge vent is one running piece. This makes it easier and quicker to install. It is available in colors to match the roofing, and is aesthetically pleasing because it is unnoticeable from street level.
Wind Turbine Vents
Installed near the roof peak, a wind turbine works by catching the wind or by air rising through the turbine. This causes the vanes to spin and provides effective ventilation near the top of the house by drawing heat and moisture out. The problem with these vents is that high winds can cause excessive spinning and wearing of the bearings. The vanes can also stick, and therefore stop rotating.
In order to achieve the most efficient roof ventilation, in addition to outtake vents it is equally important to have soffit vents, available in various sizes--3-inch round, 4X16 inch and 8X16 inch. Using a continuous length soffit vent is another option. Soffit vents are installed beneath the underside of a roof overhang. These vents permit air flow to the attic, or the space below the roof sheathing.
Gable and Dormer Vents
A gable vent in the triangular wall beneath the end of a gable roof is also required. This vent is a screened, louvered opening used to exhaust excess heat and humidity from an attic. It is available in wood or aluminum. If you have a dormer, a dormer vent is needed. Vents for both gables and dormers are available in many colors, styles and shapes to match the siding.