Roof vents reduce moisture buildup in attics, help roofs last longer and reduce energy usage. Various types of vents are used, including gable-end vents, ridge vents and soffit vents. The latter vents are installed along the roofline. The type of vents needed largely depends on the climate.
Allowing moisture to build up in an attic can cause mold, which may be toxic. If an attic is humid, moisture may accumulate on the underside of the rafters or sheathing. Installing or replacing the roof vents helps ventilate this space.
The roof vents allow the moisture to escape to the outside, either through the gables, the peaked tops or through the ridge lines. Ridge lines are the seams along the top of the roof. Ridge line vents are installed at the end of these lines, with the air channeled out from the attic. The ridge lines are at a slight downward angle to facilitate flow.
If moisture or hot air have no vent to escape through, both are likely to push through the roof's surface. Shingles may start to lift up at the edges, which leads to roof leaks. During a storm, water can be forced under these edges by wind. Snow melt can also seep down through these gaps. Hot air escaping also means the furnace has to work overtime to keep the inside of the house warm, increasing energy usage.