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The underside of a roof overhang is called the soffit. An element that allows air to pass through this space is the soffit vent. Typically, the soffit is a solid surface such as wood, plywood, aluminum, or vinyl. The vent is normally in the form of a prefabricated panel or perforated strip.
Building codes require soffit vents for the proper ventilation of attic spaces. The soffit vent allows fresh air to enter the attic space through the process of convection or by means of a power vent. Hot air is then expelled through roof mounted or gable mounted exhaust vents. The constant air flow creates a well ventilated attic space. Moisture and hot air are removed from the attic, providing better insulation performance and a longer roof life.
The soffit vent can be a continuous strip of metal or plastic running the full length of the soffit. Perforated or cut and expanded metal are common types. Some styles incorporate a screen backing to keep out insects. The materials commonly used to manufacture vents are steel, aluminum, and vinyl.
Full and partial soffit vent panels are available with vinyl and aluminum siding products. These perforated panels are cut to the full width of the soffit and can be installed continuously or at specific intervals. Maximum soffit ventilation is considered beneficial.
Products are available for older homes that do not have soffit ventilation. Holes can be drilled into the solid soffit and vent plugs can be inserted into the holes. These round vents are typically metal or plastic with louvered vents. Rectangular vent panels are also available to install over vent holes cut into the solid soffit.
The soffit vent is an integral member of the attic ventilation system. The ventilation system should include roof or gable exhaust vents. Continuous ridge vents can be installed for superior ventilation performance. The air should flow freely from the soffit vent to the ridge vent without blockage from insulation. Single roof vent units are also available and should be installed near the highest points on the roof.
The power attic vent may be the best choice for attic ventilation. An electric fan is controlled by a thermostat in the attic. The exhaust fan is activated when the air temperature reaches a set level. Fresh air is then drawn through the soffit vents and exhausted through the power vent. Power vents can be roof mounted or gable mounted.