A ventilation louver is a device that enables air to flow through it while keeping out dirt, water and debris. These devices are frequently used in the roof of a house to encourage airflow in the attic, which is prone to overheating.
Ventilation louvers are units that have fixed or functional blades placed in a frame. They are used in the roof of a house to prevent hot air in the attic from melting snow and causing ice-dam formation that can wear out the roof. Louvers also prevent hot air from causing condensation under roof decking in warm weather. Use of an inappropriate type of louver may lead to water leakage.