The appropriate amount of roof and eave ventilation and the balance between the two, is very important in keeping your attic and roof deck free from moisture. A poor performing ventilation system is at risk of condensation and mold spores. In the winter, the attic will be much warmer than the outside. Even with good insulation the difference in temperatures can cause moisture. If there is no airflow this moisture will not dry out fast enough and can develop mold causing damage to the roof deck and accelerated failure to the roof shingles.
An appropriate ventilation system starts with the required amount by code, of roof vents determined by the size of an attic space. The ventilation system needs to be balanced between the eave vents (in-flow) and the roof vents (out-flow). The eave vents (in-flow) and the roof vents (out-flow) must have an equal amount of free air space to create the appropriate pressure for the air to flow. Most homes that are 20 years and older are not properly ventilated and balanced.
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