Another major factor that determines how long your roof will last is ventilation. If there is inadequate ventilation, problems like condensation in the winter and excessive heat inthe summer will shorten the life of the roof system and cause major damage to the wood deck. Attics need to ‘breathe’. This picture shows what happens to the plywood when condensation builds up due to heat loss and there is inadequate ventilation.
This adds to the expense of roof replacement. To solve the problem, make sure there is at least R-30 insulation in the attic, and soffit vents and attic vents in the upper part of the roof. Here are 3 different types of roof vents available: