Proper roof ventilation, or lack thereof, is the reason many asphalt shingle roofs reach the end of their life spans early. Many homeowners think the elements on the outside is the reason for a roof aging when in reality it’s the heat in the attic space that is to blame. The FHA (Federal Housing Administration) recommends 1 square foot of attic ventilation (intake and exhaust) for every 300 square feet of attic space. Many homes do not have the proper ventilation. Many times in re-roofing we will find that the only means of both intake and exhaust are gable vents. The idea was once good but in reality a full cross ventilation is rarely seen. If the wind enters a gable vent at any other direction than dead straight on, a negative air pressure will occur and the wind will turn around and exit the gable that it entered. This leaves static dead hot air in the attic which will transfer through the plywood to the asphalt shingles depleting the petroleum from the asphalt causing the shingle to age rapidly. Far faster than the manufacturers estimation. (i.e.: 25-50 years)
Many times we will see Ridge Vent with no source of intake or intake with no source of exhaust. The bottom line is that the manufacturers want to see intake at the lowest point of the attic (i.e.: the soffit or eve) and exhaust ventilation at the highest point of the roof ridge line. To ensure you have the proper balance consult with a certified residential roofing contractor. To have a valid warranty is to have the proper roof ventilation.