Homeowners aren't often told about the importance of roof ventilation to the longevity of their roof. They also aren't usually told that an improperly vented roof will reduce or void the warranty of their shingles. It's a very important subject that homeowners need to know something about.
Will reduce or void warranty
The simple fact of the matter is that an improperly vented roof will build up heat during the summer months which will cause the shingles to wear out prematurely. They will start curling and bending and/or losing granules way before their time.
CertainTeed is one of the top shingle manufacturers and Absolute Roof Solutions use its products. Their 2019 Asphalt Shingle Products limited warranty states: "Any shingles applied to inadequately ventilated or non-ventilated decks ... are subject to a reduced limited warranty period of ten (10) years..." Depending on the product installed, their usual warranty period is from at least 20 years to a lifetime.
Causes of improper ventilation
Improper ventilation happens for four reasons:
1. the roof has an insufficient number of vents for the size of the roof,
2. the vents are too small,
3. the vents are in the wrong places, or,
4. the vents are plugged.
A roof might have any combination of these factors.
How ventilation works
It is important to understand how roof ventilation works. The sun heats the roof and air in the attic becomes hot. So the hot air rises and wants to escape. Vents placed at the highest points of the roof allow this to happen. Ridge vents are the usual solution today. Older homes sometimes had gable vents.
But this hot air can't rise if there is no way for other air to come in and take its place. So, to allow cooler air to come into the roof to replace the hot air, there needs to be vents lower down in the soffits.
Complications come into play when attic insulation blocks the soffit vents, or there are not enough vents in the right places, or they are not big enough to properly allow the airflow.
It is even possible to create a massive problem for a roof by installing a new ridge vent on a home with gable vents. Because the ridge vent is higher, the gable vents will now flow air in, rather than out. This change in airflow direction will cause the gable vents to suck water into the roof when it rains, creating leaks and damaging insulation. Knowledgeable roofers know is essential to plug these vents if a ridge vent is installed.
This is why a roofer needs to have access to your attic. He needs to check these things. It is even in the building code that for every 300 square feet of a house, there needs to be one square foot of ventilation. This needs to be split 50 percent on the perimeter and 50% on the ridge.
It is not a matter of just putting in a few vents willy-nilly. There is a precision that is needed here.
How to tell a good roofer
A good roofer will ask to check your attic. If he doesn't, he probably doesn't know what he is doing.
At Absolute Roof Solution, we do know what we are doing. We have been doing roofing right for over 20 years. It is a standard procedure for us to check the attic of every roof we replace.