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Cars intake fresh air and exhaust spent air. Do roofing structures need the same?
As the laws of physics dictate, air flow and temperature play a great part in the durability of your roofing structure.
Why is airflow important?
Like a pond where still water grows stale, so too will air. This is especially true for air inside of attic space. Pests, mold, mildew, and moisture can spread rapidly, causing great amounts of damage that may be expensive to address. Additionally, without a proper way to exhaust air, hot attic air will evaporate through a roofing structure. This dries out shingles long before the end of the product life, causing them to become brittle and prone to cracking.
What components comprise proper airflow?
A great roofing structure will intake fresh air from outside via soffit vents or newer smart vents. Because air rises as it warms, this air pushes out stale hot air out from the top of ridges/peaks, through exhaust vents.
Intake Vents
These components allow fresh air into a roofing structure. Residential properties typically have several common types:
Soffit Vents - These are holes cut into where the roof meets the siding of the house, often covered up by grating or ornamental coverings. These allow fresh cool air to flow into the bottom of a roofing structure.
Soffit Channels - Shafts that are kept clear of insulation, roofing, or other material, to allow air to flow in and up to the peak/ridge of a roof.
Smart-Vents - These vents are placed not at the soffit, but lower to mid-level on the roofing slope. These also rely on special channels being cut into the roofing structure to push fresh cool air up to the top levels.
Exhaust Vents
These vents allow hot stale air and moisture to be exhausted out from the top of a home. There are several types of vents that can accomplish this:
Raised Ridge Vent - The very top part of a roof's ridge is actually cut, to allow hot air to exit. This cut is covered by rubber or other material, to prevent moisture and pests from entering the vent opening.
Box / Turtle Vents - Named because they sometimes look like 'turtles' on the side of a roof, these are located towards the top of a ridge. While they are easier for roofers to install and generally cost less, since they are not at the highest point on a roof ridge, hot air cannot exhaust completely.
Powered Vents - Consisting of powered exhaust fans that blow hot air out, these can be custom set to trigger upon the attic reaching certain conditions. Depending on attic square footage space, these may be the most effective for larger spaces.
How does lack of ventilation affect a roof?
Lack of good ventilation can affect your roof in a variety of negative ways - shingles dry out much faster, become more brittle, and can even crack from ice or hail impacts. Due to moisture escaping through the decking, nails oxidize much faster, and lose the ability to secure shingles to the decking.
Plywood decking can build up moisture and start to grow mildew or worse, mold. This puts occupants of the structure at risk for health ailments, while also greatly increasing the cost of tackling the problem. Finally, if not addressed, soft decking caused by moisture buildup could even collapse, given the right conditions.
All in all, having proper ventilation in a roofing structure can save property owners much grief and expense!
DGB Construction, Inc
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