Attic Ventilation

One of the most interesting aspects of a home inspection is going into the attic space. This is an area where few homeowners venture and provides plenty of valuable information as to the condition of the home. One such important detail is ventilation. Do unfinished attics where nobody spends any time in really need ventilation? Absolutely!
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There are several reasons why poor ventilation needs to be corrected:

• Excessive summer heat can warp and prematurely age asphalt shingles.
• Cold temperatures can lead to a phenomenon known as ice damming, where snow melts and then refreezes, leading to potential roof leaks: most sloped roofs are designed to shed water and are NOT waterproof.
• Excessive humidity can buildup, leading to moisture in the attic. This can contribute to mold growth, reduction in insulation effectiveness and other issues that I have previously covered. As I have mentioned previously, moisture is the #1 enemy of homes and needs to be controlled.

While it is important for a roof to have adequate ventilation (usually about 1/300ths of roof’s surface) it should also be noted that too much ventilation can introduce too much moisture and can also lead to premature roof failure. A roofing contractor can offer recommendations to the appropriate level of ventilation.

Fortunately, attic spaces generally don’t need a lot of regular maintenance, but they should be checked at least a couple of times a year. One of the biggest issues I see are rafter baffles that have been knocked out of place by high winds. They are pictured in the diagram below and keep the soffit vent free of insulation.

How do you know if you have ventilation problems? Of course, you can always contact your friendly neighbourhood home inspector for help but here are a few clues that it may be time for further investigation.  

• An unexpected uptick in heating or cooling bills.
• Icicles or ice buildup near the gutters and edge of roof.
• Significantly less snow buildup compared to similar homes.
• Frost, microbial growth, or moisture buildup on the roof sheathing.​

There are many types of attic ventilation, but the most common type is a combination of soffit and ridge (roof peak) vents and has been very popular since the 1980s. There are other options that a roofing contractor can discuss should you have any concerns about inadequate insulation.