Attic Ventilation & Asphalt Shingle Roofs

Attics are in the realm of movies – scary and filled with ghost, cobwebs – or full of romantic and nostalgia of things long forgotten. In the movies that is, in real life they are an essential barrier and complex system designed to keep your family and property safe from the elements. The issue of attic ventilation and the amount of ventilation necessary however is controversial, as well can vary depending on the roofing system installed.

At A Clark Roofing and Siding Lp., we know your roof is your home’s first defense against harsh weather. As one of the most respected roofing and siding companies in Edmonton, we specialize in roofing solutions that are affordable, long lasting, and that meets both manufacturer’s and Alberta Building Code standards.

When it comes to ventilation and asphalt shingles, some asphalt shingle manufacturers’ warranties may make coverage conditional on meeting their minimum ventilation requirements. Homeowners should consult manufacturers for specific ventilation requirements when selecting an asphalt shingle product.

According to the US-based National Roofing Contractors Association, “the strongest case for ventilating asphalt shingle roof assemblies with outside air exists for residences located in cold climates and where snow accumulations persist on roofs for extended periods of time [like Edmonton, for example]. Under those sets of conditions, ventilation has been shown to be a valuable strategy for removing excess moisture from attics, thus preventing condensation that can damage roof sheathing and preventing ice dam formation.”

The most common way to provide attic ventilation for asphalt shingle roof assemblies is by passive ventilation, relying on natural air convection – the upward movement of heated air because of its lower density – and wind-generated pressure differences. Natural convection is responsible for initiating the upward flow of air through an attic. Convection-assisted ventilation is most effective when approximately equal amounts of ventilation opening areas are placed at the soffits or eave and at or near the top of the attic space.

According to Municipal Affairs Alberta’s Performance Guide: NHBPO (09/01/15, page 279), Section 15.22 Attic ventilation is inadequate, states that “attics shall be ventilated in accordance with the Alberta Building Code,” with a one-year warranty for defects in materials and labour. Roof vents should be kept free of obstructions as inadequate attic ventilation can lead to heat and moisture problems.

If you have concerns about your attic, it could be a vent issue call A. Clark Roofing & Siding LP at 780.465.7571 today for a free quote – we’re the neighbor you can trust for your roofing and siding needs.

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