attic ventilationAs roofing contractors, our job is actually more than just providing external waterproofing to the roof of your home or commercial building. In fact, the choice of attic ventilation, and the volume of air brought into and out of the attic has a very large impact on the energy efficiency of your home.

The Basics of Ventilation

Attic ventilation, at first glance, may seem to be counterintuitive. After all, how can allowing a stream of cold air into your attic in the winter actually be a good thing? Even more perplexing is the idea of allowing hot air into the attic in the summer, that be a good thing either, can it?

In reality, this exchange of air from the exterior of the home through the attic vents, or soffit vents, is important to keep the attic at a constant temperature level. In the heat of the Florida summers, the outdoor air is still cooler than the superheated air trapped in the attic, and the vents bring in that cooler outside air and force the superheated air outside.

In the winter, the exchange of air from the interior and the exterior prevents moisture from building up in the attic, something that can lead to damage over time if not addressed and corrected.

How is it Calculated

Determining the amount of intake and exhaust needed for your attic ventilation is based on very specific calculations. This determined by the attic square footage, so it is relatively simple to calculate once the attic is measured.

The quick formula is actually the square footage of the attic divided by two. This will give you the square inches of both unobstructed intake and exhaust needed for the home. All non-motorized vents will have an NFA (Net Free Area) number which is the unobstructed area for air to pass.

It is important to have approximately a 50 percent intake and a 50 percent exhaust in square inches to allow maximum ventilation efficiency. Keep in mind in our hot climate reducing the interior attic heat in the summer months not only helps to reduce your air conditioning energy use, but it also helps to prevent excessive wear and tear on shingles.

Incorrectly vented attics that accumulate heat can result in shingles that lift, cup and curl, leading to increased risk of leaks and the need to replace your roof much earlier than you anticipated based on the average life of your roofing system.