Posted on: 10 November 2014
Attic ventilation is something that all builders, like those at John Criner Roofing Inc, would agree is a good thing; however, there are several ways to ventilate an attic, and that can be confusing to homeowners looking for information. To help you understand how to effectively keep air moving, you should learn why attic ventilation is important, as well as a few principles of good ventilation. Here is what you need to know:
Why attic ventilation matters
Even though most people believe that attic ventilation is beneficial only in summer, it actually benefits your home all year long. Here are the problems caused by unventilated or poorly ventilated attics:
Summer - when the sun beats down on your roof, it can raise temperatures inside your attic over 140 degrees Fahrenheit. Temperatures at that level will cause several problems:
- Damage your roof - The heat causes the asphalt in your shingles to melt and break apart, thus reducing their usable lifespan.
- Dry your rafters - Excessive dry heat can cause your rafters to "bake", and all interior moisture will evaporate. Extremely dry rafters are weaker than those that contain a normal moisture content.
- Heat the interior of your home - While it is true that heat rises, radiant heat also will pass through your insulation into the ceilings of your home's interior. This results in uncomfortable temperatures inside living spaces that will cause higher energy bills as your air conditioner tries to keep up with cooling demands.
Winter - during the winter, cold temperatures can create significant problems for your home:
- Introduce moisture into your attic - Attics without adequate air movement will tend to develop moisture problems in the winter. Due to rising heat from the interior of your home, condensation will form on rafters, flooring and the underside of roof decking. This condensation can soak into building materials and cause mold or wood rot.
- Create ice damming - In areas that experience significant snowfall, one of the most serious consequences that can occur from poorly ventilated attics is ice damming. Ice damming starts at the highest points of the inside of the roof; trapped attic heat melts snow on the exterior of the roof, resulting in water flowing down the roof where it is trapped by snow and re-frozen.
If snow stays on the roof for extended periods of time, the cyclical process of melting and refreezing will create an ice dam with multiple layers. The dam will collect water that pools and soaks into the spaces between and underneath shingles. This constant moisture will break down shingles and cause damage to the roof deck; leaks are a common occurrence in the presence of ice damming.
How to properly ventilate your attic
The consequences for not properly ventilating your attic can be serious and result in expensive damage to your home. Fortunately proper attic ventilation is a fairly straightforward, and it can be accomplished by following a few best practices:
- Keep air flowing along the underside of the roof from bottom to top - for ideal ventilation, exterior air should flow into the attic through vents located near your eaves, rise along the underside of your roof decking and out through vents at the peak of the roof. This movement will carry out excess heat that collects in your attic during the summer, and prevent moist air from condensing inside your attic in the winter.
Upward air movement also prevents ice damming in the winter by creating an even temperature gradient along the exterior surface of your roof. This prevents warm air from melting snow that will eventually form ice in the lower edges of your roof.
- Evenly distribute attic vents as much as possible - to avoid pockets of hot air from collecting in your attic during summer and to prevent areas of excessive dampness in the winter from forming, spread out intake and exit vents along the full length of your roof.
- Be cautious when using powered attic fans - powered attic fans that use electricity can increase the volume of air movement, but they can also suck air conditioned or heated air out of your home's interior through the ceiling. This wastes valuable cooled or heated air that is better used if it stays inside the living spaces of your home.