PROPER ROOFING VENTILATION
*WHAT IS ATTIC VENTILATION?
INTAKE AND EXHAUST
"Ventilate" comes from the Latin word for "to fan." Simply put, it's the action of moving air. Out with the hot. In with the cool. And that's exactly how ventilation works. It provides conditions that allow air to flow. Every time stale, overheated air in your home or attic is vented out and fresh air is pulled in to replace it, you have what is known as an "air exchange."
A BALANCED SYSTEM
But ventilation is much more than a simple breeze blowing through your house. It's a process that provides a steady, high volume of air movement. Think about it as a system of components, all sized and positioned to provide constant intake and exhaust of air.
BENEFITS OF ATTIC VENTILATION
A well-ventilated attic will help reduce your energy costs several ways. Improved air circulation in the summer months will help remove hot air and reduce the temperature of your attic. This will keep the hot, stagnant attic air from seeping through into your living area. It will also help reduce the surface temperature of your attic floor and your interior ceilings.
The reduced temperature in your attic will also assist your air conditioner by keeping the ductwork and the air inside cooler. The resulting effect will be cooler air flowing through your HVAC system and reduced strain on your a/c unit.
Extend the Life of Your Roof
When your attic heats up, the roofing underlayment beneath your roof shingles can also heat up and, over time, become brittle and ineffective. By lowering your attic temperature you can extend the life of your roof and save the expense of repairs and replacement.
Remove Moisture and Reduce Harmful Mold and Mildew
During the winter months, warm, moist air from inside your home rises into the attic and collides with the colder underside of the roof. Proper attic ventilation can help remove the moisture and condensation that can build from this event.
EVALUATE YOUR NEEDS
There are a number of variables to consider when selecting the most effective ventilation system for your home. Before you make any decisions, go up into your attic and take a look around. A sure sign of poor ventilation is an unbearably hot attic in the summer. Another thing to check is evidence of moisture, such as mold, mildew, rusted nail heads, damp or compressed insulation or wood rot.
Once you've completed a general inspection of your attic, look for ventilation systems already in place, such as gable vents or roof louvers. Note the size and locations of each. Do the same with intake vents, including soffit and eave vents.
Finally, make an estimate of the square footage of your attic. Most are slightly larger than the size of one floor in your home. You'll need this figure to make sure you install adequate ventilation.
If your roof pitch is 7/12 to 10/12, plan to add 20% to your calculation for vent requirements; 30% for roof pitches of 11/12 and steeper.
According to most building codes, you need one square foot of vent area for each 150 square feet of attic floor space. The minimum is one square foot for every 300 square feet of attic floor space if there is a vapor retarder or the space is balanced between the ridge and intake vents. A balanced ventilation system means about 50 percent of the required ventilating area should be provided by exhaust vents in the upper portion of your attic with the remaining 50 percent provided by intake vents.
Please remember, building codes specify the minimum amount of ventilation. You may want to increase the requirement to ensure proper ventilation.
Too many times, homeowners install products that short-circuit their ventilation system. When designing a ventilation system, avoid these common pitfalls
*Taken from AirVent