A well-ventilated attic has lots of benefits-the most significant being a reduction in heat retention that causes roof ice dams to form in winter and makes your entire house hotter in the summer.
Proper attic ventilation reduces moisture buildup and the resulting mildew growth that rots the framing and sheathing. A cooler attic can even extend the life of your shingles by keeping the surface of the roof cooler.
The question now is whether or not your attic needs more ventilation.
Do the math
Start with a simple calculation. Most building codes require approximately one square foot of venting for every 150 square feet of attic space, so a 1,500 square foot attic requires about 10 square feet of venting, including the soffit and roof vents in the calculation.
But don't assume that every 12" x 12" vent gives you a square foot of ventilation area; the vent framework and insect screening that covers the hole reduces the amount of air that passes through-sometimes by as much as half. Thankfully all attic vents have a Net Free Area (NFA) rating-the actual amount of open ventilation area, all things considered. The NFA number is printed directly on the vent by the manufacturer. Use this number when making calculations.
Other checks
Once the cold weather arrives in late fall, grab a flashlight and inspect your attic, looking for the following: frost on the underside of the roof or rafters; water-stained or blackened wood; and heavily rusted nails-all signs that warm, moist air is getting trapped inside the attic space.
There are several specific solutions to this problem. Most of the time it's simply a question of adding some more passive vents; however, in some cases, you will end up with a roof that requires more vents than you have room for. If this is the case, a solar-powered vent, which actually sucks the air from inside the attic, may be the answer. The Solar Star, solar-powered vent can provide up to 1,200 square feet of circulation coverage in one small unit. And because it's solar-powered you don't need to worry about wiring. The built-in motor exchanges air at a rate of up to 800 cubic feet per minute. For more information on the Solar Star contact www.solatube.com.
What you'll need:
A Reciprocating saw, cordless drill, tape measure, caulking gun, roofer's knife, marking chalk, hammer, small crow bar and a broad flat knife should be all you need to complete this simple project. Schedule the job for a warm (but not hot) and dry day to make working on the roof safer.
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