More roof venting basics
SPY ON THE NEIGHBORS
If your roof is bare while neighboring roofs are still snow-covered, it could be a sign of trouble. While your roof may just be warmer because of its design or its more extensive southern exposure, it could also mean that you have poor ventilation or inadequate insulation.
CUT COOLING COSTS?
Attics get super-heated by sunshine, and some of that heat is radiated to rooms below. So it’s reasonable to think that better ventilation would lessen the radiated heat and reduce the load on your cooling system. But most studies find only minor savings with
improved ventilation. Adding attic insulation is usually much more effective.
WHAT ABOUT ‘HOT ROOFS’?
A “hot roof” has insulation directly under the roof sheathing and doesn’t require ventilation. With careful design and installation, a hot roof can be trouble-free.
COOLER SHINGLES LAST LONGER
Heat slowly degrades asphalt shingles. Ventilation helps to keep them cooler, extending the life of the roof. However, the effect of ventilation on shingle life depends on many factors, especially climate; venting matters most in hot, sunny regions. Most shingle manufacturers void their warranties if roof venting standards aren’t met.
HOW MUCH IS ENOUGH?
Building codes generally require 1 sq. ft. of vent area for every 300 sq. ft. of attic floor. That assumes half of the vent area is high on the roof and half is low (in or near the eaves). Otherwise, doubling the vent area is required (1 per 150 sq. ft.) These are minimum requirements; there’s no such thing as too much ventilation.
VENTS GET PLUGGED
Soffit vents often get plugged by debris, cobwebs or stray insulation. You can clear them with a compressor and an air nozzle or a leaf
blower. Wear eye protection!