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Homeowner’s Guide to Proper Attic Ventilation
Why Ventilate?
More than any other part of your house, the roof is subject
to extremely high heat, both on and under the roof deck. In the summer,
on a clear 90°F day, the sun can heat the roof shingles to 170°F.
Left unvented, heat can build up to as high as 140°F inside the attic,
temperatures which can damage shingles. Eventually
this uncontrolled hot air can penetrate the home's living space, warming
the area below and causing increased demands on air conditioners and increased
utility costs. A properly ventilated attic enables this extreme heat to
escape outside.
The result: Lower air conditioning costs in the Summer.
In the winter, moisture from the house condenses in the attic and settles
in the insulation. When wet, insulation loses its effectiveness (sometimes
dropping to as little as one-third its original R-value) and allows valuable
heat to escape through the attic. Even worse, soaked insulation can cultivate
mold or mildew, as well as stain or crumble ceilings. A properly ventilated
attic provides an exhaust system, and moisture can escape.
The result: Better insulation performance and lower heating
costs in the Winter.
An additional danger during the winter months is the formation of ice
dams. Properly vented roofs help prevent the formation of ice dams.
The result: Less damage to the interior of the house and longer lasting
roofs.
Of
all the reasons to ventilate an attic, however, the most important
is to preserve the structural integrity of the roof. At all times
during the year, heat and moisture accumulate in every attic, and
when left uncontrolled, excessive heat and moisture often result
in significant damage to the roof and structure—reducing their
normal life expectancy. Proper ventilation validates the shingle
manufacturer's warranty, and protects the roof and ceilings from
both heat and moisture.
The result: Long life, beauty, and optimum performance
from roofing and housing structure.
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