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TO VENT OR
Not to Vent…
Deciding on which strategy is best for attic applications
by Mason Knowles
Photo courtesy CertainTeed
FOR DECADES, DESIGNERS OF ATTICS
AND CRAWL SPACES HAVE USED
CROSS-VENTILATION TO MINIMIZE
THE POTENTIAL FOR MOISTURE
ACCUMULATION AND CONDENSATION.
HOWEVER, SPURRED BY RECENT CLAIMS
OF ENERGY SAVINGS AND MOISTURE
CONTROL, UNVENTED ATTICS HAVE
BECOME POPULAR IN BOTH RESIDENTIAL
AND COMMERCIAL APPLICATIONS. WHILE
THESE ATTICS CAN BE USED IN MANY
CIRCUMSTANCES, THIS AUTHOR BELIEVES
THERE ARE REASONS TO USE VENTED
ASSEMBLIES IN MANY SITUATIONS.
Traditional methods of insulation materials and
design call for using air circulation within the attic
space to assist in drying excess moisture. In heating
and cooling climates, this moisture could potentially
travel through ﬁber insulation in building cavities.
The traditional remedy to this wetting is to slow
the inﬂux of moisture-laden air into the cavity by
using an interior vapor retarder, and by ventilating
the roof cavity to the exterior in order to facilitate
the carry off of moisture (i.e. drying).
When done correctly, attic venting can reduce the
potential for condensation in winter and summer.
During winter, the primary cause of attic moisture
issues stem from warm moist air inﬁltrating into the
32 the construction speciﬁer | july 2013
6/14/13 8:28:00 AM