Page 53 - October 2015 Green Builder Magazine
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Conditioned Attics: A Hot Topic
ABY JULIET GRABLE foam attic (http://bit.ly/1VkSrha). At the very least, monitoring www.greenbuildermedia.com 10.2015
CONDITIONED, ALSO CALLED unvented, attic is a the air can warn of potential moisture problems.
relatively new alternative to the vented attic, which
has long been the standard. In these attics, the Another reason builders have steered clear of conditioned
insulation—usually spray foam—is installed right up attics is the conventional wisdom that hotter temperatures
to the underside of the roof sheathing. The push for high- compromise the shingles on asphalt roofs. Research
performance homes is in part driving the trend. One of the by Building Science Corporation has shown that the
primary benefits of conditioned attics is that the HVAC unit, temperature differences are not as great as suspected,
when located in the attic, doesn’t waste energy heating or and that roof color and orientation have a greater effect.
cooling an unconditioned space. Consequently, some manufacturers now approve warranties
for asphalt shingles installed over so-called “hot” roofs, which
Although conditioned attics are gaining in popularity, included unvented SIPs roofs.
especially in hot, dry climates, many builders are reluctant
to accept them. Much of the controversy has been over Until now, spray foam has been the go-to option for
the potential for attics insulated with open-cell spray foam conditioned attics; however, blown-in fiberglass insulation
allowing the underside of the roof sheathing to become (and is part of the new ProPink High Performance Conditioned
remain) moist. This is a bigger problem in cold climates, so Attic System from Owens Corning. The system consists of
codes require a vapor barrier be used with open-cell spray PROPINK One foam sealant, ProPink Boxed Netting and
foam in climate zones 5 and higher. Building science expert ProPink loose-fill fiberglass insulation. It is approved for use in
Joe Lstiburek recommends conditioning the air in any spray- IRC/IECC climate zones 2B and 3B; Owens Corning requires
the use of a vapor retarder in zone 3B.
New Solution? Owens Corning recently developed a system for conditioned attics using blown-in fiberglass insulation. It has
been approved for use in parts of the warm, dry Southwest.
