This message has been cross posted to the following Discussion Forums: Committee on the Environment and Technical Design for Building Performance Knowledge Community .
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A recent review of USDA plant hardiness maps for the US published in 1990 and 2006 indicate significant shifting northward of the climate zone borders as the US heats up from climate change. While the changes to date and very likely changes to come will affect everyone in every way, architects and building owners should be especially mindful about vapor drive from warmer exterior air through building enclosures during warm or hot months in humid areas. Extensive use of nonbreathable vapor retarder or barrier materials at exterior building enclosures such as foil or plastic sheets or the use of vinyl wall coverings or radiant barriers on the interior side of the insulation or enclosure assembly may lead to increased instances of condensing moisture within enclosures leading to mold, bacterial growth, rot, and corrosion. Buildings with such barriers should be inspected and reanalyzed regularly to address current and future environmental shifts. Where warranted and when technology is available, conditions such as these should be monitored. Where problems are discovered or determined as likely to occur, owners may need to consider renovations to prevent damage and hazards. For new work and renovations, design professionals should in most cases eliminate nonbreathable barriers from exterior enclosures to address current and likely future environmental conditions. Where hygrothermal analysis indicates barriers are required, they should be designed as part of the exterior side of the enclosure assembly in manners that allow condensation to dry harmlessly to the exterior over the life of the building. -------------------------------------------
Drake A. Wauters, AIA
TDBP Advisory Group
Architectural Technical Director
Arlington, Virginia
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