XPS with tape sealed joints and penetrations has been demonstrated to perform as a code compliant air barrier layer in accordance with ASTM E2357 testing. Also, CI, extruded polystyrene (XPS) in particular, is sometimes used as the air barrier layer as well as the CI layer. Using a layer of CI to “wrap” the building enclosure in a “blanket,” covers the “holes,” the short circuits, maximizing wall system performance, minimizing energy cost and reducing the likelihood of deterioration. These thermal short circuits can also contribute to long-term moisture accumulation, condensation, wall system deterioration and reduce thermal comfort. If buildings are thought of as “buckets,” then these thermal short circuits are essentially “holes in the energy bucket” and can place additional demand on HVAC systems, wasting energy and costing money. These high conductivity components penetrate through cavities and/or cores where the traditional insulation layers in the wall are located, creating thermal short circuits that may reduce the thermal effectiveness by as much as 50 percent. Components including steel columns/beams, steel or wood studs, solid concrete or hollow core concrete masonry units (CMU) all have high conductivity elements that extend from inside to outside. In building enclosures, the structural wall layer, often steel stud, CMU, concrete or wood stud, has elements that by structural or mechanical necessity extend through the traditional insulation layer of the wall system. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope.” “Insulation that is uncompressed and continuous across all structural members without thermal bridges other than fasteners and service openings. It is defined in ASHRAE Standard 90.1-2013 as: Think of CI as a “building blanket,” wrapping the building in a layer of insulation to improve envelope/enclosure performance.
University of Mississippi Student Housing Phase II in Oxford, Miss.
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