Ashrae Journal - December 2008 - (Page 62) Photo 1 (left): W estford House. A happy architect surveying the ἀeld of battle—built tight and ventilated right—2,300 ft2 of conditioned space including the basement. Photo 2 (right): Advanced Framing. 2×6 studs on 24 in. (centers, stack framed, single top plates, two stud corners, no jacks, no cripples). Almost 40% of the framing elements that are typical in traditional wood frame construction have been removed. The framing factor is reduced from 25% to less than 15%. The exterior sheathing was foam board insulation. Racking resistance was provided at corners by structural sheathing Photo 3 (left): Benchtop Testing. Screws experience mostly shear and not moment (bending) loads because the scr ews can’ t r otate into the foam due to the compressive strength of the foam pushing back against the 1×4 wood furring. Photo 4 (right): Cladding Attachment. Standar d cladding attac hment is used to attach cladding to the 1× 4 wood furring. Published tables for cladding attachment that are f ound in the model b uilding codes are followed. Designing a High Performance House The Westford House is a product of the Building America program (BAP), which is a U.S. Department of Energy initiative to develop innovative system engineering approaches to advanced housing. The technology developed under BAP was applied by architect Betsy Pettit in the Westford House designed for the local chapter of Habitat for Humanity who also was responsible for its construction (Photo 1). The house features an R-66 roof, R-46 walls, R-26 basement perimeter insulation and R-10 under slab insulation. The framing is an “advanced frame 2×6” where studs are 62 ASHRAE Journal on 24 in. (609 mm) centers, stack framed, single top plates, two stud corners, no jacks, no cripples. Almost 40% of the framing elements typical in traditional wood frame construction have been removed. The framing factor was reduced from 25% to less than 15%. Enough board footage was removed such that the 2×6 frame package cost approximately 5% less than a traditional 2×4 frame package. The exterior sheathing was foam board insulation; racking resistance was provided at corners by structural sheathing (Photo 2). The exterior of the wood frame structure was insulated with 4 in. (100 mm) of foil-faced polyisocyanurate rigid ashrae.org December 2008 http://www.ashrae.org
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