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Metal studs cause thermal bridging when erected next to existing masonry walls. To mitigate this thermal bridge, the authors propose to move the studs away from the masonry and install thicker batt to fill the entire cavity. This experiment addresses two questions: (1) How much does R-value improve when using batt that is thicker than the studs? (2) How much do gaps between batts degrade this improved R-value? A 4 ft (1.22 m) square test wall was constructed with a 5.25 in. (133 mm) deep cavity. Steel studs, spaced 16 in. (406 mm) on center, were set 1.75 in. (44 mm) away from the masonry (simulated by gypsum). Three insulation configurations were tested using a scanning heat flux meter. Clear-wall R-values were calculated from the heat flux profile across the center stud cavity. The base case used R-11 batt (RSI-1.94) and yielded R-8.5 (1.50). Completely filling the cavity with batt having an installed thermal resistance of R-17.2 (3.03) improved the R-value to R-14.2 (2.50). Introducing gaps the width of the studs decreased the R-value to R-12.8 (2.25). The apparatus was calibrated against a transfer standard obtained from National Institute of Standards and Technology (NIST).

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Citation: ASHRAE Transactions, 1998, Vol 104, pt. 1A, San Francisco