This paper presents and analyzes the experimental results from a full-wall (guarded hot box) thermal testing study performed by Architectural Testing, Inc., of York, PA. The tests were performed on 8 ft. x 8 ft. wood frame walls insulated with three types of cavity insulations: fiber glass batts, open-cell spray polyurethane foam (ocSPF) and closed-cell spray polyurethane foam (ccSPF). In addition, thermal performance of a combination of ccSPF and polyisocyanurate insulated sheathing is also measured. This full-scale test method goes beyond simple thermal conductivity testing of insulation materials and includes real-world effects of air infiltration and mean temperature. Specifically, it includes the effect of air infiltration by simulating a 15 mph wind applied to the outside surface of the test walls. In addition, the effect of mean test temperature on wall thermal performance is measured using outdoor temperatures of-15°F, 25°F and 115°F. A Wall Performance Index (WPI) is determined for the different walls tested, providing a rating of actual versus expected thermal performance. Results show WPI is dependent upon mean temperature and air infiltration. The WPI for fiber glass insulated walls are significantly reduced by wind loading and changes in the mean test temperature. Walls made from open-cell foam show consistent WPI values that are lower than expected, but relatively unaffected by wind load and external temperature. Closed-cell spray foam shows WPIs that are consistently at or above expected values, regardless of mean temperature and air infiltration. Reasons for these observed effects are discussed.
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