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Heat-release-rate measurements were extended to fire tests of full-scale wall assemblies using the substitution method. Through use of the methodology, which involved comparing fuel input rates required to maintain a standard fire exposure for a wood-stud wall assembly with those required to maintain the same exposure for a reference steel-stud wall assembly, information on the heat release performance of wood wall systems was obtained.
It was found that the heat released from protected wood wall assemblies, made of fire retardant treated framing and 5/8 in. Type X gypsum board, and detectable during a 1-hour ASTM E119 fire test, was so low as to be within the limits of experimental error. Based on tests of three wood assemblies and three paired steel reference assemblies, heat released from the wood members and detectable in the fire compartment ranged from +3.5 to -2.8 percent of the total external fuel required to maintain the standard temperature/time fire exposure.