Analysis of three-year Wisconsin temperature histories for roof systems using wood, wood-thermoplastic composite, and fiberglass shingles

Temperature histories for various types of roof shingles, wood roof sheathing, rafters, and nonventilated attics were monitored in outdoor attic structures using simulated North American light-framed construction. In this paper, 3-year thermal load histories for wood-based composite roof sheathing, wood rafters, and attics under western redcedar (WRC) shingles, wood-thermoplastic composite (WTPC) shingles, and black and white fiberglass shingles are reported and analyzed. The maximum hourly-average temperatures experienced were 70.7 degrees C and 61.8 degrees C for black and white fiberglass shingles, respectively; 48.2 degrees C for WRC shingles; and 45.7 degrees C and 46.3 degrees C for WTPC shingles applied over lath or directly over felt, respectively. On hot summer days, black fiberglass shingles were commonly found to be almost 10 degrees C hotter than white fiberglass shingles and more than 20 degrees C hotter than WRC or WTPC shingles. Other components in the roof assemblies and the attic air temperatures followed similar trends. The implications of these thermal loads under different types of roof shingles on comparative service-life for the shingles and the various wood components in the roof systems are discussed.