As part of a research program on the thermal performance of translucent fabric-covered buildings, a comparison between measured and predicted fabric roof heat transfer was made. Predictions, based on a steady-state ASHRAE calculation technique, were compared against measured heat transfer through three different roof systems operating under outside weather conditions. The goals of the study were to evaluate the ability to predict the net energy transfer through the fabric roof systems tested, to identify parameters that would contribute to major differences between the measured and predicted results, and to recommend improvements to those parameters. It is expected that those improvements could be made in the computer program, DOE-2.

The heat transfer through a single-layer, a double-layer, and a translucent insulated fabric roof system was measured in a vertical heat flow, guarded hot box located outdoors in Granville, Ohio. The results obtained by comparing the measured and predicted net heat transfer through the three roof systems indicated that the ASHRAE calculational technique predicted heat loss to within about ± 25%, but it consistently overpredicted the heat gain during cooling load situations. The critical parameters in predicting the heat transfer through the roof systems were found to be the interior and exterior combined convective and radiative heat transfer coefficients and the shading coefficient. For the roof systems tested, the measured values of the overall outside film coefficient were found to be lower than those given in the ASHRAE Handbook 1981 Fundamentals. Also, the average measured value of the shading coefficient for the different roof systems was found to be lower than the calculated shading coefficient value for the different roof systems as determined from measurements of the shading coefficient in the outdoor calorimeter.

Units: Dual