Conduction Z-transfer Function Coefficients for Common Composite Wall Assemblies

Results of the conduction z-transfer function coefficient calculations are presented for clear walls and separated details listed in the ASHRAE research project, 1145-TRP, "Modeling Two and Three-dimensional Heat Transfer through Composite Wall and Roof Assemblies in Hourly Energy Simulation Programs." Resistances, three-dimensional response factors, and the so-called structure factors have been computed using the finitedifference computer code HEATING 7.2. The z-transfer function coefficients were derived from the set of linear equations (relationships with the response factors), which are to be solved using minimization procedures. Comparison of the response factors and z-transfer function coefficients for three-dimensional and one-dimensional equivalent wall models indicates that, in general, the one-dimensional model produces some delay in dynamic thermal response to the external excitation, whereas response to internal excitation may be overestimated. Test simulations show perfect compatibility of the heat flux calculated using three-dimensional response factors and threedimensional z-transfer function coefficients derived from the response factors.

Authors: Elisabeth Kossecka, Ph.D.; Jan Kosny

Citation: Thermal Performance of the Exterior Envelopes of Buildings VIII

Keywords: December, Florida, 2001