A method of derivation of the conduction z-transfer function coefficients from response factors, for three-dimensional wall assemblies, is described. Results of the conduction 7-transfer function coefficients calculations are presented for clear walls and separated details which are listed in 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 so-called structure factors. have been computed using the finite-difference computer code HEATING 7.2. The z-transfer function coefficients were then derived from a set of linear equations. constituting relationships with the response factors, which were solved using the minimum-error procedure. Test simulations show perfect compatibility of the heat flux calculated using three-dimensional response factors and three-dimensional z-transfer function coefficients, derived from the response factors. (C) 2004 Elsevier B.V. All rights reserved.