The aim of the present work is to investigate the transient conduction heat transfer in structural walls. The developed finite difference numerical simulation code, which is suitable to run in conventional microcomputers, has the flexibility to incorporate a wide range of boundary and initial conditions and time-dependent forcing functions for the investigation of the transient heat transfer in walls of any design. The analysis was employed for the prediction of the dynamic thermal behaviour of two wall designs under the effect of a step temperature change and a combined time varying ambient temperature and solar radiation corresponding to typical local weather conditions. The results allow the prediction of the transient duration, the transient temperature fields as well as the quasi-steady state heat fluxes. They also allow the investigation of the dynamic effects of realistic time varying meteorological forcing functions and the strong influence of the wall surface absorptivity, something which confirms its importance as a handy instruction and research tool in the renewable and rational use of energy fields. (C) 2002 Elsevier Science Ltd. All rights reserved.