Energy saving policies are necessary to control energy consumption, use energy efficiently and effectively, and reassess available production and consumption systems. In this context, the objectives of this study are to investigate the thermal behaviours of opaque wall materials under solar energy change, and the interaction between thermophysical characteristics of opaque wail materials and solar energy falling onto exterior surface of the wall affects interior environment. Parameters of characteristics used in wall formation, their positions, wall thermal behaviours, and "time lag" and "decrement factor" having effect on the changes of conditions of interior space were investigated experimentally for different wall formations. The experimental findings were compared with the results of equations derived by using an analytic methodology.