Trombe wall, which has been proposed in 1960s, became interesting nowadays as a method for additional heating of buildings. The main problem of the Trombe wall is the fact that this type of wall is a passive element. There have been attempts at solving this problem by introducing various active models of insulation. This paper presents a model of active insulation of buildings, whereby the control of insulation is achieved by a bridging method. The model is simulated in MatLab under conditions of non-stationary heat conduction, that exist in real conditions. We have calculated the effects of different combinations of layers of insulation and load-bearing walls and their thickness, on the temperature distribution, both inside the insulation system-load-bearing wall and the air temperature inside the building. We examined the time lag of air temperature inside the building in relation to the outside air temperature, i.e. thermal inertia of such systems.