A mathematical model describing the process of heat transfer through windows with heat-reflecting screens, taking into account physical and geometrical parameters of the building construction, was developed. The computer program for the calculation of heat transfer through the window has been developed and results of numerical heat transfer simulation for different parameters of indoor and outdoor air are given. Expressions to determine the thermal resistance for the specific types of glazing with a heat-reflecting screens installed outside were derived on the basis of the developed method. The adequacy of the suggested mathematical model was confirmed by experimental data.