The article considers the ways of optimizing the existing calculation procedure for the heat input through infilling the area lights. While maintaining public buildings with large areas of translucent structures during the warm season, it is possible to encounter the premises overheat due to a large volume of incorrectly accounted in the heat balance heat input from the solar irradiation. The calculation procedure presently in use in the Republic of Belarus does not account for diversity of the existing forms of glazing employed in construction and needs revision. The authors adduce and analyze the heat-input calculation principles from solar irradiation through translucent structures applied in designing ventilation and air-conditioning systems in Belarus, FRG and USA, and make comparisons between them. Based on the analysis, they establish the ways of optimizing the existing heat-input calculation procedure. Firstly, on account of small geographical latitude difference it is possible to average the flows of direct and dispersed solar irradiation over the territory of Belarus. Secondly, in calculation it is proposed to discard use of heat fluxes of the solar irradiation that passed through the single glazing and to utilize the fluxes falling onto the surface. Therefore, the paper considers the notion of the solar factor of glazing and offers an expression for determining the radiative heat-input component from the solar irradiance appreciating the heat fluxes falling onto the surface. The authors consider the variants of decreasing amount of heat entering the premises through the area lights: glazing type optimal choice, engineering apertures with certain ratio of dimensions, and the use of out-of-door solar protection.