Energy preservation and reduction in greenhouse gas emissions into the atmosphere can be partially gained through decentralization of heat supply. In the case of cultivation facilities, a solution is a combined heating system which includes soil infrared heating and air heating in the winter greenhouse up to the required values by means of autonomous convective heaters. Upon analysing domestic and foreign scientific publications, there has not been found any comprehensive calculation method of the combined heating system. The target of research is normally one of the space heating ways: either radiant or convective. The calculation method considered in the article is based on the solution of the coupled equations set of the greenhouse heat and material balances, its walling and soil surface. It takes into consideration both the features of radiant heat transfer between distant bodies, and convective air heating from heaters. The developed calculation method has been tested using the modern industrial greenhouse “Fermer 7.5” for year-round cultivation of crops. As shown by the results of software calculations, at low temperatures of the outside air, the heat power of winter greenhouse radiant heating should be twice as high as the heat consumption for convective heating of the cultivation facility. There have been obtained heat power change patterns of the winter greenhouse combined heating system depending on a number of important factors, such as: temperature of the outside air; walling thermal resistance; absorption coefficient of the soil surface. Due to the fact that according to the calculations results, the heat loss via the winter greenhouse ventilation proved to be significant, it makes sense to consider further the option of preheating outdoor air necessary for air exchange indoors.