The term "window" in architecture usually stands for an opening in a wall or roof for penetration of natural light, sunrays and fresh air in premises. Recently, the requirement of contact with environment is added to this condition. It is especially relevant for residential buildings where rooms are considered residential if they have windows. The energy consumption of a building depends on sizes, form and location of windows. In winter, windows cause huge heat losses, in summer, on the other hand, large heat enters a building via the windows and is required to be removed by means of air conditioning. Moreover, windows are used for penetration of natural light in premises, which assists in saving of large amounts of power for artificial illumination. This article discusses partial solving the problem of the energy efficiency of residential buildings by determining the most efficient area of windows in terms of energy spending for compensation of heat losses via windows in winter, elimination of heat penetration through them in summer and energy losses for artificial lighting throughout the year. The analysis of the results of calculation of power consumption for residential premises in conditions of monsoon climate of the Russian Far East and Northern areas of China (PRC) is provided.
