Abstract: A heat energy system which can be used to heat or maintain thermal balance in the interiors of buildings or buildings parts. According the invention there are containers built near and/or instead of surrounding surfaces of a room: of upper and lower surrounding surfaces to at least certain extent, and at least two parts of opposite side surrounding surfaces; and the neighboring containers are connected, and all containers define one closed fluid volume which is filled with heat transporting fluid. The typical layout of the invention is shown in FIG. 3.