Abstract: For the exchange of thermal energy between flowable media and the surroundings, said media are directionally conveyed in sectional structures, etc. The invention relates to sectional elements and sectional modules which are used in combination with paste-like, solidifiable coating materials. The coating material passes through the perforated, flow guiding walls of the elements or modules and results, amongst other effects, in an increase of the surface area and in an intensification of the interaction between the flowing material and the surroundings. In a use according to the invention, the external walls, etc., of buildings are provided with a surface composite comprising sectional elements and modules according to the invention in combination with coating materials, for the purpose of effecting economical air-conditioning of the building from the bottom of the basement to the roof.