Abstract: In order in a facade comprising hollow uprights and hollow upper and lower transverse crossbars to be able to dispense with an expensive air-conditioning installation, a cross-stream blower is arranged under a railing crossbar. Over the cross-stream blower there is either provided a star ribbed pipe or the railing crossbar is constructed in several parts and provided with laminations the function of which is to serve in the pre-cooling or pre-heating of air drawn from a room of the building by the cross-stream blower, the pre-cooling or pre-heating taking place as the air is discharged from the blower and before it is sent back into the room. Pre-heated or pre-cooled air may be returned to the room by way of the railing crossbar, by way of and from the hollow uprights or by way of and from the upper transverse crossbar. A filter provided in advance of the cross-stream blower inhibits the passage of any health-hazardous dust or bacteria from reaching the blower or being transmitted back into the room.