Abstract: The daily variation of the outside temperature is utilized for control of the air temperature in a premise, in such a way, that outside air is directed to the premise through channels in the building structure surrounding the premise. The channel walls are adapted to absorb or give off heat to the air flowing through the channels. This utilization is, for example, such that that cold night-time air during the night might flow through the channels and cool the mass surrounding the channels, for example a framing of joists of concrete, which cooled mass during the day-time cools warm outside air prior to its entering the premise.