Abstract: A dryer for drying dry materials having heating and cooling chambers, wherein the two chambers are sealed gas-tight to each other and/or to the outside environment, a connecting line that fluidically connects the chambers to each other and has a closing valve, a vacuum pump that is actively connected to the cooling chamber, a heat pump that is actively connected to the two chambers, and a steam generator which feeds generated steam via a steam line into the heating chamber, The steam mixes with moisture of the dry materials in the heating chamber and the resulting moist steam is supplied to the cooling chamber via the connecting line, wherein positive pressure is generated through evaporation and negative pressure is produced through the condensation such that a pressure difference is produced between the heating and cooling chambers, and wherein the vacuum pump pumps dry air from the cooling chamber as required.