The plaster floor is made from an air-permeable material such as glass foam or quartz gravel. Two pipes are laid one inside the other in this layer so that the inner pipe serves to transport the heating medium and the outer porous pipe is used to transport air which is heated up by the heating medium and then diffuses upwards through the floor. Air preheated externally can be introduced into the outer porous tube. Plates (3) can be laid on the plaster floor (1).
