Heating device

A heating device comprising a combustion chamber 4 and a stack 3 spaced from said combustion chamber, with a plurality of relatively long ducts 17 for flue gases between said combustion chamber and said stack. The ducts 17 and optionally the combustion chamber are surrounded by a heat storage material 20, and means are provided for the discharge of heat from the heat storage material. According to the present invention, the flue gas ducts are substantially straight ducts, and the means for the discharge of heat stored in the heat storage material consist of a plurality of pipes or conduits 19 extending through or along the heat storage material between a first compartment 12 to which a heat transporting medium can be supplied, and a second compartment 13, from which the heat transporting medium can be discharged after passing through the pipes or conduits 19. <IMAGE>