A heat pump using zeolite as an adsorbent (Fig. 3) wherein thermal energy from adsorbent zeolite in a one hermetically sealed space (121) is used to heat desorbing zeolite located in another hermetically sealed space (120), such heat being conveyed by heat exchanger conduits containing a fluid which, before heating the desorbing zeolite, has its temperature increased to about 400 F (205 C) by a gas flame (at 151), the adsorption and desorption phases being changed between the zeolites in each cycle by reversing the fluid flow in the conduits. Cooling and heating for a building or other purposes are provided through the condenser (122) and evaporator (124) respectively for the working gas (water) which is desorbed and adsorbed into the zeolites. A propagating temperature front is established through the fluid - to-zeolite heat exchanger conduits to provide utilization of as much as ninety percent of thermal energy available during the desorption/adsorption phases.