Abstract: An indoor space environment heating and cooling system in which a massive thermal storage unit is interposed between a geothermal heat energy storage capacity--the earth--and a heat pump heating and/or cooling apparatus for controlling and maintaining the environment in an indoor living space. A fluid circulation apparatus is provided to circulate a working fluid from the massive thermal storage unit directly to a heat exchanger in the indoor space environment conditioning apparatus, to provide cooling when the temperature of the thermal storage unit is less than the temperature in the living space.