A heating and cooling system for a building having a passive source of heat energy, a heat sink reservoir to store heat energy in, and a first heat exchange system operating a temperature of 15 degrees Celsius or less and being operatively connected to said reservoir. There is a second heat exchange system operating at a temperature of above 15 degrees Celsius which is also operatively connected to the heat sink reservoir and a thermal mass wall which is connected to the heat exchanger systems. In one aspect, the invention provides a dynamic wall having a first insulating layer on an interior surface of the wall, a thermal mass adjacent to the first insulating layer, a second insulating layer on an outside surface of the thermal mass and a heat exchanger operatively connected to said thermal mass to add or subtract heat from said thermal mass wall.