Abstract: The current invention relates to a building installation comprising a building comprising a slab or cellar floor placed in contact with a piece of earth under the building. A fluid hose is placed in the piece of earth under the slab or cellar floor and contains earth circuit fluid which is thermally coupled to a fluid circulation circuit in or by the building such that the earth circuit fluid receives heat from the heated solar collector fluid for circulation in the fluid hose through which heat energy is released to the surrounding piece of earth.