The use of energy in the residential sector is among the most significant sources of greenhouse gas emissions. The majority of energy consumed in households accounts for space heating and the preparation of warm water. The key to decreasing energy consumption is increasing energy efficiency. The most progress in energy efficiency in the residential sector is expected to be made by improving the insulation of buildings and using low-energy equipment. However, in settlements with very high insulation standards, transport of heat becomes senseless as heat losses may be higher than delivered...