Normal conventional methods of decreasing energy consumption for the heating of buildings are: increasing the insulation thickness, reducing the air leakage of buildings, using special low-energy windows, lowering the room air temperature and recovering heat from exhaust air. Unconventional methods of reducing the energy consumption and peak energy demand for wall heat losses and ventilation, by using low temperature solar heat sources provided by nature or waste heat without a heat pump, that are especially suitable for cold climates are considered. The operation and optimization of these unconventional energy-saving methods are analysed theoretically for different Finnish climatic regions (Helsinki, Sodankyla). The peak power demand that occurs during the coldest days of the year greatly decreases in both regions, which means that the auxiliary heating devices and energy production can be dimensioned much smaller. Both absolute and relative energy savings increase from southern regions to northern regions.