Point: 12.4.2 What criteria must a high-efficiency alternative energy system other than those listed in points a)-d) meet in order to be recognized as a high-efficiency alternative system?

For the same building envelope, the characteristic values for PEB and CO2 for the energy system must not be worse than those with the systems according to a), c) and d) when calculated according to the standard. Natural gas condensing boilers in combination with solar thermal systems are also considered highly efficient alternative energy systems in residential buildings if there is no district heating connection or if the use of biogenic fuels is not possible or not economically reasonable for reasons of air pollution control or due to a lack of supply or storage options. The proportion of solar yields should be optimized. If the installation of solar thermal systems is not possible or not economically feasible due to the location, this combination can be dispensed with