Each building has a specific heating quality determining its building-specific energy demand. To be sure, the real energy consumption depends also on the user of the house. But the building and its “hard ware”, i.e. walls, roofs, windows, doors, and heating technology, determine most of the energy needs. This quality may be called Energy Performance.
The idea is used for the so called Energy Performance Certificate, as regulated by the European Union, in German “Energieausweis” or “Energiepass”. It is the result of a calculation, either beased on real heat energy consumption measured by gas or heat meters, or by a thorough analysis of the parts of the building. This certificate and its numbers are quite helpful in understanding, if the house is “energetically healthy” or if a refurbishment or retro-fitting could pay off.
However, the certificate has its back side. The first method, based on real consumption, is very unreliable as human behaviour and comfort needs vary very much, and the latter – based on building characteristica – is complex and unrealiable as well. In addition, the analysis is expensive as on-site visits of consultants are needed and the calculation has to be done by a special software. What is more, only selected professions are entitled to issue such a certificate. Such a certificate costs until a lower four digit euro amount, i.e. 1.000 or 2.000 Euro, or sometimes more, for bigger buildings.
Therefore, an alternative, reliable, objective and easy-to-do method would be very welcome. Here we explain such a method. It works basically for each type of home in every climate zone. It can be done by everybody with very little technical effort. The calculation method is explained later on. The clue: The method is based on a temperature comparison inside and outside the building for a certain period of time during the heating period. It works.