Calculation according to the German energy performance of buildings standard DIN V 18599 featuring a multi-zone model, lighting, complex configurations of heating, airconditioning and cooling technologies. The tool allows the assessment of all building energy parts such as energy need, energy use and primary energy. Detailed input for usage zones, lighting zones, building components, solar shading, heating, ventilation, cooling and lighting systems, energy carriers, etc. Different variants can be compared and an energy certificate can be printed. Detailed energy consulting is possible as well. The calculation core is the ibp18599kernel which is used in about half of the computer tools for calculations according to DIN V 18599.