This European Standard is the general frame for the calculation of the energy use and the energy performance of heating and domestic hot water systems. This standards is only dealing with the heat, provided by water based systems, needed for heating, domestic hot water and cooling (e.g. absorption chiller). It specifies how to perform the calculation of the entire installation using the calculation modules (see Table 2) corresponding to the methods defined in the respective standards. It deals with common issues like operating conditions calculation and energy performance indicators. It standardises the inputs and outputs in order to achieve a common European calculation method. It allows the energy analysis of the heating and Domestic hot water systems and sub-systems including control (emission, distribution, storage, generation) by comparing the system losses and by defining energy performance indicators. The performance analysis allows the comparison between systems and sub-systems and makes possible to evaluate the impact of each sub-system on the energy performance of a building. The calculation of the system losses of each part of the heating sub-systems is defined in subsequent standards. Ventilation systems are not included in this standard (e.g. balanced systems with heat recovery), but if the air is preheated or an air heating system is installed, the systems providing the heat to the AHU (Air Handling Unit) are covered by this standard. Table 2 shows the relative position of this standard within the set of EPB standards in the context of the modular structure as set out in prEN ISO 52000-1. NOTE 1 In prCEN ISO/TR 52000 2 the same table can be found, with, for each module, the numbers of the relevant EPB standards and accompanying technical reports that are published or in preparation. NOTE 2 The modules represent EPB standards, although one EPB standard may cover more than one module and one module may be covered by more than one EPB standard, for instance a simplified and a detailed method respectively. See also Clause 2 and Tables A.1 and B.1.