This standard specifies the required inputs, the outputs and the links (structure) of the calculation method in order to achieve a common European calculation method. This standard covers energy performance calculation of water based heating and cooling space emission sub-systems. This standard specifies the structure for calculation of the additional heat losses and energy requirements of a heat emission system or cooling system for meeting the building net energy demand. The calculation method can be used for the following applications: ¾ð calculation of the additional energy losses in the heat emission system or cooling system; ¾ð optimisation of the energy performance of a planned heat emission system or cooling system, by applying the method to several possible options; ¾ð assessing the effect of possible energy conservation measures on an existing heat emission system or cooling system, by calculation of the energy requirements with and without the energy conservation measure implemented.