As a next step, RES calculation procedures currently being used in energy performance regulations for new dwellings and energy performance methods for existing buildings have been collected and analysed. The main choices that Member States have to make when starting up the development of an energy performance method or the development of RES calculation modules in an existing energy performance method are based on the complexity of calculation. The complexity of a calculation can be expressed in a number of items such as the time frame, detail of input and calculation principle. Figure 5 presents an overview of characteristics of RES calculation methods used in energy performance methods for new housing in which the calculation period, limitations, input, calculation procedure and explicit RES calculation are described (Buscarlet, C., 2004). It appears to be very difficult to give an objective judgement about the preferred level of complexity, since this is very much dependent on the present ideas about such policy instruments in a member state. While some will state that the calculation procedure should be as detailed as possible, as long as this would be covered by an easy-to-use user interface, others say
that since this considers a policy instrument it doesn’t need to be very detailed, as long as it is possible to compare buildings and to set a regulation level. Another thing is that some member states already use certain (energy performance) methods and may tend to look for additional calculation procedures, such as RES procedures, that suit their current calculation principles.

Figure 5 Overview of characteristics of solar thermal calculation procedures in energy performance methods used for building regulations for new dwellings4

Figure 6 Overview of characteristics of solar thermal calculation procedures in energy performance methods used for building regulations for existing dwellings5 [22] 2 [23] [24] [25] [26] [27]

Figure 6 presents an overview of characteristics of RES calculation methods used in energy performance methods for existing housing mainly used for certification purposes. The calculation period, limitations, input, calculation procedure and explicit RES calculation (Cruchten, G. van, 2004) are described. In fact the calculation of RES techniques in existing dwellings doesn’t need to differ from the calculation in new housing. Considerations as regards the complexity of calculation are similar to new housing.