District heating and cooling

I am going to model a building that is connected with a district heating/cooling system. I’m going to use the simplified option of the document “Treatment of District or Campus Thermal Energy in LEED V2 and LEED 2009 – Design & Construction” (i.e. the Building Stand-Alone Scenario – the building is treated separately from the DES; all upstream equipment is ignored). Since the system is of the same owner of the building, the energy is not paid by the manager of the building, but by the manager of the district system (and the situation is the same for all the buildings that are connected with the district network). Therefore the cost of the energy that is exchanged between the network and the building is not considered. The management of the system buys natural gas, but I don’t know the efficiency of the systems, which are very complicated and we want to avoid to model them. I see two possible solutions: 1. I consider standard prices for purchased heated/chilled water for the region. 2. I don’t consider the energy cost, but the primary energy. Are those solutions acceptable? In both cases I would consider the same values for the baseline model and the design model. With Regards Francesco Passerini