AbstractThe purpose of the research was to examine the savings potential and verify how to reduce the energy consumption in new hospitals by about 50%. Our results are also very relevant in other buildings complex with surplus heating, cooling and thermal storage.Conversion and utilization of surplus heat sources represent well known technologies and are under constant development. In large building complexes there is a potential for coordinated production, storage, and distribution of energy. Heat pump, chiller and thermal storage technologies enable re-use of surplus heat/cool energy throughout the year. Energy supply and demand are typically modelled with separate tools and timescales.Through our study new methods are developed for operation of interacting simulating models. These methods provide tools to step into optimization of combinations of integrated energy systems. The main issues focus on hydraulic water flow and storage systems as a basis. The layout is important not only with regards to utilize the energy quality, i.e. the temperature. In addition, control strategies are shown to have a highly relevant impact on the possible savings. Some details of new hydraulic layout and control design will be described and discussed in the paper. Both in combination with heating, cooling and storage system.Our research indicates that it is possible to save between 20-50% of the energy consumption with optimizing the technical installations in Oslo area.Another benefit of integrated thermal modelling is to reduce the risk of permafrost in ground source heat pump installations. This risk is relevant for large buildings in northern Norway, at annual mean temperatures are below 0̊C.This paper shows how integrated simulation and design can be used to avoid permafrost.