Dynamic simulations for the retrofit of an office building in a mild climate by means of reversible heat pumps

Office buildings are one of the most critical items for enhancing energy efficiency in buildings. In these buildings there is the need for heating and cooling and many times, in order to achieve a proper productivity, set-point temperatures are fixed and have to be respected. For this reason 4 pipes plants are quite common, especially when buildings present large glazing facades. The paper present a quite recent building with large glazing surfaces and compli-cated envelope in the centre of London. The building has 11500 m2 as net surface area. The energy analysis has to deal with the complex envelope, the shading of surrounding buildings as well as the HVAC systems. Dynamic simulations for evaluating the heating and cooling hourly energy needs have been carried out with TRNSYS. The simulations and the model have been tuned on measured heating and cooling energy and, based on the energy profiles, a reversible air to water heat pump has been proposed (in particular a unit for simultaneous and independent production of heat and cold water). Results have shown the possible improvements in the HVAC plant and the benefits of the replacement of usual boilers and chillers with those multi use units. The analysis has been carried out based on both the environmental and economical points of view.