Multi objective optimization, indoor thermal comfort, building management, building retrofitting, dynamic simulation
The enhancement of the existing buildingsâ€™ performance requires the choice among a wide selection of energy efficiency measures by means of a cost-optimal approach. Although the cost-optimal analysis represents a useful tool to guide the investment in building renovation, it does not explicitly include the occupant comfort. The retrofit strategy should not only enhance the energy performance of the building in a cost effective way, but also improve, or at least, not deteriorate the indoor thermal comfort during the all year, even when system is off. One of the well-known problems in highly insulated buildings is that, if not correctly managed, they can undergo overheating issues, hampering the indoor environment livability. On the other hand, under discomfort conditions, occupants tend to react, making adjustments (operating the windows and/or the shading devices) in order to improve their thermal comfort, possibly compromising the building energy performance. In this paper the influence of the occupancy behavior on the definition of the cost-optimal level has been investigated on a set of reference buildings, representative of different building typologies, construction periods and windows orientations, located in two typical Italian climates, Milano and Messina, representative of respectively heating and cooling dominated climatic regions. A wide selection of energy efficiency measures has been evaluated, combining a genetic algorithm for the multi-objective optimization and a dynamic simulation code. The search of the best combination of strategies has been conducted optimizing energy efficiency, global costs and the indoor thermal comfort at once. At a first stage, the optimization has been carried out evaluating only the performance of the envelope, without considering the building management operated by the occupants. At a second stage, the optimization has been repeated including the user-operated building management. This allows evaluating the importance of an appropriate management of the building by the occupants, through windows and shading operation, and its impact on the definition of the optimal retrofit strategies. The comparison of the results of the two optimizations also highlights the possible performance gap between asset and tailored rating of refurbished buildings.