University building: Energy diagnosis and refurbishment design with cost-optimal approach. Discussion about the effect of numerical modelling assumptions

The paper discusses a methodological approach for designing energy refurbishment measures basing on a deep energy diagnosis with in-situ measurements that allow the complete characterizations of building /HVAC system and the indoor conditions. Then, the Cost-Optimal approach is applied to compare several retrofit scenarios considering interventions both on the building envelope and on plant systems. The case study is a University building in heating dominated climate of South Italy. According to a macroeconomic perspective, with a discount rate of 3%, the package of energy efficiency measures that combines installation of heat recovery systems, regulation dispositive for HVAC and LED lamps with automatic control induces considerable energy saving and reduction of polluting emissions (−33%) as well as the largest reduction in the overall cost (−35%). Moreover, the importance to use validated models is examined exhaustively by proposing a sensitivity analysis on uncertainties due to modelling assumptions mainly referring to the adoption of stochastic schedules for occupant behaviour and equipment or lighting usage. First of all, this analysis shows that the calibration indexes are always dissatisfied; besides it is demonstrated that refurbishment design can appear more convenient, with wrong assumptions. For instance, one of proposed scenario brings to energy saving of −41% and reduction of global cost of around −36%.