Abstract
Since 2005, several legislation Acts have been issued in Italy prescribing higher energy-efficiency requirement for buildings. However, the effectiveness of those requirements in existing building renovation is not clear enough and energy efficiency in building refurbishment is often pursued through subsidization policies. The energy performance of most of the Italian buildings is much lower than the law prescriptions. For this reason, retrofit actions represent an important opportunity for energy saving. The crucial issue of refurbishment of building is that, in most of the cases, the decision maker, either a public manager or a private owner, is not able to individuate the best solutions. In this context the energy certification could represent an important instrument to lead decisions, even if by now the impact of energy certification on the existing buildings is not so clear. In this paper a method to analyze the possible retrofit actions to attain a certain energy class and to determine the optimum solutions under energetic and economic constraints is described. Different starting configurations (different window sizes and orientations, envelope materials, ratios between the dispersing envelope and the conditioned volume) of an uninsulated single-storey model sited in three climatic zones of Italy (Belluno, zone F, Milan, zone E and Pisa, zone D) have been considered. Different refurbishment interventions have been analyzed: the improvement of the thermal transmittance of opaque and transparent envelope, the use of efficient energy supply technologies and RES-based solutions. The energy consumption for space heating and DHW has been calculated using the quasi steady-state method proposed by the Technical Specifications UNI/TS 11300. The contribution of each individual retrofit measure to the building energy needs and the corresponding cost impact have been determined allowing to define which is the combination of different refurbishment actions that optimizes the achievement a certain energy label (A, B, C).