Analysing the "performance gap" between energy performance certificates and actual energy consumption of non-residential buildings in Malta

Abstract

The updated EU energy performance of buildings directive 2018/844 stipulates that measures need to be taken to accelerate building renovation to achieve carbon neutrality by 2050. A key tool is the energy performance certificates (EPCs), which so far have proved to be virtually ineffective in driving change, due to the low level of trust in their credibility. This is mainly manifested by the existence of a significant energy “performance gap” between the EPC and the building’s actual energy use intensity. This thesis has investigated this “performance gap” between the non-residential national software SBEM-mt and the actual energy use intensity for three non-residential clusters having different building services’ engineering complexities, and found it to be both significant and unpredictable for all of them. An alternative approach based on operational rating has been proposed, which considers the actual energy consumption of a building, in order to determine its energy use intensity (EUI). Inspired by the UK benchmarks for non-residential buildings, a dynamic, transparent, reliable and repeatable tool has been developed, whereby good practice benchmarks for 29 non-residential categories have been calculated for Malta, based on the concept that energy use in buildings may be split into weather-independent and weather-dependent components. The tool considers a systematic bottom-up approach taking into consideration Malta’s total degree days, ventilation requirements, heating load as well as sensible and latent cooling loads, besides others. Results showed that the total EUI for the different categories is very similar to that of the UK. Malta’s total degree days are lower, yet, the latent load for cooling more than counterbalances the lower heating demand. Comparison between the results of this tool and the actual EUIs for the three cluster buildings was found to be convergent and consistent. The tool can be used to provide Malta with verified benchmarks upon which policies and energy investment decision making can be based to achieve an improved efficient energy rating towards the road to carbon neutrality.