Pushing the limits of applying energy efficiency measures to Maltese non-residential buildings

Abstract

According to the Energy Performance of Building Directive (EPBD), 2010/31/EU, new and renovated parts of buildings should be ‘Nearly-Zero’ Energy Buildings (NZEB) by 2020. In this dissertation, the requirements (energy and financial) to reach NZEB for three selected non-residential buildings on the Maltese Islands, belonging to three different building categories, were studied. The Building Regulation Office (BRO) so far has conducted cost optimal studies to establish minimum energy requirements for residential buildings and offices only. Currently, studies on 6 different non-residential buildings are on-going. These studies will help to identify which are the top priority Energy Efficiency Measures (EEMs) for each building type, and will eventually help to set minimum energy requirements for each building type. The software used to run simulations is the Simplified Building Energy Model for Malta (SBEM-mt), which is the official software used in Malta to issue Energy Performance Certificates (EPCs) for non-residential buildings. However, SBEM-mt is not a design tool, thus one of the objectives of this dissertation was to provide insight to the output of SBEM-mt software, given that results are used to setup energy efficiency policies. This was achieved by making use of another software, DesignBuilder, to create and define three selected buildings using the data available from SBEM-mt, following which simulations were then run, both with no improvements implemented as well as after applying various EEMs. The buildings selected were: 1. Lidl - representing supermarkets; 2. Scoglitti - representing small restaurants; 3. Boutique Hotel - representing 3-star hotels. Comparing the results between SBEM-mt and DesignBuilder shows that the delivered energy in SBEM-mt is higher than that in DesignBuilder for all the 3 buildings considered in this study, thus giving an indication that SBEM-mt is overestimating results. Another fact that came out was that buildings with a substantial amount of glazing incorporated in the building envelope, as in the case of Scoglitti, have an important negative impact on the heating and cooling end-uses in SBEM-mt. DesignBuilder and SBEM-mt EEMs results for each building were also compared. It was observed that EEMs including shading, high efficiency HVAC systems and instant water heaters resulted in a better overall percentage improvement for SBEM-mt than for DesignBuilder, as opposed to EEMs including PVs and water heat pumps where the overall percentage improvement was higher for DesignBuilder. Following the simulations, a cost optimal study was conducted using the primary energy (kWh/m2) and LCC (€/m2). Results showed that for Lidl (representing supermarkets), EEMs including PVs are the measures that approach cost optimality. Nonetheless, other alternatives were considered given that for supermarkets or similar retail outlets, there could be roof area limitations inhibiting PV installations. For Scoglitti and the Boutique Hotel, representing restaurants and 3-star hotels respectively, water heat pumps were found to be the most effective measures in improving energy efficiency. To conclude, sensitivity analysis was carried out for PV systems and water heat pumps. Outcome of the analysis showed that the lifetime of PV systems, as well as that for heat pumps is the most sensitive parameter. For PVs, it was determined that if the lifetime is decreased by 50%, the LCC will go up by ~1.2, whereas increasing the output by 50% will not see the same decrease in LCC. The same is valid for heat pumps.