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In this study, a lightweight residential building in Greece was investigated, focusing on the summer comfort when wallboards with phase change materials (PCM) were installed in the external and internal walls. The effectiveness of the PCM wallboards installed was numerically assessed, while the energy performance of the building was examined, in order to quantify the effect of PCM in the annual cooling load needs, as a way of saving energy. Potential bigger energy savings were evaluated by defining the appropriate PCM melting temperature range and the 'energy-conscious' occupant behaviour (passive vs. active). Results were expressed in terms of percentage savings of cooling loads and with comparison to wall elements incorporated with plain gypsumboards instead of the PCM wallboards. The optimum phase change temperature change for the specific location was investigated by examining two-phase change transition temperatures of the PCM wallboards (PCM24 and PCM26 respectively). The use of PCM24 produced a 29% reduction of annual cooling loads, compared to 16% reduction produced by PCM26. Five scenarios were also examined, showing the behaviour of the PCM which was enhanced when a cooling system was installed. The cooling needs were lowered by an average of 25.7%, compared to the respective no-PCM scenarios.

In this study, a multi-criteria assessment approach is performed for a residential apartment located in Athens, for a combination of different energy systems, building envelope and shading systems. 24 alternative cases in total are fully simulated via EnergyPlus software aiming to the calculation Key Performance Indicators (KPIs) in terms of energy consumption for heating and cooling, thermal comfort, visual comfort and environmental impact. The results of KPIs are fed to a decision-making process that takes into consideration the preferences of stakeholders. The optimum solution is selected by the use of the Analytic Hierarchy Process (AHP). In the most optimum scenario, the potential of primary energy savings and CO2 emissions are approximately 35% while the discomfort hours for thermal and visual comfort are respectively 17% and 67% less than the cases with the worst comfort conditions. The results suggest that such a multi-criteria assessment approach can be useful at an early stage of building design or renovation in order to better inform decisions and avoid sub optimizations.