Hybrid energy renovation of existing buildings: A case study of collective housing in Skikda

Abstract

The actual worldwide alarming energy and environmental situation has led to a call for action and the search for strategies to achieve energy savings, to end the dependence on fossil fuels and to opt for a clean environment, adapted to human and non-human life in the best possible conditions. One of the sectors targeted is the building industry sector, because of its significant contribution in this vulnerable situation. This present research is a comparative study that analysed and evaluated the initial state of four (4) existing collective housing structures in Skikda, a Mediterranean town in north-eastern Algeria, before proposing and testing the effect of nine (9) energy renovation scenarios. The study used several tools, including ArcMap, Autodesk's Revit via Insight 360, and the CEA software. The models of the latter were calibrated and validated against real electricity and gas consumption data obtained from SONELGAZ local agencies of Skikda. The study's first phase focused on the initial state and examined the solar, topographical, and urban factors and their impact on energy consumption and ecological footprint. A multi-spatial scale analysis was used, including the exploitation of topographic sections, various data collected on buildings and their urban environments, and also areduced-order UBEM approach as well as solar estimation approach based on a 3D model. The second phase of this study interested on the effects of ameliorative interventions that was by single measures (passive or active), or through hybrid improvements. The passive measures were by changing the existing single glazing with double or triple glazing. Hybrid PVT panels as active measures were also used by changing their quantities and locations between fixings on roofs or south facades, according to different scenarios. Another scenario proposed the use of electric boilers to cover domestic hot water needs. The results reveal that overall energy consumption in the four archetypes was primarily influenced by the thermal transmittance of the envelope and its age throughout the year, except during the coldest period when the altitude of the building and its exposure to prevailing winds had the greatest impact. On the other hand, the building's shape and urban surroundings did not significantly affect energy consumption, but did impact the reception of solar rays, which influenced the choice of placement of hybrid PVT panels. At apartment-scale, the height and orientation can significantly impact its energy consumption, where lower floors apartments and north-facing ones, tend to consume more energy. The energy and ecological assessment of the initial state of the various archetypes, and of the most of the apartments, in relation to European benchmarks showed that they were of medium performance. The various energy renovation scenarios have offered varying degrees of energy and environmental improvements and optimization. Synergies in hybrid energy renovations have yielded very high performance levels, especially by combining the use of triple-glazed windows with the integration of PVT hybrid panels over the entire roof together with seasonal thermal energy storage system, making the buildings highly energy-efficient and environmentally friendly, despite their different reactivity in the four (4) cases, due to differences in the morphologies of the archetypes, their urban and topographical context, and their exposure to external weather fluctuations. The results also showed the interaction and interdependence that exist between architectural, urban, topographical, solar and human behavioural aspects, whether at a single scale or at several spatial scales, and their effect on energy consumption, on the carbonic emission rates, and also on the performance of renovation methods and technics.