Architectural Design Strategies for Building-Integrated Photovoltaics in residential building renovation processes

Abstract

Tomorrow’s European cities are already largely built, as much of the existing building stock – with a low level of energy performance – will still be standing in 2050. Urban renewal processes therefore play an essential role towards their sustainable transition. In this context, Building-integrated photovoltaic (BIPV) systems can potentially provide a crucial contribution to achieve current energy and midto long-term carbon targets based on the 2’000-Watt society concept in Switzerland, and to fulfil the objectives of the energy turnaround for 2050. Functioning both as envelope material and electricity generator, BIPV systems can simultaneously reduce the use of fossil fuels and greenhouse gases (GHG) emissions, while providing savings in materials and electricity costs. These are precisely the objectives of most European energy directives, from zeroto positive-energy buildings. However, despite continuous technological progress and increasingly favourable economic conditions, the significant assets of BIPV remain broadly undervalued in the current practice. Various obstacles related among others to technology choice, low demand (which induces small volume production of BIPV products), and lack of information and of aesthetically convincing renovation examples, tend to increase the costs and prevent the acceptance of BIPV solutions. Considering that BIPV can be integrated into the design process, but in a casespecific rather than in a systematic way, this thesis aims at offering support to stakeholders – especially architects – involved in the design process of renovation projects. Focusing on an integrated architectural design process for addressing renovation projects of residential buildings, the approach involves four main phases: (1) building stock analysis to identify representative (archetypal) situations, (2) detailed analysis of real case studies, (3) architectural design of different renovation scenarios using BIPV strategies, and (4) multicriteria assessment of each scenario. The concrete contributions of this thesis are twofold. First, a set of integrated design strategies – illustrated through real case studies – is defined to promote the integration of BIPV in urban renewal processes. It integrates: (i) passive strategies, to improve the envelope through low embodied-energy materials and construction systems, (ii) BIPV strategies, using innovative photovoltaic products as a new material for façades and roofs, and (iii) active strategies, adapting heating, ventilation, and air conditioning (HVAC) systems to improve the efficiency of the BIPV installation and reduce the dependence on feed-in-tariffs to ensure the profitability of investments. Second, a multi-criteria assessment methodology is developed to compare the different intervention scenarios, based on a qualitative and quantitative approach. The proposed workflow thus allows comparing different design solutions in terms of BIPV performance, final energy balance, Life-Cycle Analysis (LCA) and Cost (LCC) of the whole renovation process. This approach shall provide architects and engineers with advanced BIPV renovation strategies that depend on the building typology, the architectural design goals, and the level of intervention, thus supporting and inspiring them towards a low-carbon built environment.