Towards active façades ?



The public defense of the doctoral thesis presented by Angela Clua Longas took place on November 27 at Ecole polytechnique fédérale de Lausanne (EPFL). Conducted under the supervision of Prof. Emmanuel Rey, Laboratory of Architecture and Sustainable Technologies (LAST), this doctoral research is entitled "Designing Energy-Efficient Façades to Meet Energy Transition Targets" and related to the design of low-carbon active facades for residential buildings in the context of the energy transition.

The contemporary energy context can be considered as a period of the energy transition, where the latest protocols focus on limiting greenhouse gas (GHG) emissions and improving energy efficiency across the different energy consumption sectors. As the largest single energy consumer in Europe, the building sector faces the unique challenge of meeting the latest energy efficiency requirements in the prospect of a growing population, whose growing demand results in increased construction activity and energy consumption.

In line with the objectives of the energy transition, the European Union (EU) is committed to drastically reduce its GHG emissions by 2050. This objective is applied to the construction sector through new building energy efficiency requirements specified in the latest building directives. The latter highlights the potential of the building envelope to yield energy efficiency by passively reducing energy demand and through the incorporation of active energy generation systems, including solar systems. Among the latter, Building-integrated photovoltaic (BIPV) systems have a demonstrated potential to increase energy efficiency, especially when they are an integral part of the building’s design and construction.

However, despite their energy-efficiency improvement potential, BIPV systems are not widely used among architectural practices. This results simultaneously from the special attention required by BIPV in terms of design and construction, the still low number of examples of successful architectural integration, the generalized lack of awareness among professionals, and the perception of the high cost of this technology. These barriers, among others, reveal a tangible gap between the potential of energy-efficient technologies and their application to current architectural practices, specifically with regards to façade design due to its public character as an urban landscape generator. 

To contribute to bridging this gap in the context of the energy transition, this thesis proposes a research-by-design methodology structured in different interdisciplinary research phases. These phases aim to design and assess an energy-efficient façade solution with the potential of contributing to the building sector's energy transition. The research adopts an architectural approach to explore the collective residential façade design potential and improve its construction energy efficiency. The research process entails an analysis of the contemporary residential façade design currents and the advanced practices on energy-efficient construction. The research methodology is structured in three iterative phases: the design of an energy-efficient façade, its quantitative assessment, and the evaluation of its transfer potential towards professional practices.

The concrete contribution of this research is to provide architecture professionals with energy-efficient architectural visions that can guide them to explore such energy-efficient strategies, integrate these issues in their own design processes and thus contribute to the energy transition at that scale. Similarly, the design methodology and the assessment processes can support construction stakeholders’ decisions concerning the integration of energy-efficient design strategies into building development, improving contemporary façade construction practices.


This thesis was produced as part of the PV 2050 interdisciplinary research project, in the framework of the National Research Program NRP 70 of the Swiss National Science Foundation (SNSF).