Designing Energy-Efficient Façades to Meet Energy Transition Targets

The contemporary energy context can be considered as a period of 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 particular 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 highlight 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 buildingâs design and construction. However, despite their energy-efficiency improvement potential, BIPV systems are not widely used among architectural practices. This results simultaneously from the particular attention required by BIPV in terms of design and construction, the still low number of examples of successful architectural integration, the generalised 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 faÃ§ade design due to its public character as an urban landscape generator. To contribute bridging this gap in the context of 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 faÃ§ade solution with the potential of contributing to the building sector's energy transition. The research adopts an architectural approach to explore the collective residential faÃ§ade design potential and improve its construction energy efficiency. The research process entails an analysis of the contemporary residential faÃ§ade 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 faÃ§ade, 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 stakeholdersâ decisions concerning the integration of energy-efficient design strategies into building development, improving contemporary faÃ§ade construction practices.

Active façades : life cycle environmental impacts and savings of photovoltaic power plants integrated into the building envelope

Gianluca Cattaneo, Angela Clua Longas

Aim and approach used Increased energy supply from photovoltaics is a main priority in the “Energy Strategy 2050”. Within the joint research project "Next generation photovoltaics" funded by the Swiss National Science Foundation, we analysed different options for the enhanced integration of photovoltaic technologies into the envelope of Swiss buildings (BIPV). The PV modules for building integration are using novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC) with adaptions to improve the visual acceptance. In a joint effort of product developers, architects and scientists, this project aimed at providing pathways for the wide-scale use of BIPV façade solutions, and developing integrated designs based on emerging high-efficiency module technologies to improve the visual aspect and acceptance of PV systems installed in Switzerland. These so-called active façades incorporating BIPV modules to generate electricity can provide a significant contribution to the energy transition away from fossil and nuclear fuels. We compared the environmental impacts of different façade construction systems with and without SHJ-PSC BIPV modules with improved visual design, using a prospective life cycle assessment with a time horizon of 2025. The comparison includes a conventional brick and roughcast façade, a timber frame façade, and the Advanced Active Façade (AAF), which integrates SHJ-PSC BIPV modules in a low embodied impact façade substructure. In addition, we compared the environmental impacts caused by the construction of the above described façades with the environmental impacts saved due to the electricity produced by BIPV modules incorporated into the AAF. 2. Scientific innovation and relevance Our research focuses on the combined expertise of life cycle thinking, PV module development and façade design. The major scientific innovations are: 1) the prospective life cycle assessment of novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC); 2) the comparison of different façade construction systems and their environmental impacts; 3) the quantification of the saved environmental impacts arising from the electricity generated by the active façade; and 4) the visual adjustments of PV modules to improve their acceptance. The main advantage of integrating PV into building façades is the large available area, which can be limited on rooftops. In order to reach the market penetration for PV required for the energy transition, PV modules must be integrated into façades as well as into rooftops. 3. Results and conclusions An equilibrium must be achieved among different technical and aesthetic issues when integrating energy generation systems into the building envelope, especially into the façade for its public condition and exposure. Based on these prerequisites, the research team has developed the AAF which combines passive and active energy design strategies while meeting contemporary architectural requirements. This façade design is based on low-embodied-energy construction principles, it is defined by a non-loadbearing wood-panel substructure and it integrates a double layer of natural insulation: cellulose and wood-fibre. In addition, its design incorporates an opaque SHJ-PSC BIPV façade-cladding following contemporary façade design trends. (Figure 1). The use of photovoltaic modules integrated into the façade cladding or roof will increase the environmental impact of the building envelope, compared to using conventional construction materials. The environmental impacts of the AAF using PV modules are two to four times higher compared to a conventional façade. The PV modules cause the highest share of greenhouse gas emissions of the AAF with about 375 kg CO2-eq per square meter (see Figure 2). The additional materials required to build the AAF including exterior panels, insulation and other materials cause about 75 kg CO2-eq per square meter of façade. The brick and timber frame façades cause greenhouse gas emissions around 200 and 100 kg CO2-eq, respectively. If the greenhouse gas emissions caused by the PV module is excluded this will result in a reduction between 25 and 125 kg CO2-eq per square meter of façade. However, the environmental impacts of the AAF are significantly reduced if the whole life cycle is considered due to the PV electricity produced by the building. Therefore, we calculated the saved greenhouse gas emissions due to the electricity produced by the advanced active façade and fed to the European electricity grid using the greenhouse gas emissions caused by the current European electricity mix as reference. These calculated savings due to the electricity produced by the BIPV are about 4 times higher than the impacts of the advanced active façade. Incorporating BIPV panels into building’s façades will cause net savings of about 1700 kg CO2-eq per square meter over the whole life cycle of BIPV façades, while simultaneously saving up to 125 kg CO2-eq per square meter of façade for the reduced material demand to build the façade (see Figure 3). We performed this analysis for 16 different environmental impacts according to the recommended midpoints by the Joint Research Council of the European Commission. The results were comparable to greenhouse gas emissions with the net saved environmental impacts being many times higher for all the environmental impacts analysed except mineral resource use caused by the indium used in the novel SHJ-PSC tandem module (see Figure 4). To conclude, the use of PV modules in AAF can reduce the greenhouse gas emissions per square meter of façade between 25 and 60 % if the production of the PV module and its produced electricity are excluded. If the production and life cycle of the PV modules are included into the analysis the AAF will cause net greenhouse gas savings up to four times higher than the production of the AAF itself. The results for environmental impacts other than greenhouse gases were similar except for mineral resource depletion. Overall, the building integration of photovoltaic modules as AAF will reduce the environmental impacts of the building while simultaneously providing a visually appealing building envelope.

2019

Le mur à haute performance thermique

Thierry Voellinger

The scope of this research includes the development of composite concrete façade elements that are thin, loadbearing and of high thermal performance. The research applies to manufactured precast concrete elements and focuses on improving their structure in terms of their construction but also their cost and environmental impact. During the last four decades, society’s energy efficiency awareness has been steadily growing in everyday life and in scientific circles. The Swiss Federal Institutes of Technology are promoting a plan known as the 2000 Watt Society (Société à 2000 Watts) which would reduce the energy consumption of the country’s inhabitants. In the context of Swiss construction, Minergie type labels are a requirement ensuring improved living conditions at lower energy consumption levels. These new ambitions increase the thermal requirements which in turn lead to the inevitable thickening of the building envelope. In a Swiss urban context, such as the Geneva region in particular, land is increasingly rare and the price of leasable surface continues to rise. As a result, the materials commonly used for insulation are economical but bulky ; they increase the thickness of the façades and significantly reduce the usable surface available for buildings. In an urban context such as this, what is the suitable dimension and fair price of a wall ? The method used was to analyze the strategies that would result in the correct dimensions of high thermal performance walls. Diminishing their width increases the area of livable surface while maintaining the wall’s thermal, static and sustainable standards. The objective was to establish a process for determining the composition of products that carry the Minergie-P and Minergie-Eco label. To this end, several tests and a pilot project for an individual house were carried out using optimum high thermal performance precast concrete walls as a model. The test demonstrated the feasibility of this type of wall. The innovation was to place between the two layers of concrete, a high thermal performance Vacuum Insulated Panel (VIP) type material and a traditional one. This combination allowed optimizing the thickness of the wall while responding to construction constraints. The proportion of the combination of insulation materials was selected according to their thermal performance, environmental impact and price. The goal was to maintain a constant thickness from the stages of project design to its completion. The argument of this dissertation is based on the conviction and the importance to commit to the use of high thermal performance construction materials overall in the future. At present, in the midst of a fossil fuel crisis, this is no longer just an individual concern. Indeed, the scarcity of fossil fuels and global warming are vital and critical problems that can be solved by using appropriate architecture solutions such as heat traps.

EPFL2012

Intégration des critères de durabilité dans le processus de conception des constructions temporaires à vocation événementielle

Loïc Vivien Fumeaux

Sustainability is a constant search for balance between the needs and the means implemented, which implies meeting the needs present without compromising those of generations to come. Later generations will indeed imperative to consider. So that their scope for action not be mortgaged by human activities of previous generations, it is necessary to provide some leeway, especially from the perspective of the built environment transmitted by inheritance. Alongside these general theoretical considerations, it is now observed a glaring mismatch between the rapidly changing socio-cultural practices and the very slow renewal of the built environment . Whether in the way to live or work , or occupy constructed in the need for research space flexibility , the frame is characterized by the notion of "impermanence" increasingly important, in contrast with the perennial character commonly accepted and implemented in current practices . Most buildings are built to last, but are part of a society where everything is changing rapidly and so are facing frequent shifting situations between form and function of spaces. In this context, the temporary architecture can therefore be a good potential to seek to meet the challenges of multiple time frames and offer a potential mutation. This architectural approach is thus fully in sustainability concerns mentioned above, since it aims to offer a potential for adaptation rather than fixed solutions. Aware of the extent of the issue and complexity of reflections on the question of the impermanence of the frame, especially in view of the nature of architectural practices, this work focuses specifically on a little explored area that day at the research for which the notion of temporality is short intrinsic data: the field of temporary constructions events vocation. Through an exploratory approach, research methodology convene an archetype of the temporary architectural design to examine it as an object of study that can ideally translate the challenges of a design associated with an approach based on time restricted use. The research first observed in detail these practices sometimes considered at the margin of the architectural discipline. The structured analysis of four representative case helps highlight their limitations in terms of sustainability. part of the research, evaluative approach includes the development of an assessment methodology, specifically adapted to this type of construction. The approach then proposes the development of an alternative solution, which optimizes its multiple performances in a perspective of sustainability and overall quality. Through an approach of "research by the project" an integrated design process (IDP), both interdisciplinary and participatory, is experienced first sketches to detailed development of a prototype. Finally, from the product of this reflection, research in general rises and explores many possibilities of using this new system. This approach allows to demonstrate the potential contribution of multiple functional areas, illustrating what could be the conceptual foundations of an "architecture of the event." The result is a research methodology both "multi-scale" and "multidisciplinary", which demonstrates the great potential for optimizing this type of construction and the need to achieve to grasp the design simultaneously at multiple scales and integrating all stakeholders.

EPFL2016