Data-driven method for low-carbon building design at early stages

The Paris agreement on climate change called for carbon neutrality as of 2050. The built environment is one of the major contributors to the greenhouse effect, representing 39% of global emissions. As a result, this sector is targeted by green standards and regulations to set limits for building carbon emissions. Life Cycle Assessment (LCA) is widely recognized as an appropriate method to measure these emissions. This is particularly critical at the early design stage where the decisions that most influence the project are made. However, previous studies show that current LCA methods, both time-consuming and requiring a high resolution of detail, are most inadequate, which makes them too rarely used by practitioners today. This thesis aims to tackle this issue by proposing a novel approach to LCA adapted to the early design context. The first step was the identification of obstacles responsible for the current low use of LCA. This analysis was based on an extensive survey about the practice of 500 architects and engineers in Europe. Secondly, a literature review identified four appropriate techniques to overcome these obstacles: parametric assessment, sensitivity analysis, target cascading and data visualization. Combining them to the LCA led us to the data-driven method for low-carbon building design at early stages we adopted in this thesis, removing the need to set premature assumptions about future design developments. The method proposes a knowledge-database of design alternatives generated with a parametric approach that applies a combination of user-defined design options, using the Saltelli sampling technique, to a project-specific massing scheme. Later, the carbon emissions of each of these design alternatives are calculated. It is thus possible to explore thousands of alternatives and understand the consequences of architectural choices on the carbon emissions by using data visualization techniques. Moreover, the method proposes Sobol sensitivity indices quantifying the design parameter influence on the carbon emissions, in order to limit the scope of building components that designers should prioritize. Finally, the method specifies carbon budgets, the upper limit of carbon emissions a building component should not exceed, with the possibility to compare this budget with any product available on the market that would not have been included upfront as a design option in the parametric approach. To assess the usability of the method, a computer-based prototype was thereafter developed to get it tested in the frame of a real design project. By taking advantage of the architectural competition for the Smart Living Lab in Fribourg, Switzerland, this critical testing phase was carried out by asking the practitioners involved to actually use the developed prototype to meet the SIA2040 carbon objectives set for the project. This thesis proposes a new method for effectively integrating GHG emission targets into the early stages of the design process with the aim to increase both acceptance and use of LCA in the design field, but also to inspire developers towards a new generation of LCA software.

Towards a pre-design method for low carbon architectural strategies

Marilyne Andersen, Arianna Brambilla, Stefano Cozza, Endrit Hoxha, Thomas Bernard Paul Jusselme

To face climate change, Switzerland proposes the 2050 energy strategy by fixing greenhouse gas (GHG) emission targets for the built environment. Designers will then have to increase operating performances while inimizing embodied impacts. This represents an issue for the building design process. In addition, there is a relationship between the design efficiency and the early integration of the knowledge about design. The purpose of this paper is to highlight the potential of a pre-design method to identify the building design parameters that reach the 2050 climate change objectives. To that end, four major steps are developed in this project. First, design parameters (e.g. wall thermal transmittance) which influence the building GHG emissions the most, are identified thanks to a literature review. Morris method (Saltelli et al, 2004) is used to create combinations of design parameters changing their values one by one. Secondly, these combinations are attributed to architectural feasibility studies (Sinclair, 2013) developed in the brief design phase to perform lifecycle analysis. Thirdly, KBOB database (KBOB et al., 2014) and lifetime of components proposed by PI-BAT were used for assessing GHG emissions. Lesosai software was used for primary energy assessment. Lastly, the combinations of design parameters and their relative GHG emissions are interpreted with data mining and visualization techniques. The smart living lab building has been chosen as a case study: this building aims at achieving the 2050 goals of the 2000-watt society vision and will be built by 2020 in Fribourg, Switzerland. Thanks to the preliminary results it is possible to rank the design parameters according to their GHG contribution, in order to highlight them during the early building design stage. The method offers combinations of design parameters allowing to reach the 2050 climate change objectives. Data mining and visualization enable designers to easily find the values of these parameters to fit into the architectural strategy. In order to offer a wider range of design parameter values, techniques to enhance the database should be further investigated.

2016

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

Sergi Aguacil Moreno

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 mid- to 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 zero- to 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 case-specific 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) multi-criteria 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.

EPFL2019

Design guidance from a Data-Driven LCA-Based Design method and tool prototype

Marilyne Andersen, Thomas Bernard Paul Jusselme

As of 2020, every new building in the European Union will have to reach the nearly Zero Energy Building (nZEB) performance. However, building nZEB will not be sufficient to reach carbon neutrality in 2050 as required by the last IPCC report: indeed, even nZEB consume energy due to their embodied impacts. Thus, life-cycle assessment will become a mandatory approach to mitigate environmental impact of buildings beyond the nZEB performance. However, the complexity of Life-Cycle Assessments (LCA) continues to make it difficult for it to be effectively used at the early design stage. A promising theoretical framework called LCA-based data-driven method had been proposed in prior work by the authors to tackle these issues (Jusselme et al. 2018a). This paper presents the prototype that has been built for the developed method to be tested in a first application. The case study chosen for this application is the future building of the smart living lab in Fribourg, which aims to reach the SIA2040 performance threshold. A specific knowledge database of 20’000 design alternatives – with a LCA performed for each of them – was thus generated with a parametric approach. First, the method provides sensitivity indices so as to better understand the influence of different design parameters. Second, performance target values are provided at the building component level in order to choose building techniques and materials in accordance to the SIA2040 objectives. Ultimately, the method offers site-specific guidance with an exploratory perspective. By literally exploring a database of design alternatives generated specifically for that site and urban context, the user (designer) gets valuable insights about the choices still available when other decisions are made if the SIA2040 performance ambitions are to be kept. In comparison to current practices, this case study demonstrates the ability of the method to provide a highest amount of design insights beyond the simple assessment process, in a shorter time. Further research needs to be carry out to verify the benefits of the method in the frame of a real design process, thanks to practitioner’s evaluations and feedbacks.

2019