A Modular Timber Construction System for the Sustainable Vertical Extension of Office Buildings

Most European cities are facing urban densification issues. In this context, a solution to create usable spaces without additional pressure on land consists in the vertical extension of existing buildings. Given their abundance in the building stock, tertiary buildings offer an important potential. The paper introduces the Working Space project, which aims to develop an innovative, modular and prefabricated timber construction system adapted to the vertical extension of existing office buildings. The dimensions of the system can be adjusted to a great variety of structural grids and allows for any new typological organisation. Based on the principles of bioclimatic architecture, the extension’s envelope provides high-performance insulation, a smart management of passive solar gains, natural ventilation and free cooling, but also offers large surfaces dedicated to photovoltaic energy production and urban biodiversity. The system is made up of eco-friendly, local materials with very low environmental impact. The project’s outcomes are presented at a variety of scales, from urban design to construction details, as well as the outputs of an extensive life cycle assessment including the induced mobility impacts. Finally, the paper introduces a first application of this innovative architectural concept, which is currently being completed in Lausanne, Switzerland.

Working Space – An innovative modular timber construction system for the sustainable vertical extension of office buildings

Aleksis Dind, Sophie Lufkin

Urban densification issues are one of the key challenges for most European cities. In this context, the vertical extension of existing buildings provides a solution to create usable spaces without wasting additional land. Little attention has been given to office buildings, although, given their abundance in the building stock, they offer an important potential. The 'Working Space' project gathers an interdisciplinary research team around the development of an innovative, modular and prefabricated timber construction system. The dimensions of the latter can be adjusted to the structural grid of existing buildings and to a great variety of new typological organizations. The extension’s envelope is based on the principles of bioclimatic architecture and combines active and passive elements. It features a high-performance insulation, provides a smart management of passive solar gains, natural ventilation and free cooling, and offers large surfaces dedicated to photovoltaic energy production and urban biodiversity. The system is composed of local materials with very low embodied energy. This paper presents the project’s outcomes at different scales, ranging from urban design to construction details, and the outputs of an innovative life cycle assessment. A first application of the system, comprising 40 workspaces, is currently being conducted in Lausanne, Switzerland.

2017

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

Towards Solar Decathlon: Concepts for a Sustainable Urban Water Management in a new eco-district

Gianluca Antonio Paglia

Water is rarely considered to be a crucial aspect in sustainable housing. In fact, water sustainability in eco-districts and in ecological architecture is frequently limited to recycling and reuse solutions. Why less water? What could explain the choice of an installation, of a specific strategy or of a criterion trying to decrease water needs? Terms as ecological footprint or sustainability are becoming more and more used, however, how can sustainability be measured? What does sustainable water mean? What are the parameters that quantify the ecological footprint of a water management system? Within this project, some possible concepts of optimization and valorization of sustainable urban water system have been defined and explored. Numerous studies about water management, water distribution, sanitary technologies, recycling, etc. have already been done. Nevertheless, it is less common to identify the reasons that are able to justify a reduced consumption of water. Eco-district labels propose several solutions for sustainable water, however they are limited by scale or simply focused on one stage of the water cycle. The aim of this project is then to consider water from a larger point of view: through a Life Cycle Analysis approach, needs and properties of different urban water management systems are compared and evaluated. The scale considered for such reflections is effectively a central parameter; in this case, hypothesis will be applied to collective habitations inserted in a district and part of a specific urban context: the city of Fribourg. The urban environment has particular features in relation to surrounding rural areas: energy exchanges, hydrology characteristics and limited ecosystems. The relationship between the use of natural resources and urban development is becoming more and more important; the purpose of this thesis is then to define a methodology able to suggest a sustainable use of water through environmental, political and economic issues. A real urban case study with its current water management system defines what has to be analyzed and allows evaluating the limits and the possible enhancements of such system. Thus, in order to have an idea about the potential of sustainable water management solutions, an ambitious analysis of energy related to water uses and disposals is created and is used to show the reasons for change in a real model as the city of Fribourg. A comparison between two extreme scenarios of Fribourg’s selected zones is finally developed, discussed and implied in the conclusions through specific actions and facts. The results show that a high potential of improvements exist. Using them to elaborate new strategies in collaboration with the several stakeholders contacted may contribute to achieve many of today’s objectives for a sustainable urban water management. The best scenario, chosen with a new concept of eco-label, summarizes and concludes the analysis.

2015