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Selective demolition and high-quality recycling of construction and demolition waste are crucial for the implementation of a circular economy in the built environment. To investigate this further, we conducted a case study on a building to assess the environmental and economic potential of selective demolition and advanced recycling. Two demolition strategies (highly and partially selective) were assessed, in combination with four mineral waste recycling scenarios that differ in plant type (mobile or stationary) and recycling technique (conventional or advanced). Highly selective demolition resulted in lower environmental impacts across most categories. The global warming potential results range between −33.8 and − 15.1 kg CO2-eq/m2, with the highly selective options performing substantially better, considering the avoided impacts. The environmental differences between mineral waste recycling options were minor in most impact categories, although two exceptions occur in terrestrial ecotoxicity and ionizing radiation categories. Also, different impact methods for mineral resources lead to different outcomes, depending on whether the construction aggregates are considered within characterization factors. From an economic perspective, the difference between highly selective demolition and partially selective options is rather smaller due to higher labor costs and low market conditions for higher quality recycled aggregates. Estimates of material flows through detailed modelling of selective demolition and different options for recycling of mineral waste are essential in the context of the circular economy. The availability of primary data for detailed modelling is crucial together with the inclusion of different impact assessment methods for resource indicators and critical interpretation through sensitivity analysis.

The idea of "CircuClarity" was born at the last glasstec 2022. The vision of Lisa Rammig and Linda Hildebrand was to create a platform for the exchange of knowledge that would lead to real progress and innovation in the glass industry. The focus is on circularity, resource efficiency and environmental impact. In this interview, the two explain what drives them and what they would like to see in the glass sector.

In the winter semester 22/23, students at RWTH Aachen University investigated various deconstruction scenarios for a building in Aachen that had been released for demolition. The task was set by the chair of Reuse in Architecture under the direction of Prof Linda Hildebrand. Representatives of the City of Aachen, Wienerberger, KadaWittfeldArchitektur and Alsecco were present as critics to provide input for the review. This brochure is based on the submissions of the aforementioned students, whose contributions were edited by Linda Hildebrand, Kim Tran and Anna Kollmann. We would like to thank Wienerberger for making this publication possible, which was supported by the PR agency Kopfkunst.

Prof Linda Hildebrand is a Professor for Reuse in Architecture at RWTH Aachen University and co-founder of Concular. In her teaching and consulting practice, she is committed to a sustainable approach to existing buildings. In this interview, she tells us what needs to change in today's construction practice and what role digital tools play in this process.

The environmental impact of the construction sector can be improved in various life cycle phases of buildings. With the reductions in the operating phase, the building fabric as a potential is moving more into focus. A building that cannot be reused or repurposed as such ties up valuable materials that, if utilised, can replace primary raw materials and environmental impact for new production. In Germany alone, around 28 billion tonnes of material are tied up in construction and consumer goods, with mineral fractions accounting for the largest share. The intrinsic value and potential uses of materials from demolition vary and depend on material properties, the size of the material stream, purity of type during demolition, available processing routes and the possibility of substitution, i.e.

products that can use recycled raw materials.

The construction sector is responsible for around 40 percent of greenhouse gas emissions worldwide. Its transformation is therefore central to achieving the climate targets. One important approach to this is circularity in the built environment. Raw materials, which are often energy and CO2-intensive to produce, should be reused and recycled in line with the circular economy. This includes the preservation and upgrading of existing buildings, which are perceived as a valuable source of materials.

Three important insights of the conversation:

1. We need to build less. We need to make better use of existing building materials and buildings and design new buildings to be circular.

2. The transformation of the construction sector can only be achieved through new forms of collaboration.

3. Digital twins and detailed building and material passports are key to the measurability of value chains.

New impetus for the construction industry: thinking in cycles beyond the life cycle of a property has enormous ecological potential. The advantages are obvious: even if this requires nothing less than a holistic change in companies.

This feature looks into different ways to design buildings in climate neutrally in an as-if approach. A variety of construction principles is presented such as using reused, recycled or renewable material. Different experts are interviewed such as Natalie Essig and Linda Hildebrand.

The question of the environmental impact of buildings is increasingly taking centre stage. Designers and engineers should make much greater use of the "urban mine" and reuse building products from existing cities, demands researcher Linda Hildebrand from RWTH Aachen University.

Current instruments such as the EU taxonomy are intended to promote the sustainable financing of buildings. With their implementation, the framework conditions for the introduction of building resource passports (GRP) in new and existing buildings are changing. The GRP bundles information on the products installed and their construction and can be used as a verification tool to fulfil regulatory requirements. In addition, its use offers added value, especially for planners, which can stimulate ecologically motivated planning in the long term.

Building envelopes are not only the prime element of the exterior aesthetic quality of buildings; they have also become a major driver both for building construction cost and operational performance. The importance of prefabrication is growing in the building industry as it allows faster, high-quality, and cost-effective construction while reducing risks associated with onsite labour. Although prefabrication for structural components is a relatively recent development, it has been widely used in the manufacturing of building envelopes for many years, particularly in the case of unitized curtain wall systems. However, whether using prefabricated components or not, façade design development remains a challenge due to the need for façade engineers to rapidly develop technically viable and financially feasible solutions that achieve the desired architectural design intent. Particularly at the early stages of the design process, the turnaround for multiple iterations is often fast-paced, and abortive work is, therefore, not uncommon. This paper outlines an approach to addressing this challenge, attempting to bridge the gap between façade design, fabrication, and installation. A new design approach and tools are presented that allow designers to iteratively validate concepts based on a pre-engineered system that is optimized for performance and take fabrication, transport, installation costs, maintenance, and circularity into account. As a result, the tool/design workflow will ensure consistent quality, meeting budgets and timelines while enhancing material efficiency and fostering energy-conscious and circular envelope design approaches.

The NRW-wide residency programme for urban art and urban research made a guest appearance in its second programme year in East Westphalia-Lippe with the Rochdale Barracks project location. In collaboration with the city of Bielefeld, Bielefeld University of Applied Sciences in the departments of architecture and design, a wide-ranging local programme network and the Roman architecture collective orizzontale, the project artistically negotiated the co-productive neighbourhood development of Rochdale and activated the former barracks for a subsequent socio-cultural interim use. The residency opens the gates of the barracks to the public for the first time since its inception.

Climate design and climate engineering are now standard components of the design process in contemporary architecture. The more successful we are in this, the less energy we need to run the building during its useful life and we can focus instead on an additional aspect: the embodied energy, the energy we need for the material production and construction process. This aspect triggers us to reconsider the design potentials of focusing on less energy in the construction. Which materials make sense energy-wise? Do we need to build with simple materials for 500 years or should we go high-tech and design the complete life cycle for a perfect reuse with maximum recyclable materials? Or should we build out of materials that can be used as energy after being a building? This publication focuses on the embodied energy aspects of building materials, their life cycle and their potentials for reuse as energy or in construction, and presents some far-reaching design ideas.

Architects much prefer to design new buildings. It gives a clear style and language, defines a position and contributes to developments in architecture. But today’s reality is that most buildings we will use in the future have already been built. We are required to reimagine them, whether refurbishing them for a better performance or giving them an entirely new duty.

This is the theme Reimagining Housing is targeting: the potentials of refurbishing an existing building not just to better insulate it but also to generate a new idea for the existing house, whether in the sense of retaining its spirit, refreshing it, spicing it up or renovating it completely.

This theme is placed in relation to the various existing dwelling and housing types in the region that combines the provinces of Groningen in the Netherlands and Niedersachsen in Germany – a typical non-urban European region. The book concludes with a welter of ideas, sketches and concepts that will challenge and provoke the thinking of architects.

In the last three decades, architects and engineers have learned about the environmental impact of building materials in addition to the impact caused in the operational phase by heating, cooling and electricity. The method that helped to raise awareness for this topic is life cycle assessment (LCA) that quantifies environmental impact related to the building fabric. This chapter discusses the interdependencies of environmental impact in facades, explains the relevance of façade typology and the scope of LCA in the design process. It introduces the basics of the method itself and provides an overview of software tools. It concludes with a reflection on the application in different national contexts.

With decreasing energy demand, the ecological impact related to the building fabric becomes more relevant and climate goals can only be reached when considering both. In the last decades, political regulation and standards were released to promote the reduced consumption of primary resources. Architects and planners approached this topic with different strategies by working with reused building elements, developing new products or using types of connection which provide easy disassembly in the future. In the last decade, the instruments to quantify the ecological impact advanced from life cycle assessment (LCA) data in spreadsheets to tools which connect ecological data with building volume and self-optimizing solutions. The treatment of the building materials after the use phase is subject to speculations as framework conditions in the future will develop. Today deconstruction (in difference to demolition) is rarely executed and research is limited. Construction and material choice impact the environmental qualities by the energy and emissions related to the production and the treatment scenario at the end of life. Against this uncertain background, a method is needed to indicate the environmental impact by evaluating the suitability for further use, like reuse or recycling. The paper introduces three approaches to indicate parameters available in the planning phase to possible treatment paths for the material after usage regarding practicability and reliability.

Building industry impacts natural cycles and has potential for optimization. While impairment on nature reached a new dimension already some three centuries ago the building industry started to realize the dependency in the second half of the 20th century. With LCA method all life cycle phases can be monitored and the environmental impact of each can be quantified. The energy consuming and emission generating components in the building context can be distinguished in the groups transport, operation and material. An architect deals with the operational energy and the building substance. With nearly zero (not renewable) energy for operation an ecological building is defined by the building substance.

Environmental aspects have shaped façades in various ways over the last decades. The decreased demand for operational energy and the growing share of renewable energy lowered the amount of greenhouse gas emissions during this phase. Based on this improvement, the building fabric becomes the relevant parameter with environmental potential to unlock. Buildings in stock store energy and greenhouse gas emissions linked to their production and can provide spatial quality with low environmental impact. Keeping the buildings as an active part of the built environment requires technical solutions as well as adaption in the design and fabrication process. PowerSKIN 2022, titled “Build in stock – renovation strategies: inorganic, circular materials vs organic, compostable materials”, presents different approaches grouped into the themes “Energy”, “Envelope”, and “Environment”. As an international scientific event, the PowerSKIN Conference builds a bridge between science and practice, between research and construction, and between the latest developments and innovations for the façade of the future. The Technical University of Munich, Prof. Dipl.-Ing. Thomas Auer, TU Darmstadt, Prof. Dr.-Ing. Jens Schneider and TU Delft, Prof. Dr.-Ing. Ulrich Knaack, are hosting the PowerSKIN Conference this year together with the local hosts from RWTH Aachen, Prof. Dr.-Ing. Linda Hildebrand and Prof. DrIng. Daniele Santucci. It is the fourth event of a biennial series. Architects, engineers, and scientists present their latest developments and research projects for public discussion and reflection.

The challenges to which contemporary building design needs to respond grow steadily. They originate from the influence of changing environmental conditions on buildings, as well as from the need to reduce the impact of buildings on the environment. The increasing complexity requires the continual revision of design principles and their harmonisation with current scientific findings, technological development, and environmental, social, and economic factors. It is precisely these issues that form the backbone of the thematic book, Sustainable and Resilient Building Design: Approaches, Methods, and Tools.

Earth is one of the oldest and till now intensively used natural building material. Around 30% of the world population still lives or works in buildings constructed out of earth. Most of them dwell in simple huts of rural communities or traditionally hand-crafted buildings. However, a growing number of people looking for healthy, environmentally friendly buildings in so called developed societies experience benefits of earthen construction materials. Due to the hygrothermal potential of clay, these benefits of earthen constructions include evaporative cooling during cooling periods and stable relative humidity levels indoors during the heating season. In addition, earthen building materials may contribute to the urgently needed circular economy, as earthen constructions like earth blocks or earth dry boards are reusable and earth plasters and mortars are replasticisable through the addition of water, as long as no chemical binder is added. Research gaps regarding physical properties, missing standardisation concerning building law and modern construction methods, and a limited number of manufacturers are hindering a wide application of earthen construction worldwide. Meanwhile, new digital production techniques evolve, which may elicit the potential of earth as future building material. Therefore, this Ten Questions article presents the state-of-the art and research gaps related to earth as building material in light of the potential of new digital production techniques like robotic fabrication or additive manufacturing. Such discussion includes new opportunities to combine the natural performance of the material with future-oriented construction systems and a new growing circular economy.

A focus on embodied emissions in building materials has been notorious in the last years, mostly due to high improvements in optimisation of operational energy in buildings. The environmental impact of building materials reflected in embodied energy and potential (re) life options that stimulate circular flows has become the focus of discussion. During the design process, designers and engineers are confronted with different decisions that might impact the embodied emissions (EE) of a façade system. This paper focuses on the EE of different curtain wall configurations whilst applying the Kit-of-Parts approach in a case study in California. The study was carried out under the LCA methodology applied from the A1 to A4 stages and limited to five main parameters: façade typology, span and grid size, different LCA phases, material choice, and supply chain. The results are compared against each other to understand the relevance of each parameter and level of impact of each parameter.

Additive production techniques such as 3D printing and robotics enable new production methods and possible uses for earth, as one of the most ancient building materials in the building industry. This study examines the potential of different building elements and components and their possible combinations made of or containing earthen building products. In addition to the 3D printing of lightweight, highly insulating external and heavy internal wall elements and load-bearing rammed earth walls for use as inner and outside walls are compared. Furthermore, the activation of the walls with water-based heating and cooling elements is taken into consideration. In particular, the sensitivity of earth to humidity and water has a positive effect on all life cycle phases from production through operation as a low-tech building to the end of use, i.e. the reuse as well as the possible return to natural cycles. The focus of the study is to assess the building material earth in light of modern production methodologies, the impact on indoor comfort and indoor air quality as well its life cycle assessment.

In this special episode recorded at Glass Performance Days 2025, we talk with Sophie Pennetier, Graham Dodd, Linda Hildebrand, and Bertrand Cazes about circular design, material reuse, policy frameworks, and the future of sustainable facades. Hosted on Acast.

Assessing the ecological footprint of building materials is becoming an increasingly important factor in the planning process for construction projects. In energy-intensive industries such as the flat glass industry in particular, the high energy requirements in production mean that there is enormous potential for reducing environmental impact through more efficient use of existing resources. In addition to high-quality recycling of flat glass cullet, other options for reusing or reprocessing existing glass are also being considered. This case study examines the global warming potential (GWP) of glass products manufactured using reprocessed float glass (‘remanufactured float glass’). Using a simplified, model-based life cycle analysis based on existing environmental product declarations (EPDs), different configurations of common glass products are compared.

While BIM-based LCA is widely adopted in later project stages, its integration into early phases remains challenging. In this study, we focus on the most common problems that hinder early phase BIM-LCA integration and possible approaches to address them. Among the various issues raised, this contribution concentrates on three recurring themes that were emphasized across multiple discussion groups in our practitioner workshop and that closely align with unresolved gaps identified in the literature.

Architects for Future have articulated 10 demands for a transition of the building and construction sector to sustainable practices. This shift must be embedded and construction sector. This shift must be embedded in educational programs, and we need to establish new networks and teaching initiatives.Together for the the building transition, the “Bauwende”! Since 2019 Architects for Future has been the leading voice in the movement for the Bauwende in Germany. More and more people are joining our cause, which has now become international. In 2023 we were invited to hold a visiting which has now become international. In 2023, we were invited to hold a visiting professorship in “Architecture for Future” at TU Berlin, where we integrated Bauwende in the architectural curriculum. In 2024, we launched a new network of professors who are committed to incorporating the Bauwende into their courses. We also started a new hybrid lecture and dialogue series, with 13 universities participating and 22 experts providing insights on the 10 demands of Architects for Future. Each week, we reached over 750 students. We intentionally sought to introduce the topics of the Bauwende and the climate movement into education to raise students’ awareness and knowledge, while also encouraging political engagement to some extent. Architecture is far more political than many realize, but these connections have yet to be adequately addressed in academic programs.