Rethinking construction practices
5' read - published March, 25th 2025
The buildings and construction sector stands as the largest emitter of greenhouse gases globally, contributing a staggering 37% of total emissions(1). This article delves into the lifecycle of construction materials and their significant impact on pollution. Construction and demolition waste (CDW) alone constitute more than a third of all waste generated in the EU. Depending on the country and its progress, anywhere from 10% to over 90% of this waste could be repurposed rather than ending up in landfills post-demolition(2). In addition to addressing waste management, we will explore not only repurposing of materials but also how we can conceive durable constructions.
With the looming specter of resource scarcity, escalating construction material costs, and increasingly stringent regulations, this not only carries ideological weight but also holds growing economic potential.
Designing for durable construction
Durable construction involves creating adaptable designs to minimize intricate building structure changes over time. High-quality materials, capable of lasting centuries, are essential, alongside meticulous maintenance and consideration of physical parameters. Ideally, the materials should be easily reusable without excessive effort and locally sourced. If every third builder in Switzerland were to opt for entirely circular building materials, the construction material cycle could be closed(3). The following two projects provide interesting examples in this regard. The Triodos Bank office was designed as a wood building that can be completely dismantled to facilitate adaptations and the reuse of materials. Similarly, the dismountable urban roadway, CUD, was developed to be easily removed during construction and then reinstalled.
Reusing materials
The building cost ratio of the load-bearing structure is around 32% of the whole construction(4). In terms of CO2 emissions, the ratio varies depending on the project, ranging between 30% and 80%(5). These two levels offer opportunities for optimization, particularly in skeleton structures, which provide additional flexibility within the construction grid. Furthermore, it is important to note that research has revealed that only 0.5% to 1.0% of existing buildings require demolition, as the rest are able to stand for another 30-50 years(6).
Si Advisors embraced these facts and developed a concept in which, as part of a real estate fund, they purchase aging apartments, swiftly renovate them in a plug-and-play manner for instant occupancy, and then resell them at elevated prices in just 90 days after the contract signing. Park house retained the existing load-bearing structure of a parking lot and constructed housing units within it.
Embracing an Urban Mining approach recognizes the city as a valuable source of raw materials, potentially enabling on-site reuse and reducing transportation and stocking costs, as demonstrated by Good Cycle. However, material reuse presents various challenges, which some companies have innovatively addressed.
Challenges such as careful dismantling are crucial and should not be underestimated. Rotor DC specializes in the dismantling, processing, and trading of salvaged building components. They've also developed a meticulous technique for tile dismantling, enabling complete reuse. Another major challenge is to maintain a well-structured inventory containing all the necessary information about materials slated for reuse. Superuse Studios, an international architectural collective, has created a map to locate materials seeking a second life.
Incorporating elements with complex shapes may benefit from digital twins to aid in the planning process. A practice not only used in rehabilitation projects, the digital twin of Shanghai was developed for city planners and engineers. It enables them to study virtual models, improve services, plan developments, optimize buildings, and monitor traffic flows.
Upcycling and Downcycling
Upcycling transforms existing materials into construction materials with added value. The environmental benefits are significant; aside from minimizing the volume of discarded materials sent to landfills annually, it also reduces the need for production using new or raw materials, leading to decreased air and water pollution, greenhouse gas emissions, and conservation of global resources. It is important to note that the added value of a brick may not necessarily be linked to its strength. A brick may be considered "upcycled" because it is now indefinitely circular, unlike the previous materials used to create it. However, in terms of stress resistance, it may be weaker.
BC Materials specializes in transforming ordinary earth streams, often considered waste, into circular building materials like clay plasters, compressed earth blocks, and rammed earth. This approach can be implemented on-site, enabling the avoidance of valuable excavated earth disposal, reducing transportation costs, and preserving resources.
Today, upcycling can be more economical than manufacturing new elements. However, each project presents unique challenges. The type and quantity of waste vary, and the processing methods depend on the material type.
Rotor DC, mentioned earlier in this article, upcycles lighting equipment and furniture. Arequipeña beer brand in Peru offers UV-resistant bottle tiles for roofing. Companies like Lana Bhalta and Byblock are transforming plastic waste into bricks, while StoneCycling produces biobased tiles and waste-based bricks from recycled inert materials.
Recycling is the process of converting waste materials into new materials of comparable value to the original material. Downcycling involves processing elements into lower-grade products. This can serve as a cost-effective alternative to reuse and upcycling, especially for materials with limited reusability, such as chemically bound materials. It often serves as the final option before landfill disposal. For instance, concrete walls can be processed into granulate, which can then be utilized for various applications like recycled concrete, rammed earth walls, bricks, and foundations.
Cities and lawmakers could take the first step towards facilitating more projects of this kind by providing the necessary expertise and streamlined paperwork guidance. This support would include expediting permits for specific individual materials, as they vary based on local availability and site conditions, while also safeguarding citizens from using inappropriate materials.
In conclusion, it's important to recognize that not all projects can be generalized, and each element should be approached in a specific manner based on the individual project's context. For instance, using untreated compressed earth bricks for highly exposed exterior walls is not advisable, just as it is impractical to keep excavated soil with high organic content or expansive clays on-site for brick production, as these soil types are unsuitable for this material.
However, a key guiding principle should be considered:
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Can the element remain in its current location?
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Can it be reused elsewhere on-site?
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Could it potentially be reused in another project? If so, how should stocking and logistics be addressed?"
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Is upcycling a viable option? -> Is on-site remanufacturing possible and effective?
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Can the element be recycled? -> Is on-site remanufacturing possible and effective?
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Is downcycling feasible? -> Is on-site remanufacturing possible and effective?
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Where can the element be disposed of cost-effectively and in an environmentally conscious manner?
Through the art of reuse, upcycling, and downcycling, we can revolutionize construction practices, close the material cycle, thereby minimizing landfill waste and reducing our environmental footprint. By embracing these practices, we can not only address environmental challenges but also unlock economic opportunities and foster a more sustainable future for generations to come.
Harnessing the power of digitization allows us to inventory and analyze materials with unprecedented precision, enabling informed decisions about their reuse and repurposing. However, navigating the financial, regulatory, and design challenges of sustainable construction requires concerted effort, with flexibility, innovation, and collaboration being key. Ultimately, sustainability in construction is about more than just compliance or cost-saving measures; it's about redefining our perception of beauty and embracing a new, sustainable aesthetic.
(1) Source: UN environment program, Building Materials And The Climate: Constructing A New Future, September, 12th 2023.
(2) Source: European Commission, Construction and demolition waste, 2018.
(3) Source: Urban mining, Fakten und Zahlen Urban Mining, 2024.
(4) Source: Bilfinger Tebodin, Construction cost analysis, 2019.
(5) Source: ScienceDirect, Embodied greenhouse gas emissions in structural materials for the German residential building stock — Quantification and mitigation scenarios, November, 1st 2023.
(6) Source: ScienceDirect, Embodied GHG emissions of buildings – The hidden challenge for effective climate change mitigation, January, 15th 2020.