s one of the largest contributors to worldwide CO2 emissions, the construction industry plays a crucial role in global sustainability efforts. Modular building, plus the reformulation of buildings for reuse, are two important pieces in the industry's sustainability puzzle.
By its very nature, the construction industry is a significant consumer of natural resources. Every building, from a single house to a towering skyscraper, creates demand for new materials. When these structures outlive their usefulness, demolition typically creates large volumes of waste – most of it bound for landfills.
The European Commission estimates that 50% of all extracted material is consumed by construction, which is responsible for more than 35% of the European Union’s total waste generation. Though volumes have fallen since the Paris Agreement in 2015, the United Nations still estimates that the construction and subsequent operation of buildings accounted for 37% of energy-related carbon dioxide emissions worldwide in 2020.
As a result, players in the construction industry are under pressure to reduce their CO2 emissions and solid waste. Construction companies and their clients in the private and public sectors are, therefore, moving toward a more efficient, sustainable system of operations known as circular construction.
Whereas current construction practices which dispose of materials at the end of their original use, circular construction aims to keep materials in use for as long as possible, extracting maximum value before recovering, recycling or repurposing them at the end of a building’s useful life.
MATERIAL GAINS
The first challenge in achieving circular construction: choosing which materials to use and how to use them.
Traditional concrete, for example, is produced with processes that generate significant CO2 emissions – and it generally cannot be reused to build something else.
“Concrete contributes more than 6% of our planet’s greenhouse gas emissions,” said Fabrice Bonnifet, director of Sustainable Development & QSE (Quality, Safety, Environment) at international construction firm Bouygues Group. “Currently, it is a low-cost material, but a €100 [US$121] per ton tax is expected soon in Europe and elsewhere. This prospect is forcing the industry to innovate its material science and usage.”
Andrea Charlson, built environment lead and CIRCuIT project manager at ReLondon, a governmental partnership formed to improve waste and resource management, says that while it will be difficult to eliminate the use of concrete entirely, a different approach to the material could lessen its impact.
“Concrete is widely available and cost effective, so it’s going to be hard for us to stop using it and similar materials entirely,” she said. “The question, therefore, is: how do we make concrete reusable? If we begin to use it in modular, precast forms designed for deconstruction, then it’s much more easily reusable than if it is poured onsite. Used concrete can be recycled directly back into new, high-strength concrete or disintegrated back into its individual components. In this way, we can hopefully continue to use these materials, but in the right places and in the right ways.”
In addition, reusing the structure of existing buildings instead of demolishing them completely can reduce the demand for raw material. Achieving this will require a new approach from the very outset of construction projects.
Concrete is widely available and cost effective, so it’s going to be hard for us to stop using it and similar materials entirely. The question, therefore, is: how do we make concrete reusable?
Andrea Charlson
Built Environment Lead and CIRCuIT Project Manager, ReLondon
“At the moment, we like to start with a nice blank sheet of paper when we're designing something new,” Charlson said. “That mindset needs to change, even before the design process itself begins. When the brief is being created, the developer needs to be thinking about how they can retain as much of the building as possible and how they can add as much value to it as possible. It is possible, for example, to make a building taller or shorter, or separate it into two. Then the existing concrete can be maintained, providing the long life that is key to a circular economy model.”
International engineering and construction company Laing O’Rourke is on the path to change as well. “As part of our work to reduce carbon at every stage of a building’s lifecycle, we have developed a prototype demountable systemic building solution – or D-frame, for short,” said Adrian Spragg, global head of digital, Laing O’Rourke. “It’s demountable to enable circularity and this, allied to the use of lower-cement concrete, means it can deliver significant double-digit carbon savings compared to traditional building using components like solid floor slabs.”
MODULAR CONSTRUCTION
Choosing reusable materials is only part of the battle, however. Traditional construction methods also generate significant waste, with materials cut-to-fit or formed onsite. Excess material – cut away pieces of wood and miles of wiring, carpeting and other materials that are too difficult to organize, transport and store – lands in the dumpster, wasting money. Sequential construction – completing each step before moving onto the next – also leads to unnecessary rework, wasted time and wasted money as one trade’s installations must be reworked to make way for another’s.
Modular construction offers a promising alternative. Modular – also known as design for manufacturing and assembly (DfMA) – involves precision manufacturing of components in a factory, then transporting them to the building site for assembly.
“One of the key areas for us in improving sustainability is our offsite manufactured and modular approach to building,” Spragg said. “You can reduce waste by optimizing the design modules, and an offsite manufacturing approach is more efficient in production and in the transportation of materials to the site.”
Modular construction also accelerates the process by allowing contractors to build some modules while installing others. Modules produced to precise specifications also minimize waste; wire, for example, can be cut to precise lengths – never too short and never too long. Excess materials remain in the factory, simplifying recycling and reuse.
“Resource efficiency is one of the key drivers behind the concept of the circular economy,” Charlson said. “If we adopt these practices effectively, we should be using less new materials, reducing the associated costs and waste.”
VIRTUAL OPTIMIZATION
Virtual technology is particularly important for optimizing modular construction, because DfMA identifies and resolves issues and optimizes manufacturing via virtual 3D computer models, before consuming any physical materials.
Modular construction start-up Assembly OSM, for example, uses virtual design and manufacturing technology to create apartment units for 10- to 30-story buildings. The company’s goal: to complete more houses more quickly, addressing the US housing shortage. It does so using a range of components designed in virtual 3D to fit together perfectly, with every item tracked, assembled and placed according to specifications generated by a 3D virtual twin.
“Good design shouldn’t be a luxury reserved for the world’s elite,” Bill Sharples, founder of Assembly OSM and design firm SHoP Architects, said in a recent interview with Real Estate Weekly. “The platform is built to be agnostic to architects. So if a developer wants a Frank Gehry façade, it can be done using our platform. Our vision for Assembly OSM is bigger than just one building; we set out to change how buildings are built in the future.”
Because all components are easily removable and replaceable, Assembly OSM’s model will reduce material orders and budget overruns and quickly facilitate repairs and upgrades.
Virtual twins also deliver benefits beyond the design phase. For example, Spragg said, a similar approach can help a building owner operate it more efficiently and facilitate maintenance and renovations in the future.
“We see great potential in virtual twins to help our clients across the project life cycle,” Spragg said. “The construction sector has an opportunity to make huge strides in optimizing building design, construction and operation using this technology, and I absolutely think we can get to that point – learning from similar approaches in more digitally mature industries.”
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