Do You Speak Circular?

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Renovation of a building in Sweden, for which the old windows were recovered and sent to a foundry to be reprocessed. An illustration of the virtuous circle of the circular economy.

Circularity
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Reading time: 5 min 5 min
22/12/2025

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The vocabulary of the circular economy is becoming established in the building sector. From upcycling to CMUR, including secondary raw materials or EPDs, this glossary deciphers the key concepts to better understand and implement the circular transition in construction.
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Upcycling


Refers to a process of transforming waste or by-products into new products or objects of higher quality than that of the original material or product. Unlike traditional recycling, which involves energy-intensive transformation, upcycling does not degrade the physical or chemical properties of the material but aims to enhance used products by giving them a new, higher-quality life. In other words, it gives a “high-end” new life to the original material (wood planks, old tarpaulins, fabric, cardboard, plastic packaging, etc.), often very far removed from its initial use. In doing so, it reduces demand for virgin resources and helps limit environmental impacts.

In the building sector, a project such as Upcycle House, carried out by Lendager Arkitekter in Denmark, made it possible to reduce embodied CO₂ emissions by 86% compared with an equivalent conventional construction project.


Downcycling


In contrast to upcycling, refers to a process in which materials are transformed into products of lower value than the original material. This practice causes a loss of functional or mechanical properties, reducing the range of future reuse possibilities. As a result, the material’s life cycle is only rarely extended.

For example, crushing glass to turn it into road aggregate degrades the material, limiting its reuse to a range of only 10 to 20%.


Virgin raw materials


Refers to raw materials extracted directly from natural resources, such as wood, minerals, or oil. As such, they do not result from a recycling or reuse process. Consequently, their extraction carries a high environmental cost for natural ecosystems, in addition to requiring significant water consumption. It is also one of the main causes of greenhouse gas emissions, since most of the energy used to extract materials from mines and quarries and to process them is fossil-based energy.

According to the Ellen MacArthur Foundation, adopting circular economy principles could reduce emissions by up to 50% in the construction sector by improving material efficiency, increasing recycling rates, and reducing waste.


Secondary raw materials


Unlike virgin raw materials, this term refers to materials obtained at the end of a recycling or recovery process involving waste or end-of-life products. They therefore replace virgin raw materials in the production cycle, with a lower environmental impact and reduced pressure on ecosystems. Provided they meet sufficient quality criteria, secondary raw materials help significantly reduce the carbon footprint of a product.

As an example illustrating the benefits of secondary materials, in Europe, steel recycling is estimated to reduce energy consumption by nearly 72% compared with steel produced from ore.


Circular Material Use Rate (CMUR)


Refers to an indicator developed by the European Union that evaluates, for a given production cycle, the ratio of secondary materials in the total input of materials used. The higher the CMUR, the more sparing the cycle is in virgin raw materials and the more efficient the circulation of resources. In the construction sector, it makes it possible to measure the level of circularity of the materials used and their effective recovery.

The European Environment Agency indicates that the CMUR across the entire European Union stood at 11.8% in 2023, an increase of 1.1 percentage points compared with 2010.


Environmental Product Declaration (EPD)


Framed by the international standard ISO 14025, the Environmental Product Declaration (EPD) is a document that inventories the environmental impacts of a given product or material. It includes detailed and precise information on the negative externalities generated throughout the product’s life cycle, such as the production of non-recoverable waste, toxicity, CO₂ and ozone emissions, and water consumption. The EPD is valid for five years.

Depending on the formulations used to produce lower-carbon concrete, known as “low-carbon” concrete, it is possible to achieve reductions in the carbon footprint of concrete of up to 60%.

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