Building with sustainable materials means choosing structure, envelope and finishes that reuse what already exists, draw on recycled or renewable sources and carry the lowest declared carbon for the job they do. Two events in April 2026 show where the field stands: Milan Design Week, which ran from 20 to 26 April with materials and sustainability as main themes, and the Circularity Gap Report 2026, published on 16 April, which put a price on the value the world wastes through linear use.
Key takeaways
- Building with sustainable materials follows a simple order: reuse what exists, then use recycled content, then renewable or bio-based materials, then new materials with the lowest declared footprint.
- Milan Design Week 2026, from 20 to 26 April, listed more than 100 sustainability-focused events, and Materially’s exhibition “The New State of Materials” showed bio-based, circular and decarbonised options.
- Many exhibited materials are prototypes, so performance in fire, moisture and structure has to be checked before specifying them.
- The Circularity Gap Report 2026 estimates that about 25.4 trillion euros of economic value is lost every year through linear take-make-waste practices, nearly a third of global GDP.
- Environmental product declarations make it possible to compare materials fairly.
How does building with sustainable materials work?
The approach starts with a question about function: what must this element do, and for how long? A structural frame, a facade, an insulation layer and a floor finish each have different demands, so there is no single sustainable material. What can be shared is the order of preference.
- Reuse existing buildings, components and materials wherever possible.
- Use recycled content, such as scrap-based steel or recycled glass.
- Use renewable and bio-based materials, such as responsibly sourced timber, bamboo, hemp or straw, where they perform well.
- Where new mineral or metal products are unavoidable, choose those with the lowest declared carbon and the longest life.
Durability and maintenance complete the picture, because a material that fails early cancels the savings made when it was produced. Our article on sustainable materials gives the general criteria, and the piece on low embodied carbon materials explains how to compare carbon figures.
What did Milan Design Week 2026 show about materials?
A showcase of new material families
Materially presented The New State of Materials at Stecca3, a building designed by Stefano Boeri, as part of the Isola Design Festival. According to the organisers, it presented materials developed around innovation, circularity and decarbonisation, from alternatives to plastic and wood to smart and bio-based materials. Examples reported from the show included compostable packaging made from mycelium and biomaterials made from onion peels.
Waste as a raw material
Other exhibitions at the festival explored reuse and upcycling. Reports on the week described mycelium-based tiles and surfaces made from rice husk and coffee waste, and an exhibition called “No Space for Waste” devoted to circular design, slow production and material reuse. The organisers of the week listed more than 100 sustainability-focused events in total.
A note of caution
Design weeks reward novelty. A tile or panel that looks convincing in an exhibition may not yet have the test data, supply chain or certification required for a building. Treat these materials as a source of ideas, and ask for fire, moisture, structural and durability results before putting them into a specification.
What does the Circularity Gap Report 2026 add?
Circle Economy, working with Deloitte, published the Circularity Gap Report 2026 on 16 April. It introduces a “value gap” and estimates that the world loses about 25.4 trillion euros of economic value a year through linear resource use, close to a third of global GDP. According to coverage of the report, 10 trillion euros comes from end-of-life waste, where the value of discarded products is not recovered, and 5.2 trillion euros from the deterioration of buildings, infrastructure and machinery. The report’s introduction frames circular approaches as an economic opportunity as well as an environmental one.
For building teams, the message is practical. Maintenance, adaptability and reuse protect value that would otherwise be lost, and they are easier to achieve when materials are chosen with disassembly and repair in mind.
How can you choose materials for a building project?
- Survey the site first, and list what can stay or be reused.
- Define the function, expected life and performance requirements of each element.
- Compare candidate materials using environmental product declarations prepared to the same standard.
- Check technical evidence for structure, fire, moisture and acoustics.
- Plan the end of life: fixings that can be undone, material passports and take-back options.
- Record the choices and the evidence so that the next team can learn from them.
For wider principles, see our article on sustainable design in architecture.
Frequently asked questions
What are the most sustainable building materials?
There is no single answer, because the best choice depends on the function, climate and local supply. Reused components usually have the lowest impact, followed by recycled-content metals and glass, responsibly sourced bio-based materials and lower-carbon mineral products. Compare declared data for the same function.
Are mycelium and agricultural-waste materials ready for buildings?
Some are used in interiors, packaging and non-structural products, but many are still at prototype or early commercial stage. Before specifying them, ask for test results on fire, moisture, durability and structural performance, and for evidence of supply at the quantity you need.
How can I compare materials fairly?
Use environmental product declarations that follow the same standard and cover the same life-cycle stages, and compare products that perform the same function over the same service life. Be cautious with claims that give a single headline figure without stating its scope.