What are Sustainable Materials? (why a "Green" material isn't always the best choice)

Energy use in production

The embodied energy (the amount of energy required to produce the material) plays a major role in CO₂ emissions.

Lower energy consumption in production (and transport) usually means a lower CO₂ footprint. Bricks or cement, for example, require a lot of heat (often fossil-based), while recycled materials or cold-produced elements require less energy in production.

EXAMPLE: Mimmik Tile skips the firing step entirely — it’s grown at ambient temperature through a bacterial process (MICP), not fired in a kiln.

CO₂ emissions and climate impact

Although closely linked to energy use, this specifically concerns the carbon footprint of the material.

Materials with low CO₂ emissions or even negative emissions (for example, wood that stores CO₂ during growth) are favourable. This concerns emissions across the entire lifecycle: from extraction to production, transport, use and end of life.

CO₂ storage

Some materials store carbon during their service life, such as wood, hemp or bio-based composites. This carbon sequestration lowers the net GWP (Global Warming Potential) and is factored in as a positive contribution in future regulations, such as WLC (Whole Life-Cycle) reporting.

Origin of raw materials

Raw materials that score higher on the ‘R-ladder’ (Remine > Recover > Recycle > Repurpose > Refurbish > Remanufacture > Repair > Reuse > Reduce > Rethink > Refuse) generally perform better.

Virgin raw materials that can be replaced by recyclate or bio-based raw materials are preferred.

EXAMPLE: WasteBasedBricks are made from construction and demolition waste instead of virgin clay and carry an MKI (Dutch Milieukostenindicator, an Environmental Cost Indicator) score of €1.80 versus an industry average of €3.42 (verified by the Dutch NMD).

Renewability and circularity

A sustainable material is circular — it can be reused or recycled after use, or it is biodegradable. This is also referred to as ‘future scenario’ or ‘reuse potential’.

Designing for reuse/recycling

Think of modularly applicable building products that are simply detachable or dismantlable, or bio-based materials that can re-enter the biological cycle after their service life.

Durability over time also counts: materials that last long or are infinitely recyclable (such as steel or glass) save raw materials in the long term.

Detachability

The way materials are attached to each other with the possibility/intention to separate them again in a later phase, without permanently damaging them. This allows them to be reused higher up the R-ladder.

Detachability is assessed based on the type of connection (dry or wet/chemical); its accessibility; the addition of elements such as screws, bolts and nuts; the intersections between materials and elements (think of pipework); and edge closures (e.g., is a partition wall floating or poured into the floor?).

Detachability leads to financial benefits because materials in utility construction are no longer written down to zero euros. This results in a more favourable value on the balance sheet and also leads to further reductions in replacement or maintenance situations, because materials are easier and cheaper to replace.

Health and toxicity

An often underappreciated aspect is whether the material has clean content.

Sustainable materials preferably contain no toxic substances that are released during production, use or disposal. Think of volatile organic compounds (VOCs) or heavy metals — these should be avoided to maintain both the environment and the indoor climate.

Labels such as ‘VOC-free’ or the avoidance of PVC and formaldehyde-containing adhesives are examples. 

PLEASE NOTE: This is also why virgin and recycled versions of the same material can score very differently. PVC production from virgin feedstock is a legitimate concern; PVC diverted from the waste stream, as in the Pretty Plastic Panels, removes an existing toxicity liability rather than creating a new one. The distinction matters!

Other environmental effects

Other impact categories may also be relevant, such as water consumption in production, the effect on biodiversity, or the influence on land use and ecosystems.

A material that leads to deforestation or mining in vulnerable areas scores less sustainably, regardless of other advantages.

Transport distance also plays a role: two materials with identical production footprints can differ significantly once shipping is factored in, which is one reason local or regional sourcing is often — though not always — the lower-impact choice.

A few illustrative examples

→ Wood from sustainably managed forests (with FSC or PEFC certification) is renewable and sequesters CO₂, provided it is applied well so that it lasts.

→ Aggregates from demolition for, for example, recycled concrete or bricks utilise existing waste and reduce the demand for new minerals (gravel, sand, clay).

→ Bio-based insulation materials such as hemp, flax or sheep’s wool have a low environmental impact and no harmful fibres but must be sufficiently available and functional. Especially for outdoor use, synthetic (fossil) additives are often added to make the material fire-resistant or waterproof, for example. This can negate the bio-based benefits.