What is the best sustainable insulation material?
An honest comparison based on life-cycle analysis (LCA) and environmental cost — not purchase price alone. Based on New Economy’s study of fifteen circular insulation materials for the City of Amsterdam.
No single winner, but three best choices
The best insulation material depends on the application. New Economy’s LCA of a model dwelling points to flax board for the roof, cellulose for cavity walls and LDPE foil for floors — each the best balance of CO₂, environmental cost and price. Biobased materials can even be net CO₂-negative. The cheapest material (stone wool) carries the highest environmental cost.
Read the underlying studyThe comparison by material
New Economy assessed fifteen materials on CO₂ emissions, reuse, price and building environmental performance (MPG, in euros per m² per year — lower is more sustainable). A selection of seven common materials:
| Material | Application | CO₂-eq (kg/m²) | Price (€/m²) | Reuse | MPG (€/m²/yr) |
|---|---|---|---|---|---|
| Flax board | Roof | 3.0 | 14.00 | ~95% | 0.012 |
| Cellulose | Cavity | 1.8 | 21.00 | 10–20% | 0.005 |
| LDPE foil | Floor | 2.2 | 0.50 | 5% | 0.007 |
| Glass wool | Cavity | 4.4 | 7.00 | 10% | 0.011 |
| Stone wool | Cavity | 6.0 | 4.00 | 10% | 0.026 |
| EPS | Roof | 11.0 | 100.00 | 5% | 0.095 |
| PIR | Roof | 18.0 | 13.00 | 1% | 0.021 |
Source: New Economy — Circular Insulation Materials Amsterdam study (2021). Reuse figures are real-world rates where known.
Cheap is not sustainable
At €4.00/m², stone wool is the cheapest to buy, yet it has the highest environmental cost of the cavity materials: a shadow price (ECI) of €2.07/m², against €0.41/m² for cellulose — over five times as high. Judging by the receipt alone picks the most expensive material over its lifetime. Sustainable and cheap are not the same here.
Biobased can be CO₂-negative. Biobased materials store CO₂ as the plant grows. According to a TNO model, biobased products contribute half as much to climate change once that storage is counted. Over fifty years, cellulose still holds a ~13 kg CO₂-eq advantage over glass wool, despite a slightly lower insulation value.
Why standard calculations understate biobased
Common methods leave out three advantages of biobased materials: the carbon storage in the material, the actual reuse rates (which often differ from the reference figures), and the health and social effects. Include those and the picture shifts further toward biobased.
Further reading
It depends on the application. In New Economy’s LCA, flax board is the best choice for roofs, cellulose for cavity walls and LDPE foil for floors — each on the best balance of CO₂ emissions, environmental cost and price.
Yes. Biobased materials store carbon and can be net CO₂-negative: the energy saved outweighs the production impact. Traditional materials such as stone wool and PIR have a much higher CO₂ footprint.
To buy, yes (€4.00/m²), but over its lifetime it is the most expensive in environmental cost: a shadow price (ECI) of €2.07/m², the highest of the tested cavity materials. Sustainable and cheap are not the same here.
Through a life-cycle analysis of fifteen materials on a 67 m² model dwelling (energy label D, 75-year lifespan), using the environmental cost indicator (ECI) and building environmental performance (MPG).
Evidence-based material choices for home, region and policy
New Economy calculates the environmental performance and CO₂ impact of building and insulation materials and translates them into well-founded choices.
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