Circular insulation materials with a stronger evidence base
An exploration of circular insulation materials for the City of Amsterdam, carried out with Spaak Circular Solutions. Fifteen materials were assessed through a reduced life cycle assessment, the environmental cost indicator and building performance logic, so circular insulation choices can be connected to municipal instruments.
Fifteen materials, three preferred options
From an environmental and financial perspective, flax board performs best for roof insulation, cellulose for cavity walls and LDPE foil for floors. The exploration also shows that current assessment methods still miss part of the real story: biogenic carbon storage, actual reuse rates and health effects are not yet fully reflected. See also our guide on the best sustainable insulation material.
The challenge
Amsterdam wants to renovate the existing city in a more circular way. Insulation is a practical starting point: it reduces energy demand, but the materials themselves also carry environmental impacts. This exploration helps connect material choices to renovation instruments, subsidies, loans and procurement routes.
The project assessed suitable circular insulation materials from an environmental and financial perspective, explored how these materials could be embedded in municipal instruments and made the knowledge usable for relevant market actors.
Fifteen materials
More than 35 insulation materials on the Dutch market were screened. Fifteen were selected because they are relevant now or promising for the future.
- Roof: aerogel, EPS, wood fibre board, mycelium, PIR, recycled cotton, straw panels and flax board.
- Cavity wall: aminotherm, cellulose, glass wool and stone wool.
- Floor: LDPE foil, perlite and PS beads.
LCA, environmental cost and building performance
The assessment used a reduced life cycle analysis. The environmental cost indicator combines eleven impact categories, from climate change and acidification to resource depletion, over the life cycle of each material. The building performance calculation distributes those impacts across the building lifetime and accounts for reuse potential.
The reference case was a 67 m² mid-terrace dwelling with energy label D and a 75-year lifetime. The analysis used data from NIBE, EPDs, producers, suppliers, contractors, processors and trade associations, with verification by the Amsterdam University of Applied Sciences and C-Creators.
What was compared?
Each material was assessed on CO₂-equivalent emissions, reuse potential, cost and building performance. This creates a more practical basis for choosing materials than climate impact alone.
For roof insulation, flax board and recycled cotton (metisse) have the lowest CO₂ emissions, at 3.0 kg CO₂-eq/m² each; PIR scores highest, at 18.0 kg. Flax board is also 100% reusable and has the best average building performance score of the roof materials (€0.012/m²/year); EPS has the worst (€0.095). In the cavity wall, cellulose scores best on both counts: the lowest CO₂ emissions (1.8 kg/m²) and the lowest average building performance score (€0.005/m²/year); stone wool has the highest (€0.026). For the floor, LDPE foil has the lowest CO₂ emissions, at 2.2 kg CO₂-eq/m².
Preferred choices
- Roof: flax board. Recycled cotton and flax board have low climate impact; flax board combines this with strong environmental performance and practical applicability.
- Cavity wall: cellulose. Cellulose has the lowest CO₂ impact and the best environmental performance in the cavity wall comparison.
- Floor: LDPE foil. LDPE foil scores well on CO₂ impact, cost and environmental performance.
A case study from the exploration illustrates that a higher insulation value is not always decisive for CO₂ emissions: producing glass wool (4.4 kg CO₂-eq/m²) emits almost 2.5 times as much as cellulose. For the two cavity walls together (77 m²), glass wool comes to 339 kg CO₂-eq and cellulose to 136 kg: a difference of 203 kg in favour of cellulose.
Beyond the calculation method
The exploration highlights four limitations in current methods: biogenic carbon storage is not fully valued, actual reuse may differ from database assumptions, real service life can be shorter than the model assumes, and health and social effects are often outside the calculation boundary.
From analysis to implementation
The project translated material insights into possible municipal instruments: supplier lists, buyer groups for homeowner associations and housing corporations, pilots for innovative materials, decision trees for material choice and clearer guidance for contractors and renovation programmes.
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Frequently asked questions
Insights from this project
Circular insulation materials for Amsterdam
New Economy and Spaak Circular Solutions assessed fifteen circular insulation materials for Amsterdam using LCA, environmental cost indicators and building performance logic, connecting material choices to municipal instruments, renovation practice and circular procurement.
The exploration assesses fifteen circular insulation materials for the City of Amsterdam on sustainability and cost, using a reduced life cycle assessment, the environmental cost indicator and the building performance calculation, so circular insulation can be embedded in the city’s instruments.
Looking at sustainability and cost together, flax board is the best choice for roofs, cellulose for cavity walls and LDPE foil for floors in the model dwelling used.
The environmental cost indicator combines eleven environmental indicators across the full life cycle into a shadow price per square metre. The building performance calculation spreads that cost over the building lifetime and accounts for reuse potential, expressed in euros per square metre per year. The lower the score, the more sustainable the material.
Biobased materials store CO₂ as plants grow. Based on a TNO model, biobased products contribute roughly half as much to climate change, net, once that storage is counted, but the Dutch calculation method does not yet include it.
The City of Amsterdam commissioned the exploration as part of its Duurzaam Herstel programme. Spaak Circular Solutions led the project; New Economy delivered the building performance scores and the integration into the municipal instruments.
Frequently asked questions about insulation
According to the study, the best choice depends on where you insulate: flax board for the roof, cellulose for the cavity wall and LDPE foil for the floor. These score best on sustainability and cost combined, assessed with a life-cycle analysis, the Environmental Cost Indicator (ECI) and building environmental performance (MPG).
Cellulose has the lowest environmental cost of the fifteen materials assessed (ECI €0.41/m²), followed by LDPE foil, glass wool and flax board. Perlite and PS beads score worst.
This study assesses the environment and cost, not health directly. Environmentally, biobased insulation (flax, cellulose, wood fibre) scores strongly: it captures CO₂ as the plants grow, has low environmental cost and is often highly reusable. The health of residents and installers falls outside the ECI and MPG.
Biobased materials such as cellulose and flax board: they have the lowest CO₂ emissions and environmental cost, and store CO₂ as they grow. According to a TNO model, biobased products contribute half as much to climate change once that carbon storage is counted.
No. Stone wool is the cheapest cavity option (€4/m²) but has the highest environmental cost of the cavity materials. Cellulose costs more (€21/m²) but scores far better environmentally.
Stone wool has the highest environmental cost of the cavity materials (ECI €2.07/m², 6.0 kg CO₂-eq/m²); glass wool is mid-range (€0.84/m², 4.4 kg). In the same cavity, cellulose is more sustainable than both.
Prices vary widely by material: from €0.50/m² for LDPE foil to €260/m² for aerogel. Flax board costs €14, cellulose €21, glass wool €7 and stone wool €4 per m². The cheapest option is not always the most sustainable.
Cellulose has the lowest emissions of the cavity materials at 1.8 kg CO₂-eq/m²; on the roof flax board and recycled cotton (3.0 kg), and on the floor LDPE foil (2.2 kg). Mycelium comes out at almost zero.
Related reading
Circular construction needs better material evidence
Insulation choices influence energy use, embodied impact, material reuse and indoor health. This project makes those choices more explicit for policy, procurement and renovation practice.
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