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Side-by-side conductivity, thickness for a given R-value and recycled content for the insulation families you are most likely to specify for a house extension.
This page exists to answer one question with numbers: how much thickness does each insulation family need to do the same job? The answer is governed by thermal conductivity. Aerogel blankets run 0.018–0.020 W/(m·K), EPS 0.031–0.038, mineral wool 0.032–0.040 and wood fibre 0.038–0.050.
Set the benchmark at R = 5 m²K/W — the resistance behind a U-value of 0.20 W/(m²K) before other layers are counted — and the ranking becomes tangible. Aerogel needs 90–100 mm, EPS 155–190 mm, mineral wool 160–200 mm and wood fibre 190–250 mm. The cleanest illustration is the documented equivalence: 100 mm of aerogel at 0.020 W/(m·K) delivers exactly the R-value of 200 mm of mineral wool at 0.040 W/(m·K).
For a lighter target of R = 3 m²K/W the same ranking holds at smaller depths: 54–60 mm of aerogel, 93–114 mm of EPS, 96–120 mm of mineral wool and 114–150 mm of wood fibre. Whatever the target, the method is identical — multiply the required R-value by the declared lambda.
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Recycled content is the second axis of comparison. Loose-fill cellulose is made from 80–85% recycled newspaper by weight, which gives it a high recycled-content score in the material credits of green rating systems. For the other families, recycled content varies by product and must be read from the manufacturer's declaration rather than assumed.
Fire performance, vapour behaviour and compressive strength are product-specific properties declared per product, not per family, so this reference does not assign classes. Request the Declaration of Performance for the exact product and read each declared characteristic from it.
Use this comparison as a shortlisting tool: eliminate what cannot fit the available depth, then carry the survivors into the certification checks described in Green Building Certifications and Their Thresholds and the ordering steps in How to Choose a Low-Carbon Material.
Further reading