Technical breakdowns

Facade insulation — comparing mineral wool, EPS, and PIR

Three materials, three price points, three application niches. Where mineral wool is unconditionally better, where EPS is enough, and in which systems PIR justifies its cost.

Author FLOK Editorial Team
Published April 12, 2026
Reading time 8 min

1. Selection parameters

Four figures on the packaging: thermal conductivity (λ, W/m·K), combustibility (G1–G4 or non-combustible), vapour permeability (mg/m·h·Pa), density (kg/m³). The price is tied to λ — the lower it is, the more expensive a board of the same thickness.

2. Mineral wool

λ = 0.034–0.040, non-combustible, vapour-permeable. The baseline material for facades with wet plaster and ventilated curtain-wall systems. The catch — mandatory protection against getting wet: wet mineral wool loses up to 60% of its thermal resistance.

3. Expanded polystyrene (EPS)

λ = 0.036–0.041, combustible (G3), vapour-tight. 30–40% cheaper than mineral wool. Permissible for a plaster facade up to 15 m high, provided mineral-wool fire breaks are installed floor by floor. For residential buildings above 15 m it is prohibited by the codes.

4. PIR (polyisocyanurate)

λ = 0.022–0.025, G1–G2, vapour-tight. The most efficient material — an 80 mm PIR board ≈ a 130 mm mineral-wool board in thermal resistance. The price is 2.5–3 times that of mineral wool. It is used where the structure’s thickness is critical: facade sandwich panels, low-slope roofs.

5. When to choose which

  • Multi-storey residential, wet facade: 100 mm mineral wool is the standard.
  • Low-rise, wet facade: 100 mm EPS — savings without loss of quality.
  • Industrial building with a tight installation schedule: PIR as part of a sandwich panel.
  • A cold attic or a roof with a thin structure: 60–80 mm PIR.

Calculating consumption? Open the insulation calculator on the website — you will get a specification right away, with an allowance for trimming.

Tags
  • insulation
  • facade
  • mineral wool
  • EPS
  • PIR
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