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Welcome to polystyrene insulation EPS boards FAQ! Here you'll find answers to our most asked questions. Still can't find quite what you're looking for, or have something we should know? Use Q&As section or send us an email, we're happy to help!

• Q1: What are EPS polystyrene boards used for in external wall insulation?

  A1: EPS (Expanded Polystyrene) boards are used as thermal insulation in External Wall Insulation (EWI) systems. They are mechanically fixed and adhesively bonded to external walls, then reinforced with basecoat, mesh, and decorative render to improve energy efficiency and façade appearance.

• Q2: Is EPS insulation good for external walls?

  A2: Yes — EPS is one of the most widely used façade insulation materials because it offers:
  - Excellent thermal performance
  - Lightweight handling
  - Cost efficiency
  - Easy cutting and installation
  - Compatibility with most render systems

• Q3: What thickness EPS boards are used for EWI?

  A3: Common thicknesses in the UK:
  - 50 mm – minimal upgrade
  - 70–90 mm – standard retrofit
  - 100 mm – popular energy upgrade
  - 150–200 mm – low-energy / passive targets
  Thickness depends on U-value requirements and building regulations.

• Q4: What is the thermal conductivity (Lambda) of EPS?

  A4: Typical EPS lambda values:
  - EPS 70: ~0.038 W/mK
  - EPS 80: ~0.036–0.038 W/mK
  - Graphite EPS: ~0.031–0.033 W/mK
  – IBB - Thermonium Plus has the highest Lambda 0.031 W/mK

• Q5: Is EPS insulation fire resistant?

  A5: Standard white EPS is Euroclass E (combustible).
  However:
  - It is always encapsulated within render systems.
  - Fire-retardant grades are used.
  - System fire ratings depend on the full EWI build-up.
  For high-rise buildings, mineral wool may be required.

• Q6: How long does EPS external wall insulation last?

  A6: Properly installed EPS EWI systems last 30–50 years+ with maintenance of the render finish.