External vs Internal Insulation vs Cavity Fill in Ireland: Which Is Best for Your Home?

Posted on by Baumit Ireland

External vs Internal Insulation vs Cavity Fill in Ireland: Which Is Best for Your Home?

Insulating walls in Ireland usually means choosing between External Wall Insulation (EWI), Internal Wall Insulation (IWI) or Cavity Wall Insulation (CWI). Here’s how they compare so you can choose with confidence.

External Wall Insulation (EWI)

  • Pros: Wraps the building, best at tackling thermal bridges, refreshes façade, minimal indoor disruption, helps deal with condensation.
  • Cons: May require planning permission; typically more expensive than IWI or CWI.
  • Best for: Solid walls, mixed fabrics, major upgrades, façade refresh projects.

Internal Wall Insulation (IWI)

  • Pros: Suits protected façades; room-by-room phasing possible.
  • Cons: Can reduce room size; more risk at junctions; requires careful vapour control.
  • Best for: Heritage streetscapes where the exterior must remain unchanged.

Cavity Wall Insulation (CWI)

  • Pros: Least disruptive; cost-effective where appropriate.
  • Cons: Only suitable for certain cavities; exposure and moisture risks must be assessed.
  • Best for: Sound cavity walls in low-to-moderate exposure zones.

How to decide

  1. Survey & moisture assessment: Identify wall types and exposure. Book a survey.
  2. BER target: Map the path to B2 or better with combined fabric and services upgrades. Learn more about sustainability.
  3. Detailing plan: Treat reveals, thresholds, vents and drainage correctly. See facade finishes for compatible systems.

Need advice on the right solution for your home? Get in touch with our team or explore training and technical guides for installers.