What is External Wall Insulation (EWI)?

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External wall insulation involves fixing a layer of insulation material to the wall, then covering it with a reinforcement and a special type of render. The finish is usually a textured render, pebble-dash or sometimes a brick slip or a brick effect render finish could be used.

A typical EWI System

These finishes can be used alone, or in a combination so that considerable variety in the appearance of the treated wall can be achieved.

Key Points – External Wall Insulation:

  • can save approx. £475* per property per year (source: Energy Savings Trust)
  • can save approx.1.9 tonnes* of carbon dioxide per year (source: Energy Savings Trust)
  • can be applied with minimal disruption to the household and its occupants
  • no internal access is required
  • does not reduce the floor area (living space) of the property
  • improves the appearance of the property – potentially increasing the property’s value
  • improves weatherproofing and sound resistance
  • can make the building more airtight, reducing drafts and heat loss
  • increases the life of the existing property by protecting the existing substrate from the weather
  • reduces condensation on internal walls and can help prevent damp (but will not solve rising or penetration damp)

* based on insulating a gas-heated, semi-detached home with three bedrooms (source: Energy Savings Trust)