What is EWI (external wall insulation)?

External wall insulation is a layer of insulation material puton to the outer surface of the wall and then covered by a weatherproof layer. The thickness of the insulation is usually between 80mm and 140mm.

External wall insulation is a high quality, cost effective energy efficiency measure that helps homeowners in two main ways:

  • Improve the energy efficiency performance – cutting energy bills and making a property warmer.
  • Improve the visual appearance of their property, improving the value.

With up to 45% of heat lost through the walls on uninsulated homes, the application of external wall insulation will provide a number of positive benefits to your home, over other energy efficiency measures.

Key Benefits of External Wall Insulation:

  • Lightweight, cost effective insulation
  • Save up to £455* per year on your annul fuel bill
  • Save around 0.6 Tonnes* of carbon dioxide per year
  • Improve the appearance of your home – potentially increasing the property’s value by up to 14%(1)
  • Is applied with minimal disruption
  •  Will not reduce the floor area (living space) of your property
  • Reduces condensation on internal walls and can help prevent damp (but will not solve rising or penetration damp)
  • Improves weatherproofing and can increases the life of the existing property by protecting the existing substrate from the weather
  • Assessed life-span in excess of 30 years

How does External Wall Insulation work?

EWI is an insulated finish applied to the external walls to improve the thermal Performance of a property.

External Wall Installation EWI layers

External Wall Installation EWI layers

The government refers to solid wall installation and this category encompasses EWI and internal wall installation (dry lining to internal walls).

Systems have been used in the UK for 20 years and within Europe for considerably longer.

EWI systems need to be installed as per manufactures recommendations and can be offered with 25 year insurance backed guarantee and can be funded by incentives such as green deal.

Further reading

Energy Saving Trust Solid Wall Insulation

Energy saving trust – External Wall Insulation

Energy Saving Trust – External Wall Insulation Householder Information pack

The use of thermal imaging to support area based energy efficiency schemes