External wall insulation is the provision of insulation onto the external fabric of a building protected by a specialist render. There are many benefits to this method of insulation. Low U Values for walls can be easily achieved using external wall insulation on both new build construction as well as refurbishment work.

External wall insulation systems generally comprise an insulation layer to achieve the requisite thermal performance protected with a weatherproof finish, usually a render, although brick slips, tiles, and decorative boards can also be used. Insulating render can also be an advantage in certain locations. Fixing types and sizes depend on the substrate and design exposure requirements.

Of the UK housing stock over 30% have been built with solid walls, classed as 'hard-to-treat' because they cannot be thermally improved with the use of cavity wall insulation. Unlike unfilled cavity wall homes which lose approximately 35% of heat through their walls, solid wall homes will lose as much as 45% space heat through untreated walls.

Any measures to make heating systems more efficient are made less effective as heat escapes through the external walls. Solid wall properties generally fall into two main types, traditional construction built with 9 inch solid brickwork or non- traditional housing constructed with systems using mainly precast concrete panels. External wall insulation systems are suitable for both traditional and non- traditional solid wall housing and can significantly reduce heat loss leading to lower heating bills and carbon emissions.

As well as improving thermal efficiency, external wall insulation systems at the same time revitalise the appearance of homes and can be major contributors to the regeneration of run-down housing schemes.

Solid wall properties can be insulated either internally or externally. The benefits of insulating externally include:

  • Lower U-values are generally possible through insulating externally and no internal living space is lost
  • As work is carried out to the outside walls, disruption to the household, including internal fixtures and fittings, is minimised
  • The risk of condensation within the wall structure and thermal bridging is eliminated
  • A weatherproof, attractive and generally maintenance-free new exterior is provided as part of the thermal cladding of the building
  • Work can be carried out alongside other trades such as window replacement and re-roofing