External wall insulation (EWI) offers a solution to homes constructed with solid walls to become more thermally efficient. It does so by mitigating the amount of heat lost through the walls of a building, which is estimated to be around 35%. External Wall Insulation is the application of thermally insulating materials (e.g. EPS boards) and a finished system (e.g. render) to the outside face of the external walls of an existing building to improve its thermal performance. A good analogy is that of placing a tea cosy around a building.

EWI is an extremely cost-effective way of insulating the walls of a building, the reason being EWI ensures the entire surface is fully insulated resulting in the elimination of any cold or thermal bridging. (Thermal bridging is an area of a building which has significantly higher heat transfer than the surrounding areas. This is often caused by a break in insulation, less insulation or the insulation is penetrated by an element with a higher thermal conductivity).

A layer of insulation is fixed to an existing wall using adhesive and fixing anchors and then finished with a weatherproof system such as render, pebbledash or alternatively cladding to protect the insulation and keep the system watertight.

An EWI solution can be engineered to suit practically any type of building design and construction, with established methods adopted for non–traditional housing, standard specifications of solid walls and more bespoke solutions for new builds and many non-domestic situations.