External wall insulation (EWI) is applied to the external surface of a wall and is covered by a weatherproof layer (usually render). Render coats are available in a wide range of finishes to suit a variety of building styles. EWI improves the insulation of solid-wall homes. Unlike, internal wall insulation, EWI does not affect room size, but it does change the exterior appearance of the house. EWI provides the best insulation of all of the internal and external wall insulation options.
Technical feasibility check
How do you know if you have solid walls? Solid walls are walls that are built without a gap between the inside and outside layers of bricks. Virtually all houses built before 1920 will have solid walls. You can identify if you have solid or cavity walls by looking at the brickwork.
External insulation on terraced housing or only one of a pair of semi-detached can be visually obtrusive if the whole row of houses is not to be treated, although various architectural styles (Georgian, Victorian, Edwardian) can be replicated. You need to check whether buildings insurance (fire) is affected.
Planning permission will normally be required for fitting solid wall insulation if it changes the external appearance of the home. Even if visual changes are likely to be minor, you are recommended to contact your local planning authority if the building is listed or is in a conservation area.