External wall insulation (EWI)
Wrap a solid-wall home in insulation on the outside and finish it with render. The biggest single upgrade for a hard-to-treat property, with no loss of internal space.
What it is
An insulation layer fixed to the outside face of the walls, protected with a reinforced render or a brick-effect finish. The house keeps all its internal dimensions and, done well, gets a smart new exterior at the same time. It is the counterpart to internal wall insulation for solid-wall homes.
Why it matters for 2030
For solid-wall properties EWI gives the largest heat-loss reduction of any single measure and often the biggest EPC jump, while avoiding the room-size loss and internal disruption of IWI. Because it wraps the whole building it also reduces cold bridging more effectively than insulating room by room.
Which homes suit it
Solid-wall homes where the exterior can be altered — so not most conservation areas or where planning restricts the frontage (a common reason to choose IWI at the front and EWI at the rear). Detailing around eaves, sills, doors and the damp-proof course must be right, which is why every EWI job is designed to PAS 2035. It is the higher-cost wall option, which is exactly where grants and the MEES cost cap matter most.
Grants that apply
As a solid-wall measure, EWI is prioritised by the Warm Homes: Local Grant and by ECO4 (to 31 December 2026), and is zero-rated for VAT until 31 March 2027. Grant funding counts towards your £10,000 cost cap, and if the cheapest route to C still exceeds the cap you may qualify for a solid-wall or cost-cap exemption. Details on the grants page.
How we do it
Designed to PAS 2035, installed to PAS 2030 by our accredited partner LAMTANS Engineering, lodged with TrustMark and guarantee-backed. Fixed price from our own book, as part of your free assessment.
Related: internal wall insulation · cavity wall insulation · ventilation