External wall insulation is the measure for a solid walled house, which has no cavity to fill, and it is the most expensive of the common insulation measures because it involves scaffolding, fixing insulation to the outside of the building and rendering over it. Offers of free external wall insulation normally refer to government backed schemes for qualifying households, delivered through approved installers, and the words worth reading are which scheme, who qualifies and what the household contributes.
What the schemes fund and who qualifies
Support runs through government backed schemes delivered by energy suppliers and approved installers, with eligibility based on the household and the property. Solid wall insulation is among the measures they have funded, and the qualifying rules change, so the current scheme page is the only reliable account of today's position.
Why this measure needs more care than a cavity fill
External wall insulation changes how a wall handles moisture and how it looks. Detailing at the eaves, around windows, at the damp course and at boundaries decides whether it works or traps water, and it is not a job to take from whoever telephoned. On some houses, particularly older solid walled ones, an internal or a breathable system is the correct answer instead.
What to have before you agree
The name of the scheme, the approved installer, the system and its guarantee, drawings or a specification of the junction details, and confirmation of any planning consideration where the appearance of the building changes. Cold callers offering free insulation are common and the paperwork is what separates a scheme from a sale.
Questions people ask about free external wall insulation
Is it really free?
For a qualifying household under a funded scheme it can be fully funded, and in other cases a contribution is asked for. The honest question to an installer is what the scheme pays, what you pay, and what happens if the survey changes the specification.
Does external wall insulation need planning permission?
It changes the external appearance and thickness of the walls, so it can, particularly on a flat, in a conservation area or on a listed building. It is worth confirming with the local authority rather than assuming permitted development.
What about a solid wall that already gets damp?
Insulating over a wall that is wet traps the moisture rather than curing it. The damp cause has to be found and fixed first, which is the same order of operations this site's damp section describes.