Start with the wall and the building
Gather information on the wall construction, visible condition, past repairs and water exposure. Explain discomfort, occupation and other planned work. An insulation proposal should account for the support and its behaviour. Have existing moisture or damage investigated before concealing it. An improved thermal specification does not resolve the cause of a leak.
Compare the effects of an internal solution
Discuss usable space, services, openings, existing finishes and the treatment of floors or adjoining walls. Ask how the complete lining will be built and how equipment will be fixed. The quotation should identify preparation and reinstatement as well as insulation. Consider disruption inside occupied rooms and the conditions needed before closing the work.
Compare the effects of an external solution
Examine facade access, openings, sills, roof edges and the base of the wall. Identify relevant property and planning matters through the appropriate official services. Ask for details at junctions rather than relying on a general facade description. Discuss how scaffolding, protection and neighbouring work are included or assigned.
Treat moisture, ventilation and junctions together
Request an explanation of the complete wall assembly and how it handles the actual exposure. Coordinate air supply and extraction with changes to the envelope. Identify junctions at windows, roof, ground and floor edges. A list of insulation and finish does not explain these details or establish that the same approach is suitable for every wall.
Compare full costs and agree checks
Include support work, services moved, sill changes, access and finishes when comparing alternatives. Distinguish confirmed items from investigations still needed. Agree checks before layers conceal the support and keep the installed product references. For financial assistance or qualifications, verify the current official requirements independently of the technical quotation.
Your preparation checklist
- Wall construction and condition investigated.
- Internal space and services considered.
- External access and junctions considered.
- Moisture and ventilation coordinated.
- Full scope of each alternative compared.
- Concealed work checks and references agreed.
Questions before you commit
Is external insulation always the better choice?
The appropriate approach depends on the wall, constraints, junctions and project. Compare complete proposals for the building.
Can new insulation hide an unresolved damp area?
The cause and condition need investigation before a lining or finish conceals them.
Sources and the scope of this guide
This English guide covers the same project need as its French counterpart, with an editorial explanation in English. It is not a professional survey or a translation of foreign rules to France. Check current official requirements and the documents applying to your building and contract.
French reference: France Rénov’ : isoler les murs par l’intérieur ou l’extérieur
French reference: France Rénov’ : isolation des murs intérieurs en appartement