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Can I insulate a protected structure?

Yes, but works that materially affect the character of a protected structure need planning permission, and solutions must be breathable and reversible. Internal insulation using vapour-open materials is usually preferred over external wrapping.

Solid masonry walls in older buildings manage moisture by absorbing and releasing it. Sealing them with impermeable insulation can trap moisture in the wall, causing decay to embedded timbers and internal damage, so the technical solution matters as much as the consent.

Discuss the proposal with the local authority conservation officer early. A declaration under section 57 of the Planning and Development Act can confirm which specific works would or would not materially affect the character of the structure.

Approaches that tend to be acceptable

  • Attic and roof insulation with maintained ventilation
  • Vapour-open internal insulation such as wood fibre or lime-based systems
  • Draught-proofing and secondary glazing rather than window replacement
  • Upgrading heating controls and services

Sources

Last reviewed 28 August 2026. General information only — not legal or planning advice.

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