Breathable Internal Wall Insulation (IWI) with Lime Plaster — Moisture Safe, Energy Efficient Retrofit for Solid Wall and Historic Buildings

We install breathable internal wall insulation (IWI) combined with lime plaster to improve thermal performance while preserving the hygrothermal function of solid and historic masonry. We specify vapour open, hygroscopic insulation materials (e.g. wood fibre, hemp, cork or mineral fibre systems designed for retrofit) and compatible lime plaster finishes so walls can dry to the inside and outside, avoiding interstitial condensation and salt damage.

What we do

• Forensic survey: Assess masonry type, moisture and salt profiles, internal environment and decorative or historic fabric.
• System selection: Specify breathable IWI type and build‑up (insulation board, stud+insulation, insulated plasters) compatible with the wall fabric.
• Detail design: Provide thermal modelling and condensation risk analysis where required; design junction details, services routes and ventilation needs.
• Installation: Fit breathable insulation and vapour‑open membranes as appropriate; install backing boards or render carrier; apply lime plaster scratch/float/finish coats.
• Finishing: Limewash or mineral paint decoration compatible with the lime plaster and the hygrothermal strategy.
• Documentation & handover: Supply system details, material specifications, maintenance and ventilation guidance.

Why choose breathable IWI with lime plaster

• Moisture‑safe: Hygroscopic, vapour‑open systems allow moisture movement and drying, minimising condensation and salt migration risk in solid walls.
• Compatible materials: Lime plaster and breathable insulation match the physical behaviour of historic masonry better than impermeable insulation and gypsum/cement finishes.
• Improved comfort and efficiency: Increases thermal performance and comfort while reducing risk to building fabric.
• Reversible and repairable: Systems using natural, vapour‑open materials are more easily repaired and less likely to cause long‑term damage than impermeable alternatives.
• Retains character: Allows retention of internal mouldings and finishes where possible and supports breathable decorative finishes.

Conservation & specification protocol

• Survey & analysis: Record masonry, moisture/salt mapping, thermal performance goals and existing internal finishes.
• Risk assessment: Undertake condensation and hygrothermal assessment to confirm suitable IWI strategy and detailing.
• Trial areas: Install sample panels showing insulation detail and lime plaster finish for client/conservation sign‑off.
• Minimum intervention: Prioritise retention of significant fabric; use discreet, reversible fixings and avoid unnecessary removal of decorative features.
• Controls & ventilation: Specify background and extract ventilation improvements where required to support moisture balance.
• Documentation: Provide detailed drawings, material data, installation method statements and maintenance/ventilation guidance.

Typical workflow

• Survey & risk assessment — measure fabric, moisture/salts and thermal targets.
• Specification — select breathable insulation, fixings, adhesive and lime plaster build.
• Trials — install panel(s) for texture, junctions and finish approval.
• Preparation — protect finishes, remove incompatible linings, repair substrate and prepare services.
• Installation — fit insulation and carriers, seal junctions, install plaster base and successive lime plaster coats with controlled curing.
• Decoration — apply limewash or compatible breathable paint once carbonation and drying permit.
• Handover — supply photographic records, system specifications, thermal results and ventilation/maintenance advice.

Why choose us

• Conservation experience: Expertise in hygrothermal assessment and breathable retrofit for historic buildings.
• Whole‑system approach: We deliver sympathetic detailing, correct material pairing and full documentation.
• Practical installation: Skilled operatives experienced in installing breathable IWI and traditional lime plaster finishes.