Internal Wall Insulation helps UK homeowners improve thermal performance, reduce heat loss, and make solid wall properties warmer without changing their external appearance. LAMTANS Engineering delivers PAS2035-compliant insulation upgrades from our Manchester base, providing professional retrofit solutions across the UK.
Internal wall insulation (IWI) is the most practical way to insulate solid-walled properties — reducing heat loss through walls that cannot be cavity-filled. Insulation boards are fixed to the internal face of external walls, improving thermal performance without altering the exterior appearance of your home.
Most UK homes built before 1920 have solid walls — a single layer of brick or stone with no cavity. These walls lose significantly more heat than modern cavity walls. Internal wall insulation is the primary retrofit solution for solid-walled properties where external insulation is not suitable or permitted.
Insulation boards — typically 50–90mm thick — are fixed directly to the internal face of external walls. A vapour control layer is installed to manage moisture movement and prevent interstitial condensation. The wall is then finished with plasterboard, skimmed, and decorated to match the rest of the room.
Because internal wall insulation leaves the exterior of the building completely unchanged, it is the preferred solution for listed buildings, properties in conservation areas, and any home where external wall insulation is refused planning permission or would alter the character of the property.
IWI can be installed room by room, allowing you to spread the cost over time and prioritise the rooms with the highest heat loss — typically ground floor rooms, north-facing rooms, and rooms with the greatest external wall area. Each room is complete and decorated on handover.
PIR (Polyisocyanurate) Insulation Board — 50–90mm
High-performance rigid foam board. Achieves the best U-value improvement for the least depth reduction in room width. Most commonly specified on LAMTANS installations.
Wood Fibre Board — 50–100mm
Natural, vapour-permeable insulation. Suitable for older solid stone properties where moisture management requires a breathable approach. Recommended for specific property types following free survey assessment.
Vapour Control Layer (VCL)
Installed behind all PIR board systems to control moisture vapour movement and prevent interstitial condensation within the wall structure. A correctly installed VCL is a PAS2035 compliance requirement and a critical step in every LAMTANS installation.
Both internal and external wall insulation improve the thermal performance of solid-walled properties — but each is suited to different circumstances. The right choice depends on your property type, planning position, budget, and the level of disruption you can accommodate.
| Internal Wall Insulation (IWI) | External Wall Insulation (EWI) | |
|---|---|---|
| External appearance | Unchanged — original brickwork and exterior fully preserved Advantage: IWI |
Changes external appearance — rendered or cladded finish |
| Planning permission | Usually not required — ideal for listed buildings and conservation areas Advantage: IWI |
May be required — especially in conservation areas or on listed buildings |
| Cost | £2,000–£10,000 per room (indicative) Advantage: IWI |
£8,000–£30,000 (indicative — typically whole house) |
| Flexibility | Room by room — spread cost over time Advantage: IWI |
Usually installed as a whole-house project |
| Room size | Reduces internal room dimensions slightly (50–90mm per wall) | No internal reduction — room sizes unchanged Advantage: EWI |
| Disruption | Room taken out of use for 3–5 days per room | External scaffold required — can last weeks |
Internal wall insulation costs vary by room size, specification, access, and location. Figures below are indicative guide prices — your fixed-price quote is confirmed at the free site survey.
| Room Size | Indicative Cost | Timeline | Notes |
|---|---|---|---|
| Small room (e.g. bedroom, study) | £2,000–£3,500 | 3–4 days | Up to 20m² external wall area |
| Medium room (e.g. living room) | £3,500–£6,000 | 4–5 days | 20–35m² external wall area |
| Large room (e.g. open-plan kitchen-diner) | £6,000–£10,000 | 5–7 days | 35m²+ external wall area |
| Whole ground floor (multiple rooms) | £10,000–£20,000 | 2–4 weeks | Economy of scale — combined programme |
All figures are indicative guide prices including labour and materials. Actual costs depend on room size, specification, site conditions, and location. Annual saving figures are estimates only — actual savings depend on your property, heating usage, and energy prices. Fixed-price quote confirmed at free site survey. Prices exclude VAT.
Want an accurate quote for your property? We provide a fixed-price estimate at your free site survey — no obligation.
Get a free quoteOur installation process is fully managed from free survey to final decoration. Each room is completed and handed back ready to use — with a PAS2035 compliant vapour control layer installed as a mandatory step on every project.
We assess wall construction type, existing damp or moisture issues, ventilation adequacy, and structural suitability. We confirm the correct insulation specification and provide a fixed-price quote. No charge, no obligation.
Furniture moved to the centre of the room or removed. Floor surfaces protected with dust sheets. Skirting boards and architraves removed. Electrical sockets, switches, and radiators isolated and removed from walls where necessary.
A continuous vapour control layer (VCL) is installed to the external wall face before insulation. This controls moisture vapour movement through the wall assembly and prevents interstitial condensation — a mandatory PAS2035 requirement and the step that separates professional installation from poor-quality work. Every LAMTANS installation includes a correctly specified and installed VCL.
PIR insulation boards (50–90mm) or wood fibre boards (50–100mm) are mechanically fixed and/or adhesive-bonded to the internal face of external walls. Board joints are taped and sealed for continuity of the thermal envelope.
Moisture-resistant plasterboard is fixed over the insulation boards. For wood fibre systems, a render board suitable for the breathable finish is installed. All boards are secured to a timber or metal studwork framework where required.
Skim coat plaster applied to all boarded surfaces. Edges, reveals, and junctions finished to a smooth, flat surface ready for decoration. Window and door reveals re-insulated and finished.
New, deeper skirting boards and architraves installed to accommodate the increased wall thickness. Matched to existing profile where possible or agreed with the homeowner in advance.
Electrical sockets, light switches, and radiators moved forward to the new wall face. Room fully made good and decorated to the agreed specification. Furniture moved back. Room handed over ready to use — typically 3–5 days from start.
You remain in your home throughout. Each room is completed and handed back before the next begins. One point of contact from free survey to final decoration — we manage all trades and coordinate every step.
Poorly installed internal wall insulation can trap moisture within the wall structure, leading to interstitial condensation, damp, and mould. This is why correct specification, vapour control, and pre-installation assessment are critical — and why we won't install where the conditions aren't right.
We will not install internal wall insulation where conditions increase the risk of damp or condensation damage. This protects you and your home. Where issues are identified at survey, we advise on remediation before rescheduling installation.
PAS2035 is the UK's current standard for domestic retrofit insulation. It requires assessment of the property before installation, correct material specification, vapour control, and post-installation documentation. Every LAMTANS internal wall insulation project is carried out to PAS2035 compliance — not as an optional upgrade, but as the baseline requirement for all our work.
Every internal wall insulation installation is carried out to PAS2035 — including pre-installation assessment, correct material specification, vapour control layer, sealed junctions, and post-installation documentation. Not an option. The standard.
Government-endorsed quality mark. Consumer protection and verified quality standards — from initial survey through to installation and handover.
Moisture management is the most important — and most commonly neglected — aspect of internal wall insulation. Our installations include a correctly specified and continuously installed vapour control layer as standard, protecting your home against interstitial condensation.
Internal wall insulation is often the only option for listed buildings and properties in conservation areas where external insulation is not permitted. We have experience specifying and installing appropriate systems for older and protected properties.
No-obligation site survey assessing wall construction, damp, ventilation, and suitability. Fixed-price quote confirmed before work begins. No surprises, no hidden costs.
Manchester-based retrofit and construction specialists. Serving Greater Manchester and surrounding areas, with nationwide UK coverage across all project types.
LAMTANS Engineering is a Manchester-based retrofit and construction specialist delivering internal wall insulation, external wall insulation, loft insulation, flat roof insulation, pitched roof insulation, cavity wall insulation, park home insulation, solar panels, battery storage, house extensions, loft conversions, and heating upgrades across the UK.
📍 Based in Manchester — serving Stockport, Oldham, Droylsden, Ashton-under-Lyne, Tameside, and across Greater Manchester, with nationwide coverage.
Costs vary by room size and specification. As an indicative guide: small rooms typically £2,000–£3,500; medium rooms £3,500–£6,000; large rooms or open-plan spaces £6,000–£10,000; whole ground floor programmes £10,000–£20,000. All prices are indicative guide prices — your fixed-price quote is confirmed at the free site survey and depends on room size, specification, and site conditions. Prices exclude VAT.
Yes — internal wall insulation reduces room dimensions slightly. A 50mm insulation board plus plasterboard reduces the room width by approximately 65–80mm per insulated wall. In most rooms, this is barely noticeable. However, it is a consideration in very small rooms or where fitted furniture runs to the wall. We discuss room size impact at the free survey and confirm the insulation thickness to be used.
If reducing internal dimensions is not acceptable, external wall insulation may be more suitable — it insulates the property from outside without reducing any room sizes.
Poorly installed internal wall insulation can cause interstitial condensation — but correctly installed, PAS2035 compliant IWI should not cause damp problems. The critical factor is the vapour control layer (VCL): a continuous membrane installed behind the insulation boards before plasterboard to control moisture vapour movement through the wall assembly.
Every LAMTANS installation includes a correctly specified and continuously installed VCL as a mandatory step. We also carry out a pre-installation damp and ventilation survey — and will not proceed where existing damp or inadequate ventilation means installation is not suitable.
Yes — internal wall insulation is frequently the preferred solution for listed buildings and properties in conservation areas, because it leaves the external appearance of the building completely unchanged. Planning consent for IWI in listed buildings is typically more straightforward than for external wall insulation, though we recommend checking with your local planning authority before work begins.
For listed buildings with lime-plastered stone walls, we specify breathable wood fibre insulation rather than PIR, to ensure the wall can continue to manage moisture in a vapour-permeable way. Material specification is always confirmed at the free survey.
A correctly installed internal wall insulation system has a typical lifespan of 30+ years. PIR insulation boards do not degrade significantly over time when installed in a correctly specified and moisture-controlled assembly. The plaster and decoration finishes can be refreshed as normal throughout the installation's life without affecting insulation performance.
Typically 3–5 days per room from start to completion — including removal of skirting boards, vapour control layer installation, insulation boards, plasterboard, plastering, decoration, fitting of deeper skirting boards, and reinstatement of electrics. The room is handed back ready to use at the end of the programme. You remain in your home throughout — only the room being worked on is out of use.
Larger programmes (multiple rooms or whole ground floor) are planned to minimise disruption, with rooms completed in sequence.
Have a question not answered here? Speak to us at a free, no-obligation site survey.
Ask Our TeamBook your free, no-obligation site survey today. We assess your wall construction, check for damp and ventilation suitability, confirm the right insulation specification, and provide a fixed-price quote — all at no cost. We aim to provide your quote within 72 hours following your free survey.