Internal wall insulation cost guide
The honest numbers for solid-wall homes — what's included, what affects the price, and how it stacks up against a standard replaster.
Typical installed cost — what's included
Includes survey, preparation, spray application, skim finish, and 10-year guarantee. Exact cost depends on wall area and condition.
What you're paying for
Heat Halo is an installed system, not a product you buy off the shelf. The price covers everything needed to take a cold, underperforming solid wall and leave it finished, decorated, and measurably warmer.
We assess the wall condition, moisture levels, and suitability before any work begins. This determines the preparation scope and informs the final quote — there are no surprises on the day.
Existing plasterwork is assessed and, where needed, repaired or stripped. Masking and protection are applied before any spray work begins. The quality of preparation is what makes the performance figures repeatable.
The Heat Halo system is applied in controlled layers to a defined minimum film thickness — not a single coat painted on. Application is carried out by trained specialist contractors to a documented standard.
A sprayed plaster skim is applied over the coating to produce a smooth, paintable surface. The room is left looking completely normal — no visible change to the room other than the walls feeling warmer.
You receive a full installation record: the specification applied, the wall area treated, confirmation of preparation and application standards, and the details of your system guarantee.
The installed system is guaranteed for 10 years. This covers the performance of the applied system when installed to the specified standard — not just the materials.
Pricing by property size
These ranges are based on treating all external-facing solid walls throughout the property. Treating a single room or floor costs less — we can quote on that basis if that's what makes sense for your home.
Typical total installed cost
Typical total installed cost
Typical total installed cost
Want to check if your home is suitable first? See the Homeowner page →
Understanding the variables
Every property is different. These are the factors that move the final figure up or down within a tier — and occasionally outside it.
The single most important cost factor. A property with a deep rear return or large side elevation has significantly more wall area than its bedroom count suggests. Wall area is measured at survey and drives the application cost directly.
Walls in good condition with sound, flat plasterwork require less preparation. Walls with rising damp, significant cracking, blown plaster, or previous patchy remediation require more preparation work before the system can be applied.
Treating every external-facing room costs more than treating a single problem room. Some homeowners start with the worst-performing rooms — a north-facing bedroom or a cold ground-floor living room — and extend the treatment later.
Open-plan layouts, rooms with fitted furniture, or properties with restricted access can require additional setup time. In most cases this has a modest effect on the overall price.
Listed buildings often require a breathable, lime-compatible approach to wall preparation and finishing. Heat Halo's vapour-permeable system is appropriate for listed buildings, but preparation specifications may differ from a standard solid-wall property.
If the property has active damp or extensive mould growth, this needs to be addressed at the root cause before insulation is applied. Remediation work is scoped separately at survey and is not included in the standard system price.
Context
For solid-wall homes, there are really only three routes to meaningful wall insulation. Here's how they compare on the factors that matter most for period and heritage properties.
| Factor | Heat Halo internal system | Traditional internal insulation (boards) | External wall insulation |
|---|---|---|---|
| Typical cost | Premium installed solution | Often comparable once plastering, decoration, socket relocation and making-good works are included | Typically one of the most expensive retrofit options due to scaffolding and external building alterations |
| Room space lost | Millimetres — negligible | 60–100mm per treated wall | None internally |
| Changes external appearance | No | No | Yes — render or cladding applied externally |
| Suitable for listed buildings | Yes — vapour-permeable system | Depends on specification | Usually not permitted |
| Suitable for conservation areas | Yes | Yes | Often restricted or refused |
| Disruption level | Low — residents can usually stay in property | High — rooms need to be vacated and fully cleared | External access only — minimal internal disruption |
| Independently tested performance | Yes — BS EN ISO 9869, Build Test Solutions Ltd | Manufacturer data only for most systems | Manufacturer data — in-situ data varies |
| Finish on completion | Fully finished — skim and decoration included | Requires additional plastering and decoration | External render or cladding. Internal unaffected. |
Many homeowners are surprised to find that board-based internal insulation can cost a similar amount once plastering, decoration, socket relocation, radiator alterations and making-good works are included.
External wall insulation is typically one of the most expensive retrofit options due to scaffolding, render systems and external building alterations.
The replastering comparison
A whole-house replaster typically costs £4,000–£9,000 — significantly less than Heat Halo. The relevant question is: what does the extra cost buy you?
A replaster leaves your walls flat and fresh, but performs no better thermally than they did before. You still have the same cold walls, the same heat loss, the same heating bills, and the same risk of condensation and mould on cold wall surfaces.
Heat Halo costs more because it does something a replaster cannot: it changes how the wall performs. The spray-applied system adds a thermal layer that is part of the construction — not a surface coating applied over the top. The skim finish is included, so the finishing cost is embedded in the price rather than sitting alongside it.
Whether that performance improvement justifies the additional investment is a decision only you can make — but it's worth framing the comparison correctly. You're not comparing Heat Halo to doing nothing. You're comparing it to a replaster that solves none of the underlying problems.
Independent test results
Because Heat Halo adds thermal resistance rather than delivering a fixed percentage result, poorer-performing walls benefit proportionally more. A typical uninsulated solid wall with a U-value around 2.0 W/m²K can expect an improvement of approximately 25%.
Independently tested under BS EN ISO 9869 in a live occupied property. Build Test Solutions Ltd — not self-reported data.
Read the full test methodology →Real project context
An example based on a typical Victorian or Edwardian solid-wall family home.
Typical installed cost
Actual costs vary based on property condition, wall area, accessibility and specification. A site survey confirms the fixed price for your property — no obligation.
Get a fixed quoteThe hidden cost of boards
Traditional board-based internal insulation typically requires 70–110mm of build-up. Across an entire house, this can remove a surprising amount of usable floor space.
Heat Halo delivers thermal improvement with virtually no practical loss of living space.
Funding
Solid wall insulation is eligible under two main UK government schemes: the Great British Insulation Scheme and ECO4. Both can fund wall insulation for eligible households, typically those in lower EPC bands (D, E, F, G) or on qualifying benefits.
These schemes are primarily delivered through energy suppliers, who assess eligibility and commission installers. They are not applied-for directly by the homeowner. If you believe you may qualify, your energy supplier is the first port of call.
Heat Halo is a premium specialist system. If your property qualifies for scheme funding, we can discuss whether the system is deliverable within the scheme framework at the survey stage.
For the majority of Heat Halo customers — owner-occupiers of period and heritage properties who are investing in their home — grants are not the primary consideration. The relevant question is whether the improvement is worth the investment against the backdrop of rising energy costs and the ongoing discomfort of living in a cold house.
For households with a D–G EPC rating or in council tax band A–D in England. Delivered through energy suppliers. Covers a range of insulation types including solid wall.
Energy Company Obligation scheme for households on qualifying benefits. Covers whole-house retrofit including wall insulation. Eligibility is means-tested.
Wall insulation currently benefits from 0% VAT, reduced from 20% as part of the government's energy efficiency measures. This applies to the full installation cost.
Heat Halo's performance figures come from a third-party test under BS EN ISO 9869 in a live occupied property — the same standard used to assess real-world wall performance in academic and industry research.
Get a fixed quote
Every property is different. Fill in the form and we'll confirm whether your home is suitable for Heat Halo and provide a fixed quote based on a site survey — no obligation, no hard sell.
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Frequently asked questions
Neither, exactly. The installed cost reflects the total wall area being treated, the preparation scope, and the overall complexity of the installation — not a simple per-metre or per-room rate. Wall area is the primary driver, but preparation requirements, room access, and the number of separate areas being treated all contribute. A per-metre figure can be misleading because it doesn't capture preparation, mobilisation, or setup costs, which exist regardless of area. After a site survey, we provide a fixed total price.
Yes. Some customers treat the worst-performing room first — often a north-facing bedroom or a chronically cold ground-floor sitting room — and extend the treatment to the rest of the property at a later date. Treating a single room or floor is a valid approach. The per-area cost is slightly higher for smaller scopes because mobilisation and setup costs are spread across less wall area, but it is absolutely possible.
The skim finish is included — the wall is left with a smooth, paintable surface. Final decoration (painting, wallpaper) is not included in the standard system price. Some customers choose to decorate themselves; others appoint a decorator after installation. We can advise on timing — the skim should be allowed to dry fully before painting, typically 4–6 weeks for a newly applied lime-skim, less for a gypsum-based skim.
Cavity wall insulation — injected into the cavity of post-1920s homes — typically costs £400–£1,500 and is often subsidised through energy efficiency schemes. It is not relevant to solid-wall homes, which have no cavity to inject. Solid-wall homes — Victorian, Edwardian, inter-war (pre-1935), and older — require a different approach. Heat Halo is designed for exactly this property type. Comparing the cost to cavity wall injection is not a like-for-like comparison.
Yes — treating solid walls improves the wall U-value, which feeds into the EPC calculation. In homes where loft insulation and modern windows are already in place, the walls are typically the last major source of heat loss. Improving wall performance can support a move from EPC band D to C. The exact impact depends on the property, the scope of treatment, and the assessor's methodology. We cannot guarantee a specific EPC outcome, but the direction of travel is always positive.
Wall insulation installation currently benefits from 0% VAT — reduced from the standard 20% as part of the government's energy efficiency measures. This applies to the full installed cost, including survey, application, and skim finish. All quoted prices include this VAT treatment.
