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.
Thermal treatment installation — indicative cost
Prices are for the Heat Halo thermal treatment. Optional plastering, decorating and finishing packages are available. Final price depends on wall area, condition and survey findings.
What you're paying for
Heat Halo is an installed system, not a product you buy off the shelf. The standard installation covers everything needed to apply the thermal treatment to a professional standard and leave the surfaces ready for use or further finishing.
We assess wall condition, moisture levels, and suitability before any work begins. This determines the preparation scope and informs the fixed quote — there are no surprises on the day.
Furniture and flooring are protected, and masking is applied before any spray work begins. We work through the home in stages so unaffected rooms remain usable throughout.
Existing plasterwork is assessed and, where needed, repaired or prepared to receive the system. The quality of surface 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. Applied by trained specialist contractors to a documented standard.
Every surface is documented. You receive a full installation record: specification applied, wall area treated, confirmation of preparation and application standards, and your system guarantee details.
The installed thermal treatment is guaranteed for 10 years — covering performance of the applied system when installed to the specified standard, not just the materials.
Pricing by property size
These ranges are for the thermal treatment installation across all external-facing solid walls. Treating a single room or floor costs less. Optional plastering, decorating and finishing packages are available on top.
Thermal treatment installation
Thermal treatment installation
Thermal treatment installation
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 | Treated surfaces ready to use. Optional skim and decoration packages available. | 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. Heat Halo's thermal treatment is priced from the thermal upgrade itself — finishing works are available as optional extras.
External wall insulation is typically one of the most expensive retrofit options due to scaffolding, render systems and external building alterations.
Direct comparison
Traditional internal wall insulation remains an effective solution for many properties. Heat Halo is designed for homeowners who want to improve thermal comfort and wall performance while avoiding the space loss and disruption associated with conventional insulated plasterboard systems.
Both approaches improve thermal performance. The right solution depends on the property, budget and objectives. The table below highlights some of the practical differences homeowners typically consider when comparing options.
| Feature | Heat Halo | Traditional Internal Wall Insulation |
|---|---|---|
| Loss of room space | Minimal | Typically 3–11 m² depending on property size |
| Window reveal alterations | Usually not required | Usually required |
| Skirting board alterations | Usually not required | Usually required |
| Decoration included | Optional — available as a finishing package | Usually separate |
| Suitable for period features | Often | Can be challenging |
| Installation disruption | Lower | Higher |
The replastering comparison
Heat Halo is a specialist thermal wall treatment designed to improve wall temperatures and reduce heat loss. Unlike a traditional replaster, the objective is not simply to create a fresh decorative finish — it is to improve the thermal performance of the wall itself.
A conventional replaster and redecoration programme leaves walls smooth and freshly decorated, but the wall performs no differently than before. Cold surfaces remain cold, heat loss is unchanged, and any condensation or mould risk associated with low wall temperatures remains.
Heat Halo addresses the underlying cause. Customers can choose to add plastering and decoration as part of the project, or arrange these works separately — perhaps as part of a wider refurbishment they already have planned.
The comparison is therefore not between Heat Halo and a replaster. It is between leaving the walls as they are and meaningfully improving how they perform — with or without accompanying decoration.
Whether that improvement justifies the investment is a personal decision. The important thing is to compare the right things.
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.
Standard installation — included as standard
Optional finishing packages
Thermal treatment installed cost
For the thermal treatment installation. Optional finishing packages priced separately at survey. Actual cost varies based on wall area, condition and specification. A site survey confirms the fixed price — 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.
Not as standard — but it can be. Many customers already have their own decorator, refurbishment plans or preferred contractors. Heat Halo can provide a complete finishing package including plastering, decoration and making-good works, or leave the treated surfaces ready for your chosen contractor. This allows you to choose the level of finishing that best suits your project and budget. Finishing options are confirmed and priced at the survey stage.
Heat Halo is not a paint product and is not priced like a decorating project.
The standard installation includes a pre-installation survey, room preparation and protection, surface preparation, specialist spray application of the thermal treatment, and installation quality assurance — all carried out by trained specialist contractors to a documented standard.
The result is a measurable improvement in wall thermal performance, independently verified under BS EN ISO 9869. Most homeowners compare Heat Halo with internal wall insulation or other solid-wall upgrade solutions, not with conventional painting and decorating.
Cavity wall insulation — injected into the cavity of suitable properties — typically costs a few hundred to a few thousand pounds, depending on property size and eligibility for grant funding.
Heat Halo is generally used where there is no suitable cavity to insulate, where cavity insulation is not appropriate, or where homeowners are seeking to improve the thermal performance of existing wall surfaces from within the home.
Many older properties, including Victorian, Edwardian and other solid-wall homes, do not have wall cavities at all. In these cases, cavity wall insulation is simply not an option.
For that reason, comparing Heat Halo with cavity wall insulation is not usually a like-for-like comparison. Homeowners are more likely to compare Heat Halo with internal wall insulation systems, major redecoration projects or other solid-wall upgrade solutions.
Traditional internal wall insulation typically uses insulated plasterboard systems fixed to the inside of external walls. While highly effective, these systems usually require 70–110 mm of build-up, reducing room sizes, altering skirting boards and window reveals, and creating significant disruption during installation.
Heat Halo is applied directly to the wall surface, resulting in a much thinner build-up and virtually no loss of living space. A plaster skim and decoration can be added as optional finishing works. For many homeowners, particularly those with older properties, period features or smaller rooms, preserving space and minimising disruption can be just as important as thermal performance.
The right solution depends on the property, budget and objectives. Heat Halo is designed for homeowners seeking a low-profile thermal upgrade without the disruption associated with traditional internal insulation systems.
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.
Heat Halo wall insulation work 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, skim finish and decoration. All quoted prices reflect this VAT treatment.
