For solid-wall homes where cavity fill isn't an option. We install the SWIP IWI System (BBA 15/5262) — thinner and more thermally efficient than traditional stud systems. 0% VAT on insulation.
Free no-obligation survey. Response within one working day.
Up to £300/yr Saved
Typical 3-bed solid-wall terrace
TrustMark Registered
Government-endorsed quality scheme
4.4
Google Rating
Verified reviews
10+
Accreditations
More than any local competitor
PAS2030
Retrofit Standard
Retrofit quality standard
£300
Up to £300/yr Saving
Typical solid-wall terrace saving
03The Problem
Stone and brick don't insulate. They just conduct the cold in.
Properties built before around 1920 don't have a cavity. The walls are solid stone or solid brick, typically 220-250mm thick. Heat moves straight through them.
No amount of draught-proofing, new windows, or boiler upgrades changes this. If the walls are losing 35% of your heat, the house will never feel properly warm.
New windows, new boiler, new doors — still cold? Rooms on front and back elevations still don't hold heat through the night.
Told cavity wall insulation isn't suitable? You have solid walls. There's no cavity to fill — standard for most pre-1920 housing in South Wales.
Bills high, EPC rating low? Heat loss through solid walls shows up on every single gas bill, through every winter.
Where your heat goes
Percentage of total heat lost per source, uninsulated property
Walls
35%
Roof
25%
Windows
25%
Floor
15%
For a solid-walled property, walls are the single biggest source of heat loss. Internal wall insulation directly addresses this. Combined with loft insulation, you can address 60% of your property's heat loss in one project.
04The Solution
The SWIP IWI System — Thinner, Warmer, BBA Certified
We install the SWIP IWI System (BBA certificate 15/5262). It's engineered specifically to solve a problem in traditional internal wall insulation: cold bridging through the studs.
Traditional timber or metal stud systems lose heat through every stud. The SWIP Stud is a thermally-engineered composite — extruded polystyrene bonded to 15mm OSB — so the stud itself insulates. Combined with SWIP Batt glass mineral wool (Euroclass A1 non-combustible), the whole wall keeps warmth in, with no cold bridges.
Result: at 95mm total thickness, a U-value of 0.30 W/m²K — equivalent to 120mm of traditional timber-stud insulation. 13% more thermally efficient than a like-for-like timber stud build-up.
35%
of home heat lost through solid walls
Internal wall insulation directly addresses this. No other single retrofit measure comes close for this property type.
1
Survey and specification
Confirm wall construction and check for damp (damp must be resolved first). We specify 65mm or 95mm SWIP Stud, confirm fixing method and any detailing at reveals, corners and party walls.
2
SWIP Stud and Batt installation
Skirting boards and architraves removed. SWIP Studs fixed horizontally and vertically at 600mm centres. SWIP Batt glass mineral wool friction-fitted between studs. Vapour control layer sealed to prevent interstitial condensation.
3
Plasterboard and skim finish
12.5mm plasterboard screw-fixed to SWIP Studs, joints sealed airtight with SWIP multi-purpose sealant. Skim coat. Skirting and architraves reinstated. Walls ready to decorate.
05Why It Matters
What changes when your walls stop losing heat
Rooms that actually stay warm
External-facing rooms that previously cooled overnight, no matter how long the heating ran, become genuinely comfortable. Stone and brick walls that were cold to the touch become neutral. The difference is noticeable from the first cold spell after installation.
Lower heating bills, year after year
Addressing 35% of your property's heat loss directly reduces what you need to spend to keep the house warm. Estimated savings of up to £300 per year for a typical 3-bed solid-wall terrace in South Wales.
The only route for solid-walled homes
Most pre-1920 properties in South Wales have solid walls. If a survey has confirmed there is no cavity, the SWIP IWI System is the only viable retrofit route to address wall heat loss. BBA-certified insulation brings a pre-1920 home up to modern thermal performance.
Improved EPC rating
Internal wall insulation typically improves the property's EPC rating by one or two bands. For rental properties, this matters increasingly as minimum EPC requirements tighten. For homeowners, a higher rating affects mortgage deals and future sale value.
Most effective when combined with loft insulation
Internal wall insulation and loft insulation together address around 60% of a solid-walled property's total heat loss. If you haven't yet insulated the loft, doing both in one project is significantly more cost-effective than treating each measure separately.
06Is It Right For You
Internal wall insulation suits some properties very well. For others, there is a better option.
Good fit
Property built before approximately 1920, with solid stone or brick walls and no cavity
EPC band E, F or G, with rooms on outer walls that never reach a comfortable temperature
A previous survey has confirmed cavity wall insulation is not suitable for this property
You have tried draught-proofing, new windows and boiler upgrades, and the house is still cold in winter
Properties where a previous cavity survey found the cavity unsuitable (too narrow, too damp, or too exposed)
You want the most significant improvement possible from a single retrofit measure
Probably not the right option
Properties built after approximately 1920 with standard cavity wall construction. Cavity wall insulation is faster, cheaper and far less disruptive for these properties.
Properties where significant structural damp has not been investigated and resolved. Damp must be addressed before any insulation work, we will identify this at survey.
Rooms where losing 60 to 100mm per treated external wall is genuinely not acceptable due to the size of the room. We will measure and advise honestly.
If you are not sure whether your walls are solid or cavity, our free survey will confirm the construction type and recommend the most appropriate route for your specific property.
Absolutely first class from start to finish. The survey was thorough, the team turned up when they said they would, and the finish was excellent. The house felt noticeably different through the first cold week after installation. Very glad we went with First Choice Energy.
Luke Jenkins
Swansea, South Wales
Google Review
"Professional, knowledgeable and honest"
Professional, knowledgeable and honest. I'd had two other companies look at the property and neither was straightforward about what the work involved. First Choice Energy explained everything clearly, gave us a fixed price, and did exactly what they said they would.
Dan Evz
Cardiff
Google Review
"From the initial survey to completion, faultless"
From the initial survey to completion, faultless. They flagged a damp patch we weren't aware of before starting work, which was the right thing to do. Once sorted, the installation was carried out quickly and to a very high standard. Would recommend without hesitation.
Sarah B.
Bristol
Google Review
08How It Works
From your first call to a warmer home
Six straightforward steps from enquiry to completion. No surprises, no pressure, clear timelines at every stage.
01
Get in touch
Call us on 0808 502 2308 or submit the form on this page. We respond within one working day to arrange your free home survey at a time that suits you.
Response within 1 working day
02
Free home survey
An ABBE qualified assessor visits the property. We confirm the wall construction type, check for any signs of damp, measure each external wall, and specify the board thickness and fixing method appropriate for your walls.
Typically 1 to 2 hours
03
Fixed-price quotation
You receive a written fixed-price quotation within two working days of the survey. The quote sets out exactly what is included, which rooms are being treated, what preparation is needed, and what the finished walls will look like.
Within 2 working days of survey
04
Installation day preparation
Before we arrive, rooms being treated need to be cleared of furniture and soft furnishings. We remove skirting boards, door architraves, and any wall-mounted items on external walls. Access to power sockets on those walls will be temporarily lost during the work.
Rooms cleared before we start
05
Boarding and plastering
SWIP Studs fixed to the inner face of external walls, SWIP Batt glass mineral wool friction-fitted between them. Vapour control layer sealed. 12.5mm plasterboard screwed over, skim-finished. Skirting and architraves reinstated. Walls ready to decorate at handover.
1 to 3 days depending on scope
06
Completion and sign-off
We walk through every room with you before we leave. You receive your PAS2030 completion certificate, which is required for your records and serves as a verified record of the work for future property sales. Decoration is yours to arrange at your convenience.
PAS2030 certificate issued
Why First Choice Energy
What sets us apart from every other insulation company in South Wales
01
PAS2030 certified, ABBE qualified
PAS2030 is the retrofit quality standard required for work. ABBE qualification means our assessors are formally qualified to specify insulation measures. Most local companies have neither. These are not optional extras, they are the minimum standard for work done properly.
02
NEBOSH qualified director
Aaron Davies, our director, holds NEBOSH qualification in Health and Safety Management for Construction (June 2025). This is not a standard qualification in the domestic installation industry. It means site safety, correct practice, and quality of finish are managed at director level.
03
South Wales specialists
Our base is Llanelli, Carmarthenshire. We know the pre-1920 housing stock across South Wales, the specific construction types in mining community terraces, coastal stone-built properties, and the rural valleys. Local knowledge changes how we survey and how we specify.
04
Survey to signed-off completion
We survey, specify, install and sign off under one roof. You receive a PAS2030 completion certificate and a single point of contact throughout. We don't subcontract assessment to one company and installation to another. The team that surveys is the team that installs.
Case Study
Mid-terrace house in Llanelli. Stone solid walls. Cold every winter for years.
The problemStone solid walls with no cavity. Front bedroom and rear reception room never held heat through the night despite a new boiler two years prior. Previous company advised cavity wall insulation was not suitable for the property.
The solutionSWIP IWI System fitted to all external walls — front, rear and gable. 95mm SWIP Studs with SWIP Batt glass mineral wool infill, sealed vapour control layer, plasterboard and skim finish. Skirting and architraves replaced throughout. Project completed over two and a half days.
TimelineFree survey to installation: 11 days. Installation and plastering: 2.5 days. PAS2030 certificate issued same day as completion sign-off.
~£290
Estimated annual saving
2 bands
EPC improvement (E to C)
2.5 days
Installation to completion
11Accreditations
The accreditations that matter for insulation work
Not every insulation company carries these. PAS2030 and ABBE qualification are requirements for correctly specified work.
PAS2030 Certified
The retrofit quality standard required for insulation work. Certified by Blueflame. Confirms that installation is specified and completed to the correct standard.
TrustMark
Government-endorsed quality scheme covering consumer protection, complaints resolution and quality assurance for home improvement work.
ABBE Qualified
Formal qualification in retrofit assessment. Our assessors are qualified to correctly specify insulation measures for each property type, a requirement for PAS2030 compliance.
Trading Standards Approved
TSI Approved Code. Consumer protection, clear pricing, honest conduct. Independent verification that our trading practices meet the required standard.
Competent Persons Scheme
Blueflame registered. Allows self-certification to Building Regulations, confirming work meets the required technical standards without separate building control inspection.
NEBOSH, Director Qualified
Aaron Davies, our director, holds NEBOSH qualification in Health and Safety Management for Construction (June 2025). Site safety and correct practice managed at director level.
12Honest Pricing
What internal wall insulation costs
Internal wall insulation involves more work than loft or cavity fill, and pricing reflects that. The SWIP IWI System is zero-rated for VAT. Figures below are indicative — exact quote confirmed at free survey.
Single Room
One Room Treatment
External walls in a single room treated. Suitable for a front reception room or main bedroom where heat loss is most noticeable.
Indicative range
£500 – £900
0% VAT included. Subject to room size and number of external walls. Fixed price at survey.
SWIP IWI System (BBA 15/5262)
Plasterboard and skim finish
Skirting and architrave reinstatement
PAS2030 sign-off
Most common
Two Rooms
Two Room Project
Front reception room and main bedroom treated together. Addresses the two rooms that typically lose the most heat in a solid-walled mid-terrace.
Indicative range
£900 – £1,600
0% VAT included. Better value than single-room treatment. Fixed price at survey.
SWIP IWI System across both rooms
Mobilisation saving vs two separate jobs
One visit, one disruption
PAS2030 sign-off
Whole Property
All External Walls
Internal wall insulation to all external walls throughout the property. Delivers the maximum possible improvement and fully addresses wall heat loss.
Indicative range
£2,000 – £4,000+
0% VAT included. Depends on property size and specification. Fixed price at survey.
SWIP IWI System to all external walls
Maximum EPC improvement
PAS2030 sign-off
Finance options available
0% APR available on shorter-term plans. Finance up to 120 months available at 9.9% APR representative. No upfront cost option available. All finance subject to status. We confirm your options at the time of quotation.
13FAQ
Questions we hear every day
Honest answers to the questions that matter most before making a decision about internal wall insulation.
How much does internal wall insulation cost?
Priced per room or per project. Single room with external walls treated: £500-£900. Two rooms: £900-£1,600. Whole-property project from £2,000, rising with property size and specification. 0% VAT included on insulation. Exact price confirmed at free survey.
How do I know if my property has solid walls?
A quick check: measure the thickness of an external wall at a window or door reveal. A solid wall is typically 220 to 250mm (around 9 inches). A cavity wall built after roughly 1920 is usually 270 to 330mm (around 12 inches). Properties built before 1920, especially the terraced miners' housing common across Carmarthenshire, the Rhondda, Swansea and the South Wales Valleys, are almost always solid-walled. If you are unsure, our free survey will confirm the construction type before we recommend anything.
How much room space will I lose?
The SWIP IWI System is designed to be thinner than traditional stud-and-board systems. The 95mm specification takes approximately 100-110mm off the wall depth. The 65mm specification takes approximately 70-80mm. This is less than traditional timber or metal stud systems, which typically need 120mm to achieve the same thermal performance. We measure each room at survey.
What type of insulation do you install?
The SWIP IWI System — BBA Certificate 15/5262. Two main components: SWIP Stud (extruded polystyrene bonded to 15mm OSB, eliminates the cold bridging found in timber and metal stud systems) and SWIP Batt (glass mineral wool, Euroclass A1 non-combustible). Finished with a sealed vapour control layer, plasterboard and skim. At 95mm, achieves U-value 0.30 W/m²K — 13% more thermally efficient than a like-for-like timber stud system.
Does First Choice Energy do the replastering and redecoration?
Yes. Our scope includes removing skirting and architraves, fitting the SWIP IWI System, plasterboarding, skim finish, and reinstating skirting and architraves. Walls ready to decorate at handover. Painting and wallpapering are your responsibility. Socket faceplates are fitted. Exact scope confirmed in your quote.
How long does the installation take?
A single room typically takes one day. A two-room project is usually one to two days. A whole-property project covering multiple rooms and all external walls is typically two to four days depending on property size, wall construction, and complexity. We give you a clear timeline before we start and commit to it.
How do you decide which specification is right for my property?
We specify either the 65mm or 95mm SWIP IWI System at survey based on your walls, the rooms being treated, the space available and the U-value target. 95mm delivers the deeper thermal performance (0.30 W/m²K) and is the typical specification for a pre-1920 solid-walled property. 65mm (0.43 W/m²K) is used where room space is tight, or where partial treatment of specific rooms makes sense. We confirm the specification in your written quote before any work begins.
My house has cavity walls, should I consider internal wall insulation?
If your property has cavity walls, cavity wall insulation is almost certainly the better option. It is faster, less disruptive, cheaper, and achieves a very similar improvement in heat retention. Internal wall insulation makes sense when the cavity cannot be filled, because it is too narrow, too damp, too exposed, or absent entirely. Our free survey establishes which applies to your property, and we will recommend the most cost-effective route honestly.
Should I get loft insulation at the same time?
Yes, if you haven't already. Loft insulation and internal wall insulation together address approximately 60% of a solid-walled property's total heat loss. For a 3-bed South Wales terrace with no loft insulation and solid walls, doing both in one project makes a substantial difference to winter comfort and heating bills, and is more cost-effective than two separate jobs. We can survey and quote for both at the same visit.
Internal Wall Insulation · South Wales & South West
Stop losing 35% of your heat through the walls
Free no-obligation survey. BBA-certified SWIP IWI System, PAS2030 installation. If solid walls are the problem, internal wall insulation is the answer.
