IWI Done Right
A designed, property-specific build-up reduces heat loss through solid walls, with junctions detailed and ventilation considered as part of the system.
Internal Wall Insulation In South Wales
Warmer solid-wall and hard-to-treat homes, using a designed, moisture-aware insulation system. Every install starts with a survey and a risk assessment, not a sales pitch.
- PAS 2030 Certified
- Design-Stage Risk Assessment
- TrustMark Registered
- Insurance-Backed Guarantee
- Free Inspection
- PAS 2030 Certified
- Design-Stage Risk Assessment
- TrustMark Registered
- Insurance-Backed Guarantee
- Free Inspection
Get Started
Book Your Free Inspection
Submit your details to arrange your free, no-obligation inspection and design-stage risk assessment.
We Design Before We Install. We assess wall construction, existing and penetrating moisture, thermal-bridge junctions and ventilation. Any moisture issue is resolved first.
PAS 2030 Certified, TrustMark Registered, Insurance-Backed
Why It Matters
IWI Done Right Vs IWI Done Badly
Internal wall insulation can transform a cold solid-wall home, but only when it's designed for your property, with junctions detailed and ventilation considered as part of the system.
Poorly Executed IWI Creates Risk
Skipping the design stage, ignoring thermal-bridge junctions or covering untreated moisture can lead to interstitial condensation and mould.
Ventilation Is Part Of The System
Once a wall is insulated internally, moisture behaviour changes. A balanced ventilation strategy keeps the room healthy rather than hiding the problem.
Common Signs
What We Often See On Site
The signs below frequently point to solid-wall heat loss, a junction detailing issue or a previous IWI install that missed the design stage.
Cold Solid Walls
Why It Matters
Walls that feel cold to touch in winter are a common indicator of heat moving straight through the fabric.
Condensation Or Mould At Junctions & Reveals
Why It Matters
These are the colder spots where moisture concentrates first, often where existing IWI stopped short.
Previously Failed IWI
Why It Matters
Damaged finishes, mould patches or rooms still feeling cold suggest the original install missed design or detailing.
Hard-To-Heat Rooms
Why It Matters
Rooms that need the heating on hard but still feel cold often have un-insulated solid-wall sections losing heat.
Our Process
1
Survey & Design
Heat-loss assessment, moisture check and thermal-bridge mapping. We confirm wall construction, identify junctions that need detailing and design a system specific to your property.
- Heat-Loss Assessment
- Moisture Readings
- Thermal-Bridge Mapping
- Designed Build-Up
2
Moisture & Ventilation Plan
Any existing damp or penetrating moisture is resolved first. We review ventilation provision and specify what's needed so the insulated room stays healthy.
3
Supervised Installation
Installed by a competent, supervised CRS team to the designed specification: boards fixed, junctions detailed, perimeters treated, ventilation integrated.
4
Aftercare & Guarantee
Installation record, guarantee registration and aftercare guidance handed over on completion. We remain available for any follow-up questions.
- Property-Specific Timeline
- Supervised Install Team
- Breathable / Appropriate System
- Insurance-Backed Guarantee
- Payment On Completion
Signature Approach
How We Manage The Risks Other Installers Miss
Most IWI failures don't come from the boards, they come from what happens at the edges. This is where the design stage and supervised install earn their keep.
Junction & Reveal Detailing
Window and door reveals, sills and corner junctions are detailed so the insulation envelope doesn't stop where it matters most.
Floor & Ceiling Perimeter Treatment
Perimeters where walls meet floors and ceilings are treated to reduce thermal bridging and the cold spots that drive condensation.
Breathable Build-Up Where Appropriate
Where the wall, exposure and existing fabric call for it, we specify breathable systems so moisture can move rather than become trapped.
Installer Competence & On-Site Supervision
Installed by a competent, supervised CRS team to the designed specification, with quality checks on detailing, not just board coverage.
Ventilation Strategy
Background and extract ventilation reviewed as part of the design so the insulated room stays healthy after work is complete.
Installation Day
What Happens On The Day
- 1
Protect the room and prepare the work area.
- 2
Prepare or treat the substrate to spec.
- 3
Install the designed insulation system.
- 4
Detail junctions, reveals and perimeters.
- 5
Integrate ventilation provision.
- 6
Make good finishes to agreed scope.
- 7
Document the install for the completion pack.
After The Install
Completion Pack & Aftercare
On completion we hand over a system description, register your insurance-backed guarantee, and provide aftercare and ventilation guidance covering how to look after the room over time.
System Description
Guarantee Registration
Aftercare Guidance
Honest Sequencing
Not Every Wall Is Suitable Right Now
Untreated damp, penetrating moisture or the absence of a ventilation strategy must be resolved before insulating internally. CRS handles damp and ventilation, so we can sequence the work honestly rather than insulating over a problem.
Related: Damp Survey · Ventilation & Extraction
Done Properly
Why Our IWI Approach
Designed To Your Wall
A property-specific build-up based on what we observe, not a one-size-fits-all kit.
Thermal Bridges Managed
Reveals, perimeters and junctions detailed where insulation stops, where risk concentrates.
Moisture-Aware Approach
Breathable or vapour-controlled, chosen for your fabric and exposure, never a guess.
Supervised Competent Install
Installed by a CRS team under on-site supervision to the designed specification.
Social Housing & Commercial
Solid-Wall & Hard-To-Treat Stock
EPC uplift programmes and retrofit-coordinated delivery where required. Design-stage QA, tenant liaison, supervised install and full completion documentation as standard.
Pricing
What Affects Your Quote
Every property is different. We base your written, property-specific quotation on these key variables, confirmed at the free inspection and design stage.
Wall Area
Construction
Junction Complexity
Moisture / Ventilation Works
Reinstatement
£ Finance
Finance Options:
Spread The Cost
Monthly payment options are available for internal wall insulation installations, provided through our partner Ideal4Finance, with 0% finance available on selected agreements.
Choose a term that suits your household, see the full agreement before you commit, and pay a fixed monthly repayment for the length of the term.
Finance is a regulated credit agreement arranged through Ideal4Finance. You apply directly, the agreement is subject to status, and you'll see the full terms, including the total amount repayable, before you sign anything.
Your Payment Options
Monthly Payment Options
Spread the cost over an agreed term with a fixed monthly repayment.
Full Terms Up Front
Every agreement shows the complete cost and term before you commit.
No Obligation
Finance is a payment option, not a requirement. You can pay for your installation without it.
Find Out If You're Eligible
Enter your postcode below to check your eligibility and explore finance options for your installation.
Evidence-Led Design, Certified Install
Every recommendation traces back to something we observed in your property: wall construction, moisture readings, junction risks and ventilation provision. We install under PAS 2030 with an insurance-backed guarantee on completion.
Real Homeowner Reviews
Loved By Homeowners, Trusted By Experts
We're proud to help South Wales homeowners protect the property they live in every day. Here is what some of our customers have shared after working with us.
Independent ReviewsPAS 2030 CertifiedFully Accredited & Insured
They surveyed properly before quoting and explained the design choices for our solid-wall room. The reveals look neat and the room is noticeably warmer.
Honest sequencing. They flagged a small damp issue first and sorted it before insulating. Tidy supervised install team and a clear pack at the end.
4.6
Rated 4.6 On 50 Google Reviews
4.6
Rated 4.6 On 55 Trustpilot Reviews
Transparent Pricing
Every Quote Is Built Around Your Property - Not A Price List.
No guesswork. No off-the-shelf packages. We measure, assess, and quote based on your home's actual floor area and construction type - so you only pay for what's needed.
Floor area (m²)
The primary measure - total heated floor space determines the scope of works.
Insulation type
Cavity wall, loft, internal wall, room-in-roof - each has a different material and labour rate.
Construction type
Cavity, solid brick, timber frame - affects product choice and install method.
How It Works
- 1We attend your property and measure the floor area and external wall areas
- 2We assess construction type and insulation suitability
- 3Your written quotation is issued - priced per m²
- 4No obligation - no hidden extras
Ready To Get Your Quote?
Get in touch and we'll arrange a visit. We'll measure up, assess your property and give you a clear, itemised quote - calculated on your actual floor area.
Frequently Asked Questions
Not when it's designed correctly. Risk arises when IWI is installed over untreated moisture, thermal-bridge junctions are ignored, or ventilation isn't considered. Our process resolves moisture first, details junctions, and reviews ventilation as part of the design.
It depends on the system chosen for your wall. Insulated boards typically add a relatively thin layer to the inner face, while framed build-ups are thicker. We confirm the build-up depth and any reinstatement implications at the design stage.
Yes. Reveals, sills, floor and ceiling perimeters are detailed as part of the designed system, because that's where heat loss and condensation risk concentrate when IWI is fitted poorly.
Most solid-wall and hard-to-treat constructions can be suitable, provided existing moisture is resolved, ventilation can be integrated, and the build-up is designed for the wall. We confirm suitability at the free inspection and design stage.
It depends on your wall construction, exposure and existing fabric. Some properties call for a breathable build-up so moisture can move; others suit a vapour-controlled approach. The choice is made at the design stage based on what we observe.
Yes. Reinstatement scope, including skirtings, sockets, radiators where relevant and decoration, is agreed at quotation so there are no surprises after the install.
Book Your Free Inspection
Complete the form and we'll arrange your free, no-obligation inspection and design-stage risk assessment. Or call 0800 009 2992.