Insulation remains the foundation of UK retrofit policy because its energy savings are durable and its lifetime cost per saved kWh outperforms most other measures. This page consolidates UK insulation statistics for 2026 covering loft, cavity wall, external wall and internal wall installation rates, the certified retrofit assessor and PAS 2035 coordinator workforce and EPC band distribution. Figures are drawn from BEIS/DESNZ, the EPC register and certification bodies.
Insulation installation rates by measure type
Approximate annual UK insulation installation volumes (cross-scheme: ECO, GBIS, BUS-adjacent and private-pay) are as follows for 2024-2025:
| Measure | Approximate annual installs (UK) |
|---|---|
| Loft insulation (top-up + new) | ~140,000-170,000 |
| Cavity wall insulation | ~65,000-90,000 |
| External wall insulation (EWI) | ~25,000-35,000 |
| Internal wall insulation (IWI) | ~15,000-22,000 |
| Underfloor insulation | ~8,000-12,000 |
| Room-in-roof insulation | ~12,000-18,000 |
These approximate figures combine ECO4 supplier-funded measures with private-pay activity. Loft and cavity volumes have been supressed compared to the early 2010s peak as the easiest-to-treat housing stock is now substantially treated; the remaining solid-walled and hard-to-treat stock is more expensive and slower per measure.
Cumulative UK insulation coverage
Approximate UK housing stock coverage by insulation measure (residential dwellings):
| Measure | Approximate share of UK dwellings with the measure installed |
|---|---|
| Loft insulation (any depth) | ~78-82% |
| Loft insulation (recommended 270mm+) | ~50-55% |
| Cavity wall insulation (treatable cavities) | ~70-75% |
| Solid wall insulation (EWI or IWI) | ~10-12% |
| Underfloor insulation | ~5-8% |
Source: BEIS/DESNZ English Housing Survey aligned data, Scottish House Condition Survey and Welsh Housing Conditions Evaluation.
DEAs and PAS 2035 retrofit workforce
The UK retrofit assessor workforce expanded sharply from 2020 onwards, partly driven by ECO4's PAS 2035:2019 compliance requirements. Approximate certified workforce numbers by mid-2025:
- Domestic Energy Assessors (DEAs) certified to issue residential EPCs: approximately ~10,000-12,000 active
- Retrofit Assessors (RAs) certified under PAS 2035: approximately ~6,500-8,000
- Retrofit Coordinators (RCs) certified under PAS 2035: approximately ~1,800-2,400
- Retrofit Designers (RDs): approximately ~500-800
- Retrofit Evaluators: approximately ~700-900
Source: TrustMark and certification body data through 2025.
EPC band distribution UK-wide
According to the EPC register through 2024-2025, approximate distribution of UK domestic dwellings by EPC band (current rating, all tenures):
| EPC band | SAP score range | Approximate share of dwellings (England/Wales) |
|---|---|---|
| A | 92-100 | ~1% |
| B | 81-91 | ~5-6% |
| C | 69-80 | ~42-45% |
| D | 55-68 | ~36-38% |
| E | 39-54 | ~10-12% |
| F | 21-38 | ~2-3% |
| G | 1-20 | ~0.5-1% |
The share of dwellings rated band C or above has trended upward from approximately 30% in 2015 to approaching ~50% by 2025, driven by ECO measures, building regulation upgrades and natural new-build dilution.
Retrofit Coordinator capacity vs ECO4 demand
PAS 2035 requires a Retrofit Coordinator to oversee any whole-house retrofit project funded under ECO4. Industry analysis suggests:
- Average annual ECO4 measures requiring PAS 2035 coordination: approximately ~150,000-180,000
- Approximate active Retrofit Coordinators in the UK: ~1,800-2,400
- Implied annual coordination workload per RC: approximately 70-100 retrofit projects
- This workload sits at the upper end of practical capacity, contributing to scheme delivery bottlenecks
Insulation supply chain and material market
The UK insulation material market is a substantial supply chain. Approximate annual UK insulation material market value 2024-2025: ~£2.0-2.5 billion. The split by material category is approximately:
- Mineral wool (rock and glass): approximately ~45-50% of UK installs by area
- EPS / XPS (expanded/extruded polystyrene): approximately ~15-20%
- PIR / PUR (polyisocyanurate / polyurethane): approximately ~15-18%
- Wood fibre and natural fibre: approximately ~3-5%
- Other (perlite, cellular glass, sheep wool, hemp): approximately ~3-5%
Material choice is driven by application (cavity, internal lining, external render, roof), thermal performance per millimetre and fire-safety requirements. The 2018 Approved Document B revisions following Grenfell materially restricted combustible insulation in mid-rise residential applications.
Building Regulations Part L and new-build insulation
Building Regulations Part L (Conservation of Fuel and Power) sets minimum insulation standards for new dwellings and major refurbishments. Approximate U-value standards over time:
| Element | Pre-1990 | 1995 update | 2002 update | 2013 update | 2021/2022 update |
|---|---|---|---|---|---|
| Walls (W/m²K) | ~0.6-1.0 | ~0.45 | ~0.35 | ~0.28 | ~0.18-0.22 |
| Roof (W/m²K) | ~0.4-0.6 | ~0.25 | ~0.16 | ~0.13 | ~0.11-0.15 |
| Floors (W/m²K) | ~0.4-0.6 | ~0.45 | ~0.25 | ~0.22 | ~0.13-0.18 |
Values are typical mid-range for England; Scotland and Wales operate parallel standards with similar trajectories.
The Future Homes Standard, expected to come into force during 2025-2026, further tightens new-build insulation and effectively requires low-carbon heating systems in new homes.
Pre-1919 housing and the solid wall opportunity
UK housing stock is unusual in its long tail of pre-1919 buildings, most of which have solid walls. Approximate UK housing stock by construction era:
| Era | Approximate share of UK dwellings | Wall type / typical insulation |
|---|---|---|
| Pre-1919 | ~20-22% | Solid wall (stone or brick); typically uninsulated |
| 1919-1944 | ~17-19% | Solid or early cavity; mixed insulation |
| 1945-1964 | ~21-23% | Cavity wall; many CWI-treated |
| 1965-1980 | ~15-17% | Cavity wall; high CWI rates |
| 1981-2000 | ~14-16% | Insulated cavity walls (later regs) |
| 2001 onwards | ~9-12% | Modern building regulations; high insulation specification |
The pre-1944 solid-walled stock represents the largest remaining insulation opportunity by stock count, contributing disproportionately to the band E-G distribution observed in the EPC register.
PAS 2035 compliance and audit findings
PAS 2035 compliance has become a defining operational standard under ECO4 and is increasingly used in private-pay whole-house retrofit. Approximate PAS 2035 audit data through 2024-2025:
- Estimated annual PAS 2035-coordinated retrofit projects in the UK: approximately ~150,000-200,000
- Approximate audit non-conformance rate (TrustMark routine audits): typically ~25-35% of audited projects show one or more non-conformances
- Most common non-conformances: ventilation strategy, moisture risk assessment, retrofit design notes, evidence of risk path A/B/C selection
- Approximate share of audits resulting in formal corrective action: typically ~10-15%
Industry analysis suggests audit findings are concentrating around documentation completeness rather than fundamental measure quality, although a smaller subset relate to genuine moisture or ventilation risk.
Long-run UK insulation install trend
Annual UK insulation install volumes have varied sharply over the past 15 years, peaked under the 2010-2012 CERT/CESP schemes and rebounded under ECO4 plus GBIS. Approximate UK loft and cavity wall installations by year:
| Year | Loft installs (approx) | CWI installs (approx) |
|---|---|---|
| 2010 | ~1,200,000 | ~600,000 |
| 2012 | ~1,000,000 | ~500,000 |
| 2015 | ~250,000 | ~150,000 |
| 2018 | ~120,000 | ~70,000 |
| 2021 | ~100,000 | ~55,000 |
| 2024 | ~155,000 | ~80,000 |
Source: BEIS/DESNZ household energy efficiency stats and ECO/GBIS programme data.
The 2010-2012 peak reflects exceptional CERT scheme intensity and the gradual exhaustion of easy-to-treat housing stock. The post-2022 rebound is driven by ECO4 plus GBIS plus rising private-pay activity.
Insulation longevity and refit rates
Insulation measures have varying expected lifetimes and refit/top-up rates. Approximate guidance:
| Measure | Typical design lifetime | Common reasons for refit |
|---|---|---|
| Loft insulation (mineral wool) | 40+ years | Compression, damp ingress, top-up to current standard |
| Cavity wall insulation | 25+ years | Moisture, slumping, original fill defects |
| EWI (rendered) | 30+ years | Render cracking, mechanical damage |
| IWI | 30+ years | Damp/condensation issues if poorly designed |
| Underfloor (suspended timber) | 40+ years | Moisture, rodent damage |
An estimated ~3-5% of UK loft installs require remediation/top-up annually due to compression or damp; CWI failure rates are typically ~1-3% requiring extraction or remediation.
Solid wall insulation cost and savings
Solid wall insulation accounts for over 60% of UK pre-1919 housing stock and is the largest remaining insulation opportunity. Approximate cost and saving figures:
| Measure | Typical install cost (full house) | Typical annual energy saving | Indicative payback (private-pay) |
|---|---|---|---|
| External wall insulation (EWI) | £9,000-£15,000 | 2,500-4,500 kWh | typically 15-25 years |
| Internal wall insulation (IWI) | £5,000-£9,000 | 2,000-3,500 kWh | typically 12-20 years |
| Cavity wall insulation (treatable) | £700-£1,800 | 1,000-2,000 kWh | typically 3-6 years |
| Loft insulation (top-up) | £500-£1,200 | 500-1,500 kWh | typically 2-4 years |
Indicative paybacks assume 2024-25 energy prices and full private-pay; ECO4 or GBIS funding materially shortens payback.
Solid wall insulation also delivers comfort, condensation and durability benefits not captured in pure kWh terms.
EPC band distribution by tenure
EPC band distribution varies sharply by tenure, with social housing typically performing best (driven by sustained Decent Homes investment) and private rented stock the worst. Approximate share of dwellings rated EPC band C or above by tenure:
- Social rented sector (housing association + local authority): approximately ~70-75% at EPC C or above
- Owner-occupied: approximately ~45-50% at EPC C or above
- Private rented sector: approximately ~45-50% at EPC C or above (post-MEES uplift)
- Holiday lets / second homes: approximately ~35-40% at EPC C or above
Minimum Energy Efficiency Standards (MEES) for the private rented sector currently require an EPC of E or above, with proposed increases to band C subject to consultation outcomes.
Data caveats
The following caveats apply to UK insulation statistics:
- BEIS/DESNZ insulation installation data is published on a delayed quarterly basis with periodic restatements.
- Some installs are recorded across multiple schemes (e.g. partial ECO + householder co-pay), creating overlap risk.
- EPC band distribution captures dwellings with a current EPC; properties without an EPC (older non-traded stock) are excluded.
- Retrofit Coordinator counts include certified individuals but not all are actively delivering projects.
- Workforce numbers are TrustMark-aligned approximations and certification cycles can cause month-to-month variation.
- Cost and saving figures are typical mid-range; actual project economics vary by property and tenure.
UK insulation deployment continues at scale but is increasingly weighted toward solid-walled and hard-to-treat stock, with delivery bottlenecks at Retrofit Coordinator capacity. Roughly half of UK dwellings are now EPC band C or above, reflecting steady progress but a long tail of band D-G stock - particularly in private rented and owner-occupied sectors - still requires upgrade. Solid wall insulation is the single largest remaining intervention by housing-stock impact. Use this data freely with attribution to ecosavinghub.co.uk. Last updated: 2026-05-08.
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