INCA, the recognised trade association for the external wall insulation (EWI) industry in the UK, have published findings of their industry survey which reveals the size and split of the market in 2023.The first of what is planned to be an annual sector review.

Key Findings:  

  • 5.9 million square metres of EWI was installed onto buildings across the UK in 2023 
  • 73% of this went into the refurbishment of homes and buildings and 27% into new build construction 
  • Mineral fibre insulation was, at 56%, the main insulant used with expanded polystyrene (EPS) making up 37% of the market (low rise only) and other insulants accounting for the remaining 7% 
  • Various types of specialist render proved by far the most popular finish and were incorporated within 79% of systems. Brick slips (and similar) decorative finishes accounted for the remaining 21% 


External wall insulation systems are widely used throughout the UK construction industry both in the highly effective thermal upgrade of existing buildings (especially solid wall, hard to treat and non-traditional buildings) and as an efficient method of constructing thermally efficient new buildings across all sectors of the market. 

The industry commissioned survey was undertaken by NEMS Market Research on behalf of INCA and targeted all main system manufacturers with a near 100% participation rate reported. 

Considering the variations in cost of the different systems and finishes along with different types and thicknesses of insulation used, the findings revealed 5,895,000 square metres of EWI was installed in the UK during 2023 on projects across all sectors of the market.  

The refurbishment (retrofit) market (often supported by government funding measures) accounted for around 4,303,000 square meters (73%) of this total with most contributors forecasting market growth in this sector in 2024. New build construction accounted for the balance of 1,592,000 square meters (27%) but there was less confidence for growth in this sector during 2024 with most participants forecasting sales to be static. 

Used across 56% of EWI installations, it’s no surprise that mineral fibre was by far the most frequently incorporated insulant – regulations mandate its use on high rise buildings and in the installation of fire breaks / fire barriers. EPS remained a popular choice of insulant for low rise and was used in 37% of all system installs in 2023. Other insulations (extruded polystyrene, PIR, wood fibre etc) accounted for the remaining 7%. 

Specialist renders remain the most common decorative finish, being incorporated within 79% of systems. These come in a wide variety of different materials, thicknesses, colours and textures. This number includes those which incorporate an additional dash aggregate within the overall finish and those projects where render is used to create the effect of stone / brickwork. Brick slips (clay or lightweight brick effect systems), stonework and tiles accounted for the remaining 21%. 

John Sparrow, Executive Director of INCA, said:

This report is long overdue and something that the industry has been requesting for many years. INCA, as the recognised trade association for the external wall insulation industry in the UK, was perfectly placed to commission, facilitate and fund this research. 

Being the first industry survey in recent years it was decided to keep things simple and to analyse at headline level only initially. Moving forward, it’s intended that we make this an annual survey which will allow year on year comparison and a drill down from this benchmark into a more in-depth analysis. 

Coming at a time when we have a clear focus on competence, training and the development of a new industry apprenticeship scheme we regard the results to be of particular importance to better evidence the need to attract new blood into the EWI industry and support our efforts to facilitate this. 

We would like to thank all our system designer membership and close industry partners for their input, support and contribution.

Sean Stevenson, Chair of INCA, said:

Whilst the numbers demonstrate that the industry is delivering well at current levels, they also highlight the scale of the opportunity on the horizon as the Government looks to ramp up its retrofit program to deliver on net zero targets. The latest official numbers published by DESNZ* show that 90% of solid wall homes (some 7.6 million properties) are still without insulation! The data also highlights significant potential within the new-build sector and an opportunity to grow our share of the market through innovation and greater awareness of the commercial and environmental benefits of EWI. 

In turn this justifies the efforts INCA are making to address any skills shortage, not just by way of promoting the industry, but directly in relation to training and upskilling. We currently spearhead the steering group tasked with defining and mapping out a route to EWI competence, co-chair the IfATE employer group commissioned to deliver the EWI pathway of a new apprenticeship by the end of 2024 and collaborate with colleges and training facilities across the UK in support of multiple regional and national training initiatives. 

These are positive numbers which we hope will drive further investment in the EWI sector, encourage more operatives to join us and to help us to future-proof our industry.




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Notes to Editors:

About INCA

  • INCA is the recognised trade association for the External Wall Insulation (EWI) industry representing system designers, specialist installers and key component suppliers
  • INCA has proven longevity as a trade body dating back 40 years. Current membership is 75, please refer to the INCA website for a current breakdown of our membership types: contractors, manufacturers, and associates
  • INCA’s vision: The delivery of growth in sustainable fabric performance solutions as the primary focus in combating fuel poverty and protecting the environment
  • INCA’s mission: To represent and support members of the External Wall Insulation industry through technical excellence, effective collaboration, strong communications, and member benefits