Our journey over the last 10 years has been filled with valuable lessons, challenges, and breakthrough moments. We’ve worked on some of the UK’s most pioneering retrofit projects alongside our brilliant partners, including the Mayor of London’s Retrofit Accelerator Homes – Innovation Partnership and now the Zero Carbon Accelerator – as well as the Innovate UK-funded Transform-ER and other local authority and housing association initiatives.
From this real-world experience we’ve distilled the five most important things we’ve learned about accelerating retrofit at scale and speed. These are lessons that we’ve shaped and that have shaped us and are now transforming the way we work.
We said that there's no retrofit silver bullet, and we stand by that. None of these will solve the challenges alone – they are five interventions that need to work together.
“Energiesprong? That's really expensive.” We know this is a common reaction when our name is mentioned. And we understand why.
The initial Energiesprong performance specification focused on high-performance outcomes rather than detailed specifications to enable ‘solution providers’ flexibility and allow innovation to achieve net zero targets, resident comfort and affordability in one step, with a business case that was viable in the medium term.
It's a powerful approach, but it initially led to drawn-out design periods – extensive "optioneering" to find the right cost-benefit balance. That created a frustrating cycle: costs came back too high, designs got revised, timelines stretched, and residents dropped out, pushing per-home costs up further.
Our initial pilots were also small and fragile. Retrofitting 10 - 20 houses means one home’s three-week delay can derail the whole timeline as there's no flexibility to work around it. And while we started to scale to projects of 80 - 100, we realised these as standalone projects weren’t enough – there needs to be co-ordinated pipelines of projects across the country.
Lack of initial market volume has also left the UK’s supply chain for manufactured, innovative solutions without the signals or money for development. And homes are in poor condition after years of underinvestment with lots of remedial works compounding the issue.
So, one of our key intervention points for driving down cost is focusing on ways to aggregate homes into pipelines with data-led archetyping to find the right solutions for different typologies. This means solutions can be adapted rather than designed from scratch each time, streamlining preparation, simplifying the customer journey, and cutting costs.
Scale means more robust programmes, less sensitive to an asbestos discovery or a resident’s holiday. And beyond day-to-day resilience and reducing design costs, aggregating demand into longer-term pipelines will also give manufacturers a way in.
Systemised programmes based around typologies shine a light on product requirements and market size and potential, enabling investment in new designs and skills and offering the opportunity for continuous improvement. We think this will equal better quality retrofit that can be deployed at scale with consistency and guaranteed performance.
See this in practice: Aggregating demand is at the heart of our work with Transform-ER – a new integrated bold retrofit model for social landlords and local authorities that’s built on 13 industry leaders’ experience. Watch its new animation, which explains how its portfolio assessment and pipeline development digital platform helps landlords with strategic asset management - bringing together the right homes with the right solutions.
Reducing the cost of retrofit is only one part of the financial puzzle. The other is getting homes to cut energy use enough so that a share of the bill savings can be collected as revenue, and finding a reliable way to collect it.
This is not a new idea. Organisations have long championed using energy savings to make the finance case for retrofit stack up, including us, after seeing it work well in the Netherlands. We've spent a long time working on a pay-as-you-save 'Comfort Plan' model but, for a complex host of political, logistical and technological reasons, it's been tricky to deploy in practice.
Fabric energy-efficiency measures alone don't always deliver the expected savings. We have found that many residents understandably take the improved comfort and spend the same amount, so the financial saving disappears. Also, the cost of collecting revenue has stayed high, partly because policy doesn't easily enable social landlords to increase their revenue streams.
We've learned a lot, though, and the numbers are becoming much more compelling. Solar and battery prices have plummeted over the last decade, and grid balancing offers numerous new revenue streams. Our evolving thinking, tested through work including a market analysis for Enfield Council on financing solar, points to a hybrid model.
Energy efficiency can be funded through landlord investment and grant funding, while energy system upgrades (heat pumps, solar, batteries) blend grant funding with private finance, generating revenue when managed together for grid balancing. Each source of money does what it's best suited for: that's the "holy grail" of retrofit financing.
Making this work requires building robust business cases underpinned by better-quality portfolio data to show which measures pay back and which revenue streams are dependable. You can read more about that via our Innovative Retrofit Finance Playbook with Healthy Homes Hub, which outlines how landlords can put revenue-generating retrofit models into practice, including how data determines investability.
See this in practice: We’ve supported Enfield Council with market analysis for solar + battery finance and have created a decision-making digital tool for landlords which will be publicly available soon via the Zero Carbon Accelerator. We're also working closely with other landlords to help build business cases for decarbonising their portfolios.
It’s no secret that resident engagement continues to be a challenge for retrofit. Our research shows that landlords repeatedly report high dropout and refusal rates (sometimes as high as 50%) – which contribute to slow programmes and high costs – as well as tenants who find using new technologies challenging.
Meanwhile residents say they feel uninvolved, confused and ultimately distrustful of the whole process. Retrofit is done to them, rather than with them. Word-of-mouth from previous schemes means many think retrofit programmes require multiple surveys, highly disruptive works and/or poor-quality outcomes – and we know those concerns are often justified. It’s no wonder that residents don’t want to join schemes, or drop out along the way.
But there’s another way. Our deep dive into success factors shows that early engagement, two-way dialogue, careful management of expectations, and thoughtful communication about benefits can help. We’ve also found that digital archetyping solutions improve the process for residents – reducing visits for surveys by providing better data.
But most importantly: effective resident engagement isn't just about communication or logistics. It requires genuine co-design – involving residents in shaping solutions that work for their lives and circumstances, not just informing them of what's coming. We saw this in practice with our Transform-ER demonstrator home - delivered with Bow Tie Construction and Ultrapanel Building Technologies - which incorporated small fixes requested by the resident, and reaped huge benefits in goodwill in return.
See this in practice: We’ve helped define Transform-ER’s resident-first approach. Residents are involved early and share what their expectations are upfront, which we think will help create quicker programmes that deliver outcomes for everyone. This approach continues to influence our own work too.
We've long championed modern methods of construction – Netherlands-based factories building parts for Energiesprong retrofits have improved labour productivity by 75% and reduced waste by 90%. Germany’s investment-backed, industrialised retrofit programme has already completed or started construction on more than 5,000 homes.
Modern methods also offer real potential for quicker, easier onsite installation, and open up the sector to more diversity. Melius Homes, for example, offered "work what you can" shifts at its factory manufacturing insulated wall panels, making roles more accessible for parents and carers. Ultrapanel Building Technologies, another manufacturer of wall panels, has specially designed its 6m panels weighing 25kg - meaning they can be lifted by one person onsite making for easier, quicker install.
But manufacturing-led retrofit at scale will demand fundamental shifts in how the industry operates and we just aren’t there yet in the UK. Unsupportive accreditation and certification processes, supply chains built for traditional methods, and natural reluctance to change all create friction – and we've seen first-hand how costly it can be when planning delays leave factories full of uninstalled panels.
These aren't challenges unique to retrofit; high-profile new-build companies have faced the same growing pains. But the potential benefits – higher quality, faster installation, less waste – make solving them essential to scaling retrofit. Change will require targeted support and investment.
See this in practice: Keep your eyes peeled, we're currently working on putting together a call for government investment in ‘manufacturing-led’ retrofit to turn home energy upgrades from a net-zero challenge into an industrialisation opportunity for the UK. Get in touch if you’re interested in this.
Perhaps our most complex lesson has been creating genuine collaboration in a sector traditionally built on adversarial contracting – which we think is directly leading to slow programmes, inflated costs and poor-quality outcomes.
ESUK started as a collaborative endeavour that recognised these challenges, and we initially experimented with ‘solution provider’ roles intended to integrate supply chains. This worked brilliantly where companies were small enough for leadership values to run through the whole team, creating strong partnerships.
With larger companies, though, we more often found standard main contracting approaches, where risk was passed down and suppliers kept at arm's length from clients. Performance guarantees, while ultimately driving better outcomes and quality, added significant supplier risk, drove over-specification, increased design time, and made pricing hard for solutions that didn't yet exist – dampening market engagement in the process.
One of our most successful approaches was creating a Collaboration Hub through the Mayor of London's Retrofit Accelerator Homes - Innovation Partnership, which opened up space for genuine problem-solving. But without changing contracts, we saw the same challenges emerge in practice.
We've pushed this a big transformative step further through Transform-ER – embedding an alliancing approach at its heart to create value-aligned partnerships with shared outcomes, building the contracting and procurement arrangements to make it work and helping nurture the culture change needed alongside. Our demonstrator home was delivered on time, to budget and at half the cost of previous comparable schemes.
See this in practice: Dive deep into what alliancing means and its benefits in this blog from our Director Emily Braham - and download Transform-ER's collaboration toolkit, which is jam-packed with practical tools to help you embed better ways of partnership working at the heart of your retrofit programmes.
These insights represent hard-won knowledge from years of real-world retrofit delivery. The challenge of achieving net-zero homes at scale requires us to embrace flexibility, invest in data-driven approaches, think beyond individual projects to programmes and systems, innovate in finance and construction methods, rethink commercial relationships, and put residents at the centre of everything we do.
As we continue to develop and refine these approaches, these lessons provide a foundation for the next phase of retrofit acceleration – one that can deliver on the UK’s climate commitments while creating better homes and stronger communities. You can see how we’re working to accelerate better retrofit with landlords, suppliers and policymakers via what we do. Our mission hasn’t changed, just some of the ways we are going about it.
Get in touch if you are interested in finding out more! Read part 1 of this blog for more insights into how our approach has changed and adapted to the UK market over the last decade.
The insights in this blog post are drawn from extensive experience with retrofit programmes across the UK, including work with the Energiesprong model, the Mayor of London's Retrofit Accelerator, and various local authority and housing association initiatives. A huge thank you to all those who have helped shape them.
