As 2025 comes to an end, our head of communications Emmelie Brownlee has crowdsourced ideas from the ESUK team on what we've all learned about accelerating better retrofit - from a year crammed with insights, innovation and inspiration.
When I joined Energiesprong UK in 2021, I did what I always do in a new job – I asked my colleagues how they would describe our mission. And what my new colleague Zack Gill said has stayed with me ever since: that we aim to make “iterative learning the industry standard.”
I loved this because it acknowledges something fundamental: if we’re serious about accelerating better retrofit, we're never “done” learning. We must keep challenging assumptions, testing ideas, and being open to better ways of doing things.
And 2025 has exemplified that more than any year so far – from tackling industry barriers through Transform-ER, to sharpening the business case for home energy upgrades via the Mayor of London’s Zero Carbon Accelerator, to growing our understanding of archetype-led scale through our DESNZ Heat Pump Ready project.
So after some careful research (aka Whatsapping the team), here’s what we’ve learned alongside our brilliant partners in 2025:
Transform-ER’s industry-wide collaboration survey revealed something clear: technical competence isn’t enough. Relationships matter.
Trust, empathy, integrity and shared goals are what enable meaningful collaboration between landlords, contractors, manufacturers and residents. If we want retrofit at scale, trust must be part of the infrastructure we build. Explore industry perspectives on collaboration >
Transform-ER’s Define the need report, developed by project partner the MTC, revealed the current retrofit market is valued at ~£1bn a year – with the potential to grow as big as £60bn. With roughly 60% of homes still rated at EPC band D or lower, the sector must scale quickly to meet this demand. The answer? Manufacturing-led retrofit. Discover Define the need’s top five findings >
“By aggregating demand and applying technology, we can start to develop standardised kits-of-parts to enable us to produce large-scale volumes of common solutions to be applied to different archetypes with custom-made components. We’re calling it ‘Manufacturing-Led retrofit.’ Steve Nesbitt, Engineering Design Director at the MTC.
Through the Mayor of London’s Zero Carbon Accelerator, we explored how Clarion Housing Group, Hackney Council and Camden Council are testing new ways to finance solar at scale.
Each model is different, but they are all driven by the same goals:
• Prioritising residents
• Reducing energy bills
• Achieving scale without compromising governance
• Attracting long-term investment
• Accelerating the transition to net zero
Check out the report’s top insights >
Together with long-standing partners RJ Barwick Ltd, Studio Partington, Melius Homes and KIN, we’ve shown how an archetype-led approach can improve cost-effectiveness, reduce risk and unlock a replicable pathway for upgrading homes at scale.
Focusing on non-traditional archetypes, we:
• developed optimised whole-house retrofit solutions for non-traditional archetypes
• tested these through two pilot schemes on 20 Wimpey No-fines homes in Wolverhampton and Kent
• created a design guide – summarising our insights and providing template retrofit solutions for three other common non-traditional archetypes: BISF, Cornish Unit and cross wall.
“By providing practical insight and data-driven retrofit pathways, the guide aims to support housing providers in commissioning projects and developing retrofit designs that improve energy efficiency, reduce carbon emissions, and enhance comfort for residents.” Jon Warren, Energiesprong UK’s Policy & Innovation Director.
Watch our Wolverhampton pilot video >
Ok, we already knew this one but it’s always good to have our theories confirmed. Our Director of strategy and operations Emily Braham was one of three people on Unlock Net Zero’s climate champions power list.
It was a well-deserved acknowledgment of her tireless efforts to drive the scale and pace needed to meet the UK's net zero targets – and how her commitment to championing systemic change, collaboration and diversity has never wavered.
The judges said: “Emily has been an integral part of transforming the UK’s retrofit sector to meet net zero targets.” Explore Emily’s story >
As Transform-ER embarked on our mission to revolutionise the retrofit industry, one thing was crystal clear: retrofit at scale isn't just about the technologies, it’s a collaboration challenge.
Our research and experience showed how projects must build trust early and maintain it, engage all stakeholders meaningfully and focus on solutions, not blame.
So, we created a culture change programme to support this transformation – and turned it into a toolkit jam-packed with practical tools for the whole industry to use. Download and get started! >
“Culture change requires people willing to work differently, lead by example, and rewrite the narrative from difficulty to possibility.” Energiesprong UK’s culture change lead Stéphanie Ah Tchou
Building on Transform-ER’s work exploring certification challenges, led by BRE, we held a sold-out retrofit certification event back in September – bringing together insurers, certification bodies, product manufacturers, researchers and retrofit professionals. Consensus was clear:
• The current landscape is fragmented and inconsistent
• A national “lily pad roadmap” is needed, moving from initial checks to full certification
• Funding, procurement and insurance must align with certification to manage early risk
• SMEs need better guidance and matchmaking
• Residents and installers need clearer information to counter misinformation.
Next steps - developing recommendations for key stakeholders to drive change. Read our full write up >
“Retrofit certification is incredibly complex with no clear path. To open the market, we need a clear set of rules.” Max Bloomfield, Co-founder and COO at Vundahaus
As part of the Thames Freeport regional transformation initiative, we’re demonstrating Transform-ER’s new retrofit model on a home in the Becontree Estate.
Designed by Bow Tie Construction, the demonstrator uses Ultrapanel’s next-generation EWI with integrated ventilation, plumbing and renewable energy – offering a full home kit-of-parts solution. We’re testing:
• Installation time
• Manufactured product performance
• Low-disruption ventilation installation
• A new resident engagement approach that identifies high-impact, low-cost improvements.
“The team is lovely and hardworking. It was really exciting to see my extra loft storage completed – something I’d requested.” Ms M., the resident
Find out more about testing Transform-ER >
We’re proud to be part of the Energiesprong Global Alliance – a network across the Netherlands, France, Germany and Italy. We don’t get to join international meetings as much now that we have less access to European funding, but we are always on the lookout to learn from our international friends as each country navigates its own unique successes and challenges.
This year our Lillian Lochner attended the EGA International Convention and was particularly interested in Germany’s investments in manufacturing in light of our Transform-ER project. Recent analysis shows that standardisation has helped costs fall by around a third, and construction times were halved from 14 to an average of 7 weeks. Take a peek >
As ever a huge thank you to all our partners who enable us to discover these insights. We couldn't do it without you! Wishing you all a restful festive break and see you in 2026 for another year of accelerating better retrofit.
