Sparks of 2026 #25: We Left The Best For Last - PHIRST
Why a public-health evaluation of nearly 5,500 homes is the most important signal shaping retrofit in 2026
Sparks of 2026 exists to do one thing well: to identify the signals that tell you not what is fashionable, but what is fundamentally changing the direction of retrofit. Some Sparks are technologies. Some are people. Some are methods. This year, the most important Spark is none of those things. It is a report. Reports are not exciting by their nature, but this one provides something the retrofit sector needs more than ever: independent, scientific reinforcement of what practitioners already know to be true.
At the end of January, a major public-health evaluation of housing retrofit will be published. The report is titled: Evaluation of a housing retrofit programme delivered across Liverpool City Region. Research is being conducted by an organisation that sound like bond villains - but they are the good guys. If you haven't heard of them yet - you will PHIRST.
What makes this report different? It has not been written for industry marketing. It has not been commissioned by manufacturers. It is not a pilot dressed up as a breakthrough. It is a rigorous assessment of retrofit delivered at scale, analysed through the lens of public health. And in our judgement, it will be the single biggest influence on how retrofit should be understood, targeted and defended in 2026.
Here's the report summary page. Delivered by PHIRST.
The research phase is complete and the report is being written on this ground breaking study.
My Dad left school at 14 to support his family, he worked in farms in Scotland, oftern sleeping in the byres, the cattle sheds, elevated above the cattle and warmed by their body heat, farts and manure.
Fast forward 70 years and byres are converted into homes. The point of this story - building physics hasn't changed but they way people live in them has, and we have technology, not farts, to power our future.
The social value, the impact of health improvements from better housing, is underestimated. But soon, we will have factual evidence. Empirical evidence of the health benefits of retrofit measures is gold dust for selling the story to the public.
When we talk about homes now. Energy metrics dominate. EPCs are treated as gospel. Carbon accounting becomes the primary language. Meanwhile, the human outcomes that actually drive value remain peripheral.
The PHIRST report exists because that gap has finally been acknowledged. As one of the researchers remarked during our research into this study "Local authorities are running interventions that clearly influence people’s lives, but without evaluation it’s very difficult to know whether they’re having the impact that was intended.”
That sentence captures the problem retrofit has faced for more than a decade. The work has been happening. The benefits have been real. But without structured evaluation, decision-makers have been left to rely on assumptions, proxies and blunt metrics.
Follow Aventus Eco on LinkedIn and follow the story in January of a Scottish byre and country house converted using a heat pump, solar PV and battery system into a luxurious, all year round energy efficient dream home.
What makes this report different is not simply that it evaluates retrofit, but how it does so. It starts with people, not products. The evaluation includes qualitative work with residents who have received retrofit interventions, exploring not just whether measures were installed correctly, but how those changes affected daily life. The research team are trying to 'understand the experiences people have had, not just of the retrofit itself, but the impact it's had on their health and wellbeing'. That framing matters enormously. It recognises that comfort, stability and ease of living are not secondary outcomes. They are the point.
Alongside that lived experience sits the scale that gives this work its authority. The evaluation draws on detailed delivery data from just under 5,500 homes over a sustained period, covering roughly two years of retrofit activity. This includes information on property types, tenure, measures installed, costs, timing, and changes before and after intervention. As one researcher described it,
“We’ve got data covering just under 5,500 homes over a two-year period, with detailed information on the properties, the measures installed, and what changed before and after.”
This is system-level evidence.
That scale shifts the conversation entirely. Five hundred homes might tell you something interesting. Five thousand five hundred homes tell you something structural. It moves retrofit out of the realm of pilot projects and into the territory of national relevance.
It allows patterns to be identified. It allows assumptions to be tested. It allows claims to be made with confidence. And crucially, it allows retrofit to be discussed in the same analytical terms as healthcare, transport and social infrastructure.
The most important move this report makes is to connect housing improvement with health outcomes directly. Rather than relying solely on energy performance as a proxy for benefit, the evaluation examines how retrofit intersects with health need. Respiratory conditions, cardiovascular health, mental wellbeing, frailty and mobility are all considered in relation to housing interventions. This matters because health is the language the system understands. You can debate energy efficiency endlessly, but when housing conditions influence hospital admissions, GP demand, falls risk and long-term care needs, the conversation changes.
The researchers involved are careful not to overstate conclusions, but the implications are clear. As one of them noted,
“What we’re really interested in is what happens if you don’t just target homes by energy performance, but also by health need.”
That question goes to the heart of how retrofit is currently delivered. EPC-led targeting has value, but anyone working on the ground knows its limits. People do not live according to SAP assumptions. Vulnerability does not always align neatly with energy ratings. This report begins to quantify what retrofit professionals have long understood intuitively: that smarter targeting can deliver better outcomes.
That insight leads to one of the most important consequences of the work. If health need is recognised alongside building performance, retrofit stops being framed as a blunt instrument and starts being understood as a precise one.
Smaller interventions can deliver outsized benefits. Local knowledge becomes valuable rather than inconvenient. Flexibility is no longer a risk, but a strength. As the research team observed,
“You could potentially get greater benefit by better targeting, but current programmes don’t always have the flexibility to do that.”
That sentence should resonate across the sector. It validates the frustration many practitioners feel when prescriptive schemes prevent sensible, human decisions.
For people working in retrofit, the “so what” is profound. This report does not tell you to abandon what you are doing. It does the opposite. It reinforces it. It confirms that comfort is not subjective, but measurable. That warmth is not indulgent, but preventative. That calm indoor environments matter. That how people use their homes is as important as how those homes score on paper.
It gives retrofit professionals something they have rarely been afforded: evidence that the transformation they deliver is real, systemic and defensible.
This is why Refurb & Retrofit has placed this report at number one in the Sparks of 2026 list.
We did not commission this work. We do not influence it. We did not select it because of relationships or agendas. We identified it the same way we identify everything we cover: by listening, paying attention and following the work.
Over years of interviews, site visits and conversations, the same truth has surfaced repeatedly. Good retrofit changes lives, but the system struggles to see it clearly. This report clears that fog.
It aligns independent science with lived practice. It connects housing to health in a way that policymakers cannot ignore. It provides retrofit professionals with a foundation that goes beyond belief and into proof. When it is published at the end of January, it will not end the conversation about retrofit. It will begin a new one. One that is more grounded, more credible and more difficult to dismiss.
Sparks of 2026 are not predictions. They are indicators of direction. This report tells us that retrofit is moving away from narrow definitions of success and toward a fuller understanding of value. From energy alone to wellbeing. From compliance to care. From metrics to meaning.
For an industry built on improving existing homes, that shift could not be more fitting. This is not just data. It is validation - with a human voice. It is scientific reinforcement of the success of the improvements being made to people’s homes every day. And that is why, in 2026, nothing will influence retrofit thinking more.
If you've missed on of the Sparks stories, you read them all here.
