The idea
Conceived in 2020 at a moment when the Welsh social housing sector was grappling seriously with decarbonisation, Optimised Retrofit set out to do something genuinely new: create an open, collaborative framework that any Welsh social landlord could join, and that would deliver real homes to real net-zero-ready standards — not just modelled predictions.
The programme was built on the recognition that no single organisation could solve this alone. Every home is different. Every landlord has different stock, different maintenance budgets, different resident demographics. What was needed was not a top-down specification but a systematic, data-driven method for tailoring the right blend of measures to each individual home — and then mapping out the financially viable route to get it there.
“You’ve got to measure in carbon to achieve zero carbon.”
What “Optimised Retrofit” means
The approach rests on three mutually reinforcing elements, calibrated for each home:
Fabric
“Do no harm” fabric measures that economically reduce energy demand — airtightness and ventilation, loft insulation, high-performance doors and windows, wall insulation where appropriate.
Technology
Low and zero carbon technologies that reduce, balance and generate energy — hot water tanks, battery storage, photovoltaic panels, mechanical heat recovery, heat pumps.
Intelligence
Smart, user-friendly control of the home — app-controlled heating, smart room sensors, energy demand forecasting, and grid connectivity to minimise bills and balance the wider system.
These three elements don’t have to be delivered at once. The programme established the concept of a “Building Journey” — a digitally stored, PAS2035-compliant home assessment and design that maps multiple flexible routes to net-zero-ready status. A home could be retrofitted in a single coordinated visit, or incrementally over several years, without prejudicing or precluding later stages.
Delivery in three phases
Targeting c.1,000 social home retrofits across participating landlords, with Welsh Government as “funder of last resort” once all other funding streams were exhausted. Demonstrator tools launched September 2020.
Expanding to c.4,000 homes, deploying v1 tools at scale, opening the collaboration to new partners, and refining the approach based on real delivery data from Phase 1.
Expansion to private sector landlords and homeowners, using energy bill savings ‘tithes’ and Special Purpose Vehicles to close the funding gap without relying primarily on public grant.
Open tools for the whole sector
A defining feature of the programme was that its tools were free and open to all. The Simplified Home Retrofit Survey — a tablet-based, guided assessment built on PAS2035:2019 — was made freely available to social housing providers, mortgage surveyors, construction professionals, and private landlords. The Clear Pathways to Zero portal gave everyone from individual homeowners to government an accessible route to their home’s options. A Collaborative Database mesh allowed data holders to share information securely, with GDPR requirements embedded from the outset.
The programme directly influenced the Welsh Government’s requirement for “Target Energy Pathways” — a national policy tool that embeds the Optimised Retrofit principle of a mapped, funded journey to net zero into mainstream Welsh housing policy.
What it took
Running a programme of this complexity — with 28 RSLs, Welsh Government, local supply chains, training providers, data specialists, mortgage lenders, and insurers all in the same collaboration — was genuinely hard. Managing the consortium, maintaining momentum through Covid, aligning funding streams, and bringing resident communications up to the standard the programme needed all required continuous effort.
The closure review — commissioned to learn openly from the programme — was candid about governance challenges: the blurring of roles between Sero, Pobl, and Welsh Government; the light-touch grant arrangements that gave flexibility but complicated accountability; and the difficulty of maintaining board oversight as the programme transitioned between funding phases. These are real lessons, taken seriously.
But the same review also recorded something more important: all parties reflected on the benefits of the consortia approach and how it drove collaboration and transformative change across the sector. WHQS — the Welsh Housing Quality Standard — would not have progressed as far without the innovation enabled by this programme. Phases 1 and 2 delivered considerable value for money, magnifying funding from elsewhere. And a steep learning curve on governance and partnership working produced lessons that the sector is still drawing on.
“All parties lauded the clear ambition and focus on innovation.”
The numbers behind it
Over the programme’s lifespan, Optimised Retrofit mobilised over £466m of public investment, involved 68 partners, and touched more than 1,700 homes directly in its demonstrator phases. Its projection for Phase 3 was 6,000 home retrofits per month by Year 10 of operation — a scale that puts the potential of the methodology in sharp relief.
We conceived the overall collaboration via Sero, coordinated and led the programme, and delivered with the active participation of social landlords, local trades, and Welsh Government throughout. It remains one of the most ambitious and detailed attempts to operationalise whole-home social housing retrofit in the UK at genuine national scale.