Retrofitting the UK housing stock: what lessons from Scotland's tenements?

The report “Retrofitting the UK housing stock: what lessons from Scotland’s tenements?” is published by the Economics Observatory, a research platform that analyses economic policies and trends. It is authored by Kenneth Gibb, an economist associated with the Observatory, who has contributed extensively to studies on housing and energy efficiency. The work draws on data and evaluation from a deep‑retrofit demonstration project undertaken in Glasgow’s pre‑1919 tenement flats, a partnership initiated in 2019 between a Southside housing association, Glasgow City Council, and Scottish Government funding.

The United Kingdom’s housing stock, over 80 % of which will exist in 2045, presents a massive retrofit challenge both financially and physically. Existing buildings are often old, varied in quality, and require substantial upgrades to meet net‑zero targets. The Glasgow tenement case illustrates these challenges, highlighting issues such as fragmented ownership, heritage conservation, and the high energy demand of dense, walk‑up flats.

Glasgow contains approximately 73 000 pre‑1919 tenement flats, representing more than a fifth of the city’s dwellings. These buildings are typically poorly insulated, leak carbon, and are costly to heat. The demonstration project focused on an eight‑flat block on Niddrie Road, applying the EnerPHit standard – a deep‑retrofit benchmark comparable to PassivHaus for existing homes. The retrofit included fabric‑first airtight insulation, mechanical ventilation, waste‑water recovery, and, in half the units, air‑source heat pumps.

Each unit’s total retrofit cost was £148 000, comprising £60 000 for acquisition, £44 000 for basic refurbishment, £32 000 for EnerPHit‑level upgrades, and a £12 000 contingency. Funding was split roughly equally between direct grant contributions from Glasgow City Council and the Scottish Government, with the remaining balance to be recouped through rental income. The cost‑benefit analysis, using HM Treasury’s Green Book methodology, indicates that both EnerPHit and a lower‑level EPC B retrofit are financially preferable to demolition and rebuild, though the net‑benefit advantage between the two retrofit options varies with assumptions.

Evaluation, led by the Scottish Funding Council, combined a decision‑making account, cost‑benefit analysis, technical energy performance assessment, and tenant surveys. Early results show strong cost‑benefit performance despite high absolute costs, with EnerPHit delivering 80‑90 % reductions in fuel costs and achieving net‑zero carbon emissions. The project benefitted from being unoccupied during works, eliminating the need for resident decanting, and from a single tenure structure, simplifying coordination.

1. Fabric‑first approach – airtight insulation and good ventilation are the most impactful measures for energy reduction.
2. Partner commitment – successful deep retrofit requires strong leadership and coordinated funding across public bodies and housing associations.
3. Financial models – blended grant funding coupled with rent‑based repayment can make high‑cost retrofits viable.
4. Scalability considerations – not all tenements will need the full EnerPHit package; a tiered approach can balance performance with affordability.
5. Legal and organisational reforms – the Scottish Law Commission is examining reforms to promote ownership associations and sinking funds, addressing the classic challenge of collective repairs in multi‑owner blocks.

The Glasgow tenement case demonstrates that deep‑retrofit standards, while expensive, can deliver substantial carbon reductions and long‑term fuel savings, offering a replicable model for other historic, high‑density housing typologies in Europe. Emphasising fabric upgrades before renewable installations ensures that energy demand is minimised, making subsequent renewable technologies more effective and cost‑efficient. Policy makers and practitioners are encouraged to consider blended financing, strong multi‑stakeholder governance, and legal mechanisms that facilitate collective action on retrofits, thereby advancing the EU’s broader sustainable housing objectives.