Forty per cent of UK homes were built before 1965. Most of the rest went up before 2000. That means the vast majority of British housing stock was designed for an average summer temperature of 18°C, not the 26°C-plus summers that are now routine, and certainly not the 30°C-plus heatwaves that the Met Office now models as a near-certainty by 2050.
A new report from the London School of Economics, as reported by the London School of Economics, makes the case bluntly: the UK is ‘built for a climate that no longer exists’. The authors, from the Grantham Research Institute, argue that the country’s infrastructure, especially its housing, needs systematic retrofitting, not marginal tweaks.
Overheating is the blind spot
Most UK homeowners think of energy efficiency in winter terms: draughts, lost heat, high gas bills. But the LSE report flags summer overheating as the bigger structural failure. A typical 1930s semi with single-glazed sash windows and no external shading can hit indoor temperatures of 32°C during a three-day heat spike. This causes discomfort and poses a health risk for the elderly and those with respiratory conditions. The NHS already records excess deaths during every prolonged heat event.
The fix goes beyond air conditioning, which pumps carbon back into the grid. The report calls for passive cooling: external shutters, reflective roof coatings, improved loft insulation that also blocks radiant heat, and, importantly, mechanical ventilation with heat recovery (MVHR) to circulate air without opening windows that let in hot air. These measures are not standard in UK new builds, and they are even rarer in the existing housing stock.
Who pays, and who doesn’t
The government’s current retrofit programmes, the Boiler Upgrade Scheme (£7,500 toward a heat pump), the Great British Insulation Scheme (free or subsidised loft and cavity wall insulation for low-income households), and the Social Housing Decarbonisation Fund, are mostly pitched at winter efficiency. None explicitly fund overheating measures. The LSE report argues that this is a policy gap that will cost billions in health spending and property damage over the next decade.
But the catch is that retrofit costs fall unevenly. A full deep retrofit, external wall insulation, triple glazing, MVHR, solar PV, and heat pump, can run £40,000 to £60,000 for a typical three-bed semi. The Energy Saving Trust estimates that most households recoup that in bill savings over 15–20 years, but the upfront capital is prohibitive. Mortgage lenders are beginning to factor EPC ratings into loan terms, meaning a D-rated home could attract a higher interest rate than an A-rated one within five years. That is the market signal that might accelerate action faster than any grant scheme.
What homeowners can do now
No single measure solves the problem. But the LSE report’s logic points to a hierarchy. Start with fabric first: loft insulation to 270mm, cavity wall fill where possible, and draught-proofing. Those three steps alone can cut heating demand by 30–40% and reduce summer heat ingress by about 15%. Next, address glazing: secondary glazing or low-e double glazing on south- and west-facing windows. Finally, consider a heat pump: even if you keep a gas boiler as backup, a hybrid system halves your gas use and qualifies for the £7,500 BUS grant.
The timeline matters. Ofgem is consulting on a future EPC reform that would require all rental properties to reach a C rating by 2028 and owner-occupied homes by 2035. The LSE report suggests that the government will need to bring those targets forward, given the accelerating climate data. Households that retrofit before the regulatory deadline will avoid the scramble, and the premium pricing that will inevitably follow when demand spikes.
Frequently Asked Questions
Some insurers already ask about overheating risk, especially in areas prone to heatwaves. A home without adequate ventilation or shading may be considered higher risk for mould and structural damage. It is worth checking your policy wording and asking your broker whether retrofit measures could reduce your premium.
Not directly from central government schemes today. The Great British Insulation Scheme focuses on fabric insulation. However, some local authorities offer discretionary grants for heat resilience measures. Check your council's website or contact your local energy advice centre. The Energy Saving Trust also has a postcode-specific grant checker.
