Why we should follow the cooling hierarchy before installing air conditioning in UK homes
Recent heatwaves and the ongoing spell of record-breaking hot summers have generated fresh policy debates about how best to protect new and existing homes from overheating.
These debates are in danger of becoming polarised and uninformed by good evidence. Across summer 2026, several calls have been made to immediately prioritise air conditioning (AC) in both new and existing homes.
AC has a clear role to play in some homes. The Climate Change Committee (CCC) has stated that in likely future climate conditions of 2°C global warming, around 22 per cent of UK homes will require it.
However, the UK’s approach to tackling overheating should be based on the principles of the cooling hierarchy, not AC. Our approach should prioritise passive cooling, particularly external shading, with AC installed only if necessary to guarantee safe indoor temperatures.
Our argument is in other words a simple one: the government should resist the rush to AC, and adopt the cooling hierarchy as the foundation of overheating policy across the UK.
Why do homes overheat?
The CCC states that 55 per cent of UK homes are currently at risk of overheating. By 2050, on current estimates, this will have risen to 92 per cent.
It is well-established that the main cause of overheating in homes is solar radiation entering through the building fabric, especially windows. Heat enters the home and is then absorbed and reemitted by internal surfaces like floors and furniture, creating a kind of greenhouse effect that raises indoor temperatures.
Homes that are south facing, with large windows and poor insulation, also tend to be more at risk of overheating. Many homes created through common office-to-flat conversions fall into this category, as does a lot of poor-quality temporary accommodation.
Using the cooling hierarchy
Calls to prioritise AC in UK homes are implicitly based on the view that we cannot stop the heat getting in, so an active process is required to circulate it out. This is wrong: there are various measures we can take to stop heat entering homes in the first place. To do this, we should follow the cooling hierarchy.
The cooling hierarchy describes an approach to reducing overheating in both new and existing homes that prioritises passive cooling.
External shading, natural ventilation, and correctly installed insulation all reduce the risk of homes overheating without requiring AC. External shading is especially important, with academic studies showing that it can reduce indoor temperatures by around 2–3°C while reducing cooling demand by more than 60 per cent, depending on the type of building and design of the shading.
Even in homes where AC may be needed, prioritising passive cooling and shading first is a vital way of reducing carbon emissions, minimising the discharge of waste heat into the environment, softening demand on the energy grid, and decreasing the ongoing electricity costs of running it, which may be difficult for lower-income households to afford. It is also more cost effective, with shade sails, awnings, external blinds, and shutters providing options at a range of price points for different household budgets.
The cooling hierarchy should be the foundational pillar of the UK’s approach to tackling overheating in homes. The government should follow the London Plan in adopting it as a more equitable approach to heat adaptation that reduces overheating risks without placing undue pressure on household finances, the electricity grid, or the climate.
Integrating the cooling hierarchy into UK heat adaptation policy
The UK Government’s Warm Homes Plan commits to integrating heat adaptation measures into future retrofit programmes aimed at low-income households. In England, where heat adaptation challenges are most pressing, especially in London and the South East, major work is also underway to reform building regulations and the planning system .
The cooling hierarchy should sit at the centre of these policies. This means focusing on shade and other passive solutions first when retrofitting homes, strengthening building regulations for new homes, and strongly emphasising the use of trees and innovative design in planning policy to create shaded, heat resilient communities.
Prioritising AC without taking steps to stop heat getting in the home in the first place is like trying to fill a bath without putting the plug in; wasteful, inefficient, and unsustainable. Going forwards, passive cooling and external shading should no longer be viewed as an optional architecture feature or retrofit nice to have.
Matthew Scott is policy manager at the Chartered Institute of Housing, the
professional membership body for people who work in housing in the UK. His work
focuses on climate adaptation, sustainability, and energy affordability in housing. He holds a PhD from Newcastle University and has previously held several research and policy roles in the academic and third sectors.
