Overheating is not a future problem. It is already here.
24th June 2026
Jenny Danson
When we planned the Summer Ideas Exchange, we could not have arranged a more fitting backdrop for our closing keynote. An amber heat alert was in force, the temperature outside had pushed past 30 degrees.. So when Professor Rajat Gupta stood up to talk about overheating, nobody needed convincing that this was a live issue.
Rajat is Professor of Sustainable Architecture and Climate Change at Oxford Brookes University, where he directs the Oxford Institute for Sustainable Development and the Low Carbon Building Research Group. Over two decades he has become one of the country's leading voices on the relationship between buildings, heat, health and energy, and he has secured more than £21m of research funding. Healthy Homes Hub are fortunate to be involved in one of the projects he came to talk about, the HEARTH National Hub, so it was a real privilege to have him as the last keynote of the day.
From summer comfort to public health risk
His central message was simple. Overheating is not something that is coming. It is already here, it is widespread, and once you start looking you find it in almost every type of building and every kind of setting. He reminded us that when he began this work in 2005, a focus group told him to bring the warm weather on. Twenty years later we are talking about a serious public health threat, and the data has caught up with the warning.
The figures he shared were sobering. Heat related deaths could rise to more than 10,000 in an average year by the 2050s if we do nothing. The 2022 heatwave alone was associated with more than 3,200 excess deaths. By the mid 2030s around 90 per cent of UK homes could be vulnerable to overheating. We risk making this worse rather than better, because retrofit can unintentionally increase overheating risk if we forget to design for heat at the same time, especially if we insulate and don’t ventilate.
Why social housing residents face the greatest risk
For those of us in social housing, the equity argument is the stark. The people most at risk are very often the people least able to adapt. Older residents, very young children, disabled people, those with long term health conditions and pregnant women are all exposed, and residents frequently cannot afford a fan, let alone air conditioning, and cannot simply move somewhere cooler. Rajat told the room about domiciliary care, a sector he is now adding to his research, where around a million people receive care in homes that can reach 37 or 38 degrees in summer. Care staff have fainted on visits due to the temperatures of the homes they have visited.
He was candid that the regulatory ground is shifting, and that this is no longer something we can treat as an afterthought. Excess heat is already a recognised hazard under the Housing Health and Safety Rating System, and under Phase 2 of Awaab's Law landlords will be legally required to investigate and address hazards relating to both excess heat and excess cold within set timescales. If a resident complains about heat, we will have to act, just as we now do for damp and mould.
Heat is becoming a regulatory issue
The HEARTH hub, a five year, 7.4 million pound programme that began in early 2025, is taking what he called a whole systems approach, following the chain from climate to neighbourhood to building to room to person to health, and crucially studying climate adaptation and net zero together rather than in separate silos. His team is already gathering real data from homes during the May heatwave, where indoor temperatures reached 33 degrees and night time bedrooms stayed well above the 24 degrees at which healthy people start to struggle to sleep. He made an open offer to the sector. If you have homes with net zero measures, or homes assessed for Part O, his team will study them at no cost to you. I would encourage members to take him up on it.
Practical solutions that can be implemented now
On solutions, his guidance was practical.
Keep the heat out first, with external shading, reflective surfaces and tree cover.
Then remove the heat that is inside through ventilation and night cooling.
Then cool the neighbourhood with greening and water sensitive design.
Just as important, he urged us to empower residents, because so much can be done quickly and cheaply. Homes need to be intuitive to use, residents need clear advice on when to open windows and deploy shading, and the indoor temperature data many of us already collect for asset management could be repurposed into heat alerts. He pointed to the cool packs being delivered by councils such as Westminster, a simple kit with a temperature monitor, water and guidance for around £35 , as a low cost idea ready to scale.
Five priorities for housing providers
He left us with five priorities that any housing organisation can act on.
Identify your heat vulnerable residents and high risk homes using the data you already hold.
Monitor indoor temperatures.
Assess overheating alongside energy efficiency in every retrofit.
Adapt by prioritising passive cooling rather than reaching straight for air conditioning.
And protect the most vulnerable through heat action plans and support during extreme weather.
The discussion afterwards ranged across the hidden costs of heat, the link between heat and both violence and anti social behaviour, and the danger of sustained warmth rather than just the headline peaks. Several days at 28 or 30 degrees can be more harmful than a single hot afternoon. My own reflection is that we have arrived at the same place with heat that we recently reached with air quality. The evidence is mounting, the human cost is real, and the question now is not whether we act but how quickly.
A healthy home cannot only be warm and energy efficient. It has to be safe in a heatwave too. That means designing for the summers ahead rather than the climate we used to have, and protecting the people who need it most first. That is exactly the conversation we want the Healthy Homes Hub to lead.
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