Overheating in UK Homes: Why summer comfort can no longer be ignored
For decades, UK homes have been designed with one main objective in mind: keeping heat in during winter. Better insulation, improved airtightness, and lower energy bills have rightly been priorities across both new-build and retrofit projects.
But as climate change drives longer and more intense heatwaves, the industry is now facing the other side of the thermal comfort challenge… keeping homes safe and comfortable in summer.
A Growing Risk for UK Homes
The issue is already here. The UK experienced its first heatwave of the year unusually early, and the Met Office is already forecasting another heatwave later this June, highlighting growing concerns around how suitable our homes are for hotter summers ahead.
According to the Climate Change Committee (CCC), around one fifth of UK homes are already overheating during summer conditions, with the risks expected to increase significantly in coming decades.
The summer of 2022 was a clear warning sign. UK temperatures exceeded 40°C for the first time on record, exposing just how unprepared much of the housing stock is for extreme heat. Research from the University of East London found reports of overheating rose from 18% of households in 2011 to 80% in 2022, with occupants experiencing disrupted sleep, headaches, fatigue, and reduced productivity.
Overheating Is a Health Issue, Not Just a Comfort Issue
For people in the UK, overheating is far more than a comfort issue, it is increasingly a health issue too.
The World Health Organization (WHO) describes heat as a major environmental and occupational health hazard and identifies heat stress as one of the leading causes of weather-related deaths globally. Extreme heat can worsen cardiovascular disease, respiratory conditions, diabetes, asthma, kidney disease, and mental health conditions, while also increasing the risk of accidents and reduced productivity.
Heat also affects the body in ways many people may not realise. When temperatures remain high, particularly overnight, the body struggles to regulate its internal temperature and recover properly. This puts additional strain on the heart and kidneys and can increase the risk of heat exhaustion and heatstroke. The WHO also highlights that prolonged periods of elevated daytime and night-time temperatures create cumulative stress on the human body, increasing the likelihood of illness and death from heat exposure.
Sleep disruption is another growing concern. Excessively hot bedrooms can contribute to fatigue, poor concentration, weakened immune response, and reduced mental wellbeing. For vulnerable groups, including older people, young children, pregnant women, and those with pre-existing conditions, overheating can quickly become dangerous.
The CCC reports that around 2,000 heat-related deaths already occur annually in the UK, while the 2022 heatwaves were associated with nearly 4,500 excess deaths.
Why Energy Efficiency Measures Must Consider Summer Performance
Ironically, some measures intended to improve winter efficiency can unintentionally worsen summer conditions when overheating risk is not properly considered. Highly insulated and airtight homes can trap heat during prolonged warm weather, particularly where homes are over-glazed, or where large areas of glazing on south- or west-facing elevations lack adequate ventilation or shading to mitigate solar gains.
Flats and dense urban developments are especially vulnerable due to solar gain and the urban heat island effect, where cities remain significantly warmer overnight than surrounding rural areas. This gives homes less ability to disperse heat overnight and exacerbates overheating during prolonged periods of hot weather.
This is becoming increasingly important as retrofit activity accelerates across the UK housing stock. Energy efficiency upgrades carried out without considering summer performance may improve EPC ratings while creating unintended overheating risks for occupants. The industry therefore needs to move beyond a winter-only approach to building performance and adopt a more balanced view of thermal comfort all year round.
Passive Cooling and Practical Design Solutions
Passive cooling strategies are likely to play a crucial role. Measures such as external shading, solar control glazing, ventilation and orientation considerations, green spaces, and tree planting can significantly reduce overheating risk without increasing reliance on air conditioning.
Simple Steps Occupants Can Take During Hot Weather
As we move into another potentially hot summer, there are also simple steps occupants can take to help keep homes cooler:
- Keep windows and curtains closed during the hottest part of the day
- Open windows overnight when outdoor temperatures drop
- Use light-coloured blinds or external shading where possible
- Avoid using heat-generating appliances during peak daytime temperatures – get the BBQ out and avoid cooking indoors
- Encourage cross ventilation through the home when conditions allow
- Stay hydrated and avoid strenuous activity during the hottest hours of the day
Government Announces Full Review of Overheating Regulations Following Industry Feedback
The growing importance of overheating has also led to greater regulatory scrutiny. Following industry feedback, the Government recently announced a full review of overheating regulations, including concerns around the implementation of Part O and current assessment methodologies. Elmhurst Energy explored the proposed changes and their implications for the sector here:
As overheating becomes more prominent within both building design and retrofit standards, industry competency will be critical. Assessors, designers, and developers must be equipped to identify overheating risk early and apply effective mitigation strategies that balance winter efficiency with summer comfort.
Building Industry Competency on Overheating Risk
To support this, Elmhurst Energy offers dedicated overheating training and an overheating assessment scheme designed to improve understanding of overheating risk, Part O compliance, and practical mitigation measures within residential buildings.
The message for the industry is clear: future homes must perform safely in both winter and summer. Without greater awareness, stronger design strategies, and improved competency in overheating assessments, today’s low-energy homes could become tomorrow’s overheating problem.
Elmhurst’s Overheating Training
Find out more about Elmhurst’s overheating training and accompanying competency scheme.
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Further Information and Sources:
https://www.who.int/news-room/fact-sheets/detail/climate-change-heat-and-health