Heat stress in the UK: a growing risk for buildings, people and workplaces

Heat stress is no longer a problem associated only with tropical climates. In the UK, rising temperatures, more frequent heatwaves, and a built environment designed for cold weather are combining to create a significant and growing challenge.

In this blog, we examine how and why heat stress is becoming a major issue for the UK's property stock, its communities and businesses.

What is heat stress?

Heat stress occurs when the human body can no longer effectively regulate its internal temperature. Normally, the body cools itself through sweating and increased blood flow to the skin. However, when temperatures are high, especially alongside humidity, physical exertion, or poor ventilation, this system can fail.

Symptoms can range from mild discomfort to serious illness, including dehydration, fatigue, dizziness, and in extreme cases, heat stroke, which can be fatal.

Closely linked is the concept of overheating in buildings, which refers to indoor environments exceeding comfortable or safe temperatures. This is increasingly recognised as a major public health issue in the UK.

Why the UK is particularly vulnerable

The UK’s building stock is fundamentally ill-suited to hot weather. For decades, homes and workplaces have been designed to retain heat, not release it. Insulation, airtight construction, and limited shading or ventilation all contribute to rising indoor temperatures during summer months. (1)

Climate change is amplifying the issue. Heatwaves are becoming more frequent and intense, with the likelihood of extreme temperatures (such as 40°C) now dramatically higher than in previous decades.

As a result, overheating has surged. One study found that the proportion of UK homes experiencing overheating rose from 18% in 2011 to around 80% in 2022. (2)

How heat stress affects properties

Heat stress doesn’t just affect people, it exposes fundamental weaknesses in UK buildings.

Poorly adapted properties often suffer from:

- Excess solar gain through large windows or unshaded glazing.

- Internal heat build-up from appliances and occupants.

- Inadequate ventilation, preventing heat from escaping.

Modern homes can be particularly problematic. While energy-efficient designs reduce winter heating demand, they can trap heat in summer if not properly ventilated.

Older and historic buildings also face challenges. Many lack the design features needed to cope with prolonged heat, leading to uncomfortable and sometimes unsafe indoor conditions.

The consequences include:

- Indoor temperatures exceeding 30°C even when outside temperatures are lower

- Increased reliance on air conditioning (with energy and cost implications)

- Reduced building usability, particularly in schools, hospitals, and offices

For example, more than 90% of NHS buildings in England are now considered vulnerable to overheating, with some wards exceeding 30°C even on mild days. (3)

Impacts on people in poorly adapted buildings

The human impact of overheating is significant and also unevenly distributed. People living in poorly adapted homes may experience:

- Sleep disruption, particularly during “tropical nights” when temperatures remain high.

- Reduced productivity and concentration.

- Increased health risks, including respiratory and cardiovascular issues.

Heat-related deaths are already a concern. There are an estimated 2,000 heat-related deaths annually in England and Wales, with projections suggesting this could rise sharply without intervention. In the summer of 2022, which saw temperatures exceed 40°C in the UK, there were nearly 3,000 heat-related deaths recorded in England alone.(4)

Vulnerable groups are most at risk, including:

- Older people

- Young children

- Those with pre-existing health conditions

- Low-income households unable to afford cooling measures

Social inequality plays a major role. People in rented or poorly maintained housing often have limited control over ventilation, shading, or retrofitting improvements.

Where are the worst-affected locations?

Heat stress is not evenly distributed across the UK. Some regions face significantly higher risk due to climate, urban form, and housing characteristics.

London and the South East are among the most affected areas. These regions experience higher average temperatures, dense urban environments which are characterised by the “urban heat island” effect, where buildings and roads trap heat

Materials like concrete and asphalt absorb heat during the day and release it at night, preventing cooling and prolonging exposure to high temperatures.

Other high-risk locations include:

- Major urban centres such as Birmingham and Manchester

- Areas with large numbers of flats or high-rise buildings

- Regions with newer, airtight housing developments lacking adequate ventilation

In contrast, rural and coastal areas tend to experience slightly lower risks due to better airflow and less dense construction, though they are not immune.

Effects on workplace employees

Heat stress is also an increasingly important workplace issue across the UK. According to the Health and Safety Executive, heat stress arises when factors such as temperature, workload, clothing, and humidity combine to overwhelm the body’s cooling system. (5)

In workplaces, this can lead to:

- Reduced concentration and decision-making ability.

- Increased fatigue and errors.

- Higher risk of accidents.

- Serious health conditions such as heat exhaustion or heat stroke

Certain sectors are particularly exposed to heat stress, including construction and outdoor work, manufacturing and industrial settings, kitchens, bakeries, and confined indoor environments, as well as offices without adequate cooling or ventilation.

Unlike during cold conditions, UK law does not specify a maximum working temperature. Instead, employers are required to maintain a “reasonable” environment and manage risks appropriately.

However, rising temperatures are testing these frameworks and workplace productivity has been significantly affected.

Looking ahead: The Need for Better Data

Heat stress in the UK is no longer a future concern, it is a present reality. The combination of climate change and buildings designed for a colder climate has created a mismatch that affects health, comfort, and productivity.

It will ne a vast challenge to address the issue and make or nation more resilient, perhaps requiring government funding intervention for the most vulnerable. Mitigations may include:

- Retrofitting existing buildings with shading, ventilation, and cooling measures

- Designing new buildings for both winter and summer conditions

- Improving public awareness of heat risks

- Strengthening workplace protections

Without action, overheating will continue to worsen, placing increasing pressure on homes, infrastructure, and the people who rely on them.

One of the first steps is to better understand where heat stress could be more acute, whether that is in your current home, before you plan to purchase or move into another location, or as an employee or director of a firm considering where to work or the welfare of staff.

As with everything, better insight comes from better data. Here at Terra IQ, we work with environmental risk data providers, developers and other property professionals to better understand how climate risks, including heat stress could impact on the enjoyment of the home and become, at its worst extent, become a serious health or workplace risk.

For more information on how Terra IQ is mapping the country to help power your understanding of Heat Stress, contact us today.

References

(1) "Overheating Britain: Can our buildings cope?" - Jordan Turner, University of the Built Environment, 3rd July 2025

(2) "Number of UK homes overheating soars to 80% in a decade, study finds" - Damian Carrington, The Guardian, 16th April 2025

(3) "Climate emergency: 90% of NHS buildings are vulnerable to overheating, warns UK health alliance" - British Medical Journal, 19th June 2025 - BMJ 2025;389:r1275

(4) Committee for Climate Change, 2015 report and July 2019: "Heat and Preventable Deaths in the Health and Social care System"

(5) Health and Safety Executive website, 2026: "Temperature in the workplace"