As heatwaves associated with climate change become more frequent and intense across the United Kingdom, the NHS faces growing challenges in protecting patients, supporting staff, and maintaining safe healthcare environments.

While the NHS has traditionally been designed to cope with cold winters, rising summer temperatures are exposing vulnerabilities in hospital infrastructure, many of which were built decades before extreme heat became a significant concern.

One of the most debated aspects of this challenge is the role of air conditioning. Although cooling systems can improve patient safety and staff wellbeing, they also raise questions about energy consumption, carbon emissions, and long-term sustainability.

The Health Impact of Heatwaves

Heat waves pose serious risks to public health, particularly for older adults, young children, pregnant women, and people living with chronic illnesses such as cardiovascular or respiratory disease. Prolonged exposure to high temperatures can lead to dehydration, heat exhaustion, heatstroke, kidney injury, and worsening of existing medical conditions.

Periods of extreme heat also increase demand on NHS services. Hospitals often experience:

• Higher numbers of emergency department attendances.
• Increased ambulance call-outs.
• More hospital admissions related to heat-related illness.
• Greater pressure on intensive care and respiratory services.
• Delays in patient discharge due to increased community healthcare demands.

One UK Climate Change Committee (CCC) modelling study ⁽¹⁾ found that heat related hospital attendances could rise from around 17,000 to around 39,000 by the 2030s and to 53,000 by the 2050s.

Meanwhile, heat related emergency admissions to hospital could increase from 2900 a year to 7250 by the 2030s and to 11,000 by the 2050s.

Challenges Within NHS Buildings

Many NHS hospitals were constructed in the mid-to-late twentieth century when overheating was rarely considered a design priority. Large areas of glazing, poor insulation against heat gain, ageing ventilation systems, and limited mechanical cooling can result in indoor temperatures exceeding safe and comfortable levels during summer.

Some clinical environments are particularly vulnerable, including:

• Intensive care units
• Operating theatres
• Maternity wards
• Older inpatient wards
• Diagnostic imaging departments
• Pharmacy and laboratory facilities

In this year’s heatwaves, resident doctors working in high temperatures have reported adverse effects in patients due to the extreme heat, including falls due to postural hypotension, and multiple pre-renal acute kidney injuries.

High temperatures can affect not only patients but also temperature-controlled medicines and sensitive medical equipment, such as radiotherapy machines, MRI scanners and data centres storing vital patient information.

The Benefits of Air Conditioning

Air conditioning offers several important benefits when used appropriately within healthcare settings.

Firstly, it helps maintain safe temperatures for vulnerable patients, reducing the risk of heat-related illness. Cooling also supports recovery by improving patient comfort, sleep quality, and hydration.

Secondly, staff working in cooler environments are generally better able to concentrate, make clinical decisions, and perform physically demanding tasks safely.

Air conditioning is also essential for maintaining environmental conditions required for certain medical procedures, operating theatres, imaging equipment, laboratories, and pharmaceutical storage.

The Drawbacks

Despite its advantages, widespread air conditioning presents several challenges.

Cooling systems consume substantial amounts of electricity, increasing operational costs for hospitals that already face significant financial pressures. If powered by fossil fuels, greater electricity demand may also contribute to greenhouse gas emissions.

Maintenance is another consideration. Air conditioning systems require regular servicing to maintain efficiency and reduce the risk of poor indoor air quality or microbial contamination.

Finally, installing modern cooling systems across an ageing NHS estate represents a major capital investment. Retrofitting older buildings can be technically complex and expensive.

Sustainable Alternatives

Air conditioning is unlikely to be the only solution. Many experts advocate a combination of passive cooling strategies alongside targeted mechanical cooling.

These measures include:

• Improved building insulation.
• External shading to reduce solar heat gain.
• Reflective roofing materials.
• Natural ventilation where clinically appropriate.
• Green roofs and tree planting around healthcare sites.
• Smart building management systems.
• Energy-efficient heat pumps capable of both heating and cooling.

These approaches can reduce overheating while supporting the NHS’s commitment to achieving net zero carbon emissions.

Planning for the Future

Climate projections suggest that extreme heat events will become more common throughout the coming decades. As a result, heat resilience is increasingly becoming an important component of NHS estate planning.

Future hospital developments are likely to incorporate climate-adaptive design from the outset, combining energy-efficient cooling technologies with sustainable architecture. Existing hospitals will also require phased upgrades to improve resilience while balancing environmental and financial considerations.

Emergency preparedness will remain equally important. Heat-health alert systems, staff training, public health messaging, and coordinated operational planning can all help reduce the impact of future heat waves on healthcare services.

Conclusion

Heatwaves are no longer exceptional events but an emerging healthcare challenge for the NHS.

Rising temperatures affect patient safety, staff wellbeing, hospital infrastructure, and service capacity.

Air conditioning has an important role in protecting vulnerable patients and maintaining critical clinical environments, but it should be implemented alongside broader strategies that improve building resilience and reduce environmental impact.

By investing in climate-adapted infrastructure, sustainable cooling technologies, and effective heat preparedness, the NHS can strengthen its ability to deliver safe, high-quality care in an environment where heatwaves are becoming more commonplace.

References

• https://www.bmj.com/content/393/bmj-2026-139955