Hot, stuffy offices are a common complaint during each UK summer. As heatwaves become more frequent, it’s crucial for employers—working closely with their HR professionals, office managers, and facilities teams responsible for health and safety in SMEs—to understand how the indoor working temperature impacts staff and to take steps to safeguard their health and productivity.
Ray Howlett examines the challenges of high office temperatures, the risks associated with extreme indoor heat, and the key measures that can be implemented to mitigate heat-related issues.
When the workplace is too hot
Heat in the workplace extends beyond mere discomfort; it can have detrimental effects on productivity and pose serious health hazards. As temperatures rise, employees can face:
- Loss of concentration
- Increased fatigue
- Dizziness
- Fainting
- Heat cramps
- Increased risk of accidents (e.g. from sweaty palms, distractions)
Research indicates that peak productivity occurs between 21°C and 23°c. Exceeding this range can result in a performance drop. Heatstroke becomes a serious issue above 39°C, and temperatures over 41°C may lead to confusion or even life-threatening conditions.
Individual tolerances to heat vary significantly. Factors like body weight and insulation (such as body fat) influence a person’s ability to dissipate heat. Groups such as young people, pregnant women, and individuals with disabilities generally exhibit lower heat tolerance, with some research indicating a decline in temperature regulation after the age of 60. Medical conditions and medications can further complicate this relationship.
Is there a maximum indoor temperature?
In the UK, there is no specific maximum temperature for indoor workplaces. However, the Workplace (Health, Safety and Welfare) Regulations 1992 require that workplaces maintain a “reasonable” temperature during working hours. What is considered a reasonable temperature depends on:
- the type of work (manual or office),
- the specific workplace (such as a kitchen versus an air-conditioned office), and
- the nature of the workforce.
The Health and Safety Executive (HSE) notes that defining a meaningful maximum temperature is difficult due to natural differences between work environments, such as glassworks or foundries, where safety can still be maintained with suitable measures.
Other factors, such as radiant temperature, humidity, and air movement, become increasingly important as temperatures rise, leading to complex interactions.
Other factors influencing thermal comfort at work
It’s important to recognise that air temperature is only one factor that affects thermal comfort. Humidity, wind speed, and radiant heat from sources such as machinery all impact thermal sensations.
High humidity levels introduce excess moisture into the air, impeding sweat evaporation—the body’s primary cooling process—and consequently raising core body temperatures.
When air temperatures rise above 35°C and are combined with high humidity, the body struggles to maintain its normal temperature, posing serious health risks.
Radiant heat from hot objects plays a more significant role than ambient air temperature in a person’s ability to dissipate heat.
Air velocity, defined as the movement of air across a person, is another essential factor. Cool air can improve comfort, but open windows only provide effective ventilation if the outside temperature is lower than the indoor temperature.
Clothing is essential for regulating body temperature, especially when uniforms or PPE limit adjustments. Non-breathable PPE prevents sweat from evaporating, increasing humidity levels and raising the risk of overheating during strenuous activities.
Risk Assessment for Indoor Working Temperature Hazards
Conducting a comprehensive risk assessment is crucial for identifying potential hazards associated with high indoor working temperatures during the summer. This assessment should identify risks, recognise vulnerable workers, and detail the precautions each organisation needs to implement to safeguard employees’ health. Areas of focus should include:
- Working climate: Evaluating air temperature, humidity, air movement, and sources of heat.
- Physical activity: Understanding how various tasks can generate excess body heat.
- Clothing and PPE: Assessing their role in increasing heat and discomfort.
- Vulnerable workers: Recognising employees who may struggle more in high temperatures, such as younger or older workers and those on medication.
How to Control Indoor Working Temperature and Humidity
Legally, employers are not mandated to install air conditioning systems. However, they are expected to maintain a “reasonable” working temperature and ensure adequate ventilation. Employers should therefore implement effective ventilation measures, which may include:
- air conditioning units,
- mobile units, or
- fans to manage high temperatures and humidity levels.
Using blinds or curtains can help block direct sunlight, and applying solar control window films can reduce glare and heat gain. Regular maintenance of air conditioning systems is essential to ensure they operate effectively; poorly maintained systems can unintentionally raise temperatures and increase discomfort.
To prioritise employee well-being during hot weather, consider offering regular breaks and rotating tasks to reduce heat exposure.
An indoor heat stress prevention plan
Developing an indoor heat stress prevention plan is essential for reducing the effects of high temperatures at work. Essential elements should include:
- Hydration: Employers should encourage employee hydration by providing easy access to cool water and promoting a switch from caffeinated drinks to water during working hours.
- strong>Education: Educating workers about the symptoms and preventive measures of heat-related illnesses helps them to protect themselves effectively.
- Clothing: Assessing whether workplace dress codes restrict temperature regulation is important; allowing more breathable clothing could enhance comfort and productivity.
- Personal protective equipment (PPE): Ensuring that PPE is suitable for hot conditions is essential. Consider the feasibility of using more breathable options and assess the necessity of PPE in extreme heat, while advising employees not to compromise their safety by removing equipment to cool down.
- Vulnerable workers: Paying attention to employees’ individual needs—especially during periods of high indoor working temperatures —is crucial. This includes providing additional breaks for workers who are young, elderly, pregnant, or chronically ill.
Employers should also consider modifying meeting schedules or working hours to better align with employees’ energy levels, particularly during fasting periods observed by some workers.
- Manual work: Manual labour produces more heat, requiring regular breaks and sufficient hydration. Where possible, adjust shift timings to avoid the hottest hours.
- Sun glare: The intensity of bright sunlight can reduce productivity in office environments. Minimise glare with window treatments or films.
Ensure that your first aiders can identify and manage heat stress symptoms, particularly during prolonged warm periods.
After a heatwave, organisations should assess their thermal comfort measures. Were they successful? What feedback have employees provided? Have there been any shifts in unsafe behaviours, accidents, or absenteeism? Has overall productivity remained stable?
As heatwaves are likely to become a regular occurrence in future summers, it’s essential for managers of indoor workplaces to implement and regularly review protocols that address the challenges of high temperatures. By adopting a proactive approach to managing indoor working temperature, employers can create healthier and more productive work environments for all employees.
High indoor temperatures can reduce productivity,
Thermal comfort depends on more than just air temperature,
Employers should consider layered solutions
