In March 2014, the Met Office published a report exploring the potential causes of the extreme weather events of recent years in the UK and what the future holds for UK seasonal weather. Among the conclusions, the paper states that ‘climate change has at least doubled the risk of a heatwave exceeding the temperatures experienced in the European heat wave of 2003’ and that ‘by the 2040s, more than half of summers are projected to be warmer than those seen in 2003’.
What is ‘thermal comfort’?
Thermal comfort is not just related to air temperature alone. It takes into account a range of other environmental and personal factors including radiant temperature, air velocity, humidity, clothing insulation and metabolic heat. These factors make up what is known as the ‘human thermal environment’.
Thermal comfort is actually defined in British Standard BS EN ISO 7730 as ‘that condition of mind which expresses satisfaction with the thermal environment’. Conversely, thermal discomfort is where people start to feel uncomfortable; ie they are too hot or too cold, but are not necessarily made unwell by the conditions.
The Health and Safety Executive (HSE) website notes that an acceptable zone of thermal comfort for most people in the UK lies roughly between 13°C (56°F) and 30°C (86°F), ‘with acceptable temperatures for more strenuous work activities concentrated towards the bottom end of the range, and more sedentary activities towards the higher end’.
Most individuals will not suffer medical symptoms due to thermal discomfort beyond irritability and tiredness. However, in some circumstances exposure to excessive heat can result in more severe conditions such as heatstroke and dehydration.
As well as affecting the health of employees, high temperatures in the indoor workplace can reduce worker morale and productivity, and increase absenteeism and mistakes.
Studies by the Centre for Economics and Business Research (CEBR) support this and estimate that, during the 2006 heat wave, work levels dropped by almost one-third when temperatures rose to more than 30°C. This resulted in UK employers losing an estimated £168 million a day in productivity.
Assessing and controlling thermal comfort
There are no fixed means of determining if thermal comfort is or will be a problem. According to the HSE, an historical indicator could be if 10–15 per cent of employees complain of discomfort.
Assessing and controlling thermal comfort can be challenging. Here are some tips to managing thermal comfort:
- Identify the problems and objectives; ie how can you manage overheating risks and maintain thermal comfort?
- Consult with your workers to establish reasonable levels of thermal comfort for the majority. Unfortunately it is unlikely you will be able to please everyone so it is best to manage expectations early on.
- Assess the risks and implement identified control measures. Be aware of issues such as temperature, air flow (including draughts), humidity, and of course the work being carried out.
- Identify and evaluate the adaptation options for keeping premises cool that are reasonable and cost-effective. This may be subject to limitations in terms of lease agreements – discuss options with your landlord if that is the case.
- Be aware that if you introduce equipment eg portable fans and air conditioners they can come with their own hazards. Electrical equipment should be included within portable appliance testing regimes and subject to visual inspection prior to use to make sure that the equipment and power leads are undamaged.
- Be aware of the implications for energy usage.
- Implement and monitor the effectiveness of the adaptations.