Excessive classroom temperatures are not only uncomfortable, but they are also a health and safety hazard, as excessive heat can aggravate existing medical conditions. Excessive heat in classrooms has also been shown in many studies to impact on pupils’ learning, with a 1°C increase in temperatures linked to a 2% decline in learning.

The effects of extreme temperatures are even more striking when considering that each additional school day with a temperature in the 30s (°C) reduces pupil achievement by one sixth of a percent of a year’s worth of learning. Disadvantaged pupils also suffer up to three times the impact of excessive temperatures than other pupils. [1]

If excessive temperatures are a problem in your school, there are a number of actions you can take to address the problem.

The Workplace (Health, Safety and Welfare) Regulations 1992 require that thermometers are provided within the workplace.

Thermometers should be available at suitable locations in every part of the workplace to allow people to measure temperatures, but do not need to be provided in each workroom. Thermometers should not be located directly in front of windows or near radiant heat sources.

If temperatures exceed sensible limits, then the employer should undertake a risk assessment and put in place measures to tackle the issue, which could include the use of blinds, fans or additional cooling/heating.

Schools and employers should also carefully risk assess outdoor activities at times of excessive heat, including PE lessons and sports days.

For PE lessons, it may be appropriate to substitute less physically demanding activities or move activities indoors.

For sports days, the risk assessment should cover all individuals, including participants in sports, those officiating and any spectators.

Sports days may need to be rescheduled if temperatures could pose an unacceptably high risk to any attendees.

Where appropriate, employers should also provide alternative rooms or, in extreme situations, order the partial or total closure of the building.

Adequate ventilation is also critical, particularly in classrooms used for subjects such as technology, where dust may be generated. Legally, classrooms must be capable of being ventilated adequately.

The Covid-19 pandemic further shows the importance of adequate ventilation on preventing the transmission of airborne viruses, including flu and colds.

Adequate ventilation is not just a health and safety issue, but is also a teaching and learning issue. There is a scientifically proven link between levels of carbon dioxide (CO2) and the brain’s ability to learn.

Adequate ventilation is therefore vital for effective learning to take place. CO2 monitors should be used to measure levels in classrooms and action should be taken where appropriate.

Further information on ventilation can be found on our Ventilation and Covid-19 page.

Employers should ensure there is an easily accessible source of drinking water available for both staff and students and consider operating flexible working arrangements, where possible, to avoid using classrooms particularly susceptible to high temperatures during the hottest hours of the day.

Although there is no legal maximum temperature in the UK, the World Health Organization recommends a maximum temperature of 24°C. UK legislation requires working temperatures to be reasonable, and employers have a duty to take any action that is reasonably practicable to achieve this. Further details are given below.

If the school does not resolve the problem, contact the NASUWT for advice.

The law

Employers are required by the Health and Safety at Work Act and the Health and Safety at Work (Northern Ireland) Order 1978 to ensure, as far as is reasonably practicable, the health and welfare of their employees. More specifically, Regulation 7 of the Workplace (Health, Safety and Welfare) Regulations 1992 and (Northern Ireland) 1993 require that:

  1. during working hours, the temperature in all workplaces inside buildings shall be reasonable;
  2. a sufficient number of thermometers shall be provided to enable persons at work to determine the temperature in any workplace inside a building.

The Management of Health and Safety Regulations 1999 and (Northern Ireland) 2000 requires employers to make a suitable assessment of risks to the health, safety and welfare of their workers and take any necessary, reasonably practicable action.

The temperature in the workplace is one of the issues that employers should address to meet their legal requirements.

All classrooms should be risk assessed, and this includes for both excessive and insufficient temperatures. Temperatures can vary widely between similar rooms, due to factors including whether the room is north or south facing.

Health surveillance or medical screening may be required for staff who have special requirements, such as pregnancy, certain illnesses and disabilities, and who may be taking medication or are working in known cold/heat stress environments. Medical advice should be sought if necessary.

The Health and Safety Executive (HSE) has developed comprehensive guidance on temperatures.

Approved Code of Practice on Workplace Regulations 2013

The Workplace (Health, Safety and Welfare) Regulations 1992 lay down particular requirements for most aspects of the working environment. Regulation 7 of these Regulations deals specifically with the temperature in indoor workplaces and states that:

‘During working hours, the temperature in all workplaces inside buildings shall be reasonable.’

What is ‘reasonable’, however, is not laid down.

The Approved Code of Practice (ACoP) states:

‘The temperature in workrooms should provide reasonable comfort without the need for special clothing. Where such a temperature is impractical because of hot or cold processes, all reasonable steps should be taken to achieve a temperature which is as close as possible to comfortable.’

In respect of low temperatures, the ACoP is clear:

‘The temperature in workrooms should normally be at least 16 degrees Celsius unless much of the work involves severe physical effort, in which case the temperature should be at least 13 degrees Celsius.’

The ACoP requires that where the temperature in a workroom/classroom is uncomfortably high, for example because of hot processes or the design of the building, all reasonable steps should be taken to achieve a reasonably comfortable temperature, such as:

  • insulating hot machinery or pipes;
  • providing cooling systems;
  • shading or screening windows;
  • siting workstations away from places subject to radiant heat;
  • providing fans, increased ventilation and rest facilities.

In addition, the employer is required to provide easy access to drinking water and should consider relaxing any formal dress code.

[1] Goodman, J., Hurwitz, M., Park, J. and Smith, J. (2018). Heat and Learning. National Bureau of Economic Research


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