The UK population is becoming increasingly vulnerable to heatwaves as our climate warms with 2025 recorded1 as the hottest and sunniest year ever.
Heatwaves have caused hospitals to cancel operations and schools to close because of the harmful effects on health and wellbeing.
The disruption is set to continue according to a Met Office study2 revealing how UK heatwaves could become even more frequent and intense with ‘the chance of exceeding 40°C in the UK accelerating at pace’.
As such school buildings are becoming increasingly prone to overheating in summer, which directly affects learning, health, safeguarding and compliance.
A collaborative report3 by the Met Office and the University of London (UCL) predicts schoolchildren may miss out on 12 days of learning - not just because of extreme heat - but because of overall warmer temperatures.
The Department of Education (DfE)4 has now acknowledged overheating is a key concern schools must mitigate against to keep pupils and teachers safe.
This document is designed to help schools understand the risks of overheating and strategies they can use to overcome them.
The health and wellbeing effects of overheating on children and adults are well documented5.
As the mercury rises beyond a comfortable 22C so do lethargy and irritability while concentration and task accuracy drop considerably in the 26-28C zone.
Schools can no longer treat overheating as a rare or unpredictable event and have a legal duty of care6 to keep students safe from foreseeable harm such as heat stress.
If there is no mitigation in place and a child becomes ill from the effects of heat stress while at school, it may be difficult to prove there was safeguarding in place.
State school buildings built from the 1960s onwards are more likely to overheat than older buildings because they are better insulated, according to the Met Office and UCL report3.
This combination of insulation with large, glazed windows with limited openings, means the intense heat built up through solar glare is trapped indoors.
Poor cross-ventilation means the temperature keeps rising, a huge problem during the exam season when windows and doors are shut to reduce noise and other distractions.
While new buildings often have features such as trickle vents and ventilation grills to allow cross-ventilation, they are not effective at keeping buildings cool enough during hot weather.
Opening windows seems an obvious intervention but it only allows more heat to enter alongside the solar glare, exacerbating the problem.
Open windows can also compromise children’s safety as well as allowing noise and smells to come inside and interrupt children’s learning.
During a heatwave, nighttime and early morning are the best times to invite cooler air through windows. However, this is often difficult or impossible for schools because of security and insurance repercussions.
Air conditioning treats the effects of overheating by lowering indoor temperatures but not its cause.
It has increasingly become unsustainable and unaffordable and is a well-known cause of environmental pollution because of the chemicals used. Air con6 is responsible for nearly four per cent of the world’s carbon emissions and ten per cent of the world’s energy consumption.
With energy costs constantly rising, it can be very expensive to run, especially for schools which are struggling with increasingly tight budgets.
Everyone in schools – including students, teachers and support staff - need to be kept safe from overheating which is why the National Education Union7 (NEU) recently recommended a maximum temperature of 26°C.
Strict uniform and dress codes8 can make the situation even worse with the DfE4 now advising these should be relaxed during heatwaves.
Children are more vulnerable to overheating because they sweat less and their bodies struggle to regulate temperature.
They also become dehydrated more quickly and are less likely to be able to express what’s wrong, especially younger children and those with SEND.
Overheating9 can also exacerbate pre-existing medical conditions such as asthma, heart and kidney conditions, epilepsy and anxiety.
Heat stress or exhaustion can come on gradually with symptoms of headache, nausea, dizziness and confusion, loss of appetite, sweating, cramps in the arms, legs, or stomach, a fast but weak pulse or paler than normal or clammy skin.
Heat stress can lead to heat stroke10, a medical emergency, when the body reaches a dangerously high temperature, often above 40°C.
Not being able to sleep at night because of the heat and then being unable to go outside during the day has a big impact on us all, especially for children who need to get rid of excess energy.
Overheating can lead to lethargy, reduced concentration in lessons, irritability and anger, poor decision making11 and increased behavioural incidents in children.
This makes supervision and behaviour management harder for teachers, who feel the effects of the heat too and may feel irritable and less patient themselves.
It may be necessary to limit the time students spend outside due to the heat, and if sufficient indoor space is unavailable, it makes supervision and maintaining order and control much harder, on top of potentially heat-induced behavioural issues.
Moving lessons last minute, overcrowding cooler rooms, sending pupils home early or closing the school can all impact safeguarding and increase supervision gaps, causing problems for parents and carers who may have to leave work.
The DfE guidance on managing hot weather in schools now treats overheating as a risk and advises schools to look at thermal comfort and design standards.
Schools are expected to document and manage risk effectively, including around overheating, and are expected to put mitigatory measures in place to protect students and staff.
The Health & Safety at Work Act6 ensures schools provide thermometers and conduct risk assessments to manage comfort and safety for a safe and effective learning environment.
School buildings with windows facing south and west need to prioritise the risk of overheating because these elevations enjoy the most sunlight.
Shelters, canopies and awnings can be placed outside classrooms to reduce overheating as well as provide shaded and safe areas outside where children can play and enjoy lessons while protected from the sun.
Shade sails are a fun and colourful way to provide shade in the summer where children can play and exercise outside in safety.
Canopies like Spaceshade12 have polycarbonate roofs and provide shelter from the sun and rain and can be fitted with roof panels with advanced heat reflecting technology to reflect heat away from the building.
They are a great way to ensure children aren’t confined indoors during the hot weather and provide healthy productive spaces for play, exercise and lessons.
In the same way, dining canopies also provide a cooler, UV-protected safe and secure outdoor space for children to eat lunch, do PE or outdoor lessons.
Pros: All these are multi-use and provide long-lasting and durable protected space, an indoor-outdoor connection and shaded area for lessons and outdoor play.
Cons: They cannot shade first floor windows and may be more expensive than some other solutions. Shade sails cannot provide protection from the rain.
The DfE recommends shading sun-facing13 windows, a popular solution to prevent overheating used in schools across Europe for many years.
Studies show that first floor windows are likely to become hotter than ground floor windows and are harder to shade with awnings or shelters.
When we talk about external shading, the term encompasses shutters, venetian blinds or screens, all fitted to the outside of the windows.
External screens/blinds14 allow people to continue to see outside and preserve light levels inside a building while keeping the room up to 40 per cent cooler than rooms with no shading.
Pros: External screens/blinds retain outward visibility while keeping rooms cool and allowing light in. They are flexible in their design, durable, long-lasting and easy to operate.
Cons: External shutters or external venetian blinds will reduce the light inside a building.
Brise soleil are fitted on the outside of a window and consist of vertical or horizontal louvres (blades) which block direct sunlight and thereby help to keep rooms cooler.
Horizontal brise soleil are more common and provide protection from midday sun while vertical brise soleil protect against low-angle morning and afternoon sun.
They are most commonly made of metal like aluminium and can provide effective shade, working well on first floors windows, as well as an architectural feature to a building.
Pros: They work for windows at any height. They add to the aesthetic of a building and don’t block sunlight.
Cons: They cannot provide total shading unlike external blinds and screens. It may not be possible to fix them to the outside of some buildings.
Air con can artificially lower the room’s temperature and provide cooling airflow.
Pros: It provides effective cooling and helps maintain rooms at optimum temperature.
Cons: Air con is expensive to install and run and requires regular maintenance. It will increase a school’s energy bills and carbon footprint.
Internal blinds can provide some protection15 from the sun, but they don’t stop heat building up because it is still able to travel through the window. Once the heat is inside, it cannot escape.
Internal blinds with heat reflective fabric can help provide cooling, but they are not as effective as external shading.
Pros: More cost-effective than some outdoor shading solutions.
Cons: Less effective than outside shading.
Planting trees and shrubs provides shade from the sun and reduces the so-called ‘urban heat island effect’ where heat is trapped by high rise buildings, concrete and tarmac in built up areas.
Pros: Tree coverage blocks solar glare though windows and keeps buildings and pavements cooler. Students have a view onto nature.
Cons: Trees take time to grow and it’s not always practical to plant them strategically, particularly for first floor windows. They also block natural light.
If your budget allows, external shading is by far the best long-term solution, whether provided by structures like canopies and sail shades or by exterior shutters or blinds/screens.
Shelters and canopies offer a double benefit in the form of productive safe play area and learning space and a classroom connection to the outdoors, but they aren’t practical for first floor classrooms.
As the DfE advises, overheating is now a risk that schools need to mitigate to make sure that students don’t miss out on learning as our climate warms.
Preventing overheating by introducing shelters, canopies, awnings and external shading can stop a myriad of issues arising in the future from forced school closures and lost learning to teacher fatigue and difficult behaviour and illness among children.
Kensington Systems16 have more than 40 years of experience in advising and installing bespoke external and internal shading, canopies and shade sails at schools.
We are very happy to talk you through your needs, the options appropriate to your school and budget including site visits and quotes.
If you’d like to find out more please contact us.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10696165/#:~:text=At%20its%20core%2C%20the%20association,clothing%20is%20decided%20by%20it