When classrooms get too hot, concentration slips: what temperature data can tell us about overheating

A classroom can be perfectly functional on paper and still become a difficult place to learn when temperatures rise.

Heat is often treated as a comfort issue. But for schools, it can also be a learning issue.

Research has found a relationship between classroom temperature and performance, with higher temperatures associated with reduced performance on school tasks and psychological tests. One analysis synthesising 18 classroom studies estimated that performance could be around 20% higher at 20°C than at 30°C, with optimal performance estimated below 22°C.
That raises an important question for schools and those responsible for their buildings:

What is actually happening inside classrooms as temperatures rise?

From research to real classrooms

It is one thing to understand the relationship between temperature and learning in controlled research. It is another to see how temperature behaves across real teaching spaces, throughout the school day and across different buildings.

That is what we wanted to explore in Too Hot to Learn?, our new report on overheating in UK schools.

Twinview analysed real temperature data collected by Twinview sensors across 105 teaching spaces in three schools. The aim was not simply to identify whether classrooms became hot, but to understand when overheating occurred, how conditions changed during the school day and what the data could reveal about the spaces being affected.

The findings were clear:

Overheating was evident across all three schools.

Temperature changes throughout the school day

One of the most striking findings was how quickly the number of affected spaces changed during the school day.

At around 09:15, 5.1% of monitored spaces were above 24°C.

By 15:00, that had risen to 23.4%, more than four times as many spaces.

Across the dataset, 33.7% of monitored room-days experienced some overheating.

This matters because a school building does not experience temperature as a single, fixed condition.

A classroom may begin the morning at a comfortable temperature and become increasingly warm as the day progresses. Different rooms can behave differently depending on their location, orientation, use, ventilation and other characteristics.

A snapshot measurement can therefore tell only part of the story.

Why measurement matters

Overheating can be difficult to understand when it is experienced only as a general complaint: “This classroom gets hot.”

Temperature data adds another layer of visibility.

It can show when a space becomes too warm, how long conditions persist and where the issue is occurring.

That distinction is important when deciding what to investigate.

If temperatures consistently rise during particular periods of the day, for example, that creates a different question from a space that remains warm throughout the school day. And if some rooms repeatedly experience higher temperatures than others, there may be building or operational factors worth investigating.

The data from our study also showed that building age alone did not explain differences in performance.

That suggests that understanding overheating requires more than simply categorising buildings by age or type.

The wider climate risk

This is also becoming a bigger issue as the climate changes.

DfE climate-risk modelling estimates that rising temperatures could be equivalent to 6.7 learning days lost at current warming levels, 8.2 days at +2°C warming and 11.4 days at +4°C warming. The DfE describes these as indicative averages based on emerging evidence.

The question, then, is not simply whether schools will experience hotter days.

It is how well we understand what those temperatures mean inside the spaces where children spend much of their day.

From “too hot” to evidence

The first step towards addressing overheating is being able to see it clearly.

Real temperature data can help schools move beyond a general sense that a building is getting too hot and towards a more detailed understanding of where, when and how conditions are changing.

That visibility can support better questions about the building and how it is being used, and help identify where further investigation or intervention may be needed.

Our Too Hot to Learn? report explores this in more detail, using real temperature data from 105 teaching spaces across three schools.

Because if we want to design and operate schools for the climate we are getting, rather than the climate we had, we first need to understand what is happening inside them.

Download the full report, Too Hot to Learn?, to explore the findings in more detail.