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With rising UK summer temperatures, bedroom temperatures are often too high for effective and undisrupted sleep, making people feel more uncomfortable.
Over the past decade (2014–2023), UK temperatures have averaged 1.25°C above the 1961–1990 baseline, with the number of 'hot days' (daily maximum temperature >28°C) more than doubling.
UK dwellings, traditionally designed for heat retention, are ill-equipped to cope with extreme heat at night. During the hot summer of 2018, more than 4.6 million (19%) of the main bedrooms in the English homes were deemed to overheat.
Air conditioning isn’t always a practical or energy‑efficient method of reducing the temperature. Researchers at Loughborough University — including PhD researcher Jaydeep Bhadra, supervised by Dr Arash Beizaee from the School of Architecture, Building and Civil Engineering, and Dr Iuliana Hartescu from the School of Sport, Exercise and Health Sciences — therefore tested a low‑energy cooling mattress topper to see if it could help people sleep better in hot UK bedrooms.
Seventeen adults were recruited to take part in the study, looking at three sleep conditions:
- Sleeping in their own homes under typical summer conditions.
- Sleeping in a test bedroom controlled at 30°C, using regular bedding.
- Sleeping in the same controlled bedroom at 30°C, using the cooling mattress topper
They measured sleep quality using wrist devices and asked people how comfortable and rested they felt after sleeping in each situation.
Published in Building and Environment, the study found that the cooling mattress topper significantly improved thermal comfort during sleep, and people felt they slept better and spent less time awake.
The objective sleep data showed that the topper increased the average total sleep time by 19 min in overheated bedroom and reduced the average time it took to fall asleep by 10 min in overheated bedroom.
Dr Arash Beizaee, Senior Lecturer in Building Energy at Loughborough University, said of the study:
“As climate change and urbanisation increase the frequency of hot nights in the UK, many homes are simply not equipped to cope. Mechanical air-conditioning is often not a viable option, whether due to cost, environmental concerns, or installation barriers in rented or multi-storey buildings. Even where it is feasible, widespread adoption would place further strain on an already pressured energy grid.
"This study highlights the potential of a low-energy, localised cooling solution to deliver targeted thermal comfort and protect sleep in overheated bedrooms. While the results are promising, plans are in place to explore this further, including longer-term testing and broader assessment of environmental factors including humidity and indoor air quality, with the aim of informing future building standards and public health guidance.”
The full study is available online here.