Wool outperformed synthetic and down-based fillings in both insulation and moisture transfer when duvets were tested under controlled conditions. Wool-filled products maintained higher internal temperatures over extended periods and moved moisture through the duvet more quickly than comparable alternatives under identical test conditions.
- Wool delivered between 17% and 30% better insulation performance than polyester, feather-and-down and down in thermal conductivity measurements at comparable tog ratings.
- Temperature sensors recorded lower heat loss in wool duvets over eight hours, with higher mid-fill temperatures maintained despite lower loft levels.
- Moisture testing showed wool moved moisture through the duvet up to 153% faster than feather-and-down and up to 120% faster than synthetic alternatives at elevated temperatures.
- The findings are based on the study Performance Analysis of Wool Bedding, commissioned by British Wool in partnership with the International Wool Textile Organisation and conducted by Bangor University.
THE STUDY: The research set out to compare the thermal and moisture-handling performance of commonly used duvet fillings under controlled laboratory conditions. Full-sized single duvets with similar tog ratings were produced using wool, polyester, feather-and-down and down to ensure comparability. Testing focused on how each filling behaved across sustained temperature exposure and varying humidity levels, allowing direct performance comparison without differences in size or construction influencing the results.
- Testing was conducted in a controlled laboratory environment with regulated temperature and humidity to ensure consistent and repeatable conditions across all duvet samples.
- Thermal performance was assessed by measuring heat transfer and temperature stability over extended periods using calibrated sensors placed within the duvet structure.
- Moisture behaviour was evaluated by tracking moisture movement through the duvet at normal and elevated temperatures designed to simulate testing conditions.
- Thermal conductivity and heat-retention tests were repeated to confirm consistency and reliability of the recorded results.
- The study focused on Welsh wool, with the authors noting that its inherent fibre characteristics are comparable to other British wools from similar breeds, allowing the findings to be read across more broadly, and was commissioned with funding support from the Welsh Government.
WHAT THE DATA SHOWS: Measured results from the laboratory tests showed consistent performance differences between the duvet fillings across both thermal and moisture parameters. Wool recorded lower thermal conductivity values and reduced heat loss over time compared with polyester, feather-and-down and down in laboratory testing. The data also showed faster moisture movement through wool at higher temperatures, indicating a greater capacity to limit humidity build-up within the duvet.
- Thermal conductivity measurements showed wool provided between 17 and 30 per cent better insulation than the other tested fillings at comparable tog ratings.
- Eight-hour monitoring recorded higher internal temperatures in wool duvets, indicating slower heat loss during prolonged exposure to temperature gradients.
- Moisture transfer testing showed wool moved moisture through the duvet up to 153 per cent faster than feather-and-down and up to 120 per cent faster than synthetic alternatives at elevated temperatures.
- Synthetic and down-based fillings showed slower moisture movement, increasing the likelihood of condensation forming within the duvet structure.
HOW THE TESTS WERE RUN: Laboratory testing followed a standardised protocol designed to compare duvet fillings under identical and repeatable conditions. Each full-sized single duvet was assessed using the same equipment, exposure periods and environmental settings to ensure results reflected material behaviour rather than construction differences. Measurements were taken continuously to capture changes in temperature and moisture levels over time.
- Temperature gradients were created by maintaining one side of the test setup warm and the opposite side cool, allowing heat movement through the duvet to be tracked.
- Sensors were positioned at the top, bottom and centre of the duvet filling to monitor internal temperature changes over an eight-hour period.
- Moisture testing measured moisture absorption and transmission by tracking water loss and transfer rates under controlled laboratory conditions.
- All tests were repeated where specified in the study to confirm consistency and reliability of the recorded results.
WHY IT MATTERS: The findings have practical implications for how duvet fillings perform during sleep, particularly in maintaining thermal comfort and managing moisture. Faster heat retention can reduce temperature fluctuations across the night, while quicker moisture movement can limit dampness within bedding. Together, these factors influence perceived comfort and sleep quality without changing duvet weight or tog rating.
- Improved heat retention supports more stable sleeping temperatures over extended periods, reducing overnight cooling that can disrupt comfort despite similar tog ratings.
- Faster moisture movement limits humidity build-up within the duvet, helping reduce damp conditions caused by trapped heat and perspiration during sleep.
- The results show that measured performance differences were observed under controlled conditions using duvets of similar size and tog rating.
- By isolating filling performance under identical conditions, the study highlights how material behaviour influences thermal balance and moisture regulation.
THE BROADER VIEW: The study adds comparative evidence to ongoing discussions about how natural and synthetic bedding materials perform under real-use conditions. By testing finished duvets rather than loose fibres, the results provide insight into whole-product behaviour that is more directly relevant to consumer use. The findings contribute to a clearer understanding of how filling materials influence comfort beyond headline tog ratings.
- Whole-product testing captures how filling distribution and material behaviour interact during extended use, offering a more realistic assessment than fibre-level analysis.
- The results underline that tog ratings alone do not fully describe thermal comfort, as heat retention and moisture movement vary significantly between fillings.
- The findings add comparative laboratory evidence on how different duvet fillings perform when tested as finished products rather than loose fibres.
- The study provides measured data on thermal and moisture behaviour that distinguishes performance between tested duvet fillings.
WHAT THEY SAID
This research is a momentous step forward for the British wool industry and something I am really proud to personally have been heavily involved in. Wool is a miracle fibre that can completely transform sleep quality, as it combats one of the most common disruptors to sleep – overheating and waking due to sweating. While we have come a long way from its itchy, wiry, school jumper connotations, I'm confident that this study will be pivotal in showcasing its true temperature-regulating benefits to a global audience.
— Chris Tattersall
Managing Director
Woolroom
