Understanding the effect of bedding on thermal insulation during sleep

The temperature of our sleeping environment has a major impact on the quality of our sleep, and good sleep is essential for our overall health and well-being. The bedding micro-environment is a key factor in maintaining thermally comfortable conditions for sleep. This includes the ambient temperature, humidity, the heat generated by the human body, and the thermal insulation provided by bedding like quilts, blankets, sheets, etc.  

In particular, the total thermal insulation, or the ability of the bedding systems to resist heat flow, significantly affects the thermal neutral temperature of sleeping environments. This refers to the ambient temperature range at which the human body can maintain a stable body temperature without needing to generate more heat (by shivering) or lose heat (by sweating). Despite its importance, there are currently no standardized methods for measuring the thermal insulation of bedding systems. Moreover, while a few studies have investigated bedding insulation, they have solely focused on the body as a whole, overlooking local thermal conditions of different body parts.  

To address this gap, a research team led by Research Associate Mizuho Akimoto from the Advanced Collaborative Research Organization for Smart Society (ACROSS) at Waseda University in Japan systematically examined the total thermal insulation of bedding systems, both for the whole body and individual body parts. The team included Assistant Professor Jun Shinoda, Assistant Professor Mariya P. Bivolarova, and Professor Pawel Wargocki from the Technical University of Denmark, along with Professor Shin-ichi Tanabe from Waseda University. Their study was made available online on April 26, 2025, and will be published offline in Volume 279 of the journal Building and Environment on July 01, 2025. 

“Since body posture and how much of the body is covered by the bedding can constantly change during sleep, it is essential to evaluate the local thermal conditions of each body part while measuring thermal insulation of bedding systems,” explains Akimoto. “In this study, we present a method for measuring thermal insulation of various combinations of bedding systems and sleepwear using a heated human manikin together with the open-source human thermoregulation model JOS-3.”  

The team conducted a series of measurements on a heated thermal manikin in a climate chamber with 84 different combinations of beddings and sleepwear, including two postures: supine (lying straight on the back) and lateral (lying on the right side); two clothing levels: nude and pajamas; two types of quilts: blanket and duvet, and four body coverage rates ranging from 23.3%, which used only a mattress, sheet, and pillow, to 94.1%, including a blanket covering the entire body except the head. The measurements were made at three ambient temperatures of 18.6° C, 22.6° C, and 26.4 ° C based on the World Health Organization’s guidelines for well-balanced room temperatures and the CIBSE criteria for overheating.  

The team measured the total thermal insulation of the bedding system, including the air layer around the body. Additionally, measurements were taken for both the whole body and 24 body segments. The results showed that the values for total thermal insulation ranged from 1.06 to 5.71 clothing insulation units (clo), depending on the posture, coverage, and materials. 

Because the manikin used in the experiment cannot simulate sweating, the researchers used the JOS-3 model to simulate how sweating would affect skin temperature and heat loss in a real human body. The simulations, which used the manikin measurements as inputs, revealed that even when the total insulation of the whole body remained unchanged under different conditions, the local skin temperature of different body parts could vary greatly depending on which parts were covered or in contact with the mattress. The simulations also provided insights into the range of bedding adjustments that can be made to avoid sweating at a given ambient temperature.  

“Our findings suggest that relying on total thermal insulation of the whole body is not enough, and new methods should be developed that account for both whole and local body effects,” notes Akimoto. “Further, these findings provide benchmarks for optimizing sleep environments and can serve as inputs for multi-segmental human thermoregulatory models, allowing predictions of thermal physiological responses such as heat stress during sleep.” 

In summary, this study provides important insights into how bedding systems can be optimized to support better sleep quality and, in turn, better overall health. 

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Reference 
Authors: Mizuho Akimoto^a,^b, Jun Shinoda^b, Mariya P. Bivolarova^b, Shin-ichi Tanabe^c, and Pawel Wargocki^b 
DOI: 10.1016/j.buildenv.2025.113074 
Affiliations: ^aAdvanced Collaborative Research Organization for Smart Society (ACROSS), Waseda University, Japan 
^bDepartment of Environmental and Resource Engineering, International Centre for Indoor Environment and Energy, Technical University of Denmark, Denmark 
^cDepartment of Architecture, Waseda University, Japan 

About Waseda University 
Located in the heart of Tokyo, Waseda University is a leading private research university that has long been dedicated to academic excellence, innovative research, and civic engagement at both the local and global levels since 1882. The University has produced many changemakers in its history, including eight prime ministers and many leaders in business, science and technology, literature, sports, and film. Waseda has strong collaborations with overseas research institutions and is committed to advancing cutting-edge research and developing leaders who can contribute to the resolution of complex, global social issues. The University has set a target of achieving a zero-carbon campus by 2032, in line with the Sustainable Development Goals (SDGs) adopted by the United Nations in 2015.  
To learn more about Waseda University, visit https://www.waseda.jp/top/en   

About Research Associate Mizuho Akimoto 
Ms. Mizuho Akimoto is currently a Research Associate at the Advanced Collaborative Research Organization for Smart Society (ACROSS) at Waseda University. She is also a member of the Shin-ichi Tanabe lab at Waseda University. She obtained her M.S. degree from the Department of Architecture at Waseda University in 2022. She has published over 20 articles, which have received over 230 citations. Her research is primarily focused on understanding bedroom environments for better sleep quality and wellness in residential buildings.