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Last edited 17 Aug 2023
Adaptive thermal comfort
“If a change occurs such as to produce discomfort, people react in ways which tend to restore their comfort” (Humphreys and Nicol 1998)/ "Considering feedback between the thermal sensation of subjects and their behaviour and that they consequently ‘adapted’ to the climatic conditions in which the field study was conducted" (Nicol and Humphreys 1973)
"Recognition of the contribution and importance of this dynamic relationship between occupant and building underpins the adaptive comfort approach. Physiologically: The body is constantly making subconscious adaptations to maintain its core body temperature of 37°C. Behaviourally: This can be conscious, semi-conscious or subconscious. Examples include changing clothing, opening/closing windows, blinds or curtains, and using local heaters or fans. Psychologically: This includes issues of expectations around the cost of energy, personality, status, ethical standards and control." (CIBSE 2017)
Adaptive comfort theory (ACT) is a concept increasingly used in building design which relates in many ways to environmental psychology. Whilst room temperature and humidity are key components that impact the thermal comfort of occupants in buildings, with other specifics such as surface temperature, air movement, drafts and exposure to natural light are also factors, as well as clothing, activity levels, age, gender and cultural context - adaptive comfort theory goes further.
It considers not only these wider factors but recognises that the relationship between an occupant and the building or its surroundings is dynamic in its nature. That is to say, people can tolerate a wide range of temperatures, as long as they have some control over their environment, and can adjust their senses and behaviour to effectively adapt or self regulate. It suggests that people undergo a period of adaptation in which their thermal perceptions and sensations may change to develop a new level of comfort. Including this adaptation factor allows a wider range of thermal conditions can be tolerated.
It was as early as the late 1930's, that warmth as a factor of workers comfort was being investigated (T.Bedford 1936), whilst in the late 1950's C.G.Webb published an analysis of some observations of thermal comfort in an equatorial climate in the British Journal of Industrial Medicine (16(3), 297-310). Then through out the 1970's and beyond, two leading researchers in the field were Fergus Nichol and Michael Humphreys, who continued the work started by Webb within the thermal comfort section of the UK Building Research Station (BRS).
Possibly the first serious discussions around an adaptive approach were generated by their work in 1973 in the developing framework for Adaptive comfort and the paper on 'thermal comfort as part of a self-regulating system' (Building Research and Practice, 6(3),191-197). Their related work continued through into the 80's and the 90's looking at various factors such as "outdoor temperatures and comfort indoors" and generally better understanding and standardising ways of measuring thermal comfort, that included interviews techniques rather than purely threshold measure leading to phrases and tools such as predicted mean vote (PMV).
In 1998 de Dear, R.J. & Brager, G. (1998), published "developing an adaptive model of thermal comfort and preference" (ASHRAE Technical Data Bulletin, 14, 27-49) whilst in 2002 Nichol and Humphreys published "Adaptive Thermal Comfort and Sustainable Thermal Standards for Buildings (Energy and Buildings 34(6):563-572) which remains a seminal piece of research in the field.
EN 15251 "Indoor environmental input parameters for design and assessment of energy performance addressing Indoor Air Quality, Thermal Environment, Lighting and Acoustics. was published in 2007 by CEN and in 2012 Nicol, F., Humphreys, M. & Roaf, S. published "Adaptive thermal comfort: principles and practice. London: Routledge."
Adaptive comfort theory is now applied to many building contexts, including the sustainability of buildings, from the optimisation of energy use to the improvement of indoor air quality. It has also been used to explain how people in different regions of the world have different thermal comfort preferences and how these can be incorporated into building design. This is increasingly relevant through the impacts of climate change and wider climate adaptation.
The Chartered Institute of Building Service Engineers (CIBSE) has adopted the adaptive thermal model to define thermal comfort and design overheating criteria in their Technical Memorandum number 52 (TM52, 2015). Stating: "The adaptive thermal comfort model is based on the principle that an individual’s thermal expectations and preferences are determined by their experience of recent (outdoor) temperatures and a range of contextual factors, such as their access to environmental controls. The adaptive thermal comfort model allows for the natural adaptation of human physiology to extended periods of hot events. By using the adaptive thermal comfort model, instead of the use of static comfort temperatures, the periods of discomfort, and so the potential energy demand for active cooling, are not overestimated."
- Climate adaptation.
- Climate change adaptation.
- Comfort in low energy buildings.
- Evolving opportunities for providing thermal comfort.
- Heat stress.
- Heating degree days.
- Human comfort in buildings.
- Maximum and minimum workplace temperatures.
- Mean radiant temperature.
- Overheating - assessment protocol.
- Overheating in buildings.
- Overheating in residential properties.
- Overheating guidance for buildings.
- Predicted percentage dissatisfied.
- Predicted mean vote.
- Psychometric charts.
- Thermal comfort and wellbeing.
- Thermal comfort in buildings.
- Thermal environment.
- Thermal indices.
 External References
- Bedford, T. (1936). The warmth factor in comfort at work. Medical Research Council, Industrial Health Research Board, Report No. 76.
- Webb, C.G. (1959). An analysis of some observations of thermal comfort in an equatorial climate. British Journal of Industrial Medicine, 16(3), 297-310.
- Humphreys, M.A. & Nicol, J.F. (1970). An investigation into thermal comfort of office workers. Journal of the Institute of Heating & Ventilating Engineers, 38, 181-189.
- Humphreys, M.A. (1973). Clothing and thermal comfort of secondary school children in summertime, In: Thermal Comfort and Moderate Heat Stress, Eds: Langdon, Humphreys & Nicol. London: HMSO.
- Nicol, J.F. & Humphreys, M.A. (1973). Thermal comfort as part of a self-regulating system. Building Research and Practice, 6(3), 191-197.
- Nicol, J.F. (1974). An analysis of some observations of thermal comfort in Roorkee, India and Baghdad, Iraq. Annals of Human Biology, 1(4), 411-426
- Humphreys, M.A. (1978). Outdoor temperatures and comfort indoors. Building Research and Practice, 6(2), 92-105.
- Humphreys, M.A. (1981). The dependence of comfortable temperature upon indoor and outdoor climate, In: Bioengineering, Thermal Physiology and Comfort, Eds: K. Cena & J.A. Clark. Amsterdam: Elsevier.
- de Dear, R.J. & Brager, G. (1998). Developing an adaptive model of thermal comfort and preference, ASHRAE Technical Data Bulletin, 14(1), 27-49.
- Nicho,F.,Humphreys,M. (2002). Adaptive Thermal Comfort and Sustainable Thermal Standards for Buildings (Energy and Buildings 34(6):563-572)
- ASHRAE Standard 55. (2004). Thermal environmental conditions for human occupancy. Atlanta: ASHRAE.
- CIBSE, 2005. Climate change and the indoor environment: Impacts and adaptation. TM 46. The Chartered Institution of Building Services Engineers (CIBSE). London, UK.
- EN 15251. (2007). Indoor environmental input parameters for design and assessment of energy performance addressing Indoor Air Quality, Thermal Environment, Lighting and Acoustics. Brussels: CEN.
- Nicol, F., Humphreys, M. & Roaf, S. (2012). Adaptive thermal comfort: principles and practice. London: Routledge.
- Humphreys, M., Nicol F. & Roaf, S. (2016). Adaptive thermal comfort: foundations and analysis. London: Routledge. (Paperback with corrections: 2020.)
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