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Principles of Adaptive Thermal Comfort

Principles of Adaptive Thermal Comfort. Michael A Humphreys Oxford Brookes University & Regent’s Park College University of Oxford. Adaptive thermal comfort rests on field-study research results. This is because adaptive behaviour is best studied in the normal habitat.

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Principles of Adaptive Thermal Comfort

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  1. Principles of Adaptive Thermal Comfort Michael A Humphreys Oxford Brookes University & Regent’s Park College University of Oxford

  2. Adaptive thermal comfort rests on field-study research results. This is because adaptive behaviour is best studied in the normal habitat. Early field studies date from the 1930s. The pattern was laid down by Thomas Bedford, who published his report in 1936. We now briefly review his study:-

  3. Dr Thomas Bedford The warmth factor in comfort at work MRC Industrial Health Board, Report 76, 1936

  4. Bedford’s field-study • Workers in light industry • 12 factories • Colder seasons of the year • Some 3085 interviews (mostly women) At each interview:- • Subjective responses were obtained • Temperature of hand, foot, etc • Thermal environmental measurements

  5. Bedford’s interview method:- Do you feel comfortably warm? If ‘yes’: are you really quite comfortable, or would you rather have the room slightly warmer or slightly cooler? If ‘no’: are you feeling too warm or too cool? If ‘too warm’: just definitely too warm, or much too warm? If ‘too cool’: just definitely too cool, or much too cool?

  6. The Bedford Scale:- Much too warm Too warm Comfortably warm Comfortable Comfortably cool Too cool Much too cool

  7. From the environmental measurements he calculated:- Air temperature (ta) Mean radiant temperature (tw) Air speed (v) Relative Humidity Continued:

  8. Continued: Physiological measurements included: • Forehead temperature • Palm temperature • Mean surface temperature of clothed body • Foot temperature

  9. Bedford was the first to use multivariate statistical analysis in a thermal comfort survey. All the calculations were done by hand or by using mechanical adding machines. Bedford’s analytical methods:-

  10. Many field studies of thermal comfort were conducted worldwide in the following years, using the basic pattern pioneered by Bedford. Few were as comprehensive, and few as thoroughly analysed. Others followed Bedford’s lead

  11. Charles G Webb • I want to say a little about Charles Webb, whom I regard as the originator of the adaptive approach to thermal comfort • Professor Fergus Nicol and I were both researchers in Charles’s research unit

  12. Charles G Webb Physicist and field-study comfort researcher at UK Building Research Station • Charles obtained data from Singapore, Bahgdad (Iraq), Roorkee (N India) and Watford (near London, UK) • He favoured longitudinal experimental designs (each respondent provided data over many days)

  13. Charles G Webb • Charles noticed that his respondents were comfortable at the mean conditions they experienced, whether in Singapore, North India, Iraq or England. • This suggested that they had adapted to the mean conditions they had experienced

  14. Charles G Webb • Charles initiated the first application of electronic data-logging and computer processing to comfort surveys (c1965) • We look briefly at this project:- (Charles retired before its completion)

  15. Charles G Webb The next two slides show the data-logging monitor unit. It automatically recorded: • ventilated wet and dry bulb temperatures, • the temperatures of a heated and an unheated globe • The ‘comfort-vote’ of the respondent

  16. 1966-69 BRE data-logging project

  17. Close-up of instrument – note the miniature 50mm globes and the automated response-scales Source: Humphreys & Nicol 1970

  18. The next slide shows the relationship between the new English data and Charles’s other sets of data. It also shows Bedford’s result. Notice how little the mean warmth sensation (the mean ‘comfort vote’) depends on the mean room temperature.

  19. Mean comfort votes: England, Singapore, Iraq and North India Source: Humphreys & Nicol 1970

  20. Mean warmth depended on the departure from the mean temperature rather than on the mean temperature itself

  21. The Adaptive Model • Fergus Nicol and I thought long and hard about this result, and Fergus drew a flow-diagram showing thermal comfort as a self-regulating adaptive system. • He included both physiological and behavioural adaptation (Nicol & Humphreys 1973)

  22. Thermal comfort as a self-regulating system – Fergus’s diagram Source: Nicol & Humphreys 1972

  23. A thermal comfort meta-analysis • But did the total evidence from all available field studies support this interpretation? • What if we collected together all their results?

  24. The available field studies were:- • 1938 Sa Brazil (Rio de Janeiro) • 1938 Newton UK (a.c.offices) • 1940 McConnell USA (a.c. offices) • 1947 Rowley USA (a.c. offices) • 1952 Ellis Aboard warships in Tropics • 1952 Rao India (Calcutta) • 1952 Mookerjee India (North, summer) • 1953 Ellis Singapore (on land) • 1953 Mookerjee India (dry tropics) • 1954 Black UK offices • 1955 Malhotra India (tropical) • 1955 Ambler Nigeria • 1955 Hickish UK Factories (summer) • 1957 Angus UK lecture-room, winter • 1959 Webb Singapore

  25. Continued:- • 1962 Hindmarsh Australia (Sydney) offices • 1963 Goromosov USSR dwellings • 1963 Wyndham Australia (N) manual workers • 1965 Lane USA (Iowa) schoolchildren • 1966 Ambler North India • 1966 Black UK (a.c. offices) • 1966 Grandjean Switzerland (offices, winter) • 1967 SIB(anon) Sweden (classroom teachers) • 1967 Ballantyne Papua (Caucasians, tropics) • 1968 Wyon UK Hospitals (operating theatres) • 1968 Grandjean Switz. (offices, a.c., nv, summer) • 1969 Auliciems UK schoolchildren, winter

  26. Continued:- • 1970 Humphreys & Nicol UK offices (year-round) • 1971 Pepler USA teachers (a.c. & n.v.) • 1972 Pepler USA Schoolchildren (a.c. & n.v.) • 1972&3 Davies UK Schoolchildren (year-round) • 1973 Auliciems UK Schoolchildren, summer • 1973 Humphreys UK Schoolchildren (summer) • 1973 Wanner Switzerland (a.c. offices) • 1974 Nicol India & Iraq offices, summer (Webb’s data)

  27. The data represented over 200,000 ‘comfort-votes’

  28. The meta-analysis From most of these studies it was possible to find: • The optimum temperature for comfort • The sensitivity of the respondents to temperature changes

  29. The meta-analysis • If people had adapted to their normal indoor environment, the optimum temperature for comfort should be correlated with the mean temperature they experienced • The next slide shows this to be true (correlation (r) = 0.95, p<0.001) The range of neutral temperatures was too wide to be explained by the newly available PMV equation (Fanger, 1970)

  30. Neutral temperature is correlated with the mean temperature Source: Humphreys 1975

  31. Subjective warmth was unresponsive to the mean temperature Source: Humphreys 1975

  32. The meta-analysis • Next the data were analysed in relation to the monthly outdoor temperatures, these being obtained from published world meteorological tables • We found the neutral temperatures to be strongly related to the corresponding mean outdoor temperatures • The strongest relation was for the ‘free-running’ mode of operation (no heating or cooling in use)

  33. neutral temperature related to outdoor temperature Source: Humphreys 1978

  34. Clothing and adaptation • Changing the clothing is the most obvious behavioural adaptation to temperature. • So studying clothing change should tell us more about how people adapt to their indoor environment

  35. BRE field-studies 1969-77 on adaptation by clothing changes • Thermal comfort & clothing, Secondary School Children • Thermal comfort & clothing, Primary School Children • Clothing & comfort outdoors: shopping & leisure • Thermal comfort & bed-clothing during sleep

  36. Percentage of children in shirt-sleeves against room temperature, c1969

  37. Primary children, clothing and comfort Source: Humphreys 1978

  38. Clothing & air temperature: shopping streets and zoo park Source: Humphreys 1977

  39. Bedclothes and bedroom temperature Source: Humphreys 1977

  40. What we learned about clothing adaptive behaviour • Little adaptive change during the day • More adaptive change from day-to-day • More still from week-to-week • Clothing changes lag behind temperature changes • People sometimes ‘trade’ thermal comfort for fashion (social comfort)

  41. After publication of the meta-analysis other researchers explored adaptive comfort: • Ian Griffiths (UK) : UK & European surveys • John Busch: Surveys in Bangkok, Thailand • Auliciems & deDear: Australian surveys • Gail Schiller (Brager) & team: USA surveys These researchers found adaptation to be taking place, sometimes to an extent inexplicable on the PMV/PPD model

  42. Adaptive opportunity • Nick Baker and Mark Standeven, working in Cambridge, UK, linked comfort to the available means of thermal adaptation – the ‘Adaptive Opportunity’. • If there was little Adaptive Opportunity, discomfort was likely to occur

  43. The Forgiveness Factor • Bordass & Leaman (working in the UK) developed protocols for the Post-Occupancy evaluation of buildings. Their results showed that people who had control over their environment were more tolerant of it. They called this the ‘Forgiveness Factor’ If the occupants could not control their environment discomfort was likely to occur

  44. Adaptation and sociology • Accepting the adaptive hypothesis, Elizabeth Shove argues that comfort is a ‘Social Construction’. Different societies, historically and geographically, have had very different comfort temperatures. • This suggests that societies can be encouraged to adopt solutions that are environmentally responsible

  45. ASHRAE Standard 55-2004 • de Dear and Brager (1998) did a meta-analysis of recent high quality field studies. Their results broadly confirmed the findings of the meta-analyses of 1978-81, as the next slides show. • The 2004 revision of Standard 55 used this result to provide a graphical relation between comfort indoors and the outdoor mean temperature.

  46. de Dear’s database of field studies • 20,000 sets of observations, each with: subjective vote (7 point scale) thermal environmental measurements clothing and activity records • 9 countries • 160 buildings • Wide coverage of climate

  47. de Dear Database, buildings with 100+ observations. Mean room temperature and the temperatures for comfort (neutrality) are correlated (r=0.94) (my analysis)

  48. Indoor neutral temperatures and daily mean outdoor temperatures for the de Dear database (my analysis)

  49. Explaining the adaptive model • I will now explain the basic principles of the adaptive model of thermal comfort, and illustrate the main features • Fundamental is the ‘Adaptive Principle’

  50. People are not passive receptors of their thermal environment, but continually interact with it

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