Transcript Slide 1

Principles of Adaptive
Thermal Comfort
Michael A Humphreys
Oxford Brookes University
&
Regent’s Park College
University of Oxford
 Adaptive
thermal comfort rests on fieldstudy 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:-
Dr Thomas Bedford
The warmth factor
in comfort at work
MRC Industrial
Health Board,
Report 76, 1936
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
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?
The Bedford Scale:Much too warm
Too warm
Comfortably warm
Comfortable
Comfortably cool
Too cool
Much too cool
Continued:
From the environmental measurements he
calculated: Air temperature (ta)
 Mean radiant temperature (tw)
 Air speed (v)
 Relative Humidity
Continued:
Physiological measurements included:
 Forehead temperature
 Palm temperature
 Mean surface temperature of clothed body
 Foot temperature
Bedford’s analytical methods: 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.
Others followed Bedford’s lead
 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.
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
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)
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
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)
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
1966-69 BRE data-logging project
Close-up of instrument – note the miniature 50mm
globes and the automated response-scales
Source: Humphreys & Nicol 1970
 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.
Mean comfort votes: England, Singapore, Iraq and North India
Source: Humphreys & Nicol 1970

Mean warmth depended on the departure from the mean
temperature rather than on the mean temperature itself
The Adaptive Model
 Fergus
Nicol and I thought long and hard
about this result, and Fergus drew a flowdiagram showing thermal comfort as a
self-regulating adaptive system.
 He included both physiological and
behavioural adaptation
(Nicol & Humphreys 1973)
Thermal comfort as a self-regulating system – Fergus’s diagram
Source: Nicol & Humphreys 1972
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?
The available field studies were:


1938
1938
1940
 1947
 1952
 1952
 1952
 1953
 1953
 1954
 1955
 1955
 1955
 1957
 1959
Sa
Newton
McConnell
Rowley
Ellis
Rao
Mookerjee
Ellis
Mookerjee
Black
Malhotra
Ambler
Hickish
Angus
Webb
Brazil (Rio de Janeiro)
UK (a.c.offices)
USA (a.c. offices)
USA (a.c. offices)
Aboard warships in Tropics
India (Calcutta)
India (North, summer)
Singapore (on land)
India (dry tropics)
UK offices
India (tropical)
Nigeria
UK Factories (summer)
UK lecture-room, winter
Singapore
Continued:
1962 Hindmarsh
 1963 Goromosov
 1963 Wyndham
 1965 Lane
 1966 Ambler
 1966 Black
 1966 Grandjean
 1967 SIB(anon)
 1967 Ballantyne
 1968 Wyon
 1968 Grandjean
 1969 Auliciems
Australia (Sydney) offices
USSR dwellings
Australia (N) manual workers
USA (Iowa) schoolchildren
North India
UK (a.c. offices)
Switzerland (offices, winter)
Sweden (classroom teachers)
Papua (Caucasians, tropics)
UK Hospitals (operating theatres)
Switz. (offices, a.c., nv, summer)
UK schoolchildren, winter
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)
The data represented over 200,000
‘comfort-votes’
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
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)
Neutral
temperature is
correlated with
the mean
temperature
Source: Humphreys 1975
Subjective warmth
was unresponsive
to the mean
temperature
Source: Humphreys 1975
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 ‘freerunning’ mode of operation (no heating or
cooling in use)
neutral
temperature
related to
outdoor
temperature
Source: Humphreys 1978
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
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
Percentage of
children in shirtsleeves against
room temperature,
c1969
Primary children, clothing and comfort
Source: Humphreys 1978
Clothing & air temperature: shopping streets and zoo park
Source: Humphreys 1977
Bedclothes
and bedroom
temperature
Source: Humphreys 1977
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)
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
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
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
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
ASHRAE Standard 55-2004
 de
Dear and Brager (1998) did a metaanalysis 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.
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
de Dear Database, buildings with 100+ observations.
Mean room temperature and the temperatures for
comfort (neutrality) are correlated (r=0.94)
32
30
28
26
24
mode:
22
H/C
FR
20
Total Population
18
12
Rsq = 0.8849
14
16
18
20
22
24
26
28
30
32
34
Mean Operative Temperature (C)
(my analysis)
Indoor neutral temperatures and daily mean
outdoor temperatures for the de Dear database
buildings with 100+ observations
32
30
28
26
24
22
Heated/Cooled
Rsq = 0.5420
20
Free Running
18
Rsq = 0.8906
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
daily average outdoor temperature (C)
(my analysis)
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’
People are not passive
receptors of their thermal
environment, but
continually interact with it
The Adaptive Principle:-
If a change occurs that
produces discomfort, people
will tend to act to restore
their comfort.
(The return towards comfort is pleasurable)
Thermal comfort is an example of a
‘Complex Adaptive System’
The properties of these systems are:
 Mathematical intractability
 Multiple equilibria
 If disturbed may settle at a different
equilibrium position
(Other examples of Complex Adaptive
Systems are the world climate system and
the world economic system)
Consequences of the adaptive
principle
Except in extreme climates
 People become adjusted to the
conditions they normally experience
 People must be studied in their
everyday habitats
 Discomfort arises from insufficient
adaptive opportunity
Types of adaptation:
It is useful to classify the different
kinds of adaptation that may occur:
 Physiological
 Behavioural
 Psychological
Physiological adaptations
To coldness:
 Vaso-constriction
 Shivering
 Eating more
 Cold acclimatisation?
To warmth:
 Vaso-dilatation
 Sweating
 Eating less
 Heat acclimatisation
Some behavioural adaptations
To coldness:
 Increase activity
 Increase clothing
 Close posture
 Cuddle up
 Heat the room
 Find a warmer place
 Close windows
 Avoid draughts
 Modify the building
 Emigrate
To warmth:
 Reduce activity
 Reduce clothing
 Open posture
 Separate
 Cool the room
 Find a cooler place
 Open windows
 Use a fan
 Modify the building
 Emigrate
Psychological adaptations
These are not yet well defined or
understood. They may include:
 Expecting
a range of conditions
 Accepting a range of sensations
 Enjoying a variety of sensation
 Accepting behavioural adaptations
 Accepting responsibility for control
Behavioural adaptation
The next slides illustrate some
behavioural adaptations
Even Pandas think
adaptively
And so do children
Clothing behaviour
 The
next slides illustrate changes in
clothing as a means of achieving comfort
Comfort in
the UK
winter at
o
about 15 C
(1906)
Notice the
heavy
indoor
clothing
Men’s clothing
was also
heavy
(mens’ club,
London, 1906)
Ice Hotel in
Lapland,
1995.
Comfortable
at -7oC?
You can show your
status without a
business suit…
Warm clothing can
be smart too….
Window-opening behaviour
 Adaptation
by opening and closing
windows.
 The following chart shows the proportion
of windows open in batches of UK data at
different room temperatures.
From such charts the adaptive behaviour
can be modelled and quantified.
Example: window opening behaviour, Aberdeen & Oxford (UK)
Proportion of windows open
Abdnox-long
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
14
16
18
20
22
24
26
28
30
32
T g [oC]
Source: H Rijal 2007
Constraints
There may be insufficient opportunity for
adaptive action to be fully effective. It may
be constrained by (for example)
 Climate
 Culture and fashion
 Work requirements
 Personality
Insufficient adaptive opportunity leads to
discomfort.
Constraints
The next slides illustrate the presence of
some constraints on adaptation
Clothing is
for display
as well as
for thermal
comfort.
This may
constrain
thermal
adaptation
Dress is partially constrained by the social
occasion (a wedding in Germany)
Posture may be
constrained by
the task
Window-opening may be constrained by noise and fumes:
Oxford Coach Station (UK)
This office shows good adaptive opportunity
An office with poor adaptive opportunity
Successful adaptation
 If
the combined effect of the various
actions is sufficient, comfort will be
achieved
 The next slides show successful
combinations of adaptive actions
Adaptation need
not be a conscious
act……
Photograph by Ruth Roberts
summary comments
 The
adaptive model shows that comfort
temperatures are variable rather than fixed
 We have seen populations comfortable in
rooms as low as 17oC and as high as 35oC
 Comfort temperatures in the free-running
mode depend strongly on the outdoor
temperature
This suggests that a society could vary its
comfort temperatures to minimise fuel use
summary comments
 The
comfort temperature can be seen as
the current equilibrium setting of a
complex adaptive system.
 Modifying the pattern of constraints acting
on the system will modify the equilibrium
setting.
 Gradual changes in the constraints are
unlikely to produce discomfort
 Inadequate adaptive opportunity (= too
much constraint) will produce discomfort
summary comments
 Thermal
physiology and heat-exchange
models are components of the adaptive
model
 The PMV/PPD model underestimates the
adaptive capacity of the human population
 The adaptive model does not fit easily into
the current ways of expressing standards
for thermal comfort
The end