Precision and thermal comfort

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Precision and thermal comfort

• Fergus Nicol
• London Metropolitan University and Oxford Brookes
  University

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Thermal comfort standards
From Olesen and Parsons, Energy and Buildings
34(6)
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Summer in Saidu Sharif, Pakistan (photo M
Humpheys)
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Winter in Saidu Sharif, Pakistan (photo M
Humpheys)
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Changing ourselves

• As the temperature changes so the level of
  clothing, the air movement (which can cool the
  body by convection and/or evaporation of sweat)
  and the moisture of the skin will change.
• It is also probable that people are less active
  in the heat, but because metabolic rate is
  measured by activity this is not clear

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Data from Pakistan
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The result of these actions is shown in this
graph of the level of discomfort at different
indoor temperatures among office workers in
Pakistan
Little discomfort
Nicol, Raja, Allauddin Jamy (1999) Energy and
Buildings 30(3)
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Fans are available in almost all Pakistani
offices this graph shows the proportion in use a
different temperatures
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A curve of p on To can then be drawn to show the
probability that a control is being used
Probability control is in use is given by p
e(abTo)/(1e(abTo)) a and b are determined by
regression analysis
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Use of fans
Details Nicol, J.F. (2001) 7th international
IBPSA conference, Rio
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Use of windows
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Use of blinds/curtains
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The use of curtains is better related to the
external illuminance
From data of Yannick Sutter, ENTPE, Lyons
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Use of heating
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Comfort is achieved by the occupants adapting to
the building
Occupant
Building
Or by the occupants adapting the building to suit
them
This has to be done within the climatic, social,
economic and cultural context of the whole system
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Cautionary note

• Whilst essentially a negative feed-back system
  aimed at avoiding discomfort, the behaviour
  resulting from discomfort can lead to a positive
  feed-back in energy use

Air-conditioning
Energy use
Global warming
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New approaches
Comfort is achieved by the occupants adapting to
the building
Occupant simulation
Empirical results
Building simulation
Or by the occupants adapting the building to suit
them
This has to be done within the climatic, social,
economic and cultural context of the whole system
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E.N. Electricidade do Norte offices, Porto,
Portugal
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• The temperatures were measured during office
  hours during a thermal comfort survey.
• It will be noticed that there is a tendency for
  the indoor temperature to be above the outdoor
  temperature in cold weather and often below it in
  warmer weather.
• There is also structure in the distribution of
  indoor temperatures at any given outdoor
  temperature

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Comfort and preference

• How do you feel? How would you prefer to feel?
• Cold
• Cool Much warmer
• Slightly cool A bit warmer
• Neutral No change
• Slightly warm A bit cooler
• Warm Much cooler
• Hot

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Most occupants want no change in indoor
temperature
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Mean outdoor temp.
The effect of separating the outdoor temperatures
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Conclusions

• Comfort is a psychological, not a physiological
  one
• Buildings must enable occupants to be comfortable
• AC is one way to do this but it is expensive in
  equipment and energy
• Buildings behave stochastically and not
  precisely, particularly when occupied
• Sustainable solutions need risk assessment not
  comfort prescriptions