# Precision and thermal comfort

## Presentation on theme: "Precision and thermal comfort"— Presentation transcript:

Precision and thermal comfort
Fergus Nicol London Metropolitan University and Oxford Brookes University

Thermal comfort standards
From Olesen and Parsons, Energy and Buildings 34(6)

Summer in Saidu Sharif, Pakistan (photo M Humpheys)

Winter in Saidu Sharif, Pakistan (photo M Humpheys)

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

Data from Pakistan

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)

Fans are available in almost all Pakistani offices this graph shows the proportion in use a different temperatures

Probability control is in use is given by: p = e(a+bTo)/(1+e(a+bTo)) a and b are determined by regression analysis A curve of p on To can then be drawn to show the probability that a control is being used

Use of fans Details: Nicol, J.F. (2001) 7th international IBPSA conference, Rio

Use of windows

Use of blinds/curtains

The use of curtains is better related to the external illuminance:
From data of Yannick Sutter, ENTPE, Lyons

Use of heating

Comfort is achieved by the occupants adapting to the 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

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 Global warming Energy use

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

E.N. – Electricidade do Norte offices, Porto, Portugal

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

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

Most occupants want no change in indoor temperature

Mean outdoor temp. The effect of separating the outdoor temperatures

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