It seems to me that researchers use two terms in literature: neutral and comfort in the context of thermal comfort, human body thermoregulation etc. Is there any difference? Is PMV=0 neutral and comfort, or only neutral and comfort depend on PPD / preferences?
Hi Karol Bandurski
When the equation of "PMV=0" is satisfied, This means the thermal comfort of the whole of human body.However, even when people in this situation may experience thermal discomfort. This difference mainly due to "Local Thermal Discomfort". Following sentences are from ISO 7730 (Section 6 - local thermal discomfort):
"The PMV and PPD express warm and cold discomfort for the body as a whole. But thermal dissatisfaction can also be caused by unwanted cooling or heating of one particular part of the body. This is known as local discomfort. The most common cause of local discomfort is draught (6.2). But local discomfort can also be caused by an abnormally high vertical temperature difference between the head and ankles (6.3), by too warm or too cool a floor (6.4), or by too high a radiant temperature asymmetry (6.5)."
Alipour
Mr. Karol Bandurski,
To my knowledge and experience, someone has to find the range of values of a relevant index where the majority of persons in a given area and/or region would feel comfortably. From this point of view, the sensation neutral (PMV=0) seems not to be identified with all possible comfort situations. Also, I consider that you may find useful the book entitled 'Human Thermal Environments: The Effects of Hot, Moderate, and Cold Environments on Human Health, Comfort, and Performance, Third Edition' by Ken Parsons (Taylor & Francis Group) and especially Chapter 4 (Psychological responses and human behaviour) with regard to your question. Further investigation of literature will surely help you deepen your research.
Best Regards
Research has shown that for thermal comfort aim for 0 to -0.5 is fresher and better for work.
On a bigger scale read the book by Ong 2013 Beyond Environmental Comfort published by Taylor and Francis. A collection of essays from luminaries in this field.
Comfort is neutral and as such is not sparkling or inspiring but more a necessary health level but we need to go way beyond this to create stimulating environments.
Dear Karol Bandurski,
Yes you are right. In thermal comfort two terms neutral and comfort.
There is a difference between these two terms.
PMV=0 means neutral. it is very rare that a subject will express neutral state. So different types regression techniques are use to evaluate neutral temperature for standard clo, met and air velocity level.
Instead subjects always express there thermal state on either side of neutral on thermal sensation scale. Comfort is always defined in range because of various personal factors associated with subjects. You have seen that in a room at particular time people tend to wear different clothing level though air temperature is almost same. It is inherent in humans because they have different experience and expectations about thermal environment. This is just one example I wrote here. There are many more. So in PMV terms we give range like ±0.5 or ±1. Because in this band subjects can easily adjust or adapt to make themselves comfortable by doing small adjustments. Usually ±0.5 is good for conditioned spaces (with heating or cooling facility) and ± 1 hold good for naturally ventilated spaces.
If you are interested you can read literature on adaptive thermal comfort or see ASHRAE-55 2013. You can read papers from Prof F. Nicol, Prof G. Brager, Prof. M. Humphreys, Prof. R. de. Dear and so on.
You can also read publications on my profile if you feel it can be some help to you.
Regards,
Manoj
Comfort is not enough. Look at work of de Dear; Ong; Barrett for example on beyond comfort.
Several papers show that 0 to -0.5 pmv is preferable for productivity .
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