Challenging the assumptions for thermal sensation scales

Figures & data

Table 1. Summary of the conditions used in the studies.

Variable	HVAC						NV
	Categorical			Continuous binned			Categorical			Continuous binned
	n	Mean	SD	n	Mean	SD	n	Mean	SD	n	Mean	SD
Outdoor temperature	3770	10.08	12.33	7064	21.37	7.47	7147	20.95	7.50	3710	22.42	6.41
Operative temperature	3770	23.83	2.06	7064	23.26	1.38	7147	25.48	6.23	3710	26.10	2.68
Clothing level	3770	0.71	0.24	7064	0.56	0.19	7147	0.74	0.39	3710	0.49	0.22
Metabolic rate	3770	1.23	0.38	7064	1.22	0.18	7147	1.17	0.42	3710	1.17	0.13
Relative humidity	3770	36.82	15.59	7064	48.83	11.51	7147	45.16	17.26	3710	58.04	14.12
Air velocity	3770	0.09	0.05	7064	0.12	0.09	7147	0.22	0.30	3710	0.19	0.17

Table 2. Transformations described by Houghten and Yagloglou (1923) to convert the answers given to three questions into a five-point scale.

Answers given	Resulting point on the scale
Comfortable and no change desired	Very comfortable
Comfortable but preferred slightly warmer	Comfortably cool
Comfortable but preferred slightly cooler	Comfortably warm
Not comfortable and preferred warmer	Too cold
Not comfortable and preferred cooler	Too warm

Table 3. Overview of the judgement scales.

Type of judgement	Perceptual	Affective evaluation	Thermal preference	Personal acceptability	Personal tolerance
Subject under judgement	Personal thermal state			Thermal ambience
Wording	‘How do you feel (at this precise moment)?’ 7 or 9 degrees from very COLD to very HOT	‘Do you find it … ?’ 4 or 5 degrees from COMFORTABLE to very UNCOMFORTABLE	‘Please state how you would prefer to be now’. 7 (or 3) degrees from (much) COLDER to (much) WARMER	‘How do you judge this environment on a personal level?’ 2 degrees, GENERALLY ACCEPTABLE, GENERALLY UNACCEPTABLE	Is it … ?’ 5 degrees, from perfectly TOLERABLE to INTOLERABLE

Source: Adopted from ISO 10551 (1995)

Table 4. Overview of scale usage in reviewed studies.

	Thermal sensation scale		Thermal preference scale		Thermal comfort scale		Thermal acceptance scale		Other scales
	Methods	Results	Methods	Results	Methods	Results	Methods	Results	Methods	Results
Becker and Paciuk (2009)	A	+	7-P	+	5-P	+			–	–
Cao, Zhu, Ouyang, Zhou, and Huang (2011)	A	+	–	–	–	–	–	–	–	–
Corgnati, Ansaldi, and Filippi (2009)	A	+	3-P	+	–	–	2-P	+	–	–
Cerpa (2012)	A	+	–	–	–	–	–	–	S 5-P	+
Goto, Mitamura, Yoshino, Tamura, and Inomata (2007)	A	+	3-P	+	–	–	2-P	+	–	–
Heidari and Sharples (2002)	A	+	–	–	–	–	–	–	–	–
Hong, Gilbertson, Oreszczyn, Green, and Ridley (2009)	–	–	–	–	B^a	+	–	–	–	–
Humphreys and Hancock (2007)	A	+	A 7-P	+	–	–	–	–	–	–
Humphreys and Nicol (2004)	A	+	3-P + 5-P	+	B	+	–	–	–	–
Indraganti and Rao (2010)	A	+	5-P	+	–	–	2-P	+	O	+
Jazizadeh, Marin, and Becerik-Gerber (2013)	A 5-P^b	+	cs	+	–	–	–	–	–	–
Lee et al. (2010)	A 9-P + O	+	–	–	–	–	–	–	–	–
Singh, Mahapatra, and Atreya (2011)	A	+	^c	–	–	–	–	–	–	–
Spagnolo and de Dear (2003)	A	+	3-P	+	–	–	–	–	O	+
Tablada, De Troyer, Blocken, Carmeliet, and Verschure (2009)	A	+	–	–	B^a	+	–	–	–	–
Wong and Khoo (2003)	A	+	3-P	+	B	+	2-P	+	O	–
Wong et al. (2002)	A	+	–	–	B	+	–	–	O	–
Yang and Zhang (2008)	A	+	3-P	+	–	–	2-P	+	O	+
Yun et al. (2014)	A	+	–	–	2-P	–	–	–	–	–
Zhang and Altan (2011)	O 7-P	+	–	–	–	–	–	–	S 7-P + O	+
Zhang, Wang, Chen, Zhang, and Meng (2010)	A 9-P	+	–	–	4-P	+	4-P	+	–	–

Notes: ^aAdjusted, i.e. not as described in the original source (e.g. much too cold – too cold – comfortably cool – comfortable – comfortably warm – too warm – much too warm)

^b5-P scale reducing three middle votes of the ASHRAE scale to a neutral vote

^cIn the method section a preference parameter is included in the questionnaire. However, the questionnaire shown in the appendix does not contain this and no results are shown

A = ASHRAE scale, B = Bedford scale, S = Satisfaction scale; cs = continuous scale; O = Others

Table 5. Example questions for the three components of perception from pain research and corresponding examples for thermal comfort research.

Component	Example questions from pain research	Possible analogical question in thermal comfort research	Explanatory notes
Sensory–discriminative	Where is the pain located? How intense is the sensation? How is the quality of the pain (e.g. burning, stinging etc.)	(1) and (2) Indicate on the following diagram: how do you feel at different body parts? (3) How comfortable is it for the particular body parts?	All three questions are generally used in thermal comfort today. Questions (1) and (2) are actually combined in the thermal sensation scale, if presented for each of the body parts. Examples can be found in Parsons (2014, p. 132) and ISO 10551 (1995). Note that while in pain research a location of pain is always an important factor, many thermal comfort studies focus only on ‘whole-body’ thermal sensation. In such a case the detailed questions about body parts are not asked
Affective–motivational	How un-/pleasant is the sensation Which emotions (e.g. anger, worry, sadness etc.) are associated with the experience? What would you like to do to change the situation? How strong is your motivation to behave in a specific way?	How un-/pleasant is the sensation?/Do you find the current condition un-/pleasant? Which emotions (e.g. annoyance, distraction, arousal etc.) would you associate with the current conditions? What would you like to do to change the situation?/Please state how would you prefer to be now. How strongly are you motivated to adapt your clothing?	(Ad 1) The question regarding pleasantness of the conditions would mean an important extension to the ‘acceptability question’ (as presented, for example, in ISO 10551 (1995). (Ad 2) Evaluation of an emotive dimension would certainly represent an innovative approach. The insight into relations between human emotional states and thermal environment would be highly beneficial with respect to the influence of thermal environments on work productivity. (Ad 3) The question can be narrowed into a simple ‘thermal preference’ question, but leaving the question open would certainly bring a new insight, e.g. with respect to human behaviour, which, in the end has a vast impact on energy consumption in buildings (Andersen, 2012). (Ad 4) Behavioural adaptation plays a significant role in buildings with and without mechanical cooling. The questions that would investigate subjects’ motivation for adaptive actions would certainly provide information beyond current knowledge.
Cognitive	Do you expect to be in pain (again)? To what extent is the pain controllable? How do you cope (mentally and behaviourally) with the pain? Do you think the pain strongly interferes with your daily activities? Are you able to distract yourself from the pain?	Do you expect to feel uncomfortable? To what extent is this sensation controllable? How do you cope (mental and behaviourally) with this thermal environment? Do you think the temperature interferes with your activities? Are you able to distract yourself from the temperature?	(Ad 1) The question deals with the issue of previous experience, ‘thermal memory’, which is mostly underestimated in current thermal comfort research ( Rohles, 2007) (see also the section of this paper entitled ‘Development of scales and related criticisms’). Questions (2) and (3) are related to the human behavioural actions as well as ‘mental adaptation’ to the given environment. The adaptive models for thermal comfort somehow suspect that adaptation is taking place not only in behavioural, but also in mental domain (de Dear et al., 1997), however the details of the latter still remain unexplained. Questions (4) and (5) are important for the evaluation of the relationship between thermal environments and work productivity or, if we consider residential environments, human well-being.

Figure 1. Distribution of the operative temperatures for different votes. The violins show the shape of the distribution. The black dots show the mean values. The lines indicate the fit of a linear regression using a linear and a quadratic component. The grey-shaded areas around the curves indicate the 95% confidence interval of the values predicted by the linear model. Note that (for better visibility of the regression slopes) the scaling of the y-axis differs between the four plots.

Table 6. Results from the multiple regression analysis for the naturally ventilated (NV) buildings.

	b	SE	t	p
(Intercept)	24.37	0.06	405.16	< 0.001
Factors
Thermal sensation vote (linear component) (tsv.l)	15.74	0.19	84.56	< 0.001
Thermal sensation vote (quadratic component) (tsv.q)	–2.85	0.16	–17.84	< 0.001
Rating type continuous binned	2.05	0.12	16.60	< 0.001
Interaction terms
tsv.l:rating type continuous binned	–12.35	0.35	–35.54	< 0.001
tsv.q:rating type continuous binned	4.68	0.34	13.65	< 0.001

Table 7. Results from the multiple regression analysis for the conditioned (heating, ventilation and air-conditioning (HVAC)) buildings.

	b	SE	t	p
(Intercept)	23.60	0.05	444.34	< 0.001
Factors
Thermal sensation vote (linear component) (tsv.l)	2.08	0.15	13.95	< 0.001
Thermal sensation vote (quadratic component) (tsv.l)	–0.95	0.15	–6.49	< 0.001
Rating type continuous binned	–0.18	0.06	–3.05	0.002
Interaction terms
tsv.l:rating type continuous binned	–0.19	0.17	–1.11	0.27
tsv.q:rating type continuous binned	1.13	0.17	6.72	< 0.001

Figure 2. Density plots illustrating distribution of operative temperature for particular categories on the thermal sensation scale; a) for data from HVAC buildings, b) for data from NV buildings.

Figure 3. Boxplots of positions of TSV labels as drawn by subjects. Major ticks on the y-axis show positions of equal distances between labels. The line indicates the fit of a linear regression using a linear and a quadratic component. The grey shaded area around the line indicates 95% confidence interval.

Figure 4. Number of times that each vote within the comfortable range was mentioned.

Figure 5. Position of verbal labels of the thermal sensation vote as drawn by the subjects. From left to right the order is from cold to hot according to the 7-point ASHRAE scale. The area of comfort as described by each subjects is shown by black dots. Subjects without any black dot did not answer this question. Subjects stating an unequally spaced scale are subjects 1 to 17, subjects 18 to 30 stated an equally spaced scale, and subject 33 did not answer this question. Each line/point on the y axis represents one subject.

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