Home > Vol. 16, No. 5
| [ Research Articles ] | |
| Journal of the Korea Institute of Ecological Architecture and Environment - Vol. 16, No. 5, pp. 29-37 | |
| ISSN: 2288-968X (Print) 2288-9698 (Online) | |
| Print publication date Oct 2016 | |
| Received 28 Sep 2016 Revised 14 Oct 2016 Accepted 19 Oct 2016 | |
| DOI: https://doi.org/10.12813/kieae.2016.16.5.029 | |
| Indoor Neutral Temperature Range using Temperature and Humidity Perception Assessment | |
Yang, Wonyoung*
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| *Dept. of Architectural Engineering, Dankook Univ, South Korea (wyang@dankook.ac.kr) | |
©Copyright Korea Institute of Ecological Architecture and Environment | |
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Funding Information ▼ | |
Indoor thermal comfort can be identified by combination of temperature, humidity, and air flow, etc. However, most thermal indexes in regard to thermal comfort are temperature dominant since it has been considered as a significant factor affecting to indoor thermal comfort The purposes of this study are to investigate indoor neutral temperature range of young Koreans with humidity perception, and to introduce a neutral temperature for temperature preference as well as temperature sensation in order to define the neutral temperature range chosen by occupants. It could be used as basic data for heating and cooling.
26 research participants volunteered in 7 thermal conditions (18℃ RH 30%, 18℃ RH 60%, 24℃ RH 30%, 24℃ RH 40%, 24℃ RH 60%, 30℃ RH 30%, 30℃ RH 60%) and completed subjective assessment in regard to temperature/humidity sensation and preference twice per condition in an indoor environmental chamber.
In RH 30%, sensation neutral temperature was 25.1℃ for men and 27.0℃ for women, and preference neutral temperature was 25.5℃ for men and 27.8℃ for women. In RH 60%, sensation neutral temperature was 23.6℃ for men and 25.9℃ for women, and preference neutral temperature was 23.4℃ for men and 26.3℃ for women. Neutral temperature increased with increasing relative humidity. Women were sensitive to humidity changes. Men expressed humidity changes as temperature variations. In most conditions, preference neutral temperatures were higher than sensation neutral temperatures, however, the preference neutral temperature for men in humid condition was lower than the sensation neutral temperature.
| Keywords: Indoor thermal comfort, Indoor neutral temperature, Thermal sensation vote, Temperature preference 키워드: 실내온열쾌적, 실내중성점온도, 응답온열감, 온도선호도 |
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The issues concerning thermal environment and quality of air were caused since most of the population in urban areas spend longer time indoors, and various researches are actively under progress to solve theses problems. Since the range of indoor thermal comfort reflects individual differences, periodical, cultural and economical characteristics,1) it is a critical element to comprehend the characteristics of occupant group to control the heating and cooling system in efficient and thermal comfort.
Researches in regard to indoor neutral temperature have been accompanied with the studies of the indoor thermal comfort range, however, researches on the indoor neutral temperature depending on the diverse change of factors such as temperature, humidity and the speed of airflow which mainly determine the indoor thermal comfort have not yet been actively conducted.
Therefore this study is to analyze the correlations between temperature and humidity by performing a subjective assessment as a basic study for indoor thermal environment perception , and predict the man and woman‘s neutral temperature based on the experimental data. The purpose of the study is to propose new neutral temperature ranges which can be used efficiently for the target temperature of the future air conditioning and heating system after evaluating indoor neutral temperature of the thermal sensation and preference respectively.
The standard of the regional indoor thermal environment is established to suit each country‘s nature based on the thermal comfort zone proposed by ASHRAE.2) To assess thermal environment, parameters such as thermal sensation, thermal comfort, thermal discomfort, thermal satisfaction, thermal dissatisfaction and thermoneutrality are in use. These various standardized parameters may lead to difficulties in comparing results directly due to the psychological meaning differences which may be implied by each word, however, have the common aim to discover the optimized indoor thermal environment for occupants. The “Comfort” or “Satisfaction” is defined as an inclusive expression inferred from the occupant’s temperature and humidity perception, not as the direct evaluation by the occupants.
This study sets the temperature and humidity as parameters among physical environments (temperature, humidity, airflow, radiation temperature) and control clothing from physiological factors (electrocardiogram, brainwave, clothing, metabolic rate). Parameters used in this study are “Thermal sensation” such as ‘cold’ or ‘hot’ at the perceptual stage, and “Thermal preference” such as ‘want to increase temperature/humidity’ or ‘reduce temperature/humidity’. The preference is the concept used in Pellerin and Candas’s3) experiment, means the degree of willingness to change the current environment conditions, and the difference between thermal sensation and thermal preference can be considered comfort range chosen by occupants. This study plans to assess only the thermal environment by evaluating thermal sensation and preference at the same time as well as excluding subjective parameters such as “Pleasant” or “Satisfaction” which are likely to contain other senses besides thermal sensation. Based on the subjective thermal sensation and preference assessed by participants in the indoor experimental chamber, the neutral temperature of not being cold nor hot, and neutral humidity of not being dry nor humid and the neutral point of thermal preference are statistically predicted.
This study supports the hypothesis that the thermal comfort is affected by genders and geographical factors, and analyzes the standard of ASHRAE4) established with the research results executed in the West, and the researches on the gender difference regarding thermal comfort studied in Asia and Korea.
Study on the indoor thermal comfort was based on the thermal comfort model proposed by Fanger.5) From the experiment performed using 128 male and female college students with 0.5 clo(50 Kcal/hr·m2), the comfort range was 27℃ ~ 30℃ in sedentary work, and if they were doing active work (150 Kcal/hr·m2) with the same clothing , the comfort range was reduced to 14℃ ~20℃ Also, it determined that the thermal comfort had no relations with age, gender and geographical differences through repeated experiments using 128 people of average age 68. de Dear et al.6) and Tanabe and Kimura7) also reported that the difference was not meaningful comparing the data between Singapore, Japan and Denmark.
However, some series of research results conducted in an actual residential building, not in the experimental chamber limited with external environmental changes, the thermal comfort range varied in external thermal environmental changes.8) The adaptive comfort model was applied for the first time in ASHRAE Standard 55-2004.9)
ASHRAE Standard 5510) defines the thermal comfort range by operative temperature, humidity and the speed of airflow. Although the comfort range changes according to the amount of clothing, it suggests to keep the indoor temperature 21℃ ~ 28℃ and the humidity under the absolute humidity 0.012 kg/kg considering typical clothing for summer and winter (0.5 clo and 1.0 clo).
Karyono11) conducted a survey on 596 Indonesian office occupants, and the regression results (93% occupants with 0.6 clo) inferred that the neutral temperature was 26.7℃. This result was 1.2℃ higher than the PMV model12) showing that the Indonesian preferred higher temperature. Maiti13) reported that the comfort range (seated, 0.47 clo) was 23.25℃ ~ 26.32℃, and the neutral temperature was 24.83℃ from the experiment conducted over 40 Indian male college students. And, from the study of 113 male and female adults in Hyderabad, India by Indraganti and Rao14) showed that gender and home ownership on the thermal comfort have weak relations, however, the economic strength shows a strong relation to the thermal comfort. The lowest economic group showed that the neutral temperature as 30.2℃, comfort range to 27.3℃ ~ 33. 1℃,which were considerably higher than 23℃ ~ 26℃ of the national standard of India. Kimura et al.15) reported that Japanese group had less sweat rate than American group from the experiment of 172 male and female college students.
Nakano et al.16) study also reported that Japanese women group (25.2℃) showed 3.1℃ difference on the neutral temperature from the non-Japanese male group (22.1℃). However, the accurate data on the foreign group‘s ethnicity were not presented. Chan et al.17) reported the temperature preference as 22.5℃ (average 0.58 clo in summer, 0.86 clo in winter) from the survey on 2,173 occupants of 13 buildings in Hongkong. Wang18) reported the neutral temperature for men was 20.9℃(Average 1.33 clo), and 21.9℃ for women (Average 1.42 clo) from the survey and indoor environment measurement on 120 adult men and women from 66 households.
It had been known that there is minimal or insignificant difference in gender regarding the perception and cognition of thermal environment from initial studies19), however, it has been revealed that gender has meaningful differences.20) From the large scale of consideration and research over the thermal comfort sensation difference in gender, Karjalainen 21) analyzed that more than half of the literacy represent women were unsatisfactory than men.
The women‘s unsatisfactory rate over the thermal comfort appeared 1.74 times (95% confidence interval 1.61-1.89) than men. Especially they were studied unsatisfactory in lower temperature. The study on the thermal comfort in 100 units of male and female teens by Katafygiotour and Serghidesn22) reported that female students were more sensitive to low temperature in winter and male students were more sensitive to hot temperature in summer. It was analyzed that it resulted from the metabolic difference and characteristics of skin area between men and women. Wang23) revealed that even though women wore more clothing (Average1.42 clo) than men (Average 1.33), the neutral temperature was 1℃ higher as 21.9℃ for women and 20.9℃ for men from the thermal comfort study in Harbin’s residential space on 120 adult males and females.
The results from Lan et al.24) showed that women‘s neutral temperature was 26.3℃ which is 1℃ than men’s. This study showed no neutral temperature difference between men and women. Karjalainen25) found big gender differences in regard thermal dissatisfaction particularly in Finish office buildings. Women felt colder in low temperature, and hotter in high temperature than men does in replay. From the Hwang‘s research targeted on Taiwanese university classroom,26) the neutral temperature and the temperature preference have no difference between men and women, however, women’s neutral temperature turned out to have narrow range. According to the overseas precedent studies, there were gender differences in thermal comfort, and the differences became larger in low temperature, however, a clear conclusion has not been made for the gender difference in high temperature.
It has been investigated that the thermal comfort in Korea is similar to the result of overseas precedent studies. From the early study on the Korean thermal sensation performed by Bae at al.,27) the neutral temperature (Standard new effective temperature) was 24.3℃ for men, and 26.1℃ for women which was 1.8℃ higher than men. The thermal comfort range was 22.3℃ ~26.3℃ for men and 25.1℃ ~ 27℃ for women, which meant women‘s was 0.7℃ ~ 2.8℃ higher than men’s, and showed particularly higher temperature limit for the thermal comfort. This study was conducted on the 213 occupants of office building in the summer season with a verage 0.51 clo.
The study performed in the winter season by Bae at al.28) reported that the men‘s neutral temperature was 20.2℃ and women’s was 21.6℃ . The study conducted by Kim et al.29) on the indoor thermal comfort in the winter time with 0.9 clo showed that the neutral temperature (Standard new effective temperature) for both men and women was same as 24.8℃, however, women responded cold when it was below the neutral temperature and hot when it was over the neutral temperature.
From the study of the indoor thermal comfort on the male and female college students with 0.42 clo in summer by Shin and Jeong,30) the indoor comfort temperature was 5.7℃ for women and 24.9℃ for men, in which women showed about 0.8℃ higher temperature. From the study conducted by the same researchers on the indoor comfort temperature in winter,31) it said 22.3℃ for men and 23.4℃ for women in regard to thermal comfort in the heating condition of winter season with 0.7 clo, in which women demonstrated 1.1℃ higher temperature. The authors speculated that women used insulating type of thermoregulatory system, while men used a metabolism type of thermoregulatory system, however, it has not been confirmed whether the thermal sensation difference comes from the gender or the difference of body composition.
From the studies of Bae et al.32) and Shim and Jeong,33) the Korean neutral temperature in summer was about 24.3℃ ~ 24.9℃ for man and 24.8℃ ~ 26.1℃ for women. In case of men, 0.6℃ difference meant the margin of error fell in the temperature sensation threshold34) and the results were in common both with field and experimental research. However, women showed wider range of deviation than man. Both studies of Shim and Jeong35) (n=14) and Kim et al.36) (n=8) in winter time applied experimental methods, but the study of Shim and Jeong37) showed lower temperature difference of 2.5℃ for men and 1.4 ℃ for women, respectively. This seemed to be resulted from the limitation caused by relatively small number of participants. The neutral temperature collected from the field research38) targeted on office buildings in winter and the experimental research39) in a chamber showed the maximum difference up to 5.3℃ concerning youth population, and this was a larger gap than the one of the study conducted in summer. However, it would commit an error if the difference is considered as simply field research against experimental research. To draw a clearer conclusion, it is required to conduct studies on multipurpose building groups and the subdivided occupant groups
Therefore, this study is to find the neutral temperature of the university students in their 20‘s ~ 30’s to pursuit of the comfort in the office environment, and reveal the impact of the humidity changes to the neutral temperature. Most of previous studies have not yet performed a detailed analysis on the impact of the humidity changes over the neutral temperature. Since the temperature and humidity are the significant factor affecting the thermal environment perception, the thermal sensation study over the relations between temperature and humidity should be taken into account thoroughly. This could be used as a ground to improve energy efficiency of air condition and heating system in buildings as well as increase thermal comfort of the occupants.
Comparisons of neutral temperature for Korean
| Year | Authors | Neutral Temperature ℃ | Humidity | clo | m/s | Type | ||
|---|---|---|---|---|---|---|---|---|
| M | W | Index | ||||||
| 1989 | Kong et al.40) | 21.0 21.1 |
ET CET |
various | 0.9 | - | Field | |
| 1995 | Bae et al.41) | 24.3 | 26.1 | SET* | RH 50% | 0.51 | 0.1 | Field |
| 1995 | Bae et al.42) | 20.2 | 21.6 | ET* | RH 50% | 1.24 | Field | |
| 1998 | Park et al.43) | 25.2 | - | SET* | various | 0.93 | 0.1 | Lab |
| 1998 | Kum et al.44) | 25.5 (M 0.7clo W 1.0clo) |
SET* | various | 0.7 1.0 |
0.1 | Lab | |
| 1998 | Kum et al.45) | 26.0 (0.36 clo) |
26.9 (0.51 clo) |
SET* | various | 0.36 0.51 |
0.1 | Lab |
| 2007 | Kim et al.46) | 24.8 | 24.8 | SET* | RH 50% | 0.9 | 0.1 | Lab |
| 2011 | Shim & Jeong 47) | 24.9 | 25.7 | Ta | 0.01114 kg/kg | 0.42 | - | Lab |
| 2011 | Shim & Jeong 48) | 22.3 | 23.4 | Ta | 0.0093 kg/kg | 0.7 | - | Lab |
| 2016 | presented paper | 23.6 | 25.9 | Ta | RH 60% | 0.73 | 0.1 | Lab |
| 25.1 | 27.0 | Ta | RH 30% | 0.73 | 0.1 | Lab | ||
The subjective thermal sensation assessment was implemented in the environmental chamber located in the Comprehensive Laboratory building of the Dankook University (Fig.1). The indoor environmental chamber has an area of 20 m2 and volume of 48 m3 (4m x 5m x 2.4 m), and the facilities and building composition is listed in Table 2. The conditions of the chamber such as 880 lux of the table surface, 0.1 m/s of indoor airflow and 45 dBA of indoor background noise were maintained. The indoor temperature and humidity were measured at the same time from the 1.2 m height from the floor where the participant‘s 4 seats are (Sato SK-L200TH) and the middle of the wall. The error in the measurement caused by the seat location and mount of the wall was confirmed in the margin of error (±0.5℃) by the specification of the instrument from the center.
Fig. 1.
Exterior and interior of the indoor environmental chamber
Indoor environmental chamber configurations
| Description | |||
|---|---|---|---|
| Room | Size | 4.0 m (w) x 5.0 m (l) x 2.4 m (h) (face-of-finish to face-of-finish) |
|
| Materials | Laminate floor on concrete and urethane layers Urethane panel with gypsum lapping Double glazed window with 5 mm glass panes and 5 mm air cavity | ||
| Control System | VRF System | Rated Total Cooling Capacity | 2.3kW |
| Rated Total Heating Capacity | 2.6kW | ||
| Humidity Control | Humidifier | Max 3000cc/hr | |
| Dehumidifier | Max 30 l/day | ||
| Ventilation | Supply Air Flow Rate | 0.03 m3/s | |
| Exhaust Air Flow Rate | 0.03 m3/s | ||
The subjective thermal sensation assessment of 26 graduate and undergraduate students (13 male student s with average age of 25.5 ± 6.3 and 13 female students with average age of 25.8 ± 7.6) was conducted for the 7 different thermal conditions in the indoor environmental chamber (Table 3). In consideration of the fatigue of the participants and to secure sufficient time for indoor temperature and humidity changes, a single experiment of thermal environmental condition in a day was performed. The amount of the participant‘s clothing was retained as 0.73 clo for typical indoor jobs in spring and fall season.
Thermal conditions and variations(measured by THD-W)
| Target Temp, RH, PMV | Measured Temperature ℃ Mean (S.D) | Measured RH % Mean (S.D) |
|---|---|---|
| 18℃ 30% -2.25 18℃ 60% -2.08 |
18.5 (0.2) 18.8 (0.2) |
33.2 (5.7) 61.3 (5.0) |
| 24℃ 30% -0.43 24℃ 40% -0.30 24℃ 60% -0.13 |
24.3 (0.3) 24.2 (0.5) 24.7 (0.2) |
29.3 (4.1) 39.5 (4.9) 63.2 (2.6) |
| 30℃ 30% 1.47 30℃ 60% 1.80 |
30.0 (0.4) 29.8 (0.3) |
32.1 (0.9) 60.6 (1.2) |
Participants were allowed to do simple sedentary works for 55 minutes of thermal adaption time, and evaluated two replicate for 5 minutes using49) VAS (Visual Analog Scale) which have no zero point in regard to temperature sensation and humidity sensation, and temperature preference and humidity preference. Since participants could freely express the size of stimulus change that they felt without any fixed criteria through VAS, it was known to identify participant‘s subjective changes effectively.
The subjective questionnaire form that used for this study is like Fig.2. At the analysis stage, –5 ~ +5 value is added to VAS, and performed ANOVA and regression analysis using Minitab® 17.3.1software. The significance level for each analysis is α = 0.05.
Fig. 2.
Subjective questionnaire form(VAS 100 mm)
The distinct gender difference regarding indoor temperature appeared at 30℃ regardless humidity. At 30℃, it showed statistically significant difference both for temperature sensation and temperature preference, and women showed lower thermal sensation and higher temperature preference than man. This result is consistent with the findings of Wyon et al. that men felt hotter than women at high temperature. There was no gender difference regarding the temperature sensation and temperature preference at 24℃, but the gender difference appeared at 18℃ only with RH 60%. Change of the temperature sensation according to the humidity change didn‘t occur to women, but men perceived the humidity change as temperature change (F(1,50) = 8.68, P = 0.005). Temperature preference according to the humidity change was not discovered for women, however, men showed lower temperature preference values at 30℃ if the humidity is high. (F(1,50) = 8.14, P = 0.006). (See Fig. 2, Table 4)
Fig. 2.
Temperature sensation and preference by gender (a) RH 30% (b) RH 60% (a.u.: arbitrary unit –5 ~ +5, Cold ~ Hot, Colder ~ Warmer)
Gender difference of temperature judgment by ANOVA results (Men: N=26, Women: N=26, α=0.05)
| Temperature | 18℃ | 24℃ | 30℃ | |
|---|---|---|---|---|
| RH 30% | Temperature Sensation | F = 0.18 P = 0.669 |
F = 0.72 P = 0.4 |
F = 8.79 P = 0.005 |
| Temperature Preference | F = 0.87 P = 0.355 |
F = 2.34 P = 0.132 |
F = 4.78 P = 0.033 |
|
| RH 60% | Temperature Sensation | F = 4.52 P = 0.039 |
F = 2.77 P = 0.102 |
F = 4.18 P = 0.046 |
| Temperature Preference | F = 0.65 P = 0.423 |
F = 2.07 P = 0.157 |
F = 10.19 P = 0.002 |
|
When the humidity was low, the thermal sensation of both men and women didn‘t have difference at low temperature nor medium temperature, but showed the difference at high temperature. And when the humidity is high, the thermal sensation of men and women showed the gender difference at high and low temperature except medium temperature. Therefore, it could be concluded that women perceived temperature and humidity sensation separately in regard to the perception of thermal sensation than man.
The difference of the indoor humidity sensation between men and women became distinct at RH 30%, and if the temperature increased, the gender difference appeared even when the RH was high. At 18℃, men did not recognize the humidity change (RH 30% vs 60%), however, recognized the humidity change significantly as the temperature increases. This tendency appears in women, too. (See Fig. 3, Table 5)
Fig. 3.
Humidity sensation and preference by gender (a) 18℃ (b) 24℃ (c) 30℃ (a.u.: arbitrary unit –5 ~ +5, Dry ~ Humid, Drier ~ More humid)
Gender difference of humidity judgment by ANOVA results (Men: N=26, Women: N=26, α=0.05)
| Relative Humidity | 30% | 40% | 60% | |
|---|---|---|---|---|
| 18℃ | Humidity Sensation | F = 13.98 P = 0.000 |
- | F = 0.03 P = 0.861 |
| Humidity Preference | F = 4.06 P = 0.049 |
- | F = 0.04 P = 0.852 |
|
| 24℃ | Humidity Sensation | F = 5.34 P = 0.025 |
F = 4.89 P = 0.032 |
F = 0.41 P = 0.524 |
| Humidity Preference | F = 4.47 P = 0.04 |
F = 1.93 P = 0.17 |
F = 1.88 P = 0.176 |
|
| 30℃ | Humidity Sensation | F = 21.67 P = 0.000 |
- | F = 5.48 P = 0.023 |
| Humidity Preference | F = 2.78 P = 0.101 |
- | F = 5.45 P = 0.024 |
|
ANOVA analysis for the gender difference under the entire experimental conditions showed that women felt cold (F(1,362)=4.97, P=0.026) and dry (F(1,362)=25.65, P=0.000) than men at the same experimental conditions. Women had more sensitive humidity sensation than man in dry environment, and men did not recognize humidity change as itself but as temperature change. This was the same conclusion made by Karjalainen51) concerning the gender differences in the thermal sensation. Gender differences in humidity sensation were not widely dealt with in the previous studies though, it was different with the result of Lan et al.52) which says women was sensitive in temperature change but insensitive in humidity. However, reanalysis needs to be carried out as their regression analysis was executed without normalization of the two different units for temperature(℃) and relative humidity(%), and analyzed the humidity only with the absolute value of the coefficient of determination for temperature and humidity. Furthermore, the presented ASHRAE‘s thermal sensation scale regression equation53) as a linear model for temperature and humidity does not seem to consider the fundamental principle of psychophysics that the subjective sensation is proportional to the log value of the physical quantity.54)
This study compared the linear model with the log scale model for regression equation (Table 6). When the RH is low, the neutral point of temperature sensation for men was 25.1℃ and 27.0℃ for women, and the neutral point of temperature preference was 25. 5℃ for men and 27.8℃ for women. Under high RH, the neutral point of temperature sensation for men was 23.6℃ and 25.9℃ for women, and the neutral point of temperature preference was 23.4℃ for men and 26.2℃ for women. The neutral point of temperature sensation with consideration of the amount of clothing fell in the neutral range of previous experiments in the chamber55) (Table 1). The gender difference of the neutral point of temperature sensation was within 2℃, which was slightly higher than the 1℃ difference from the earlier studies. This seems to be due to the differences in humidity conditions. As this research was not conducted in the comfort range of humidity, but in dry condition of RH 30% or humid condition of RH 60% with a single parameter of temperature change, the gender difference on the humidity perception seems to be represented as the temperature sensation.
Regression equations for temperature sensation (ys) and preference (yp) (x=temperature, ℃)
| Log | RH | Gender | Temperature Sensation ys=a+blogx | Temperature Preference yp=a+blogx | Difference | ||||||
| a | b | R2 | x(y=0) (℃) | a | b | R2 | x(y=0) (℃) | ℃ | |||
| 30% | Men | -30.04 | 21.45 | 81.1 | 25.146 | 24.11 | -17.15 | 52.3 | 25.458 | 0.31 | |
| Women | -23.66 | 16.53 | 57 | 26.997 | 23.01 | -15.94 | 56.9 | 27.768 | 0.77 | ||
| Difference ℃ | 1.85 | 2.31 | |||||||||
| 60% | Men | -25.55 | 18.61 | 55.1 | 23.601 | 26.95 | -19.68 | 58.5 | 23.411 | -0.19 | |
| Women | -27.06 | 19.15 | 63.3 | 25.885 | 21.72 | -15.32 | 40.9 | 26.167 | 0.28 | ||
| Difference ℃ | 2.28 | 2.76 | |||||||||
| Linear | RH | Gender | Temperature Sensation y=a+bx | Temperature Preference y=a+bx | Difference | ||||||
| a | b | R2 | x(y=0) (℃) | a | b | R2 | x(y=0) (℃) | ℃ | |||
| 30% | Men | -10.18 | 0.3976 | 81.2 | 25.604 | 8.249 | -0.3184 | 52.5 | 25.908 | 0.30 | |
| Women | -8.322 | 0.3051 | 56.5 | 27.276 | 8.241 | -0.295 | 56.7 | 27.936 | 0.66 | ||
| Difference ℃ | 1.67 | 2.03 | |||||||||
| 60% | Men | -8.428 | 0.3495 | 56.6 | 24.114 | 8.846 | -0.3697 | 60.1 | 23.928 | -0.19 | |
| Women | -9.344 | 0.3560 | 63.7 | 26.247 | 7.541 | -0.24741 | 40.9 | 27.512 | 1.27 | ||
| Difference ℃ | 2.13 | 3.58 | |||||||||
| Difference ℃ (Linear-Log) | 30% | Men | 0.46 | 0.45 | |||||||
| Women | 0.28 | 0.17 | |||||||||
| 60% | Men | 0.51 | 0.52 | ||||||||
| Women | 0.36 | 1.35 | |||||||||
In most cases, the neutral point of temperature preference marked higher than the neutral point of the temperature sensation. That means temperature sensation and reaction does not occur simultaneously, and hot temperature is preferred than cold. However, in case of men, the neutral point of temperature preference was lower than the neutral point of temperature sensation in humid environment (RH 60%) by 0.19℃. It could be interpreted that men prefer cold than hot temperature.
The difference of the coefficient between the log scale model and the linear model was similar to less than the average 0.4 %, and the difference of the neutral point between temperature sensation and the temperature preference showed similar value each other.
However, the predicted absolute values of neutral point using the linear model and log scale model were different. The neutral temperature sensation predicted by the linear model turned out to be 0.4℃ higher in average than the neutral point predicted by the log scale model, and the neutral point of temperature preference was predicted 0.62 ℃ higher in average. Therefore, the linear model in regard to the thermal perception seems to have the possibility of overestimating the neutral point.
The gender differences concerning a neutral point by the log scale model was 1.85℃ in temperature sensation, 2.31℃ in temperature preference with RH 30%, and 2.28℃ in temperature sensation, 2.76℃ in temperature preference with RH 60%. The gender differences in regard to thermal perception became larger in a humid environment, and temperature preference showed greater differences than temperature sensation. Men showed bigger differences in temperature sensation according to the humidity change than women, and the timing of requesting temperature change after passing the neutral point of thermal sensation was faster than women.
The result of humidity regression was similar with the temperature as the neutral point of humid preference marked higher than the one of temperature sensation along with explicit difference between men and women, however, the result was not included in this study because it was hard to normalize it with less than 50% of the coefficient of determination (R2).
Experiments to find out the neutral point of thermal comfort by observation of interactions of the temperature and the humidity were conducted.
To eliminate the environmental or psychological factors besides the thermal sensation which can be involved when interpreting ‘Comfort’, subjective assessment for temperature and humidity sensation were evaluated only with ‘cold’ vs ‘hot’ and ‘dry’ vs ‘humid’, and temperature and humidity preference were evaluated only by ‘want to increase the temperature or humidity’ and ‘want to reduce the temperature or humidity’, respectively.
With RH 30%, the neutral point of thermal sensation was 25.1℃ for men, 27.0℃ for women, and the neutral point of temperature preference was 25.5℃ for men, 27.8℃ for women. With RH 60%, the neutral point of temperature sensation was 23.6℃ for men, 25.9℃ for women, and the neutral point of temperature preference was 23.4℃ for men, 26.2℃ for women . Conclusions for the above results is shown below.
1. Generally women evaluated the temperature as lower and the humidity as drier than men.
2. The neutral point of temperature decreased when RH increases.
3. Women were more sensitive than man in regard to humidity change, and men perceived the humidity change as temperature change.
4. In most cases, participants preferred warm temperature as the neutral point of temperature preference was higher than the one of the temperature sensation. However, men preferred cold temperature as the neutral point of temperature preference was lower than the one of the thermal sensation in humid conditions.
To improve the efficiency of air conditioning and heating, the neutral point of the temperature preference is worth noting. It is the allowable range chosen by occupants themselves and have wider range of temperature than the neutral point of sensation if it is used directly for the air conditioning and heating system. Thus, energy saving is expected to be relatively considerable when using the neutral point of temperature preference than using the neutral point of thermal sensation. Further researches regarding this new indicator of the neutral point of temperature preference seem to be required by building usage and for all ages. And more comprehensive and precise experimental studies including airflow and radiant heat which was excluded in this study is also needed.
Kong SH, Park SD and Sohn JY. Characteristics of Thermal Indoor Environment and Thermal Comfort Zone by a Synthetic Thermal Environment Index. Journal OF the Architectural Institute of Korea. 1989; 5: 159-66.
Shim HS and Jeong WS. Preferred and suggested winter indoor temperatures of college students. The Korean Journal of Community Living Science. 2011; 22: 485-91.
Park JI, Kim KH and Choung SI. A study on characteristics of thermal comfort for artificial environmental experiment in winter. Korean Journal of Air-Conditioning and Refrigeration Engineering. 1998; 10: 721-31. Kum JS, Choi KH, Kim DG, et al. Experimental Study on Thermal Comfort Sensation of Korean ( Part I : Analysis of Subjective Judgement in Winter Experiment ) Korean Journal of the science of Emotion & sensibility. 1998; 1: 199-211.
Shim HS and Jeong WS. Preferred indoor temperature of college students in summer by body composition. The Korean Journal of Community Living Science. 2011; 22: 155-61.
Shim HS and Jeong WS. Preferred and suggested winter indoor temperatures of college students. The Korean Journal of Community Living Science. 2011; 22: 485-91.
Park JI, Kim KH and Choung SI. A study on characteristics of thermal comfort for artificial environmental experiment in winter. Korean Journal of Air-Conditioning and Refrigeration Engineering. 1998; 10: 721-31.
Kum JS, Choi KH, Kim DG, et al. Experimental Study on Thermal Comfort Sensation of Korean ( Part I : Analysis of Subjective Judgement in Winter Experiment ) Korean Journal of the science of Emotion & sensibility. 1998; 1: 199-211.
Kum JS, Kim DG, Choi KH, Kim JR, Lee KH and Choi HS. Experimental study on thermal comfort sensation of Korean (Part II : Analysis of subjective judgement in summer experiment) Korean Journal of the science of Emotion & sensibility. 1998; 1: 65-73.
This research was supported through the Basic Science Research Program by the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2015R1D1A1A01057041).
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