ANALYSIS OF RESIDENTIAL ROOM TEMPERATURE AND OCCUPANT S THERMAL COMPLAINT IN WINTER FIELD SURVEY

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1 ANALYSIS OF RESIDENTIAL ROOM TEMPERATURE AND OCCUPANT S THERMAL COMPLAINT IN WINTER FIELD SURVEY M Kojima, T Saito Graduate School of Environmental Studies, NAGOYA University, Chikusa, Nagoya, Japan ABSTRACT To evaluate safety and comfort of residential thermal environment in winter season, field study at 13 residences and questionnaire survey for these occupants were performed around Nagoya city area in Japan. Room temperatures were measured during 14 days, also occupants mentioned thermal complaint for low room temperature and temperature difference among 7 rooms. On the purpose to reveal the relation between room temperatures and recognition of occupants for them, measured room temperatures were compared with thermal complaint. As a result, their awareness for low temperature and room temperature difference were not enough to avoid the risk of heat shock between heated rooms and non-heated rooms. There is the limitation on the accuracy of occupant's recognition for room temperature. Therefore, it is necessary to moderate the room temperature differences in order to reduce domestic thermal related accidents. INDEX TERMS Residence, Temperature difference, Thermal complaint, Occupant, Questionnaire survey INTRODUCTION Residences in Japan have become more air tightened and insulated for resent years to achieve low energy consumption for heating and cooling and to keep their indoor air quality adequate. In the winter season, residents who live on relative moderate climate area in Japan, including Nagoya city area, tend to choose the individual heating method (e.g. a room air conditioner, a gas fan heater) rather than the central system. It is easy method to adopt and apply on each room if necessary but it sometimes brings about large temperature differences between heating rooms and non-heating rooms. When occupants move from one room to another room, they may be exposed to the temperature differences. It is not only discomfort but also raises the risk of domestic thermal related accidents, for example, myocardial infarct. If occupants can recognize the temperature difference exactly, the risk will be decreased. If not, some improvement should be proposed at residential environment itself. Hunt and Gidman (1994) analysed room temperature measured for short term for each 1000 houses, also an interview was conducted on thermal comfort conditions and heating patterns. They concluded that centrally-heated houses ran 3.0 K warmer on average than non-centrally-heated houses. Oseland (1994) compared thermal sensation (TS) and predicted mean vote (PMV) for residences on winter and summer condition. The neutral temperature calculated from TS was 5 C lower than that calculated from PMV in winter and 3 C lower in summer. Tochihara et al (1983) reported thermal sensation of the elderly and the young with the step movement from winter cold condition room to heating room (or opposite way), so that the elderly showed different thermal sensation and physical response from the young. It suggests that the risk of domestic thermal related accidents for the elderly is bigger than that of the young. ASHRAE Standard 55a (1992) gave clear comfort zones for winter and summer conditions. It is so useful to evaluate indoor condition but it does not concern transient indoor condition and movement of occupants that will happen frequently in general residences. Though it has been reported for many measurements of residential room temperature, the relation between room temperature and awareness of occupants is little known. It is necessary to survey residential environment for each room continually and to compare them with recognition of occupants in order to achieve comfort condition and reduce domestic thermal related accidents in winter season. The purpose of this study is to reveal the relation between room temperature and occupant s recognition for that room temperature. RESEARCH METHODS Field study for room temperature To evaluate safety and comfort of residential thermal environment in the winter season, field study at 13 residences 787

2 and questionnaire survey for these occupants were performed around Nagoya city area in Japan. For this purpose, field studies about room temperature and humidity were carried out during two weeks in winter. Amount of calibrated data loggers were set up at living room, kitchen, bedroom, corridor, bathroom, dressing room connected to bath, lavatory, and outside for every residence. To investigate thermal stratification of the room, temperature of floor level + 50mm, +1000mm, +1500mm were recorded by 5minutes interval. In this study, temperature of floor level +1000mm was regarded as the room representative temperature. Table1 shows the profiles of investigated 13 residences. Due to restrict about experimental equipment, 13 residences were divided into two groups. They were chosen in order to cover various residential conditions. Occupants of those residences were instructed to live as well as ordinary times through the measurement period. Table 1. Profiles of investigated 13 residences Group structure apartment/detached past year from construct total floor area (m 2 ) n.of occupants Group1 ( ) wooden detached wooden detached RC apartment RC apartment C, 62%RH * wooden detached outdoor condition RC apartment averaged for 14 days wooden detached RC apartment Group2 ( ) wooden detached unknown wooden detached C, 63%RH * wooden detached unknown outdoor condition Steel detached averaged for 14 days RC detached * based on data of Nagoya weather station Questionnaire survey Questionnaire surveys for these occupants were carried out mainly on thermal comfort for each room temperature. Numbers of occupants on each residence were varied from 1 to 5 persons. At first, occupants were requested to answer how they satisfied with room temperature for above 7 rooms. Occupants expressed them by choosing words from Satisfied Neither satisfied nor unsatisfied slightly unsatisfied unsatisfied. Then, occupants mentioned thermal discomfort caused by room temperature difference when they moved from one room to another room, if there were any discomfort. This movement was defined as direct movement, except for the movement via other room. All occupants who could answer the questions participated in this questionnaire survey. They answered based on actual life at their own residences. After answering, 34 questionnaires were obtained. RESULTS Room temperature and temperature difference Figure 1 shows 5 kinds of analysed room temperature for each room. The ave. temp is average temperature during survey period of 14 days. The daily max. temp and daily min. temp are mean of daily maximum/minimum temperature for 14 days. The morning time temp and evening time temp are mean of 14 days of the average temperature for particular 6 hours, 6:00-12:00 and 18:00-24:00. Except for kitchen, ave. temp is higher than morning time temp, further evening time temp is higher than ave. temp. Occupant s satisfaction with room temperature of living room and kitchen is larger than that of the others. Although bedroom is regarded as one of important rooms for long stay of occupants, occupants complaint about its room temperature as well as corridor, lavatory, dressing room, and bathroom. Due to little adoption heating into corridor and lavatory, the ranges of temperature fluctuation of these rooms are small. Bathing action of occupant raised up daily maximum temperature of bathroom and next dressing room in an instant. Figure 2 shows cumulative distribution of temperature difference among 7 rooms for 13 residences, 14 days. As 21 temperature differences exist among 7 rooms at the same time for each residence, the largest one of them was chosen to be defined as the temperature difference at some point. Occupants may be exposed to this temperature difference when they make a step movement from one room to another room. The largest temperature difference typically arised between two groups, the high temperature group consist of living room and kitchen, and the low temperature group consist of corridor and lavatory. Over 1(K) of temperature difference was observed for 8hrs somewhere in the residence. Figure 3 shows when daily maximum temperature difference occurs through 24 hrs. There are two peaks, larger 788

3 one happened at morning time and the other happened at evening time. Most of daily minimum room temperature was observed at lavatory at morning time, on the other hand, daily maximum room temperature was frequently observed at living room or kitchen at the same period. Therefore, these two situations formed most of daily maximum temperature difference at morning time. Room temperature ( C) 25.0 Thermal complaint for room temperature satisfied living kitchen bedroom corridor lavatory dressing bathroom ave. temp daily max. temp daily mini. temp morning time temp evening time temp Thermal complaint Figure 1. Room temperature (mean of 13 residence, 14 days) unsatisfied (hrs./day) ~ 4.0~ 6.0~ 8.0~ 1~ 12.0~ 14.0~ 16.0~ 18.0~ 2~ Temperature difference among rooms (K) Figure 2. Cumulative distribution of temperature difference among rooms observed frequency :00 6:00 12:00 18:00 daily min. temp daily max. temp daily max. temp difference Figure 3. Observed time of daily maximum temperature difference (13 residence, 14 days) 789

4 ( C) average temp. ( C) daily maximum temp. ( C) daily minimum temp R=-0.44 R=-0.46 R= ( C) Figure 4 Figure 5 Figure 6 morning time temp. R=-0.44 ( C) evening time temp. R=-0.52 Complain vote for room temperature 1: satisfied 2: not either 3: slightly unsatisfied 4: unsatisfied Figure 7 Figure 8 Figure 4-8. Relation between room temperature and thermal complaint vote Thermal complaint for room temperature Figure 4-8 is a scatter plot of room temperature and thermal complaint vote of occupants for it. In this figure, a kind of marker indicates plots of each 7 rooms at one residence, so 13 kinds of markers exist on this figure for 13 residences. Every room temperature is an average of 14 days. Satisfaction of occupant for room temperature is directly proportional to measured room temperature. Correlation coefficients are varied from 0.52 to 0.33, low room temperature causes more thermal complaint obviously. As measured room temperature dropped, thermal complaint of occupants increased. Although occupants seem to be able to recognize room temperature correctly, recognition for daily minimum temp is the lowest (-0.33) among them. That is, thermal complaint of occupants corresponds to the average room temperature rather than the daily minimum room temperature. To Kitchen Corridor Dressing room Living Bedroom Lavatory Living 67% Kitchen From Bedroom Corridor Lavatory Dressing room Bathroom Figure 9. Thermal complaint for step movement 790

5 Figure 9 is a babble chart of occupant s thermal complaint for step movement from a room to another room. The size of a babble means degree of complaint rate. Occupants move from the room on left side of figure, then arrive at the room on upper side of figure. 67% of occupants mentioned complaint at the situation when they would move from living room to dressing room. As shown in Figure 1, there is a large temperature difference between these two rooms. Thermal complaint for step movement tends to be large between heated rooms and non-heated rooms. DISCUSSION There is a high risk of domestic thermal related accidents in winter season on time period when room temperature differences escalate. When occupants move from a heated room to non-heated room, they will be exposed by large temperature differences. As shown in figure 3, room temperature differences escalated at morning time and evening time. It agrees with the fact that domestic thermal related accidents from the statistical data observed frequently at morning and evening. And yet, room temperature difference is nothing but one of many factors that cause domestic thermal related accidents, because they are deeply concerned with particular human actions, ex. bathing, undressing cloths, excretion. Especially, it seems that large thermal complaint for step movement to dressing room contain cold discomfort by undressing their cloths. As most of domestic thermal related accidents occur at bathroom and lavatory in the early morning and evening, large room temperature difference tend to occur between these two rooms and the other rooms. In order to reduce domestic thermal related accidents, occupants should know their environment of room temperatures correctly. However, occupants are not sensitive to daily minimum temperature and large room temperature differences. In figure 4-8, correlation coefficient for daily minimum temperature was the lowest. Although daily largest room temperature difference occurred between high temperature group (living and kitchen) and low temperature group (lavatory and corridor) as seen in figure 1, the highest reply rate of thermal discomfort (67%) in figure 9 was observed in the case that occupant moved from living to dressing room connected to bathroom. From the viewpoint of preventing thermal accidents caused by temperature difference, it should be thought that occupants may underestimate the risk of these accidents because the risk will increase in the morning and evening period, when larger temperature difference exist among rooms in a day. There is the limitation on the accuracy of occupant's recognition for room temperature, therefore, the method to moderate the difference of room temperatures at residence should be necessary. CONCLUSION AND IMPLICATIONS As compared the measured room temperature with the occupant's complaint for the room temperature for 13 residences in winter season, more discomfort was apparently mentioned to the lower room temperature. It seems that the occupant's thermal discomfort is more related to the daily average room temperature would rather than to the daily minimum room temperature or to the average room temperature in the particular period of a day. Temperature differences among rooms increased at the period of early morning and late evening. Since occupants may underestimate these large temperature differences, they should be alleviated in order to decrease the risk of domestic thermal related accidents. ACKNOWLEDGEMENTS This study was supported by TOHO Gas Co.,Ltd. and TOYOAKI Scholarship Foundation. REFERENCES Hunt DRG. and Gidman MI A national field survey of house temperatures, Building and Environment, Volume 17, Issue 2, 1982, Pages Oseland NA A comparison of the predicted and reported thermal sensation vote in homes during winter and summer, Energy and Buildings, Volume 21, Issue 1, ARTICLE1994, Pages ASHRAE ANSI/ASHRAE Standard , Comfort Zones, Atlanta: American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. Tochihara Y., Ohnaka T., Nagai Y., Tokuda T. and Kawashima Y Physiological Response and Thermal Sensations of the Elderly in Cold and Hot Environments, Journal of Thermal Biology, The Institute of Public Health, Yokohama, Japan, pages