International Symposium, Building Research and the Sustainability of the Built Environment in the Tropics, 14-15-16 October 2002, Jakarta - Indonesia Thermal comfort study of residents in Mlaten housing Semarang, Indonesia Tri Harso Karyono School of Architecture, University of Tarumanagara Jalan S Parman 1, Jakarta 11440, Indonesia Email: t_karyono@yahoo.com ABSTRACT Mlaten housing was designed as a low-cost housing complex located in the area called Mlaten. It consists of 663 houses, of which only about 25% remain in the shape they were originally initially built. The area of housing was divided into two parts: east and west blocks, by Cisadane street. A thermal comfort study was carried out between June and October 2001 to the subjects who lived in this housing complex. The study was to see if there were any comfort votes different between people lived in the original houses and those in the modified houses both inside and outside the houses. The original houses did not prove to have better thermal conditions than the modified ones. This paper discusses the whole study and analyses the thermal comfort's result in relation to the appropriateness of tropical housing design. Keywords: comfort vote, Mlaten housing, modified house, original house, thermal comfort sensation 1. INTRODUCTION In 1924, the Dutch architect, Thomas Karsten, initiated the design and building of a number of houses for the low income workers in Semarang, the capital city of the province of Central Java (Locale Techniek, 1938). The housing consisted of 663 houses, situated at about the centre area of the city, called Mlaten.
Figure 1. Location of Semarang 77 years after being built there have been significant changes in the design of the houses. Around 70% of the houses have been altered, leaving a small portion of the original houses. The reason the houses have been altered was a matter of question. However, this study did not look at the reason for the changes, but rather their implication for the thermal performance of the buildings, since the alterations will have changed their indoor climate. Figure 2 (left). Mlaten Housing in 1924: grey area indicated open spaces and green area Figure 3 (right). Housing development in 1996 (right): dark area indicated the extension of the houses. It shows a significant reduction in the open spaces and green area. (Ardiyanto, 1997) The original houses are small in size, between 18 and 24 square meters floor area, and are intended to accommodate a small family. The design of the houses had adopted Javanese vernacular architecture. This kind of housing was not common at the time since the Dutch government tended to build rather larger houses for the middle class and rich families during its colonial period in Indonesia. Figure 4 (left) and Figure 5 (right). Two typical samples of the original houses adopting the Javanese vernacular architecture.
Figure 6 (left) and Figure 7 (right). Two samples of modified houses showing typical alteration of the original forms 2. RESEARCH METHODS Preliminary visits to the area of study had been conducted prior to the actual study. The housing complex is separated into two blocks by a Cisadane street. The first block was to the east of the street, while the second block - a rather greater one - was to the west of the street. The first block, consisting of 234 houses, was selected as the area of study. The choice was based on practical reasons, firstly, the inhabitants in this block seemed to be more cooperative to participate in the study, and secondly, the houses and their surrounding environment - pathways and open spaces - were better maintained in this block. All these factors will help the researcher to conduct the study more easily. LOCATION OF STUDY Figure 8. Map of the housing complex; circled area is where the study took place
Sixty inhabitants living in 58 different houses in this block participated in the study. Subjects were selected 'accidentally' based on their willingness to be asked for their thermal comfort sensations. Comfort votes, based on the seven-point scale (ISO-7730, 1994): cold (-3), cool (-2), slightly cool (-1), neutral (0), slightly warm (+1), warm (+2) and hot (+3), were collected from subjects who lived in the selected houses. Along with the measurement of indoor thermal votes, outdoor thermal votes of subjects were also taken to see if there was any correlation between the changes in outdoor thermal environment and that of the indoors. Thermal votes were also taken to see the changes on subjects' thermal comfort sensations within a period of time, i.e. the 'present' and the 'past' time. The latter was taken on the basis of subjects' memory of the previous thermal environment they had experienced before the house was modified. The study did not measure any climatic parameters in the field, therefore, all the analysis made in this paper were based on the subjects' thermal votes only. By comparing the past and present subjects' comfort votes inside and outside the houses, analysis could be made of whether there were any thermal shifts due to the changes in the houses from the original to the modified (new) form. The terms of 'present-indoor', 'present-outdoor', 'past-indoor', 'past-outdoor' are used to indicate subjects' thermal sensations in relation to the 'time' and 'place' in which comfort votes were taken. Subjects were also asked for their ages and their length of occupation in their houses. The researcher recorded the type of the houses where the subjects lived, whether original or modified. Although subjects' sexes were recorded, no further analysis would be made regarded to this matter. 3. DATA AND ANALYSIS Amongst the 60 subjects who participated in the study, 32 subjects were living in the original houses and 28 in the modified houses. Subjects consisted of 35 females and 25 males; they were between 21 and 84 years of age. Some subjects had been living in their houses for less than five years; however, most of them had been occupying their houses for more than 5 years or even up to 20 years or more. 3.1. Subjects' thermal vote inside the original and modified houses both in the past and present conditions Table 1 shows the distribution of subjects' comfort votes 'inside' the original and modified houses for the 'past' and 'present' conditions. 'Present-indoor' votes indicates the response to thermal conditions experienced by the subjects inside the houses at the time of the study, while the 'past-indoor' votes indicated the past thermal conditions remembered by the subjects inside the houses. Table 1 shows that the present-indoor subjects' mean vote in the 'original houses' was 1.41, while the past-indoor subjects' mean vote was 0.53; the difference was about 0.88. This indicates that there was a shift in the subjects' thermal sensation from previous to present times. Subjects who occupied the original houses felt that the current indoors' thermal condition was, on average, warmer than in the past.
Table 1. Distribution of subjects' comfort votes inside the original and modified houses -3 Cold -2 Cool -1 Slightly cool 0 Neutral +1 Slightly warm +2 Warm +3 Hot Mean Original houses a. present-indoor 1 1 2 2 3 20 3 1.41 32 b. past-indoor 0 2 6 8 6 9 1 0.53 32 c. changes 0.88 Modified houses a. present-indoor 0 0 1 7 3 12 5 1.46 28 b. past-indoor 0 4 7 4 1 9 3 0.46 28 c. changes 1 Total subjects From Table 1, it can also be seen that the difference between the past-indoor subjects' mean vote and the present-indoor subjects' mean vote in the 'modified' houses showed a similar situation to that of the original houses. The present-indoor subjects' mean vote in the modified houses was 1. 46, while the past-indoor subjects' mean vote was 0.46. This figure showed a thermal shift occurred within a period of time. Subjects living in the modified houses felt that the present thermal condition was warmer than in the past. Table 1 also shows that there was a difference in the present-indoor subjects' mean vote between the original and modified houses. The present-indoor subjects' mean vote in the original houses was 0.05 lower than that in the modified houses, however, this difference was negligible and statistically insignificant at 5% level. At the time the comfort votes were taken subjects living in the original houses felt no cooler than those staying in the modified houses. This suggests that the original houses did not prove to have better thermal conditions than the modified houses. The reason subjects who lived in the modified houses felt warmer than in the past was not because of the changes in the form of their houses. Subjects who lived in the original houses felt a similar phenomenon. Both groups of subjects felt that the present indoor conditions were warmer than in the past. 3.2. Subjects' thermal vote outside the original and modified houses both in the past and present conditions Table 2 shows the distribution of subjects' comfort votes 'outside' the original and modified houses for the 'past' and 'present' conditions. The 'present-outdoor' votes indicate the present thermal conditions experienced by the subjects outside the houses at the time the study took place, and the 'past-outdoor' votes indicate the past thermal conditions remembered by the subjects outside the houses. The present-outdoor subjects' mean vote in the 'original houses' was 1.96, while the past-outdoor subjects' mean vote was 0.94. The difference was about 1.02. This figure indicated there was a shift in subjects' mean vote from previous to present times. Subjects who occupied the original
houses felt that the current outdoors' thermal condition was, on average, warmer than in the past. Table 2 Distribution of subjects' comfort votes outside the original and modified houses -3 Cold -2 Cool -1 Slightly cool 0 Neutral +1 Slightly warm +2 Warm +3 Hot Mean Original houses a. present-outdoor 0 1 0 2 3 16 10 1.96 32 b. past-outdoor 0 2 6 4 2 16 2 0.94 32 c. changes 1.02 Modified houses a. present-outdoor 0 0 0 1 3 19 5 2 28 b. past-outdoor 0 2 5 4 5 12 0 0.71 28 c. changes 1.29 Total subjects It can be seen from Table 2 that the difference between the past-outdoor subjects' mean vote and the present-outdoor subjects' mean vote in the 'modified' houses had also showed a similar situation to that of the 'original' houses. The present-outdoor subjects' mean vote in the modified houses was 2.00, while the past-outdoor subjects' mean vote was 0.71. This figure shows there was a shift in the subjects' mean vote of about 1.29 within a period of time. The subjects felt that the present outdoors' thermal condition was warmer than in the past. The present-outdoor mean vote of subjects in the original houses was 1.96 and for those in the modified houses was 2.00. The difference was 0.04; however, this was negligible and statistically insignificant at 5% level. It can also be seen from Table 2 that both groups of subjects felt cooler in the past than at present. Subjects living in the original houses gave their past-outdoor mean vote of 0.94, made it 1.02 lower than the present-outdoor mean votes. Subjects living in the modified houses gave 0.71 in their past-outdoors mean votes making it 0.68 lower than the present subjects' mean votes. Both subjects in the original and modified houses felt that the outdoors' thermal environments were changed; the current outdoors' thermal environments were warmer than that in the past. This phenomenon might have led to the shifting of subjects' mean votes inside the houses for both groups of subjects. 3.3. Correlation of the changes in subjects' thermal vote inside and outside the original houses Table 1 shows that the changes of subjects' mean votes inside the original houses from the past to present times was 0.88. Table 2 shows that the change of the mean vote of the same subjects outside the houses was 1.02. Analysing the correlation of the changes of 32 subjects' thermal votes inside these houses from the past to the present times it was found that the correlation was fairly high (r = 0.68). This figure suggests that the change in
subjects' thermal votes inside the original houses from the past to present times was related to the change of thermal environment outside the houses. Table 1 shows the changes of subjects' mean votes inside the modified houses from the past to the present was 1.00, while in Table 2 the changes of the mean vote of the same subjects outside the houses was 1.39. Analysing the correlation of the changes of 28 subjects' thermal votes inside these houses from the past to the present times, it was found that the correlation was rather lower (r = 0.56). This figure might suggest that the changes of subjects' thermal votes inside the modified houses from the past to present times, was less affected by the changes of thermal environment outside the houses. It might be concluded that the outdoors-thermal changes gave more effect to the changes of the inside thermal environment in the original houses than in the modified ones. A possible explanation for this is that the original houses were made of thinner materials, such as timbers and bamboo, while most of the modified houses were composed of rather thicker materials, such as concrete and bricks, which have better thermal characteristics than the original houses. The lower U values will keep the difference between indoor and outdoor thermal environments better. 4. CONCLUSION The original houses did not prove to have better thermal conditions than the modified houses since the subjects lived in both types of houses gave a similar mean vote. The difference in the mean votes of the two subgroups of subjects was 0.05 and statistically insignificant at 5% level. Subjects living in the modified houses feel warmer than in the past. This phenomenon was not caused by the changes in the form of the houses, because subjects living in the original houses had similar reactions. Both groups of subjects felt that the present indoor conditions were warmer than in the past. The changes of subjects' comfort votes in the original houses from the past to the present time had a higher coefficient of correlation (r = 0.68) than that of the modified houses (r = 0.56). This indicates that the outdoor thermal changes affect the indoor thermal changes more in the original houses than that in the modified ones. This may be explained perhaps, that the original houses, which mostly made by thinner materials, such as timbers and bamboo had a higher U value than that of the modified houses, which were mostly composed of rather thicker materials, such as concrete and bricks. The lower U values in the modified houses will give more difference between indoor and outdoor thermal environments than that in the original houses. The changes of outdoor thermal conditions - which might be caused by the decrease of quality of the open spaces and vegetation surrounding the housing complex - has led to changes in the indoor thermal environment of the houses. The warmer outdoor thermal environment led to increase the house thermal environment regardless whether the houses were original or modified. Reading Sources
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