Idea Transcript
日本建築学会技術報告集 第 19 巻 第 41 号,219-224,2013 年 2 月 AIJ J. Technol. Des. Vol. 19, No.41, 219-224, Feb., 2013
FIELD MEASUREMENT ON THERMAL COMFORT IN TRADITIONAL MALAY FIELD MEASUREMENT ON THERMAL HOUSES
伝統的マレーハウスにおける熱 的快適性に関する実測
Doris Hooi Chyee TOEー ーー
ドリス フーイ チー トー——— * 1
COMFORT IN TRADITIONAL MALAY HOUSES * 1
Tetsu KUBOTAーーー
*2
Doris Hooi Chyee TOE * Tetsu KUBOTA * Keywords: Vernacular architecture, Thermal comfort, Natural ventilation, HotKeywords: humid climate, MalaysiaThermal comfort, Natural ventilation, Hot-humid Vernacular architecture, climate, Malaysia キーワード : キーワード: ヴァナキュラー建築,熱的快適性,自然換気,高温多湿気候, ヴァナキュラー建築,熱的快適性,自然換気,高温多湿気候マレーシア マレーシア 1. Introduction
伝統的マレーハウスにおける熱 的快適性に関する実測 久保田 徹— ——* 2
ドリス フーイ チー トーstudy isto久保田 徹 thermal comfort levels The main purpose of this evaluate in traditional Malay houses based on a field measurement, with an The main purpose of this study is to evaluate thermal comfort levels in interest to apply its traditional passive cooling techniques to modern traditional Malay houses based on a field measurement, with an interest houses results reveal that indoor air temperatures to applyinitsMalaysia. traditionalThe passive cooling techniques to modern houses in are 1-2°C The higher thanreveal the corresponding outdoor air temperatures Malaysia. results that indoor air temperatures are 1-2°C throughout except for outdoor a few morning hours around 9 a.m. Air higher thanthe theday corresponding air temperatures throughout the movement obtained by open hours windows or ceiling required obtained to lower day except for a few morning around 9 a.m. fan Air is movement by open windows or ceiling fan is required lower the control SET* and the SET* and improve thermal comfort. to Solar heat andimprove a cool thermal comfort. Solar and a cool microclimate might be two microclimate might beheat two control fundamental traditional cooling techniques fundamental traditional cooling techniques for these lightweight houses. for these lightweight houses.
levels in traditional Malay houses, with an interest to gain insight into its
Energy-saving is a major interest in the building sector worldwide
traditional passive cooling techniques for application to modern houses in
today. In terms of passive design in order to reduce cooling and/or heating
Malaysia. It is worth to note that about 85% of the present Malaysian
energy, many recent researchers are looking into traditionally-existent
houses in urban areas use brick as their outer walls10), which may be
techniques embedded in vernacular architecture to find potential solutions.
difficult to be cooled without using mechanical means at night. The
This is because it is generally believed that vernacular architecture has
evaluation is made based on a field measurement conducted in two
already withstood time and more importantly, is developed as responses to
selected traditional Malay houses in Pontian, Malaysia.
experience of conditions and use1) including the local climate and people’s comfort needs. These recent studies are spread over various climatic
2. Methods
regions including the tropics2-4) and moderate climate zones5-7).
A field measurement was conducted in two selected traditional Malay
The traditional Malay house is one of the fine examples of Malaysian
houses (House 1 and House 2) in Pontian, Malaysia consecutively from
vernacular architecture8). Many of its thermal qualities are written in
March to April 2011 (Fig. 1). Pontian is located about 40km to the west of
1)
9)
socio-cultural texts describing the following features :
the city of Johor Bahru in Peninsular Malaysia. Pontian, like most
(1) raised on stilts lightweight construction (with open under floor space)
Malaysian towns and villages, experiences year-round hot and humid climate with high rainfall (see Appendix A). Both houses share the typical
using low thermal conductivity materials (timber, thatch, etc.); (2) having full-height operable windows, upper ventilation grilles and
Malaysian rural village setting with many trees in their surroundings. Both selected houses, which are considered typical traditional Malay
minimal partitions for adequate cross ventilation; (3) having large roof eaves and low walls to control direct solar radiation
houses, have timber structure elevated more than 1m above the ground for the front part of the houses (front living hall and all bedrooms). The rear
and protect against rain; and the
part of both houses is of brick-and-timber structure on the ground (rear
However, indoor thermal conditions of traditional Malay houses have not
zinc. As noted, traditional Malay houses used to apply thatch roof made
been studied in great detail yet – for example, a previous measurement in
from local palm leaves. However, thatch roof is gradually being replaced
Malay houses was not conducted whole-day2), etc.
by modern materials such as zinc for easy maintenance, etc. Both Houses
(4) arranged
sparsely
with
adequate
natural
vegetation
in
surroundings for shade and a cooler microclimate.
The main purpose of the present study is to evaluate thermal comfort *1
Doctoral Student, Graduate School for International Development Doctoral Student, Graduate School for International Development and Cooperation, and Cooperation, Hiroshima University Dept. of Architecture, Faculty of Built Environment, Univ. Hiroshima Univ., Tutor, *2 Teknologi Malaysia, M.ofArch. Tutor, Department Architecture, Faculty of Built Environment, *2 Assoc. Prof., Graduate School for Development and Cooperation, Universiti Teknologi Malaysia, M.International Arch. *3Hiroshima Univ., Dr. Eng. Associate Prof., Graduate School for International Development and Cooperation, Hiroshima University, Dr. Eng. *1
living hall, dining, kitchen and bathroom) (Fig. 2). The roofing material is
1 and 2 installed ceiling in the front living halls and master bedrooms. * *1
広島大学大学院国際協力研究科博士課程 広島大学大学院国際協力研究科 博士課程/マレーシア工科大学建設環境 (〒 広島県東広島市鏡山 ) 学部 チューター ・ 修士(建築学) *マレーシア工科大学建設環境学部チューター・修士建築学 (〒 739-8529 広島県東広島市鏡山 1-5-1) *2 広島大学大学院国際協力研究科 准教授 ・ 博士(工学) *
広島大学大学院国際協力研究科准教授・博士工学
219
Windows in the two houses comprise full-height timber panel windows, half-height timber panel windows and half-height glass louver windows,
outdoor relative humidity was always above 60%. Daily global solar radiation ranged from about 4000-5900Wh/m2 on these days.
with upper ventilation openings (permanently open) above some of the
In general, it is observed that indoor air temperatures in both halls
2
followed the pattern of the outdoor air temperatures, as expected for the
and 215m2 respectively. Their household sizes are 7 persons (House 1)
lightweight timber structure with low airtightness (Fig. 3). No time lag in
and 5 persons (House 2). Both houses were occupied throughout the
terms of daily maximum and minimum air temperatures between indoors
measurement period. Household behaviour regarding room occupancy,
and outdoors is seen. Indoor air temperatures are found to be higher than
opening windows and ceiling fan usage was recorded hourly throughout
the corresponding outdoor air temperatures throughout the day except for
the measurement period.
a few morning hours around 9 a.m. (Fig. 3). Further, indoor air
windows, doors and walls. Total floor areas of Houses 1 and 2 are 133m
Measurements of physical thermal comfort parameters were taken at 1.5m height above floor in the front living halls of the two houses (Fig. 2).
temperature elevations were relatively higher under closed window conditions than open window conditions (see window usage in Fig. 4).
The floor-to-ceiling heights of the halls are 2.7m in House 1 and 2.9m in House 2. The measurement instruments used are given in Table 1. Air temperature and relative humidity were also measured in all other rooms of both houses (Table 1). A weather station (HOBO U30-NRC and HOBO Pro v2 U23-001) was placed on the grass area in front of each house to record the ambient weather conditions during respective measurements
Table 1. Description of measurement instruments. Measured variable Front living halls Air temperature and relative humidity Air speed Globe temperature
(Fig. 2). All measurements were logged automatically at 10-minute Other rooms Air temperature and relative humidity
intervals. 3. Results and Discussion
Instrument model
Accuracy
Vaisala HMP155
±0.10°C; ±1.0%RH
Innova MM0038 Type T thermocouple inside 75mm diameter black globe
±5% plus ±0.05m/s ±0.1%+0.5°C plus ±0.5°C for cold junction compensation
T&D TR-72U and HOBO U12-011
±0.3°C; ±5%RH and ±0.35°C; ±2.5%RH
(a)
3.1. Thermal Comfort in the Front Living Halls
(b)
Measurement results on fair weather days, i.e. from 23-28 March 2011 and 31 March-6 April 2011, are analysed for House 1 and House 2 respectively in this paper. Fig. 3 shows the measured air temperature and relative humidity in the front living halls with the corresponding outdoor conditions measured by the weather station during the respective periods. As shown, maximum outdoor air temperatures reached 31-33°C while
Fig. 1. Exterior view of the case study houses. (a) House 1; (b) House 2. (b)
(a)
Open shed
Zinc wall Open shed Rear porch
Brick wall
Timber wall Brick-and-timber wall
Dining Bedroom 2
Open shed
Kitchen
Neighbour’s building
Bedroom 3
Rear living Walkway
Master bedroom
Rear living hall
Bedroom Middle hall 2
Kitchen
Brick wall
hall
Brick-and-timber wall
Front living hall
Timber wall Grass
Front
Front living hall
porch
Master bedroom
Grass
Legend:
Legend:
Ceiling fan Indoor main measurement Weather station
Ceiling fan
0
4
8m
Indoor main measurement Weather station
Fig. 2. Plan of the case study houses. (a) House 1; (b) House 2.
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0
4
8m
As seen in Fig. 3a, indoor-outdoor air temperature differences in the
window conditions, ventilation to remove or cool the heated indoor air
front living hall of House 1 average 0.7°C during daytime under open
would become slower, hence indoor air temperature elevations were
window conditions and 1.9°C during night-time under closed window
relatively higher in this condition despite the presence of permanent
conditions. In House 2, the same differences in the front living hall
ventilation openings.
average 1.0°C during daytime under open window conditions and 2.0°C
It is anticipated that proper prevention of solar heat gain through walls,
during night-time under closed window conditions (Fig. 3b). (The period
window openings and roof/ceiling by shading and thermal insulation
between 8a.m. and 8p.m. is considered to be daytime while the period
would be rather important, together with natural ventilation to remove
between 8p.m. and 8a.m. is considered as night-time.)
indoor heat, to lower the indoor air temperatures to the outdoor level.
Meanwhile, it was observed that maximum indoor mean radiant
Nevertheless, indoor air temperature below the outdoors is not anticipated
temperatures at the measurement point were higher than the maximum
for these lightweight timber structures which are without thermal mass
indoor air temperatures by 0.6°C in House 1 and 1.2°C in House 2 on
effect.
average. During night-time, the indoor mean radiant temperatures were
Fig. 4 gives the indoor SET* at a metabolic rate of 1.0 met and clothing
0.2°C and 0.3°C higher than the indoor air temperatures in House 1 and
insulation of 0.3 clo, assuming seated quiet activity and the light clothing
House 2 respectively on average. The higher mean radiant temperatures
commonly worn in the tropics. As indicated in the ‘occupancy’ bar in Fig.
seen in the front living hall of House 2 reflect that the radiant heat might
4a, it seems that the front living hall of House 1 was rarely used due to
cause its slightly higher indoor air temperatures compared to House 1. The
two possible reasons: the household occupied the rear living hall mostly in
radiant heat might heat the indoor air most and caused the indoor air
the daytime, and short occupancy of less than one hour might not be
temperature elevations above the outdoors, although it is possible that
recorded. SET* was calculated using a computer code in accordance with
some heat was also stored in the building structures. Further, under closed
ASHRAE provided by Waseda University11). Comparatively, it is found
(a)
(a)
Outdoor Indoor Outdoor
36
4/4
5/4
6/4
Fig. 3. Measured indoor air temperature and relative humidity in the front living halls and corresponding outdoor conditions. (a) House 1; (b) House 2.
0:00
0:00
0:00
0:00
25/3 26/3 Date/Hour
27/3
28/3
Air temperature
SET*
32 30 28 26
Comfortable (SET*) Slightly cool (SET*)
Outdoor Indoor
31/3
1/4
2/4
3/4 Date/Hour
4/4
5/4
0:00
0:00
Outdoor
Indoor
0:00
24
0:00
0:00
0:00
0:00
0:00
0:00
3/4
24/3
Slightly warm (SET*)
34
22 24 20 22 20 18 16 2.5 2.0 1.5 1.0 0.5 0.0 Window Ceiling fan Occupancy
Date /Hour
Indoor
0:00
Temperature (°C)
(b)
Indoor
2/4
Slightly cool (SET*)
23/3
28/3
Indoor
0:00
0:00
0:00
1/4
Comfortable (SET*)
0:00
27/3
0:00
0:00
0:00
26/3
Date /Hour
Rain period
31/3
24
0:00
Solar Radiation Relative (W/m²) Humidity (%)
Outdoor
26
Air Speed Absolute (m/s) Humidity (g/kg')
Outdoor
0:00
0:00
0:00
0:00
36 34 32 30 28 26 24 100 22 90 80 70 60 1000 50 800 600 400 200 0
Air Temperature (°C)
(b)
25/3
28
0:00
Indoor
24/3
30
22 24 20 22 20 18 16 2.5 2.0 1.5 1.0 0.5 0.0 Window Ceiling fan Occupancy
Rain period
23/3
SET*
32
0:00
Outdoor
Air temperature
Slightly warm (SET*)
34
Air Speed Absolute (m/s) Humidity (g/kg')
Solar Radiation Relative (W/m²) Humidity (%)
Indoor
36
0:00
Temperature (°C)
Air Temperature (°C)
Outdoor
0:00
36 34 32 30 28 26 24 100 22 90 80 70 60 1000 50 800 600 400 200 0
6/4
Fig. 4. Indoor SET* and occupant’s behaviour in the front living halls. (a) House 1; (b) House 2. Black bar indicates opened for ‘window’, used for ‘ceiling fan’ and occupied periods for ‘occupancy’. Indoor air speeds on 1-4 April in House 2 are not shown/analysed due to possible data error.
221
that indoor SET* under these activity and clothing assumptions are up to 2.1°C higher and 4.6°C lower than the corresponding indoor air temperatures in both halls (Fig. 4). These relative changes in SET* may be attributed to indoor humidity and air speed patterns, which points up the importance of evaporative heat loss for thermal comfort in hot-humid conditions. At low indoor air speed, relatively higher SET* values are seen during daytime compared to
Table 2. General perception of thermal sensation by household during the hottest period of the day for respective rooms (on ASHRAE Scale). See room legend in Fig. 5. House 1 Room MB FL M B2 K RL Thermal sensation No data +1 +1 No data +2 +3 House 2 Room MB FL RL K W B2 D B3 Thermal sensation +2 +2 +3 +3 +2 +2.5 +3 +2.5 (a) Air Temperature (°C)
night-time most likely due to the higher indoor absolute humidity of about 20-23g/kg’ during daytime (Fig. 4). Needless to say, higher clothing insulation and/or activity level would increase the SET* values. Conversely, increased air speeds, obtained either through open windows and/or ceiling fan, lower the corresponding SET* substantially (Fig. 4). It
(b) Air Temperature (°C)
resultant SET* are 2.5°C lower than the corresponding indoor air temperatures at this air speed (Fig. 4b). Cross ventilation in the front living hall of House 2 might be better than that of House 1 probably due to having more windows on several different sides (see Fig. 2). Due to the above importance of evaporation, thermal comfort is evaluated using SET* in Fig. 4. The comfort ranges for SET* provided in the peak afternoon period mostly exceed 30.0°C, which is ‘warm, because indoor air temperatures were basically high (Fig. 4). When ceiling fan was used in the daytime indoor SET* are lowered to the ‘slightly warm’ zone, i.e. 25.6-30.0°C, by the increased air speeds as observed on 26 March in House 1. Further, when ceiling fan was used at night as seen
34 32 30
28 26
WS
MB
FL M B2 Measurement Location
40
K
RL
38 36
34 32 30
28 26 24
22
are indicated in the figure. It is seen that indoor SET* during
uncomfortable and unacceptable’, even under open window conditions
36
22
living hall of House 2 through open windows during daytime and the
Parsons
38
24
is observed that indoor air speeds up to 0.56m/s were obtained in the front
12)
40
WS
MB
FL
RL K W B2 Measurement Location
D
B3
Fig. 5. Statistical summary (maximum, mean, minimum and ± one standard deviation) of measured air temperatures. (a) House 1; (b) House 2. WS: weather station, MB: master bedroom, FL: front living hall, M: middle hall, B2: bedroom 2, K: kitchen, RL: rear living hall, W: walkway, D: dining, B3: bedroom 3. (a)
on 26-27 March in House 1, indoor SET* are lowered to the ‘comfortable’ zone, i.e. 22.2-25.6°C (Fig. 4a). (‘Slightly cool’ zone is given between 17.5-22.2°C SET* in Parsons12).) This means that ceiling fan may be required to improve indoor thermal comfort. It is noted that occupants of House 2 also used another ceiling fan further from the air velocity measurement point in the front living hall whose usage is shown in grey in Fig. 4b. In fact, it was found from interview that the households generally perceive their thermal sensation in the front living halls as +1 (slightly warm) and +2 (warm) on the ASHRAE Scale on afternoons of fair
(b)
weather days (see Table 2), though they perceive it to be from 0 (neutral) to -2 (cool) from the evening until early morning. 3.2. Thermal Environment Variations in Whole House Fig. 5 illustrates a statistical summary of the measured indoor air temperatures in each room of both houses. Average daily maximum, mean, minimum and plus minus one standard deviation during the above measurement days are shown. Similar to the two front living halls, it is observed that all descriptive statistical values for all rooms are higher than
Fig. 6. Fisheye photos through open windows in the front living halls with hourly sun paths. (a) House 1; (b) House 2.
those of the respective weather station measurements. This implies that
with the lowest daily maximum, mean and minimum air temperatures (Fig.
the whole houses are generally warmer than the outdoor conditions during
5). It is considered that both front living halls also have relatively better
both daytime and night-time. Nevertheless, indoor air temperatures are
thermal comfort in the whole house. As compared in Table 2, both
largely varied among the different rooms particularly in terms of the daily
households perceive their front living halls to be less hot than most other
maxima (Fig. 5). Both front living halls are found to be among the rooms
rooms during the hottest period of the day.
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(a)
36
Indoor Air Temperature (℃)
indoor air temperature elevations above the outdoor is solar radiation heat gain through the building envelope. The room orientation and dissimilarity in the solar control and thermal performance of any part of this envelope among the rooms may thus contribute to the indoor air temperature variations. For example, the slightly higher daily minimum air temperatures in the kitchen of House 1 and dining of House 2 might be due to the effect of thermal mass as these parts of the houses have some
Indoor Air Temperature (℃)
radiation was provided by roof overhang from around noon until 4p.m. and by trees at low solar altitude on these windows (Fig. 6). It is to be noted that the shading would also reduce solar heat received on opaque walls. Moreover, though not analysed quantitatively in the present paper, it is
in two selected adjacent terraced houses in the city of Johor Bahru from June to August 2007 to examine the effects of various ventilation strategies13). Terraced houses are considered to be the most common type of modern urban houses in Malaysia10). They are constructed of brick and
34
36
July 2007
34
Daytime ventilation: y = 0.32x + 21.4 R² = 0.73, p