CLIMATE CHANGE-INTERNATIONAL SYMPOSIUM, BALI 2007

DESIGN STRATEGIES FOR IMPROVING THERMAL ENVIRONMENT AT HIGH DENSITY URBAN SETTLEMENT

B. Heru Santoso¹⁾ Sri Nastiti NE ²⁾ IGN Antaryama²⁾

¹⁾ A lecturer at Architecture Department, Sebelas Maret University, Solo

PhD Student at Architecture Department FTSP-ITS Surabaya

E-mail: hersant05@yahoo.com

²⁾ A Lecturer at Architecture Department FTSP-ITS Surabaya

ABSTRACT

            High density environment is a common characteristic in urban settlement in Indonesia. Such characteristic is recognized in influencing heating the environment, which in turn causing thermal discomfort. This paper reports the study in Kampong Kemlayan Surakarta, in which passive cooling is one of the solutions to replace the active one.

The aims of the study are as follows. Firstly is to analyze in which way the heated environment influences the climate change. Secondly, the solution in architectural point of view is analyzed, how the heated environment can be minimized.

Two methods in minimizing heating problem are indicated in this study. The use of heavyweight material contributes to lower the temperature during daytime, while increasing it during night time. The potency of wind corridor can be seen in the kampong. This might contribute in improving thermal condition

Key-words:   high density urban settlement, thermal environment, hot humid tropics

1. Introduction

Climate has a strong relationship to architecture. In the past, architecture, as shown on human settlement, used climate as one of the factors for design. This can be seen on vernacular buildings and traditional buildings (Rapoport, A, 1969; Santosa, M, 2000). From the vernacular and traditional buildings, it can be understood that climate can influences to the forming of architecturally building design, mainly on the roof form, space lay-out, building material, building spacing, building opening, building orientation, building massing, open space, vegetation etc. Finally by responding to the local climate condition it will influence to the health of the building user significantly (Boutet T, 1987; Aynsley R, 1977).

On the era changing, the characteristics of environments and buildings have experienced many changing both vertically and horizontally. These changings are also supported by the progress of high technologies mainly on using artificial air conditioner system. Many people and buildings are very fully dependent on such technologies as an instant way for air conditioning devices. May be, the users of air conditioning do not realize to the effect of such devices in long term. 

Currently many people have a difficulty to obtain an ideal house, especially in developing countries, such as: Indonesia. Because of low economic level most houses at kampongs in Indonesia are very narrow, inappropriateness to the requirement of adequate building opening, building orientation, building spacing, building material choosing, adequate open space, shaded area by vegetation, building lay-out, etc. So, from thermal and ventilation point of view, the building density becomes very high. The consequences of this condition are on the environmental (outdoor) ventilation and thermal side. The environmental ventilation is not ideal to provide adequate air movement.  

The change of environmental condition will be worse by the use of glasshouse, high fuel energy consumption from vehicles, surfaces of Earth covered dominantly by asphalt or concrete. This will create environmental heating more intensely.

            The issue of climate change actually emerges since some time ago. This is initiated by the ozone layer damage. It induces global warming phenomena (figure 1). The climate change influences many aspects. One of them is the heating on the Earth surface. Heating is the main problem to solve. The increased air temperature on the Earth surface will be much hotter than the usual. The higher heating level on the Earth surface will affect to the thermal comfort on building.

2. Urban Settlement as a Climate Modifier

            It is clear that the climate change will contribute to the heating impact. In addition heating has a relationship to the building thermal comfort. In hot humid region, the common characteristic of high air temperature and air humidity in this region is a main problem in achieving natural thermal comfort. It is very important to solve. So, natural ventilation is a main device to restore the problem.

            In the past, when climate was still moderate, not so high like now, and the population density was still very low, environmental and building heating could still controlled by building design itself. The heating problem can be reduced by building design naturally, those are: by opaque thin building material, roof form and material, building spacing, building lay-out, building orientation, vegetation around building, wide building opening, etc (Salmon C, 1999:167). Cooler wind can flow well to indoor space to low the building heating.

            The condition of high density urban settlement environment commonly characterized by narrow building spacing, irregular building lay-out, limited opening placement, inadequate vegetation around building become an obstacle for airflow. It also makes solar heating penetrate directly to the ground and buildings. Air temperature in around building is predicted be able to increase higher. It induces thermal comfort on building more difficult to be achieved.

Figure 1: The Cycle of Global Warming phenomena

3. Design Strategy

            There are two strategies in improving thermal environment. They are passive and active strategy. The passive one is the strategy by using building itself to achieved thermal comfort. This strategy uses cross ventilation system, building material, open space, building orientation, vegetation etc. It can always be integrated in all climate condition (Lippsmeier, 1994).

 The other strategy is active cooling system. It uses artificial air conditioner system. In active strategy it provides not only continuous comfort for people, but also has potential in damaging the environment. It releases heat to outdoor space and affects outdoor air temperature increase. Beside that it also damages the ozone layer. On the other hand, the ozone layer is a layer protecting the earth from solar radiation effect.

4. The Study Methods

This studies including in this paper are two studies, field and literature studies.  In field studies it was conducted by direct measurement of real thermal condition on some buildings and its environment. Meanwhile literature studies were done by using the research result from other researchers. The aims of the study are as follows. Firstly is to analyze in which way the heated environment influences the climate change. Secondly is the solution in architectural point of view is analyzed, how the heated environment can be minimized.

The data are taken a case study, Kampong Kemlayan Surakarta, Central Java. Kemlayan is a kampong that is a prototype of settlement condition in Indonesia.  Kemlayan as a common Kampong is one high density urban environment in Surakarta. It consists of many kinds of low rise building which stand very close one each other. It has inadequate open spaces, narrow street house access with high wall on the two sides, limited vegetation, narrow distance of building spacing, limited building opening, irregular building lay-out, almost similar building height, etc.

Figure 2: The Map of Kemlayan Kampong                     Figure 3: Solid and Void condition

Figure 4: The Situation of Kemlayan kampong

The measurement was done on four blocks as study samples. The four blocks within the Kampong investigated in this study have different characteristic due to the lay-out of the building and the open spaces (figure 5). Measurement in those blocks conducted includes outdoor and indoor by setting the measurement devices such as: humidity and thermometer as well as anemometer. The measurement was conducted in February (the coldest month) and May to September (the hottest month).

Figure 5: Measurement points

5. Thermal Environment in the Settlement and Buildings

a. Climate condition

            Climate condition in Surakarta can be seen on the table 1. Based on the BMG Data, the coldest month is in February and the hottest month is in September and October. In the coldest month the air temperature in Surakarta is 22.1- 30.9^o C with air humidity between 84% (RH pm) and 92% (RH am). In the hottest month the air temperature is 21.7- 33.5^o C with air humidity between 61% (RH pm) and 79% (RH am). So, from those conditions, the air temperature and air humidity in Surakarta are so hot and wet.

Table 1. Surakarta’s Climate

Source: BMG PAU Adisumarmo

            From figure 6, it can be seen that in the coldest month at Kemlayan Kampong the outdoor air temperature shows 29.2^o C- 33.5^o C   (at 09.00-11.00), 30^o C- 33.8^o C (at 12.00- 14.00) and 25.9^o C- 30.6^o C (at 15.00 – 17.00). The outdoor air humidity is 60.8 %- 74.5% (at 09.00-11.00), 58.8 %- 80.5 % (at 12.00- 14.000) and 67.1 % – 90.6 (at 15.00 – 18.00) with air flow between 0.0 – 4.5 m/s (0.0-2.5 m/s in average). It means the climate condition at Kemlayan is higher than the climate condition in Surakarta commonly.

Figure 6: Measurement Result of outdoor in the coldest month

b. Thermal Condition in Buildings

From figure 7, in the coldest month, the indoor temperature commonly is around 27.0 – 30.3^o C and still lower than outdoor air temperature. From the 3 buildings observed (Building A, B and C), all buildings mostly use heavyweight materials. In the morning, building A has a lower air temperature (27.5 – 28.8^o C) with indoor air speed between 0.1-1.2 m/s); in other hand, in the afternoon, it has a higher temperature than the others (29.6- 30.3^o C) with indoor air speed between 0.1- 0.4 m/s. Building C has a higher air temperature in the morning (28.9 – 29.4^o C) with air speed between 0.1-0.9 m/s. It has a lowest air temperature in the evening (27 -27.8^o C) with air speed between 0.1 -1.1 m / s).

                                Building A                                                                             Building  B          

Figure 7. Indoor air velocity, air humidity and air temperature at Kemlayan Kampong on Building A and B

Sources: The measurement result, February 2008

Figure 8. Indoor air velocity, air humidity and air temperature at Kemlayan Kampong on Building C

Sources: The measurement result, February 2008

From figure 9 and figure 10, in the hottest month, the outdoor temperature condition is shown on red one and on blue one. Figure 9 shows the outdoor temperature in the afternoon is between 28 – 33.8^o C. Meanwhile from figure 10, the outdoor condition shows 27 – 31^o C. In the evening until morning in the building 1 (figure 9) the outdoor temperature is between 22- 26^oC and building 2 is 22 – 27^o C  (figure 10). At those positions, the indoor temperature is always converse. That means the building provides lower temperature than the outdoor, up to 1- 3 K,  and increase indoor air temperature up to 1 -3 K during night. During the measurement period, the building opening is relatively closed, so wind cannot enter the room freely. By those conditions, the indoor temperature will theoretically always be lower in the afternoon and higher in evening- morning than outdoor temperature.

Figure 9. Outdoor and Indoor Temperature at Kemlayan Kampong On Building 1

Sources: The measurement result, Mei’2006

Figure 10. Outdoor and Indoor Temperature at Kemlayan Kampong on Building 2

Sources: The measurement result, May’2006

6. Design Strategies in Kemlayan Kampong

            Referring to the above condition, it seems that the local air temperature condition at Kemlayan Kampong is higher 5.6 – 8 K (in the morning), 1.4- 2.3 K (in the afternoon) and 0.5 – 4.2 K (in the evening). On the other hand, the indoor air temperature condition on some samples show that, in average, is around 27.5- 29.4^o C (in the morning), 28.3 – 30.3^o C (in the afternoon) and 27.0 -28.8^o C (in the evening). In the morning until afternoon the indoor temperature is lower 2-4 K than outdoor temperature. In the evening the indoor temperature is relatively similar with outdoor temperature. 

In the coldest month, the indoor temperatures seem to be lower than those in the outdoor temperatures. These phenomena can be understood that the construction used in the building can reduce the temperature. The use of heavyweight material that is commonly used at Kemlayan Kampong has an important role in improving indoor condition. Heavyweight material can low the influence of outdoor temperature. Heat load from outdoor can be stored or absorbed by wall (heavyweight material) and then it is released at night. So, the heat reaches the indoor well after the period of maximum external temperature (Oke, 1978: 225). Based on the research result done by Santosa, M (1999, 2000) and Subarto V (1999), they said that heavyweight material can low the air temperature during the day and increase air temperature at night until early morning.

Santoso (2006) also indicates that heavyweight material can mitigate the increase temperature on building. During the hot days, indoor air temperature with heavyweight material can be lower than outdoor temperature 05 – 3.2 K. Conversely at nigh the indoor temperature can be little higher than the outdoor temperature around 2.5- 3.5 K (figure 9 and figure 10)

The other strategy in improving building thermal is indoor airflow into the building. From the measurement conducted in around kampong corridor (narrow pass away), the outdoor air velocity is around 0.0- 6.4 m/ s in the afternoon- evening and 0,0- 2,1 m/s with air temperature is around 29.1 – 33.3^o C. It means that kampong corridor provides an adequate air velocity for the environment. This outdoor airflow can influence and provide indoor air velocity around 0.0- 2.2 m/s. This condition is good enough when on 2 sides of kampong corridor is high walls that can reduce the air velocity into the building. So, it can be predicted that outdoor air flow will be faster when there is not a high wall/ fence on two sides of corridor.

7. Conclusion

The heating problem on high density urban settlement environment can still be controlled by building (human settlement) through passive (natural) cooling system. The use of passive cooling system in building can minimize the use of artificial air conditioning system that can finally influence to the ozone layer damage. At high density urban settlement environment the building heating phenomenon is still possible to be controlled passively. There are two kinds of elegant ways to solve the existing heating. They are:

1.  The use of heavyweight materials to restore the heat gain

2.  The use of narrow pass away to provide wind corridor and shading device

By implementing those ways, people do not need using air conditioning system for preventing environmental heating.

8. Acknowledgment

In this chance here, I give special thanks to Building Science Laboratory of ITS Surabaya and Sebelas Maret University that have provided place and laboratory equipment to complete the paper, and also for community of Kemlayan Kampong who provide the place to observe.

9. References

Aynsley Richard  (1977), Architectural Aerodynamic, Applied Science Pub., Lon  -don

Boutet, Terry ( 1987), Air Movement, McGraw Hill Co, New York

Lippsmeier (1994), Bangunan Tropis, Erlangga, Jakarta

Luxmoore, DA, MTR.Jayasinghe, M.Mahendran (2005), Mitigating temperature increases in high lot density sub tropical Residential Development, Energy and Building 37: 1212-1224, Elsevier,New York

Oke, TR (1978), Boundary Layer Climate, John Wiley & Son, New York

Salmon, Cleveland (1999), Architectural Design For Tropical Region, John Wiley and Sons Inc, New York

Santosa, Mas (2000) Specific Responses of Traditional Houses to Hot Tropic, Senvar-ITS, Surabaya

Santosa, Mas (1999),The Role of Meaning and Technology in The Formation of Urban Space: Post TraditionalvsPost Colonial vs Modern, ITS, Surabaya

Santosa, Mas (1999), Change and Continuity in Sustainable Settlement: A Case Study in A Tropical Region, PLEA-99:333-338, Brisbane

Santoso H, M. Santosa (2006), the Thermal Comfort of the Javanese Traditional House in High Density Environment, INTA 2nd, Duta Wacana University, Yogyakarta

Subarto, Veronica (1999), a New Approach to passive Design for Residential Building in a Tropical Climate, PLEA-99, Brisbane

Rapoport Amos (1969), House Form and Culture, Prentice hall, New York

Tawit Chitsomboon and Pornsawan Thongbai (2004), Natural Ventilation in Building Using Attic and Solar Chimney, SEE-Sustainable Energy and Environment, Hua Hin