The Influences of Wind Direction of Upland Tropical Region to Site Planning

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1 The Influences of Wind Direction of Upland Tropical Region to Site Planning Author FX Teddy Badai Samodra a a Laboratory of Architectural Science and Technology Department of Architecture Institut Teknologi Sepuluh Nopember (ITS) Surabaya Address : Kampus ITS - Sukolilo, Surabaya enviarch@arch.its.ac.id enviarch@gmail.com Abstract An opening of façade is often used to promote the flow of air through a building, however in order to ensure that this process is effective the façade should face a windward orientation. This means that not only mass order is planned but also the analysis of wind speed and direction in critical months is needed to determine strategy on the working (site) area where it may result in the configuration of building, site circulation as site opening, and building envelope design. This paper aims to develop site planning model of a tropical building with traditional style of upland region as a case. The hottest and the coldest months model are formulated and used to estimate the potential of a opening placement as a wind inlet of the area with actual thermal data for the upland region. Environment and local climate were analyzed by means of CFD program in order to quantify factors influencing air movement. The air movement of tropical region is difficult to measure because of the fluctuating direction, but one approach is to parameterize it using relations between the climate analysis of the computer program and the wind direction conducted into and out of the buildings that form the surface of the site and combine them. Key findings are that the choice of site planning strongly influenced by local factors, the irregular ordering that are expected to take place in the site, and building-specific characteristics. The results of the statistical analyses of the graphic of wind speed and its direction for a definition of standard site patterns which can be used to make conclusion of buildings configuration design. Keywords : Building configuration, Site planning, Upland tropical region, Wind direction 1. INTRODUCTION The main purpose of natural ventilation as a passive cooling strategy is to achieve a high wind speed with the air that has appropriate temperature and relative humidity. It used to be the most common ventilation method of allowing fresh outdoor air to replace indoor air in a building. Natural ventilation occurs when there is uncontrolled air movement or infiltration through cracks and small holes in a building the same ones occupant want to seal to make the building more energy efficient. An opening of its façade is often used to promote the flow of air through a building, however in order to ensure that this process is effective the façade should face a windward orientation. Factors that influence these parameters can generally be divided into two parts: outdoor environment and building component. Microclimate can be defined as the climate of small areas where the geometry or physical properties of those areas has modified the general climate. It can be controlled to some extent by site design and crop management. Site plan as the microclimate of the property (wind speeds, air temperature, rainfall) is usually different to the conditions measured at the nearest standard climate observing station, even if that station is quite close. It can also be thought of in the dimension of time a sequence of atmospheric changes that occur within a small region. The analysis of wind speed and direction in critical months is needed to determine strategy on the working (site) area where it may result in the configuration of building, site circulation as site opening, and building envelope design. 2. METHODS This paper aims to develop site planning model of a tropical building with traditional style of upland region as a case. In this paper, the hottest and the coldest months model are formulated and used to estimate the potential of a opening placement as a wind inlet of the area with actual thermal data for the upland region. Environment and local climate were analyzed by means of CFD program in order to quantify factors influencing air movement. The air movement of tropical region is difficult to measure because of the fluctuating direction, but one approach C-I-5-1

2 10th SENVAR + 1st CONVEEES 2009 : Mechanical is to parameterize it using relations between the climate analysis of the computer program and the wind direction conducted into and out of the buildings that form the surface of the site and combine them. 3. RESULTS AND DISCUSSION 3.1. Mass Order on Research Location In a condition of modern site, site formation represents bunch settlement dissociated by open area in the form of agriculture farm. It has density which is varied depended on condition of geography and growth of new building. Condition of its geography has an effect on that is ground sloping and level of farm land fertilization of agriculture farm around buildings. The slightly topography position and its fertilization of farm will tend to more solid. Initially, rural area in its site is occupied by rural/village traditional house (kampung form). But, with accretion of time, modern building is growing up with more varying physical character and adding density in its scope (Figure 1.). Building with character of traditional site is single and self supporting building so that has open area on every its building orientation, both for modern and also traditional typology. Every building is dissociated by garden, yard of house, and street. Both of traditional and modern typologies have grid pattern dissociated by street of countryside or footpath. Figure 1. The Upland Village of Traditional and New/Modern Site In the Javanese traditional cosmology perspective, there is different view in determination of building orientation. The mystique view sees building direction to south (southern sea) in the north-south axis. But with religion growth, rural house orientation is complex and does not only following the mystique axis. According to traditional view, calculation of wind direction is dominant for local climate. Basically, orientation in all house typologies has façade up at sea and will be differ according to place. There are southerly as in Java southland and northwards in north Java seaboard. Traditional houses in research location area have orientation and direction (building face) southerly (south side is the largest perimeter). Modern buildings have random orientation or direction with not regular dimension The Density of Buildings Traditional Building form on research location is generally bar formation with proportion of length : width : height = 15m : 9m : 7m with the building assumption have Pekiwan as left side building. With this condition, C-I-5-2

3 The Influences of Wind Direction of Upland Tropical Region to Site Planning hence this rural traditional building is compact enough. It influences critical indoor warming because less shadow is formed by building element. But, to the condition of environment tends to be cool, it will be able to degrade underheating value. Bar formation also will give opportunity to select building orientation. The large perimeter with biggest external opening can be placed at side avoiding solar radiation. Figure 2. The Proportion of Mass Order Height of Building is always related to distance among buildings. Research location of low density and upland region (Northern of Blitar, East Java), in a condition traditional environment, building distance (L) has four times height of building (H), see Figure 2. With existence of modern building, distance among buildings (L) is equal to twice height of building (H). The buildings are regular enough because all of them are built by one floor level and formed of by the same cultural background. The height of Building is 7m from ground face until building cam roof. The average distance between buildings to the others is 11-42m at traditional site and decrease to become m with attendance of new building at modern site. Density of building on research location is measured with just KDB (building ground floor coefficient), because all building represent the same number of floor, so that KLB (building floors coefficient) will equal to KDB. In building unit scale, traditional house has KDB in traditional site = % while in the modern = %. This condition will give bigger opportunity in the traditional building in arrangement ventilate building. In every building unit, in modern and also traditional site, the sites have open area in all of their orientation and it promotes the air infiltration to the building. The cover on the research location is predominated by green surface (tree, clump, or grass) and land (street and yard of house) while building filling site in the form of house (traditional/modern), public facilities and livestock C-I-5-3

4 10th SENVAR + 1st CONVEEES 2009 : Mechanical cage. From this condition of traditional site, percentage comparison in the form of building, land, and green surface is 6.15 : : 53.62%. In a condition modern site, comparison is marked by shifting some part function of green surface cover of become modern building. Building comparison, land, and green surface is : : 43.88%. External cover comparison between land : vegetation is : 57.13% for traditional site and : 52.17% for modern. The comparison indicates that external covers also shift from vegetation to land surface with fact that vegetation remain to more dominant compared to land. The Environment which is predominated by vegetation gives opportunity for the process of forming environmental shadow and arrangement wind flow in countryside. In general, vegetation types are the form of tree and clump, while grass has very small area because it does not enable to grow better among trees closing over it from sunshine. In modern and also traditional site, the buildings mass do not have difference type, average diameter as outdoor canopy is 1-8m with average height 1-15m. The vegetation canopy accelerates wind and shadow for heat controlling into building. Site Form/Mass Order Upland (Cool) Compact Lowland/Coastal (Hot) Spread Building Volume Opening Large Small Small Large Material Heavyweight Lightweight Figure 3. Hot Humid Housing Specification (Samodra, 2009) 3.3. Hot Humid General Site Planning Site order will tend to be spread for hot tropical environment, on the contrary it will be compact for the environment of which cooler relative as in upland area. Condition of disseminating in coastal area/lowland will give to access for more ventilation (Figure 3.). Compact site will give shadow which good to building and lessen cool wind penetration especially at night (Samodra, 2009). Smaller Building volume in tropical/hot humid will decrease perimeter of building envelope which is exposed to sun. This condition is compatible for the area of which tends to heat as in coastal area and lowland. The wide of opening as larger ones in hot area than in cooler area, will give wind opportunity as a means of passive cooling of building. Lightweight material in hot area enables heat quickly come into building in the day time, but also will quickly release to environment. On the C-I-5-4

5 The Influences of Wind Direction of Upland Tropical Region to Site Planning contrary in cool area, it needs material which tends to heavyweight because to resist the heat in the day time and needed to passive warming at night when environment tends to be cold because of long time lag Site Wind Flow Distribution Measurement of wind speed pattern and distribution are conducted at 3m from ground surface (± ½ H= ½ height of building). It is determined with consideration of high wind flow at circulation level. Measurement as high as this circulation will be determined according to condition of its environmental terrain roughness (open country) for modern and also traditional site because of their low density sites. Both traditional building proportions in the site model and modern show bar geometry form. In general, there are 3 movement pattern forms, they are laminar, separated, and turbulence. In traditional site, the movement of wind in the hottest and coldest months is determined by laminar pattern because of the open area of the site plan. Separate pattern happened because the coming wind was separated by building mass, in other hand the turbulence appeared because building composition in the site was nothing which has serial pattern with reference of wind direction (Figure 4.). With accretion of amount of building (especially modern type) at modern site, movement of wind is shown by many separated pattern and turbulence at settlement area because many mass which have align pattern are solid enough. Laminar pattern happened at open country like garden among them. Both of site models in that area indicate light air pressure (calm up to breeze) because of the low density mass and low wind speed, especially in critical months. Figure 4. Wind Flow Distribution of Javanese Village Housing C-I-5-5

6 10th SENVAR + 1st CONVEEES 2009 : Mechanical Figure 5. Wind Flow Distribution of Traditional Site Comparison of building size will cause movement of turbulence in 2-1/4H in the area behind building (280 0 ) from direction of coming wind (100 0 ). In the modern and also traditional site, inclination of its mass roof hereabouts or 6/12H or 8/12H because it is using many tile roof ( Figure 5.and Figure 6.). With mass form tend to bar, hence inclination of building roof will cause the happening of wind turbulence of the size 4-1/4H Eddy current or 4-1/2H Eddy current.the building uses long enough overhang as veranda area at traditional house (1/4H) will yield 4-1/2D Eddy current at contrary area of direction of coming wind (Boutet, 1987). Figure 6. Wind Flow Distribution of Modern Site 3.5. Influence of Building Distance Height of modern and traditional building are similar, one floor is ± 7m (Figure 2.). Because they do not have the existence of variation of in mass height, laminar pattern predominates as long as flow in site. The happening of turbulence pattern and breaking because modern and also traditional site model have very large open area. Difference distance among buildings (L) with L=4H domination (traditional site) and L=2H (modern site) gives to access to wind distribution, except to clusters L=½ to 4H. Leeward area has the condition of area Eddy current as long as less than 4 times of building height and will experience of degradation of wind speed at building windward rear. This condition will decrease potency of passive cooling in the building and will happen in part of modern site at all of condition of critical time. C-I-5-6

7 The Influences of Wind Direction of Upland Tropical Region to Site Planning Influence building distance to wind flow distribution can be seen in open area within comparison building distance (L) and building height (H) according to hottest and coldest months/hour wind direction. Clusters in traditional site (Model 1) and in modern (Model 2) are shown by Figure 7. and Table 1. Some clusters with the same size and form will be made simple according to location consideration and wind direction. At extreme condition hottest month and hour, 100% of clusters (B, C, and D) have potency for the passive cooling at condition of hot environment. In coldest hour, it does not happen. Traditional site with breaking pattern (separated type) at all of open area has beneficial to reduce cold air flow of upland in the underheating time and all open country get wind distribution with potency for the passive cooling. Furthermore, it is also accepting wind speed fulfilling conditions for the physiological of cooling and has possibility for the energy conservation. All of potencies are very influenced by wind direction which has determines the position and configuration of building form and openings as one of site planning strategy. Modern site, with attendance of new building, causes many breaking pattern in its area in all of time period as shown by Figure 8. and described by Antaryama et al. (2007). Nevertheless, 100% of the open area have potency for passive cooling because they are predominated by large distance space which do not have building barrier from direction of coming wind, so that wind flows with higher speed, up to the requirement of minimum standard (0.49m/s). Wind of windward building in the clusters has speed even more than 4m/s Some building have part of building side which ought to earn wind distribution directly (functioning windward) as leeward because they are hindered by building existence in the front area. Because do not require speed of wind for cooling, all cluster have opportunity for the comfort performance. When coldest month with hottest hour, wind speed is needed by the site with minimum 0.15m/s and all building side in cluster have opportunity to get wind flow exceed requirement. At condition of coldest time (coldest month and hour), like in the same hour and in hottest month, it does not require wind for the physiological cooling and condition of external space has direct correlation with the wind direction coming from south-east (163 0 ). MODEL 1 C-I-5-7

8 10th SENVAR + 1st CONVEEES 2009 : Mechanical MODEL 2 Notes: Rumah Pedesaan = traditional rural/village house Rumah Modern = new/modern style house Figure 7. The Cluster of Buildings Tabel 1. Outdoor Wind Pattern in the Low Density Upland Buildings Month Month Month Month Wind Direction ( 0 ) Wind Speed (m/s) Temperature ( 0 C) Minimum Wind Speed Standard for physiological cooling (m/s) MODEL 1 MODEL 2 A 1/2; /3; /3; ; ; ; ; ; 0.89 B 1/4; /4; ; ; ; ; /5; /3; 0.90 Clusters (H/L) C 0; /6; ; ; /2; /3; /3; ; 0.20 D 1/4; /2; /2; /4; /3; /3; /2; ; 0.72 E 0; /3; /5; ; 0.67 C-I-5-8

9 The Influences of Wind Direction of Upland Tropical Region to Site Planning Month Month Month Month F 0; /3; /5; ; 0.60 G 1; ; /2; ; 0.30 H 0; ; /4; /3; 0.70 I 0; ; /2; /2; 0.50 J 2/3; /3; /3; ; 0.40 K 0; ; ; ; 0.70 L 0; /5; /5; ; 0.70 M 0; ; /2; /3; 0.70 N 1/2; /2; ; ; 0.60 O 0; ; ; /4; 0.80 P 0; /3; /3; /2; 0.50 Q 5/4; /3; ; ; 0.70 Notes: Model 1 = Traditional Site Model 2 = Modern Site L H = Building Distance = Building Height ~ = Infinite Distance 0 = No Building Obstruction ---; --- = Proportion of H/L; Wind Speed on Windward Building potential for passive cooling not potential for passive cooling C-I-5-9

10 10th SENVAR + 1st CONVEEES 2009 : Mechanical = physiological cooling Notes: Model 1 = Traditional Site Model 2 = Modern Site Bulan Terpanas = Mass order measured in Month Bulan Terdingin = Mass order measured in Month Kec.Angin = Wind Speed of the Site Proporsi = Proportion of the Cluster Figure 8. The Proportion of The Cluster and Wind Speed (Antaryama et al., 2007) C-I-5-10

11 The Influences of Wind Direction of Upland Tropical Region to Site Planning 4. CONCLUSION The area full of natural elements such as vegetation and water source can decrease temperature of hot wind passing by. It builds a passive refrigerator for. A functional space should have openings at least on two sides, so openings only on one side should be avoided. The positions of openings on different sides should be as far apart as possible to avoid short circuit, or preferably be located at the opposite sides. By the statistical analyses of the graphic of wind speed and its direction for a definition of standard site patterns which can be used to make conclusion of buildings configuration design. It indicates that maximum effective opening area is recommended. All of natural/passive strategies need effective site planning and the wind direction has high contribution for it. There are all sorts of conclusions for site planning for passive cooling in the tropical region: 1. By combination with wind speed, wind direction determines position of openings (windward and leeward zone) and configuration of site form (proportion of distance and height of building) 2. Site planning needs large clusters as open area of mass order, especially for high density of buildings. 3. The green/natural cover is influenced of wind speed and direction. It has direct correlation with thermal performance of outdoor comfort. REFERENCES [1] Antaryama, I G.N., Noerwasito, V.T., Srilestari, R.N., Santoso, B.H., and Samodra, F.X.T.B.S. (2007) Sistim Pendinginan Pasip (Passive Cooling) pada Bangunan di Daerah Tropis untuk Upaya Pembangunan yang Berkelanjutan. Laporan Tahun III Hibah Penelitian Tim Pascasarjana (HPTP). Direktorat Pembinaan Penelitian dan Pengadian Kepada Masyarakat, Direktorat Pendidikan Tinggi Departemen Pendidikan Nasional. Jakarta [2] Boutet, T.S. (1987) Controlling Air Movement. McGraw-Hill. New York [3] Samodra, F.X.T.B.(2009) Spesifikasi Kinerja Termal Sistim Konstruksi Kulit Rumah Tinggal Tropis dalam Variasi Altitude. Seminar Nasional Pascasarjana IX ITS. Surabaya C-I-5-11