Passive designs of low-income housing with natural ventilation in tropical region

One of the goals of Sustainable Development goals is sustainable cities and communities. Making cities sustainable means creating career and business opportunities, safe and affordable housing, and building resilient communities and economies. One of the goals of sustainable cities and communities (SDGs 11) is by 2030, ensure access for all to adequate, safe and affordable housing and basic services and upgrade slums. Because the level of housing needs in Jakarta is quite high with limited land available, housing prices soar, this is inversely proportional to the high level of poverty in Jakarta so that many people make illegal and slum settlements to overcome the lack of funds they have. One way to achieve this target is to apply bioclimatic architecture to realize sustainable buildings with affordable operational costs so that the housing built becomes affordable. One way to save energy is to use natural ventilation. This paper presents a study of the application of bioclimatic architecture that can provide good air circulation created using natural ventilation. Natural ventilation is the process of exchanging air inside the building through the help of open building elements. This research is motivated by the current development of cheap apartment architecture in Indonesia which does not support good natural ventilation, people are starting to build something that benefits the market and ignores the importance of good air circulation. Therefore, the promotion and application of natural ventilation as part of low-cost energy consumption and avoiding the sick building syndrome with good air circulation, especially after the corona virus pandemic, is an important issue. The research method used is descriptive quantitative method, in the form of research with a case study and simulation approach. The result achieved is that the building can optimize natural ventilation evenly through orientation, building shape, opening design, etc.


Introduction
The Sustainable Development Goals are 17 goals that have been set by the United Nations as a world development agenda for the safety of humans and planet earth.one of its goals is sustainable cities and communities.Making cities sustainable means creating career and business opportunities, safe and affordable housing, and building resilient communities and economies.One of the goals of sustainable cities and communities (SDGs 11.1) is "by 2030, ensure access for all to adequate, safe and affordable housing and basic services and upgrade slums".Because the level of housing needs in Jakarta is quite high with limited land available, housing prices soar, this is inversely proportional to the high level of poverty in Jakarta so that many people make illegal and slum settlements to overcome the lack of funds they have so as to achieve the target SDGs 11 point 1 requires flats to create affordable housing and also reduce existing slum settlements by building flats on former slum areas with appropriate regulatory 1324 (2024) 012051 IOP Publishing doi:10.1088/1755-1315/1324/1/012051 2 provisions.Moreover, energy conservation mandates for building with the use of low energy (low energy building).Natural ventilation is becoming the key feature for energy efficiency strategy to achieve thermal comfort in the tropics.Studies have revealed that in hot humid climatic regions can accommodate high temperature and adequate comfort can be achieved through natural ventilation [1].By making buildings that are energy efficient, it also helps in terms of low operating costs so that residential prices become even more affordable.one of the solutions to create energy-efficient buildings is the application of bioclimatic architecture which according to Ken Yeang is an energy-efficient design method that pays attention to the local climate and solves climate problems by applying it to building elements [2], so that buildings can take advantage of natural ventilation and natural lighting.
Indonesia is a country with a tropical climate which has high enough temperature and humidity, so the use of artificial air conditioning devices is often needed to reduce the temperature and humidity levels of the room so that it requires a large amount of electrical energy.According to a survey and research conducted by the WWF Institute (World Wildlife Fund) [3], it is known that the use of artificial air conditioning (AC) is the largest contributor to energy consumption in households, so that a building that can respond to the climate is needed so that thermal comfort can be achieved.Low -Cost Apartment in Indonesia are for low-income people so the building needs cheap energy consumption to help their finance.In addition to reducing the use of electricity, the use of natural ventilation also helps air circulation so that the room does not become humid, due to the pandemic that hit, a room that has good circulation is needed to inhibit the growth of microorganisms that cause disease.Air circulation also prevents the occurrence of sick building syndrome so that residents stay comfortable and healthy because most flats in Indonesia do not pay attention to comfort in terms of air conditioning in flats.The design with the concept of bioclimatic architecture will affect architectural formation because the shape of the mass and other designs will be influenced by the surrounding climate and can minimize the use of non-renewable energy [4].
Bioclimatic approach is more likely to apply a passive design.Energy savings come from using natural lighting and air passively, without converting heat and air into electrical energy sources.Several ways of implementing a passive system in bioclimatic design include [5] Building orientation, which affects the anticipated high heat radiation • Use of natural ventilation, which will affect the thermal comfort and rigidity of the building Essentially, this paper presents the initial study and it contains the study of: The influence of climate on the orientation of buildings to maximize natural energy use, the position and size of openings that allow cross ventilation.

Literature Study
Natural Air Conditioning Related to Ventilation System of Industrial Flat [6] which is in Indonesia, it was found that the orientation of the building should use east -west to reduce solar radiation to the longest side of the building but must also adjust to the orientation of the direction of the wind to facilitate air circulation in the building, orientation of openings should be not perpendicular with wind direction, dimension of openings should be following the ach standard for the minimum amount so that the room doesn't become humid.In the case study in this journal, the building has several problems, such as the direction of the openings that are parallel to the direction of the wind so that it is difficult for wind to enter the building so it is necessary to adjust the facade of the building such as forming fins on the facade of the building so that the wind can enter more easily.Natural ventilation is also influenced by the size and location of the opening so that the size of the opening needs to be adjusted to the ACH standard so that the room is not humid, and the location of the opening is not facing so that the wind can be evenly distributed throughout the room.with the openings that have been suggested by the author, it is found that the indoor wind speed is 0.5 m/s and the room temperature is 25 O C which is in accordance with the comfort standards in Indonesia, namely the wind with a speed of 0.25 -0.5 m/s and room temperature 21 -28 O C. The application used in this journal is the orientation of the building that follows the direction of the wind with the majority side exposed to excessive sun exposure is the shortest side, the size and location of the openings are adjusted to ACH standards and the surrounding environment.
The Effect of Openings on Thermal Comfort in the Residential Space of Aparna Flats Surabaya [7] which is located in Indonesia, it was found that the orientation of the building should use east -west to reduce solar radiation to the longest side of the building but must also adjust to the orientation of the direction of the wind to facilitate air circulation in the building, orientation of openings should be not perpendicular with wind direction, dimension of openings should be follow the ACH standard for the minimum amount so that the room doesn't become humid, type of openings should be considered because each type have different effectiveness in entering air into the building.In the case study in this journal, the building uses an orientation that matches the direction of the wind so that the wind can easily enter the building but has problems because the opening size is too small so that the natural air circulation is not good, because the ratio of the size of the opening to the size of the wall is not suitable.so that other types of openings are used that have a greater level of effectiveness so that the circulation that occurs is good.The wind that blows in the room has a speed of 0.5 m/s and the temperature in the room is 29 O C which is in accordance with the comfort standards in Indonesia, namely the wind with a speed of 0.25 -0.5 m/s and room temperature 21 -28 O C. The temperature in the room is a bit hot because the orientation chosen results in direct sunlight exposure to the room, so to lower the room temperature it is necessary to have passive shading such as using a canopy.

Effect of Building Orientation and Wind Speed on Filter Shape and Dimensions on The Facade of Flat
Building [8] which is located in Indonesia, it was found that the orientation of the building should use east -west to reduce solar radiation to the longest side of the building but must also adjust to the orientation of the direction of the wind to facilitate air circulation in the building, orientation of openings should be not perpendicular with wind direction, dimension of openings should be follow the ACH standard for the minimum amount so that the room doesn't become humid, type of openings should be considered because each type have different effectiveness in entering air into the building.In the case study in this journal, the building uses an orientation that is in accordance with the direction of the wind so that the wind can easily enter the building but has problems due to its geological position close to the sea so that the wind that comes has a strong speed and contains salt so that users feel uncomfortable.comfortable and prefer to close the window, so the author suggests using a double layer or secondary skin to reduce wind speed into the building and the use of plants placed on the facade of the building to reduce salt content.The building also uses double loaded corridors and voids so that air circulation in the building both vertically and horizontally becomes smoother.After using double layer and adjusting the aperture, it was found that the indoor wind speed was 0.4 m/s and the room temperature was 31 O C. The room temperature is quite hot because there are no buildings or plants in the surrounding environment so there is no shadowing on the building so that a canopy with a minimum length of 1.2 m is needed to create passive shading.After the addition of the canopy, it was found that the room temperature dropped to around 27 O C. [9] which is located in Indonesia, it was found that the orientation of the building should use east -west to reduce solar radiation to the longest side of the building but must also adjust to the orientation of the direction of the wind to facilitate air circulation in the building, orientation of openings should be not perpendicular with wind direction, dimension of openings should be follow the ACH standard for the minimum amount so that the room doesn't become humid, type of openings should be considered because each type have different effectiveness in entering air into the building, Using double loaded corridor to have void (atrium) between unit facing each other so the cross ventilation will become smoother, Using canopy to create shadow to the building to reduce exposure to direct sunlight.In the case study in this journal, the building uses an orientation that is in accordance with the direction of the wind so that the wind can easily enter the building but has a disadvantage because the orientation is north -south so that the longest side of the building is exposed to excess sunlight and also has wind entry due to most of the windows used are dead windows so that more live windows are needed.This building uses a double loaded corridor, a void (atrium) and there is also a communal space in the corridor with an open space concept so that cross ventilation is quite good and has good lighting, but the existing voids have drawbacks, namely the entry of rainwater due to the short canopy.which is only around 50 cm so that a longer canopy is needed to prevent rainwater from entering and to add shade to the building, which is at least 1.2 m.After adjusting to the bioclimatic architectural theory, it was found that the indoor wind speed was 0.45 m/s and the room temperature was 26 O C.

Effect of Opening Size on Wind-Driven Cross Ventilation [12]
, it was found Based on the velocity and pressure inside of the building model, the results show a good agreement with Bernoulli Principle that lower pressure results in higher velocity.Furthermore, when the opening size of the inlet is greater than the outlet, the higher velocity is on the side with the smaller opening size, and vice versa.Besides, when opening ratio decreases, ACH increases which leads to higher ventilation rate.When opening ratio is greater than 1, the percentage increase in ventilation rate ranges from 100% to 250%.Nevertheless, when the opening ratio is less than 1, the percentage increase in ventilation rate is less than 10%.In other words, as the opening ratio decreases, the percentage increase in the ventilation rate is not significant.In addition, the study also shows that pairing a larger outlet opening with smaller inlet opening increases the velocity at the inlet, thereby reducing the pressure inside the building model and obtaining a better ventilation rate.Therefore, it can be concluded that internal airflow is highly dependent on opening ratio.
Conclusion of the literature study are 1) the use of east-west orientation of the building to reduce sun exposure on the longest side of the building while still paying attention to the opening following the wind direction so that the orientation of the building is adjusted to which thing you want to achieve, which in this case is natural ventilation, 2) the use of a canopy or forward facade backwards for shade with a minimum length of 1.2 m, 3) the use of a transition room in the form of an atrium or double loaded corridor to facilitate cross ventilation, is the best application of aspects for natural ventilation, 4) Windows to wall ratio in addition to affecting the intensity of the incoming wind speed, also affects the room temperature so it is necessary to re-analyze which one will be prioritized to achieve because in addition to the greater the windows to wall ratio the greater the incoming wind speed and also the amount of heat from outside that enters the building, 5) The ratio of the size of the inlet and outlet affects the wind speed in the room so it must be designed in such a way as to achieve comfort.

Annual Wind Data
The following is a comparison of wind data from the literature study with the existing case studies so that you can find out the difference and can adjust the solutions obtained from the literature study with the climate in the case study location.The factor needed in the orientation of the building is the direction of the sunlight so that it can find out which areas of the building are exposed to excess light, adjusted to the orientation of the function of the building to certain spaces, health factors.The study of the building orientation divided into 2 categories:

Orientation to Sun Path
Orientation to the sun path aims to place the longest side of the building in the north -south direction, while the shortest side is in an east -west direction.This is intended so that the longest side of the building gets good solar lighting but is not exposed to direct eastern -western solar radiation, so that openings for natural lighting and ventilation can be maximally provided on the longest side of the building without worrying about excessive heat radiation from the eastern sun west.

Orientation to Wind Flow
The orientation of the building can be made based on the direction of wind movement, so that every mass of the building can be traversed by the air / wind flow effectively.From Central Bureau of Statistics Jakarta (2015), information is obtained that the direction of wind movement that most often occurs in North Jakarta during the year is from the southeast to the northwest and vice versa, such as the data in Windrose below:  From the results of the data analysis, and the standard of modular lowcost apartment window design in Indonesia then used as a reference in designing windows.In addition to the influence of wind speed and the size of the opening that affect air exchange, the open and closed ventilation system also has an important effect on the effectiveness of air that occurs: The standard modular window design for holes is sufficient in accordance with the convenience of air ventilation such as the design of the upper window that uses jalousie, the size of the ventilation hole, the use of single or double windows, so that what is applied in the design is the size of the ventilation hole, the number of windows in one adjacent frame, namely maximum of 2 or known as double window.but there are still some that must be adjusted to the calculations and conditions at the site under study, such as the type of window from the casement must be replaced with a window whose opening direction is not too far from the building such as the single hung type or others for security reasons because the project being built is a tall building so on a high enough floor the wind will be stronger and can drop or damage the casement-type window when the window is open, the window size for some rooms is also required to be adjusted according to the ACH calculation to facilitate air circulation such as for the kitchen room and family room so that the type and size of the window used is.Then the design obtained will be tested through CFD simulation.

CFD Simulation.
Simulation is the most accurate simulation for weather simulations and so on so that it is suitable in this case, CFD itself has a definition as Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows.Computers are used to perform the calculations required to simulate the freestream flow of the fluid, and the interaction of the fluid (liquids and gases) with surfaces defined by boundary conditions.With high-speed supercomputers, better solutions can be achieved, and are often required to solve the largest and most complex problems.CFD simulation itself is found in many software such as autodesk flow design, eco-tech, design builder, and so on.from the literature study, the most frequently used applications are autodesk flow design and eco-tech so the authors prefer to use eco-tech software because it has several advantages over autodesk flow design where when simulating wind movement, from the simulation results we can also get air temperature results.which is created from the movement of the existing wind, as well as the initial simulation data can be imported from weather data around the site that has been obtained from surrounding institutions using weather gauges and can also be set independently so that we can freely perform simulations with various existing data such as different wind speed and direction and so on.The design of the opening position and the size of the opening, it is then simulated using CFD software EcoTech to test its success or not and the result are: The 3 rd simulation, because the natural wind direction is blocked by other building masses so that the wind that reaches the living room becomes slower, the lowest wind speed is 0.10 m/s and the fastest is 0.4 m/s and the average wind speed inside the room is around 0.23 m/s, and the average room temperature is 26 O C which is in accordance with the comfort standard of 21 -28 O C. The results obtained have reached the target of comfort standards based on Indonesian standards because the application of the best results obtained from a comparative study of the literature where they managed to achieve comfort in terms of wind speed and comfort in terms of thermal comfort.

Conclusion
As the result of the simulation and consider to site factor, sun path factor, wind flow factor.Orientation of the building facing southwest -northeast so that the two sides of the building get airflow and the affected part excess sunlight is the shortest side so the temperature in the room not too hot or cold but comfort for occupants.Position and size of openings need to calculate using ACH formula so that natural ventilation is healthy and comfortable for residents.Because the opening is window that can be close or open, the type of the window should be considered because of the effectiveness to air change flow in the room.Based on calculation and simulation, the large of the opening of every room is different because they have different standard for ACH but the windspeed that occurs in room must be around 0.25 -0.5 m/s for comfort of the occupant and with the large of the opening based on calculation result it can reduce the windspeed from outside the building around 2,65 m/s into 0,25 -0,5 m/s in the room, and the temperature from 30 O C on outside become around 24 -28 O C. The results of the research, it can be concluded that research can answer one of the targets of sustainable design, namely by making low-income housing with natural ventilation to reduce the electricity use, that residential prices and operational costs are affordable for low-income people.This can be achieved because it has applied the concept of Sustainable architecture which is fixed and suitable for low-income housing well even though there are still some shortcomings.

Figure 2 .Figure 3 .Figure 4 .
Figure 2. 3D Unit Design (a).Air Flow Simulation (b) and Temperature Simulation (c) On simulation, the lowest wind speed is 0.15 m/s and the fastest is 0.6 m/s and the average indoor wind speed is around 0.45 m/s which is in accordance with the comfort standard of 0.25 -0 ,5 m/s and the average room temperature is 26 O C which is in accordance with the standard of comfort, which is 21 -28 O C.

TABLE 2 .
Window Type and Percentage Effectiveness