Comparative Studies of Water Conservation Application in Office Buildings in Indonesia and Around the World

Currently, clean water and environmental issues are becoming a major concern because the source of these issues mostly comes from buildings, one of which is offices. Most buildings apply the energy saving concept, and there are still few that apply the water conservation concept, especially in Indonesia. The lack of references for office buildings that implement water conservation makes it difficult for Indonesian architects to implement this concept. Therefore, this study aims to compare buildings that apply water conservation by looking for data related to similar projects that are used as a reference in a project in Indonesia. In this study, a comparative study of projects in Indonesia was carried out with several projects abroad that implemented the water conservation concept. The projects were examined based on six aspects of applying the concept of water conservation, as well as the layout of reservoir, and comparison of the water tanks amount needs. The results of this study show that projects applying water conservation aspects in Indonesian outbuildings are more diverse compared to buildings in Indonesia, which causes the percentage of water conservation in Indonesian outbuildings to be much more optimal, the location of water storage in all projects is mostly in the basement, and the average amount of water storage is 2.5 to 4 times the water needs.


Introduction
The rapid growth of businesses in Jakarta is in line with its role as a growth barometer, especially in Jakarta CBD (Central Business District) area.According to Colliers International, for the CBD area, the occupancy rate in Q2 2023 reached 73.7%, an increase of 1.7% compared to Q1 2023 [1].According to national.tempo.co, the increase in water consumption needs depends on the level of occupancy [2].Based on the case of the 73,000-square-meter Ciputra World 1 building in the Setiabudi area, when occupancy is 50 to 60%, water consumption reaches 800 to 1,000 cubic meters per day; when occupancy is 800 to 1,000 cubic meters per day, increasing from 70 to 80%, water consumption also increases around 1,500 per day [2].
According to the United Nations Environment Program in 2015, water consumption in buildings ranks second highest in the world after electricity consumption, reaching 25% [3].In-Building Tech also confirms that the amount of water usage in office buildings is relatively high compared to other buildings, reaching 25% of the total usage [4].Therefore, for the operation of office buildings, in addition to requiring electricity, also requiring large amounts of water, the operational high use of water 1324 (2024) 012102 IOP Publishing doi:10.1088/1755-1315/1324/1/012102 2 in office buildings also requires optimizing the use and needs of water in buildings or can be referred to as water conservation, one of which is by recycling wastewater (gray water) or utilizing rainwater or what is commonly called rainwater harvesting.
Rainwater storage is very useful for long hot summers.According to the Meteorology, Climatology, and Geophysics Agency (BMKG), the peak of the dry season in Jakarta is predicted to occur in July-August 2023.The BMKG Deputy for Meteorology, Guswanto, said that the entry of the dry season was accompanied by the emergence of the El Niño phenomenon starting with the Weak category in mid-2023.El Niño is a global atmospheric phenomenon that can reduce rainfall in some parts of Indonesia.According to him, the El Niño phenomenon in June 2023 is still in the weak category and is predicted to increase to the moderate category until October 2023, with a downward trend towards weak intensity in November 2023 [5].As current droughts coincide with the occurrence of El Niño, resulting in drastic climate change and long droughts, the government is taking steps to conduct weather engineering.The Meteorology, Climatology, and Geophysics Agency (BMKG) state that rain is an effect of the application of weather modification technology (TMC).This technology is used to accelerate the growth of rain clouds [6].
The concept of green building/sustainable architecture has been very widely discussed and developed to overcome weather/environmental problems as described in the previous paragraph.It is also important to apply green buildings to office buildings, both in the tropics and others.The principle of green building (Eco-friendly Architecture) is a basic study (research) of the development of architecture (building and planning science) that is in line and in harmony with nature.In other words, it comes through holistic building planning considerations or has a friendly relationship with the natural environment or with the system as a whole.This implies: adjusting building planning while maintaining and preserving the natural environment [7].
According to the Green Building Council Indonesia (GBCI), greenship or eco-friendliness can be divided into six categories:  [8] From the above explanation, there are many types of sustainablility concepts in buildings.Therefore, there are many aspects that must be applied to buildings, but there are still few who implement water conservation in Indonesia.The lack of references for office buildings that implement water conservation makes it difficult for Indonesian architects to implement this concept.Owing to the problems mentioned earlier, there are still few buildings that apply the concept of water conservation, particularly in Indonesia.Apart from that, to participate in the sustainable development goals (SDGs) program, this study also applies SGDs number 6 which reads "Ensure availability and sustainable management of water and sanitation for all".The hope is that architects will also care about water use management and through this study, it is hoped that it can be used as a reference for architects in Indonesia in implementing water conservation in buildings.Therefore, the purpose of this study is to compare buildings that apply water conservation by looking for data related to similar projects that are used as a reference in a project.This precedents the study as a reference in an office project with a water conservation approach in the framework of typology in an office building.

The Methodology
This study conducted, a comparative study of precendents in office buildings from websites, books, and several examples in and outside Indonesia.The purpose of this research is to show facts or events based on comparisons related to similar projects to reveal the circumstances or facts based on certain variables to present what actually happened as a reference for the next project.Data from descriptive qualitative research, namely by describing several facts through comparative studies related to similar projects that which consist of: • Conduct comparative studies related to similar projects from precedent studies through applied concepts.
• Data from literature related to similar projects were obtained by recording the water conservation aspects of precedent buildings for analysis.• Conduct a comparison between overseas and domestic (Indonesian) building projects that apply the water conservation concept.• Comparison between the percentage results of water conservation and the applied water conservation concept.
The data collection method used was primary data collection through observation and secondary data from various related agencies and information in the form of writings, books, or literature studies.According to the Green Building Council Indonesia (GBCI), the details of the benchmarks set by GBCI to assess the application of water conservation aspects are shown in 1A.Provide a rainwater storage tank installation with a capacity of 50% of the amount of rainwater that falls on the roof of the building calculated using the 10-year average daily rainfall intensity value.1B.Installation of a rainwater storage tank with a capacity of 75% of the above calculation 1C.Installation of rainwater storage tank with 100% capacity from the above calculation WAC 6 Landscape Water Use Efficiency 1.All water used for building irrigation does not come from groundwater sources and/or PDAM.
2. Implement innovative technologies for irrigation that can control water demand for precise landscaping, according to the needs of the plants..

Result and discussion
This research compares seven office building projects consisting of two buildings in Indonesia and four buildings abroad.Office building projects apply water conservation concepts that are compared as follows: 3.1 The Office Building of The Future (USA) Figure 1 The Office Building of The Future Source: Personal Analysis The Office Building of the Future (OBF) by Pickard Chilton is an office building based on three principles: human qualities, business objects, and sustainability.One of the systems applied in this project is the Net-Zero Water, water conservation system.This OBF manages all its water resources efficiently.That is, rainwater is directing from the roof to storage along with water run off from the Heating, Ventilation, Air Conditioning (HVAC) system to be reused throughout the building and greenery.The greenroof and landscape areas absorb some rainwater, create micro-habitats, and help reduce the urban heat island effect.On-site blackwater treatment and reuse strategies to reduce the water demand supplied to the region by 86%, waste water outflow by 95%, and run off by at least 50%.
Source: Green Building Council Indonesia, 2013 [9]  The Edith Green Wendel Wyatt (EGWW) Federal Building is an 18-story office building.The building was completed in 1974, and a subsequent renovation was completed in 2013.Water savings of more than 60% were achieved through a combined strategy that incorporated water-saving plumbing fixtures and a rainwater harvesting and reuse system.The EGWW's water conservation strategy began with an analysis of the historical water use of existing buildings.This analysis showed that 87% of the building's water use was for domestic purposes and 13% was used for irrigation of the surrounding vegetation.
Because of this large interior use, the primary strategy focused on reusing rainwater for non-potable flush fixtures.Landscape irrigation water use was reduced by more than 50% through the use of droughttolerant landscaping and incorporation of subsurface irrigation.A 165,000-gallon storage tank, created by repurposing an old firearm target range in the basement, allows rainwater to be stored and reused for toilet flushing, irrigation, and mechanical cooling tower makeup water.The 1315 Peachtree Street building was an office building that was built in 1986 and renovated in 2009.The building's water conservation efforts include collecting rainwater from the roof and 5th floor terrace and storing it in a 10,000 gallon underground tank.It was then filtered, treated with ultraviolet light, and pumped to all flush fixtures in the building.Excess water is used for irrigation or released into bioswales.More than 172,000 gallons of water are captured annually and used on-site, thereby reducing the demand for clean water supplied by the city.Additionally, the building utilizes water-efficient sanitation with low-flow flush fixtures, including 1.23 gal/flush toilets and 0.125 gal/flush urinals, as well as sensors on flow fixtures that prevent faucets from accidentally running.

The Bullitt Center, USA
Figure 4 The Bullitt Center Source: Personal Analysis The Bullitt Center is a six-story, 5426 m2 office building.It is the first commercial building to meet the stringent requirements of the Living Building Challenge, and is designed as a 'living' organism that uses only as much water and energy as the building can get.The building's water conservation concept was designed to mimic the Douglas Fir tree, which balances water intake with discharge.The building applies the concepts of rainwater harvesting, gray-water recycling, and waste compost.
Rainwater was collected from the roof, treated, and stored in a 56,000-gallon tank to supply secondary water for building fixtures.Filtered graywater is pumped to a wetland for water treatment through evapotranspiration, with the remainder flowing into a modified irrigation/drainage system designed to accommodate an average daily flow of 345 gallons.Human 'waste' from flushing toilets and urinals passes through pipes to 10 composting units underground, producing approximately 90 gallons (12 cubic feet) of compost annually from each unit, which is used as a soil amendment.The Spazio Office is the first office building in Surabaya that applies the green building concept based on the greenship rating tools category, namely Appropriate Site Development (ASD), Energy Efficiency and Conservation (EEC), Material Resource and Cycle (MRC), Indoor Health and Comfort (IHC), and Water Conservation (WAC).The concept of water conservation in this building is in the form of recycle gray water, which will be used for garden irrigation purposes and the rest for city roils (infiltration wells).

Sampoerna Strategic Square, Jakarta
Sampoerna Strategic Square is an office building that received a gold rating for greenship building certification in 2012.It receives ratings related to Appropriate Site Development (ASD), Energy Efficiency and Conservation (EEC), Material Resource and Cycle (MRC), Indoor Health and Comfort (IHC), and Water Conservation (WAC).The highest point in this building is on the concept of water conservation (WAC), which has 19 of 20 points.The concept of w ater conservation in this building is to recycle gray water which is then used for cooling towers and garden irrigation.
The description of the seven projects is summarized in

Concluding Remarks
From the seven precedents above, conclusions can be drawn as lessons and examples that can be applied to this project.1. Water conservation applied to buildings in western countries mostly uses the concept of rainwater harvesting whereas buildings in Indonesia use graywater harvesting.2. In most building precedents, the reservoir is located underground or in the basement.3. The water demand in precedent buildings in Indonesia is greater than that in Western countries.This could be due to the different habits of people in using water between Indonesians and Westerners, as well as the operation of air conditioning systems that use cooling towers.. 4.There are still few buildings in Indonesia that use the concept of rainwater harvesting, even though Indonesia has high rainfall.5.The size of the reservoir tank ranged from 2.5 to 4 times the daily water consumption.6.All buildings in the precedents use secondary water for flushing.7. Water for cooling tower needs is still a little that using secondary water.

Figure 3
Figure 3 1315 Peachtree Street Source: Personal Analysis

Figure 5
Figure 5 Spazio Office Source: Personal Analysis Figure 14 Sampoerna Strategic Square Source: www.flickr.com

Table 1 .
below.Benchmarks for Water Conservation Aspects in the GBCI Standard for New Buildings Version 1.2 2. Every 5% decrease in water consumption from primary sources.WAC 2Water Features 1A.Use of compliant water features with discharge capacity below the maximum standard of water output device capability as per the annex, amounting to at least 25% of the total procurement of water feature products.1B.The use of suitable water features with discharge capacity below the maximum standard of water output device capability in accordance with the annex, amounting to at least 50% of the total procurement of water feature products.1C.Use of compliant water features with discharge capacity below the maximum standard of water output device capability in accordance with the annex, amounting to at least 75% of the total water feature product procurement.

Tabel 2 .
Analysis of the application aspects, water demand-disposal, and water conservation percentage of the building