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CK Choi's Composting Toilets Save Water

Credits: CK Choi Institute of Asian Research

From E.Laquian, Design for a New Millennium, 1995 - In 1993 when the University of British Columbia commissioned Matsuzaki Wright Architects for the design of the C. K. Choi Building, a mandate was set to attain a new benchmark in sustainable design (and green building). From the design process to University standards, each decision was assessed for both its immediate and long term impact on the environment. The building was completed in 1996 and incorporates maximization of daylight, reduced energy consumption, occupancy and daylight sensors for optimal lighting control, atria that promote natural ventilation by inducing a stack effect, ventilation strips under windows to ensure continuous air change, double glazed windows with low conductivity insulating frames, exterior bricks that were salvaged from Vancouver city streets, 60 percent of timber beams that were salvaged from a demolished 1930s building and many others. Water conservation was a priority, with the installation of nine composting toilets and three waterless urinals, as well as graywater recycling from all sinks and rainwater collection from the roof – both of which are then used for landscape irrigation.


CK Choi Building Panorama

The CK Choi building at the University of British Columbia was constructed using materials that are recyclable or recycled, including bricks from demolished buildings and wooden beams from UBC's Old Armouries ©2010 Matsuaki Wright Architects

Reducing Impact and Consumption
The component of this building that has piqued the most interest is unquestionably the use of composting toilets. This waterless system enables the building to be disconnected from the sanitary system. The aerobic composting system is continually ventilated and reduces the volume of waste by 90 percent. The end product is a humus-like soil amendment product that is rich in nitrogen and other useful elements. Returning nutrient-rich humus to the earth restores depleted soil conditions.

The benefits of composting toilets are significant. For example, the system not only saves over 1500 gallons of potable water per day, it also reduces the load on the existing sanitary system by at least the same amount. If each new building at UBC were to use composting toilets, the existing sanitary infrastructure would not need to be expanded. The same principle applied city-wide could eliminate the need to expand central sewage treatment plants.

Embodied Energy in Construction
Reused heavy timbers from the Armouries building previously located across the street and reused red brick cladding from the streets of Vancouver give the Choi Building an aesthetic that is rich in history and energy efficiency. Many additional reused and recycled materials are also incorporated in the building.

The exact total of energy saved from extraction, transportation, refining and production of these materials has not yet been tallied. This number is expected to be substantial as it is estimated that more than 50% of the total materials are reused or recycled. Benefits in reduced greenhouse gas emissions are important as are the savings to the earth's limited supply of natural resources.

Operating Energy Over Time
Inside the Choi Building, spaces are so filled with daylight that the power consumption for lighting is less than half that required for typical office buildings. Offices have manual light switches; however, controls systems dim lights if adequate daylight is available or turn off lights if a room is vacant.

Operating energy is also reduced by the elimination of a traditional ducted air system. The building relies on natural ventilation with a few fans to assist when necessary. Operable windows and fresh air vents under each window allow a continual flushing of fresh air through the building. The cool fresh air rises as it warms through a series of high atria. When the warm air exits the building through louvres high in the atria, fresh air is simultaneously drawn in through the window vents. In total, the energy saved from the Choi Building in one year will power four Vancouver residences.

Liveable Working Space
For any building to achieve longevity and in turn be sustainable, it must be a place where people like to work or live. The occupants of the Choi Building enjoy natural daylight to work in and 100 percent fresh air at all times. Air quality within the building is improved through careful selection of building materials, finished products and construction practices. For example, the carpet is laid without adhesives, millwork is constructed from formaldehyde-free materials and finishes are solvent-free, low emission products. Features such as direct venting of the copy machines areas help to maintain good air quality over time.

As a leader in the community, the University of British Columbia sets goals and values for the community to emulate. The C. K. Choi Building is an example of a sustainable approach in the building industry. It is rewarding to see that interest to date has come from not only the local community but also from many corners of the world. As the construction of this project is finished, it is now those who will occupy and maintain the building who will face the next challenge of this project: to set new standards in sustainable operations.

Award-Winning Features
The C. K. Choi Building has won the 1996 Building Owners and Managers Association's Earth Award. The BOMA Earth Award is a new opportunity to recognize and promote "environmental friendliness" in commercial buildings. The following environmental aspects of the building were considered for the award:

Energy Usage: Based on a Building Simulation Energy Study, this 30,000 sq. ft. office building exceeds its Ashrae 90.1 prototype building by 57 percent The total electrical savings are 191,603 kWh per year. For this achievement, B.C. Hydro provided a $44,121 incentive to the Owner under the New Building Design Program. Some of the key energy savings features include: retaining an existing stand of trees along the 300 foot western edge of the building to reduce cooling loads; utilizing building forms that enhance internal stack effects to provide air change through natural ventilation and localized fans (no large mechanical air handling system); utilizing building forms that enhance daylighting to reduce reliance on electric lighting and reduce cooling loads; incorporating daylight sensors and occupancy sensors to minimize unnecessary use of lights; incorporating high efficiency luminaries with lower ambient lighting levels and task lights where appropriate; exceeding the R-values suggested under Ashrae 90.1 for walls, ceiling and glazing; careful attention to detailing and construction methodology to minimize heat loss through thermal breaks etc.; utilizing waste heat in an existing steam vault adjacent the site to preheat domestic water.

Water Conservation: Significant water savings are realized through a series of features. Composting toilets installed in this project do not require water for flushing. City water is generally only required for the low flow lavatory faucets (spring loaded to further reduce waste) and kitchen sinks. Irrigation of site planting material is provided solely from collected rain water (stored in an 8,000 gallon subsurface cistern) and recycled gray water from the building. Projected water usage is approximately 300 gallons per day.

Waste Management: Sanitary waste is eliminated through the use of the composting toilets. Waste from sinks is processed on site through a subsurface gray water recycling system and then used for irrigation. This combination eliminates the sanitary connection for this project. The significant amount of reused materials and products with recycled content in this building (60 percent of primary wood structure, 100 percent of exterior brick cladding) address waste management by diverting materials from landfills. In addition, a comprehensive waste management plan was implemented during construction. The site separated and recycled waste materials diverted more than one half of the waste generated on site from the landfill.

Ozone-Depleting Substances: In addition to being free of CFC's as required under provincial regulations, efforts were made on this project to select systems and products that minimize impact on the ozone layer. For example, rigid insulations are expanded boards foamed with pentane (not ozone depleting) versus extruded boards expanded with an HCFC, and natural ventilation eliminates the need for refrigerated coolants. The significant amount of reused and recycled materials in this project also greatly reduces the use of fossil fuels (otherwise required to extract, transport and process new raw materials) and thus reduces carbon dioxide emissions, the largest single component of current greenhouse gas emissions.

Indoor Air Quality: Three strategies were taken to ensure good indoor air quality. Material selection was carefully reviewed. For example, all millwork is constructed from formaldehyde-free medite, all finishes are solvent-free, low VOC products, carpet is laid with a tack strip method versus adhesives. Construction sequencing was specified to ensure flushing of the building during drywall installation and finishing, painting, caulking, and during the installation of carpets. As people produce carbon dioxide and everyday operations add VOC's to buildings, the natural ventilation system in the building was designed to provide 20 cfm per person of 100 percent fresh air at all times. In addition, copy machine areas are direct vented. Being continually flushed, the building does not experience peaks and valleys in lAO often found in traditional mechanized systems that operate with reduced air changes during low occupancy hours.

Building Waste Management: The Choi Building incorporates a comprehensive approach to management of building waste and surface water on site. Graywater is collected in the building and directed to an exterior subsurface graywater recycling area. The graywater recycling trench contains plant material and in turn, microbial plant life known for their capacity to neutralize bacteria in the graywater. The recycled graywater is then used for site irrigation. A subsurface holding tank is incorporated for storage of rainwater collected from the roof area. This water is used for summer irrigation of the site and to ensure that the plant life in the graywater trench is never left dry. This design results in no city service connection for graywater waste from the building and no use of city water for site irrigation. The addition of composting toilets to this system allows this building to be "off grid" for sanitary waste.

Environmental Management: The first step in environmental management was to enhance the ambient conditions of the existing site. Existing trees were retained for their capacity to remove C02 from the air and the shade they provide on the west elevation. The building replaces an existing parking lot and the dynamic building form capitalizes on the benefits of the different climatic conditions at each orientation. The second step was designing a building that minimizes consumption and impact on the environment. The total operating energy savings for this project are 50 percent greater than what is achieved under the new Energy By-Law of Vancouver. An energy meter enables the building owner and users to monitor actual energy use in the building and make adjustments in operations as necessary.

Tenant Awareness Program: Part of the commissioning process for this project includes educating users about building features and items over which they have control. For example the building has operable windows and user control over heat in work spaces. Understanding the way the stack effect for ventilation works or the operation of daylight and occupancy sensors, enables the users to participate in energy efficient operations and ensure that good IAQ is maintained.

Composting Toilets
By City Farmer
In Vancouver, British Columbia, the CK Choi 30,000 sq. ft. office complex, utilizes composting toilets and urinals for human waste disposal. The new building, which houses The Institute of Asian Research, is not connected to the city's sewer system. As well, a subsurface, graywater recycling system with phragmite (tall grasses) plant varieties, cleanses the graywater which is then used for on-site irrigation. The C K Choi Building at UBC is the first all-Clivus Multrum large-scale office-building project in Canada. There are a total of five Clivus Multrum Model M28 Composters at the Choi Building, with ten flushless toilets and, several flushless, trapless ventilated urinals attached to them. Each of these Clivus Composters has an annual user capacity rated at 45,000 visits. Therefore, the total annual rated capacity for the Clivus systems is 225,000 visits. All of the Choi building's washwater (graywater) is processed on-site separately.

Structural Engineering
by Reed Jones Christoffersen
When the University of British Columbia asked RJC to join the design team for their new Institute of Asian Research, they wanted a building that would have minimal impact on the environment. After a series of seminars with an expert on environmental design, the consulting team developed a set of targets that included minimizing the energy needed to produce building materials, lowering operating energy needs, and creating livable work spaces.

Reused heavy timber from the recently demolished Armouries building located across the street, and red brick cladding from the streets of Vancouver, give the building an aesthetic that is rich in history. But in recycling the 70-year old timbers the team encountered both logistic and design challenges. As each piece of timber was inspected and catalogued, the design of column grids and spacing, as well as the width of the building itself, was dictated by the strength and availability of timbers. Conventional grading rules were modified to take into account the actual stresses along the length of each timber so that those parts that had been repaired or flawed could be placed in non-critical locations. Since the timber connections were also recycled steel and designed to be demountable so that the wood could be reused again in the future, a North America-wide search for suitable certified material was implemented.

Careful attention to indoor air quality through the use of natural ventilation and cooling systems, composting toilets and a graywater recycling system make this building one of the few in Canada to be totally conceptualized, designed, constructed, and operated following the concepts of green engineering and sustainable design.

Environmental innovations
• The building was constructed using materials that are recyclable or recycled, including bricks from demolished buildings and wooden beams from UBC's Old Armouries.

• Water is preheated using waste heat from an existing steam line.

• Cooling and air exchange is provided by 100 per cent natural ventilation. Atriums ventilate different parts of the building through a stack effect. High ceilings and windows that open also take advantage of natural ventilation.

• Offices are placed to optimize natural light, so the building requires less than one-third the artificial lighting typically used in an office building. Daylight sensors automatically dim indoor lighting.

• Its energy-efficient design reduces UBC's electricity use by 192,000 kilowatt-hours a year, the equivalent of the amount of energy used annually by 19 single family homes. This provides a savings to the university of $9,600 a year.

• Waterless, odourless composting toilets require no sewer connections and produce fertilizer for the garden.

• Recycled grey water from sinks and captured rain water is used for landscape watering, cutting water consumption in half.

• Landscape design by Cornelia Hahn Oberlander includes gingko trees, known for their ability to clean the air of pollutants.

• The 1996 Earth Award from the Building Operators and Managers' Association of B.C.

• Progressive Architecture Award for Green Architecture, 1995

• Nominated for the 1996 Energy User News efficient building awards, a North American-wide competition

As well, the Colorado-based Rocky Mountain Institute, which investigates global issues of energy conservation, is including the Choi building in a series of case studies on the most promising example of green development.


  CK Choi Building Case Study (1,830 kb)

  CK Choi Case Study USGBC (473 kb)

  University British Columbia Campus Sustainability Map (1,026 kb)

  CK Choi Building - Process Makes the Product (228 kb)


CK Choi Institute of Asian Research Building Website

CK Choi Building 3-D Model

CK Choi Institute Building Case Study Online

Clivus Multrum Composting Toilets