October 1, 2012
By Blair T. McCarry, P.Eng., PE, ASHRAE Fellow, LEED AP
The phrase “think globally, act locally” is a good way to describe how sustainable design projects are conceptualized. From the building to the community scale, the goal is to minimize the initial and ongoing effects of development by striving for net-zero impact and focusing on ecological restoration. (Net-zero refers to a balance of resource use and restoration on an annual basis—producing as much energy through renewable sources as consumed, sequestering equal or greater amounts of carbon as emitted, or diverting all waste from landfills or other harmful means of disposal).
Some important global environmental considerations the construction industry faces include:
This article describes how these environmental challenges were addressed through two building projects: the Centre for Interactive Research on Sustainability (CIRS) at the University of British Columbia (UBC), and Edmonton’s City Centre Redevelopment (CCR)—a community development planning project.
Centre for Interactive Research on Sustainability
In 2004, the CIRS team set aggressive environmental performance goals that reached well beyond Canadian Green Building Council’s (CaGBC’s) Leadership in Energy and Environmental Design (LEED) Platinum certification requirements. In 2006, the Living Building Challenge (LBC) emerged and was determined to be well-aligned with the CIRS vision. As such, the project proceeded, pursing certification under both the LEED and LBC rating systems.
CIRS is a 5675-m2 (61,085-sf) building consisting of office, meeting, and dry-lab spaces in addition to a 500-seat auditorium (Figures 1 and 2). The facility was designed to display its sustainable systems and to be ‘net-positive’ in seven different ways:
A high-performance building envelope, passive design strategies, provisions for inhabitant control of personal space, and energy-efficient equipment were used to minimize the building energy loads and use. A heat recovery system captures laboratory exhaust waste heat from the adjacent Earth and Ocean Sciences (EOS) building and transfers it to the heat pumps in CIRS. These provide heating and cooling for CIRS through the radiant slabs and a displacement ventilation system. The heat pump system returns excess heat from CIRS heat pumps to the EOS building to heat laboratory ventilation air, reducing its heat load and the demand on the campus steam system.
While CIRS uses 530 MWh of energy annually, 640 MWh of heating energy is reduced at EOS for a net annual campus energy use reduction (Figure 3). A ground-source geo-exchange field supplements the waste heat recovery and provides heating and cooling to the heat pumps. An evacuated tube array on the roof captures solar energy to pre-heat the domestic hot water and an internal heat recovery system captures waste heat from the building systems. Photovoltaic (PV) cells on the atrium roof and window sunshades convert solar energy into electricity. Ongoing monitoring and research will study the energy consumption and effectiveness of the building systems in relation to inhabitants’ behaviour and help optimize the facility’s operation.
All wastewater is treated onsite and reused for toilet-flushing and irrigation. Stormwater is collected on the roof, stored in cisterns, and treated for use as building potable water.
The materials employed in constructing CIRS were selected considering two criteria in addition to traditional issues: greenhouse gas (GHG) emissions embodied in the materials, and health impacts to occupants related to off-gassing. Local mountain pine beetle (MPB)-affected wood was used, sequestering 600 tonnes of carbon dioxide (CO2). The embodied emissions of the other building materials such as concrete, steel, aluminum, and glass totalled only 525 tonnes of CO2, for a net reduction of 75 tonnes (Figure 4).
Comparing the building performance to the global environmental goals previously outlined, one can conclude the following:
Edmonton City Centre Redevelopment
The City of Edmonton held an international competition for a redevelopment plan of its downtown municipal airport. The project was required to be carbon-neutral for 30,000 people in a world-class sustainable neighbourhood. The local coal-fired electrical grid has an emission rate of about 860 kg CO2/MWh, so this posed a significant challenge. Figure 5 shows an overview of the proposed development.
The planned density for the project is about five times as dense as the surrounding residential areas. A large park with lakes is included in the plan with 90 per cent of the development’s residents within a two-minute walk to open park space. The lakes are used for stormwater storage and water reuse for irrigation. Portions of the park extend into the Agrihood on the west side—an area planned to support community-scale urban food production. The existing light rail transit (LRT) system is being extended through the east side of the development with a new tram system to provide local transportation.
To achieve carbon-neutral operation, a district energy system for electricity generation and heat distribution has been planned. Fuelled mainly by waste biomass, boilers will produce heat for organic-rankine-cycle (ORC) generators that send waste heat to the district heating grid. Geothermal options at 6 km (3.7 mi) deep for electrical power generation and 3.5 km (2 mi) deep for district heating will be examined. (The project will be deemed carbon-neutral with or without the deep geothermal. The deep geothermal system is an alternative, carbon-neutral energy source that will need government or other funding to occur). Planned biomass fuel includes waste wood from the forest industries, clean waste wood from the Clover Bar waste-handling facility, and dried sewage sludge from the Gold Bar sewage treatment plant. (Although transportation emissions are not included in the carbon-neutral calculation, emissions are significantly reduced compared to the current case). A significant amount of the biomass fuel for the initial project phases can come from urban waste generated by the City of Edmonton. Flue gas emissions will be cleaned.
Excess electrical power generated will be sold to the grid as green power. The district heating system will be extended offsite to nearby hospitals, colleges, the legislature, and city hall for the initial development of an urban district heating grid. In this way, full use of the electrical and heating output of the District Energy Plant can be realized in a carbon-neutral manner. In fact, the sale of electricity and heat for use offsite will reduce GHG emissions in Edmonton and create a ‘beyond-carbon-neutral’ development.
Over the potential 20-year development timeframe, this project will actually reduce the overall CO2 emitted in Edmonton by 3.2 million tonnes—a significant savings compared to a business as-usual case (Figure 6). All electrical power used onsite will be generated by the district energy system on an annual-use basis. Some power will be drawn from the grid during the day while more excess power will be supplied over the night, making for a net-positive generation of electricity.
Building energy use requirements have been suggested so developments onsite would comply with the proposed energy target of meeting American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-13, Energy Standard for Buildings Except Low-rise Residential Buildings, minus 20 per cent to present efficient building operation for the first projects opening in late 2015 or 2016. Additionally, it is hoped some projects will meet Germany’s Passivhaus standards. Meeting the proposed performance level would reduce the size of the electrical power generation plant from 24 MW (if current building standards were used) to 18 MW, with a significant capital cost savings in the District Energy Plant.
Potable water use in Edmonton is among the lowest in North America at 209 L (55 gal) per person daily. A purple pipe reclaimed water use facility is planned to provide water for flushing toilets, landscape irrigation, and lake level top-up—this will reduce daily potable water consumption to 139 L (37 gal) per person. Some of the sewage from the site will be mined and reclaimed for non-potable water; the harder-to-treat sewage solids would continue to the Gold Bar sewage plant for a high treatment level. The excess sewage gas from the Gold Bar anaerobic digesters will be scrubbed to natural gas quality and injected into the natural gas line as green gas. This green gas would be used for cooking gas onsite and could fuel a significant number of transit busses serving the site and the city.
The annual carbon footprint for the future residents of the CCR development would be about 4 tonnes per person compared to the estimated current performance in Edmonton of about 24 tonnes.
The business case for the carbon-neutral energy systems was not part of the scope of the planning team. Edmonton is now preparing to seek interest for utilities to develop the energy systems for the project. In any case, a carbon-neutral system will cost more per kWh compared to conventional fossil fuel energy systems—particularly on a small- to medium-sized development. A strategy is to have more efficient buildings that use less energy so the energy bill for the occupant is lower than if he or she stayed in the current home if it were the same size.
Comparing development performance to the global environmental goals outlined previously, one can conclude the following:
The Edmonton City Centre Redevelopment is an example of how a project of this scale can significantly improve the overall performance of urban fabric.
Both projects demonstrate a whole-systems restorative approach to development, with local solutions addressing global environmental issues. Maximizing local opportunities such as sharing heat energy between buildings, using local waste as fuel, and eliminating demand on municipal potable water can add up to significant positive impacts extending far beyond the limits of one project.
Blair T. McCarry, P.Eng., PE, ASHRAE Fellow, LEED AP, is a principal and senior engineer with Perkins+Will. He has more than 40 years of experience in engineering and energy systems, especially at a campus and district level. McCarry is a strong proponent of the ‘whole-systems sustainability’ premise and has led the systems planning for multiple projects striving for Leadership in Energy and Environmental Design (LEED) Platinum and beyond. He graduated with a bachelor of science mechanical engineering degree from the University of British Columbia (UBC) in 1971. McCarry is a Fellow of American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE), an honourary member of the Architectural Institute of British Columbia (AIBC), and a member of several other professional organizations. He was also founding chair of the Vancouver Branch of the Cascadia Chapter of the U.S. Green Building Council (USGBC), a member of the Canada Green Building Council (CaGBC) Technical Advisory Group (TAG), and is a current CaGBC board member. McCarry serves as an adjunct professor in the School of Architecture and Landscape Architecture at UBC. He can be reached at firstname.lastname@example.org.
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