Decarbonizing cement

By Jeff Ranson, Senior Associate, CaGBC

As we move towards 2050 targets for green building, embodied carbon is increasingly important to staying under the emissions budget and limiting global warming below 1.5 degrees Celsius. What is embodied carbon? It’s the product of the materials and construction methods we choose. This value is often stretched over the life of the building to reflect durability, the idea that a building built to last is likely better than one that will need constant repairs. However, the reality  is that those emissions are all fully released up front. Like net-present value in the financial world, a ton of carbon emissions today is worth more than a ton of carbon emissions tomorrow.

Of all the opportunities to reduce embodied carbon, the most significant is in concrete. Concrete is the most widely used building material, cutting across both buildings and infrastructure. And despite strong and promising market growth of alternative low-carbon materials including wood and biomaterials, concrete will continue to be a critical material for construction.

Potential as a climate solution

Reducing greenhouse gas emissions from concrete is a national priority. Natural Resources Canada and the Cement Association of Canada have committed to develop a decarbonization roadmap for the industry. For the designing construction industry, there are a few significant ways to reduce emissions today, and some very promising opportunities emerging.

In the immediate term, there are two opportunities to reduce emissions from concrete. The first is simply to minimize the amount of concrete projects use. This involves looking at how much concrete is required for the project and optimizing its use. This requires designers be conscious of how design choices such as massing impact material requirements. In many cases, designers are evaluating alternative low-carbon materials like mass timber to replace concrete, but nothing is as effective as just using less material.

One area in relation to embodied carbon that has been overlooked is the impact of land use planning. Infrastructure like roads, sewers, and transit require concrete.  There is no realistic substitution. Low-density suburban development oriented around the automobile results in huge amounts of embodied carbon, seldom considered in any municipal carbon strategies. CaGBC has been in discussions with researchers at the University of Toronto to better understand the relative carbon impacts of different development patterns, but at present there isn’t a well-established practice for evaluation. With more research we hope to understand the impact of embodied carbon from infrastructure and the importance what we build and where we build it.

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Bank of Canada Renewal, Ottawa, ON

Existing Building Upgrade Award | Perkins+Will

Jury comments: This major rehabilitation and revitalization project, driven by quantitative issues of obsolete infrastructure, poor energy performance and related carbon impacts, and an outdated working environment, has been addressed with aesthetic sensitivity and restraint. Innovative structural upgrades enabled the restoration of the integrity of this 1970s office tower by Arthur Erickson,  while the 1930s centre building and its immediate surroundings  have been transformed into valuable new public amenities.

Located just west of Parliament Hill in Downtown Ottawa, the Bank of Canada Head Office complex comprises 79,500m² of offices and operation spaces. The original Centre Building was built in the 1930s; the twin office towers and connecting atrium being added in the 1970s. Completed in 2017, this project included the comprehensive renewal of the existing complex, including some reconfigurations and additions to the program.

A new museum invites and educates the community about the Bank’s role in the Canadian economy. The pyramidal glass entrance pavilion and the enhanced public realm that surrounds it form an abstraction of the Canadian landscape and functions as an accessible, multi-faceted public realm throughout the year.

Major drivers for renewal were the performance and infrastructure deficits of the facility, energy upgrades and carbon reductions, and modernization of the workplace. Within the towers, floor plates and waffle slab ceilings were restored to their original open plan concept.

The renovated towers were designed to be modular, allowing for a diverse range of uses so that each contains a combination of private and collaborative spaces.

The Centre Building accommodates both offices and conference facilities, while the atrium provides a variety of social spaces.

The design looked to maintain as much of the existing building infrastructure as possible, to lower both costs and negative environmental impact. Passive design strategies include revealing floorplates, allowing for deeper daylight penetration and greater access to views to the exterior and atrium.

PROJECT CREDITS

  • Client:  Bank of Canada
  • Architecture/Interior Team: Perkins + Will
  • Civil Engineer: Novatech Engineering Consultants
  • Electrical/Mechanical Engineer: BPA Engineering Consultants
  • Structural Engineer:  Adjeleian Allen Rubeli Limited
  • Project Manager:  CBRE Limited/Project Management Canada
  • General Contractor:  PCL Constructors Canada Inc.
  • Landscape Architect:  DTAH
  • Food Service/Commissioning Agent:  WSP
  • Heritage ConsultantEvoq Architecture
  • Building Envelope:  ZEC Consulting
  • Building ScienceCLEB
  • Sustainability Consulting Team:  Perkins + Will
  • Security:  LEA
  • A/V:  Engineering Harmonics
  • Acoustic:  HGC
  • Cost Consultant:  Turner & Townsend
  • Lighting:  Gabriel MacKinnon/Perkins + Will
  • Code & Life Safety:  Morrison Hershfield
  • Photos:  Younes Bounhar

PROJECT PERFORMANCE

  • Energy intensity = 183 kWh/m² /year
  • Energy savings relative to reference building = 44%
  • Water consumption = 4,645L/occupant/year (based on 250 days operation)
  • Water savings relative to reference building = 35%

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Building Blocks on Balmoral at Great West Life – Winnipeg, MB

Institutional [Small] Award | Prairie Architects Inc.

Jury comments: This project comprehensively and creatively addresses multiple aspects of sustainability simultaneously. The adaptive re-use of a heritage house as the centrepiece of a new and much needed daycare facility not only achieves LEED Platinum environmental performance, but also acts as a powerful catalyst in the revitalization of the fabric of Winnipeg’s West Broadway neighbourhood through the addition of this community amenity.

Building Blocks on Balmoral at Great-West Life comprises  the adaptive re-use of the 110-year old Grade II listed Milner House and two new structures, which together provide 100 licensed childcare spots to Great-West Life employees and the West Broadway community.

In addition to upgrading and extending the useful life of a heritage structure, the new facility has achieved LEED Platinum certification with the integration of sustainable features that include: a geothermal ground source heat-pump with in-floor radiant heating and chilled beams for cooling; displacement ventilation that requires lower fan power than ducted systems; significant use of salvaged, refurbished and re-used materials; substantial water use reduction (a particular priority in the Prairies); abundant daylight and views and use of low-emitting materials.

In order to create a sense of “home” for children, the facility was deliberately divided into two smaller additions on either side of the existing Milner House: one for toddlers and infants and one for preschool aged children. Each addition has direct connection to accessible exterior play yards, designed with naturalized landscapes and an age-appropriate focus.

The need to replace the deteriorating foundation of the Milner House provided an opportunity to make the ground floor of the facility fully accessible.

In order to keep the entire main floor on one level without introducing ramps and stairs, the original structure was lowered approximately 610mm onto a new foundation, and the north end of the site was built up 1,220mm to provide an accessible outdoor play area  for the children.

This also enabled the implementation of two site planning moves that facilitate on-site stormwater management: the elimination of an impervious lane connecting Balmoral Street to the Great- West Life parking lot; and the creation of a retention area for stormwater run-off at the north end of the site.

With a particular concern for indoor environmental quality, the project has been designed with 100% fresh air displacement ventilation. The system, which introduces low velocity fresh air at low level, was selected not only because of the significant energy savings it offered, but also because it was the most effective way to deliver fresh air close to the floor in spaces occupied by small children and crawling infants.

PROJECT CREDITS

  • Owner/Developer:  Great West Life Assurance Company
  • Architect:  Prairie Architects Inc.
  • General Contractor:  Manshield Construction
  • Landscape Architect:  Nadi Design & Development Inc.
  • Civil Engineer:  WSP
  • Electrical/ Mechanical Engineer:  KGS Group 
  • Structural Engineer:  Wolfrom Engineering Ltd.
  • Commissioning Agent:  Pinchin
  • Energy Modelling:  Stantec
  • Photos: Lindsay Reid

PROJECT PERFORMANCE

  • Energy intensity (building and process energy) =  145.5KWhr/m²/year
  • Energy intensity reduction relative to reference building under MNECB 1997 = 56%
  • Water consumption from municipal sources = 2,993 litres/occupant/year
  • Reduction in water consumption relative to reference building under LEED = 50%
  • Recycled material content by value = 14%
  • Regional materials (800km radius) by value = 36%
  • Construction waste diverted from landfill = 89.5%
  • The chilled beam around the perimeter. Daikin contributed fan coils and its Enfinity water-source heat pumps to the HVAC system. Each of the four new buildings use an Uponor manifold and in-floor radiant system to provide  even heating across the floors. 
  • The project uses an ERV system by Winnipeg-based Tempeff North America. The Dual-Core technology recovers both heat and humidity in winter allowing for continuous fresh air supply and a frost-free operation in extremely cold conditions. This ERV simplifies system design and does not require preheat or any form of defrost strategy.
  • East-facing childcare space where large windows admit natural light. DUXTON Windows & Doors supplied the fiberglass fenestration, in FiberWall™ Series 328 and 458, high performance triple glazing. The windows came complete with a 350 Panning exterior extension, providing a seamless, prefinished flashing detail for easy installation.

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