25 St Clair Avenue East Rehabilitation

Deep green retrofit a flagship model of fed’s sustainability commitments

By Charles Marshall

The rehabilitation of 25 St. Clair Avenue East in Toronto is a flagship project for the federal government; signifying its intention to reduce operating carbon emissions across its real estate portfolio while supporting the health and wellbeing of building occupants. The project demonstrated the viability of deep green retrofits for government stakeholders and the real estate industry at large.

Deep green retrofits are major projects that remake an existing building with the result of saving 30-50% or more in operating energy and greenhouse gas (GHG) emissions while targeting improved environmental quality and outcomes for human health. Achieving our climate action goals, such as Canada’s pledge to achieve net-zero emissions by 2050, will depend on substantial reductions from the real estate sector. Deep retrofits represent an achievable approach to substantially reducing GHG emissions while improving quality of life for building occupants and the members of the surrounding community.

URBAN CONTEXT

25 St. Clair Ave. E was chosen as a candidate for rehabilitation because of its central, transit-connected location and the significant remaining service life of the existing structure. The east-west orientation of the building lends itself very well to the implementation of passive design principles, including a reduced window-to-wall ratio.

The building is exceptionally well connected to public transit, including the Yonge subway line and the St. Clair streetcar line. The retrofitted building also provides exemplary infrastructure for cyclists; with over 120 bicycle parking spaces; as well as shower facilities. All parking is located below grade. EV charging stations are provided, with more roughed in to meet future demand.

Street trees and planters have been provided on St. Clair Avenue to reduce the urban heat island effect  and contributing to streetscape improvements. These trees require no permanent irrigation systems. A 110 cubic meter stormwater cistern conserves runoff from storm events to reduce strain on municipal infrastructure and release of untreated stormwater into waterways.Both the north and south facades have generous windows, providing daylight and views for building occupants.

A feature stair on the north side allows light to permeate into the building and at the same time, provides a vertical ‘neighbourhood’ for circulation and socializing. The compact form of the building contributes to air tightness and lowered heating and cooling loads, enabling the deployment of low-carbon energy systems.

New walls, windows, and roof surfaces were constructed to remake the façades and allow for appropriate levels of daylight and environmental quality, and to upgrade significantly the thermal performance and air tightness of the building envelope. Glazing surfaces were optimized to maintain thermal comfort and energy efficiency while providing ample daylight; thermally broken punch windows and curtainwall systems with triple-pane glazing were installed to target extremely low U-values for vision glazing.  Solid wall sections were provided with 200mm of semi-rigid insulation and thermally broken cladding supports to achieve an effective RSI value of 4.9 W/m2K. 

BUILDING SYSTEMS

Building systems are designed to complement the highly thermally efficient building envelope and minimize the energy required to provide comfort while eliminating combustion on-site and minimizing operating energy and carbon emissions.

Ventilation is provided from central dedicated outdoor air systems (DOAS), improving air quality and reducing the energy required to heat and cool ventilation air. MERV 14 filters remove pollutants and contribute to improved air quality. Ventilation units are sized to exceed the minimum requirements of ASHRAE 62.1 while outdoor air quantities are modulated according to the reading of zone level CO2 sensors.

The DOAS system includes a dual-core regenerative heat recovery unit for very high efficiency. A geo-exchange field is connected to a ground coupled heat pump chiller that will direct heating and cooling water throughout the building as required, including water-side heat recovery.

The design team at Geo-Xergy Systems worked with the architects to create an integrated heating and cooling solution.

The combined system leverages the available energy of the ground source system to provide the highest efficiency in both heating and cooling, while also carefully managing the energy source to ensure it operates reliably over the life of the building.

Project Credits

• Architect  DIALOG
• Owner/Developer  PSPC / Government
• of Canada
• Constructor  Urbacon
• Project Manager BGIS
• Landscape Architect  DIALOG
• Civil Engineer  LEA Consulting Ltd.
• Electrical engineer  DIALOG
• Structural / Mechanical Engineer  DIALOG
• Building Envelope Consultant 
• RDH Building Science
• Commissioning Agent  WSP
• Renewable Energy Systems  ZON Engineering
• Ground Source Energy Consultant
• Geo-Xergy Systems
• PhotoS  Scott Norsworthy

Charles Marshall, P.Eng. MBA LEED® AP BD+C is partner Engineering & Sustainability at DIALOG.