25 St. Clair East Rehabilitation Project

A zero carbon model for the Canadian government

Civic & Culture, Office & Workplace, Renewal

The 25 St. Clair East Rehabilitation Project presented a significant challenge: preserving as much as possible from two 1950s era office buildings while improving their function and performance. 25 St. Clair East is a pilot project in the Canada Green Building Council’s zero carbon initiative, and will be the federal government’s flagship for sustainable building. The new design will reduce greenhouse gas emissions by over 80%, and put occupant health and wellbeing first. The project combines two buildings into one, with a new façade and a visual separation that runs diagonally across the building. This is manifested an unbroken open staircase that allows active circulation within the space while permitting an abundance of light to filter towards the back of the deep floorplate.

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Toronto, ON
442,235 sq ft
Government of Canada
DIALOG Services

Electrical Engineering
Interior Design
Mechanical Engineering
Structural Engineering


The envelop uses non-combustible terracotta panels that are durable, easy to maintain, and prevent water infiltration. Argon-filled glass windows will reduce solar heat gain while maximizing daylight.

The roof is equipped with a special membrane that will reflect radiant heat in summer and reduce convective heat loss in winter. It will also house a solar photovoltaic system to generate electricity.

The heating and cooling systems will take advantage of the latest geo-thermal technology. The lighting will be enabled by a system of daylight and occupancy sensors that adjust light levels.

Following principles of biophilic design, natural materials, access to light, and views to nature are incorporated into the design, increasing comfort, reducing stress, and enhancing creativity.


The building is fully accessible and is already part of the Canadian National Institute for the Blind’s (CNIB) Shop Talk: Blind Square Enabled program.

This allows visually impaired individuals the opportunity to independently navigate within a neighbourhood with the use of Bluetooth-enabled personnel devices.

The Team

This project embodies our commitment to improving how we manage the energy performance of federal buildings. Through this and other initiatives across government, we are taking steps to reduce our [carbon] footprint and green our buildings.

Steven MacKinnon, Parliamentary Secretary to the Minister of Public Services and Procurement
In Pursuit of Carbon Neutral A zero carbon model for the Canadian government
Merging buildings

The 25 St. Clair East Rehabilitation Project brings together the two buildings in this sketch into one new cohesive space.

The two buildings are interconnected by the large, amplified height. Across from a connecting staircase, the two previous buildings speak to one another across a cavern.

Light floods this part of the building, drawing people to circulate up and down the staircase.

Uninterrupted sight lines offer opportunities for people to connect from a distance.

The walls are lined with gardens, naturalizing the space.

Solar energy in the form of light and heat enters the building in the upper corner of one building, but needs to be carried town to the lower levels of the other.

One way to achieve this heat and light transfer would be through a diagonal connection between the two spaces.

Once the rectangular blocks and constraints associated with floorplates were removed, a path emerged.

The next challenge was connecting the two buildings with one unified façade…

… and adding windows wherever possible to ensure that the building was flooded with natural light.

The new façade acknowledges the coming together with a visual separation that runs diagonally across the building.