Calgary Public Building

Heritage landmark brought up to speed from the inside

Over its 80 year life, the interior of this landmark heritage building in downtown Calgary had been compromised by several insensitive renovations, although the exterior remained largely intact and in excellent condition. The challenge posed to the design team, was to create a leading edge, energy efficient and sustainable office environment within the building, while preserving  and enhancing the historic character of the exterior.

By Jerry Hacker

The first step was a condition assessment of the existing envelope. A thermographic camera was used to photograph the building and determine where the greatest heat loss was occurring. This process revealed that the original single pane windows were the most significant source of heat loss, and the exterior walls were the second largest contributor.
However, these original windows and exterior masonry were also two of the most significant character defining elements in the building. In response to this dilemma, the design team proposed upgrading the building from the inside by adding a layer of insulation and a second layer of high performance windows on the interior. This would permit the retention of two critical heritage defining elements, while achieving the energy efficiency goals of the Owner.
As installed, this interior envelope upgrade system comprises several components:
• High-performance, spray-applied polyurethane insulation and air barrier system
• New high-performance operable windows installed independently from the heritage windows on the interior of the building.
• Restoration of all heritage windows for operability and natural ventilation
• New high-performance mechanical system incorporated into the new interior liner.
During the condition assessment, it was also discovered that there was no outdoor air being brought into the building by the mechanical system. Although the existing envelope was quite leaky, the only outdoor air being brought into the building was from exterior air infiltration. All of the existing windows had also been permanently fixed shut.

The existing mechanical system used steam radiators and had no make up air component. This meant the indoor air quality could be improved significantly by making the windows operable again and implementing a mechanical system that introduced outdoor air to the space when outdoor temperatures dictated that windows could not be opened.
Approximately 360 heritage windows were completely restored, including installation of functioning counterweights, to allow for full operation and natural ventilation. All of the new interior windows forming part of the high-performance interior liner are also fully operable.

Other sustainable strategies include the extensive use of daylight for illuminating the office spaces based on the existing U-shaped configuration of the building, and the use of solar energy for hot water heating.
Daylight studies indicated the areas of adequate and inadequate daylight. These studies ensured the space planning and design was done to maximize the occupant’s exposure to natural light, and to optimize the positioning of artificial light sources. Luminaires are direct-indirect fixtures that use the re-exposed ceiling as a reflector to provide diffuse and evenly distributed artificial lighting without glare.

On the top most floor of the project, there were originally six large skylights that had been covered over at some point in the past. The top floor also has the smallest punch windows in the building. In order to ensure adequate natural light was provided to this floor, the heritage skylights were restored and re-implemented in the building. Where possible, the heritage components of the skylights were refurbished and re-used.

The skylights dramatically improve the daylight in the space. Because the skylights are horizontal, the heat gains within the skylight wells were modelled and a system of natural ventilation through exterior grilles was designed to ventilate any heat build up that might occur in the wells.

The rooftop solar hot water system supplies a minimum of 60% of the domestic hot water heating load for the project, and the cooling towers and air handling unit are able to provide “free” cooling to the building through the use of outdoor air up to temperatures of approximately 19° C.

With its many integrated retrofit strategies, this project has provided a unique and quantifiable cold climate case study. It demonstrates that existing heritage buildings do not have to be demolished or liquidated to make way for “more modern, energy-efficient structures”. Instead, heritage buildings can be successfully renovated to the highest standards of environmental stewardship without sacrificing cost, energy efficiency, or preservation standards.

Jerry Hacker, B. ENV. DESIGN, M. ARCH is the project coordinator for the marc boutin architectural collaborative inc. in Calgary.

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