Overcladding

Close to 2,000 highrise residential towers were constructed in the Greater Toronto Area during the early 1960s and 1970s. This was a time when Canada was experiencing a remarkable building boom, along with rapid urbanization.

One of GRG Building Consultant’s recommendations in a 2012 PIEVC case study report1 was to consider “overcladding” as a way of extending the service of these 50-year old towers. This solution was also part of the solutions considered in the Toronto Tower Renewal Guidelines.2

The skill and effort that was involved in constructing the 1960s-era towers was remarkable. With various improvements in techniques and technologies, workers were able to put an average of 40,000 apartment units on the market every year! Toronto has the highest concentration of these buildings of any city in North America outside New York, so they represent an extremely valuable asset.

However, when these buildings were designed and built southern Ontario was an entirely different design and construction environment from what we see today. Energy consumption was not a priority. Also our expectations of buildings were quite different. The majority of these buildings, for example, were constructed without central air-conditioning, and most had minimal insulation.

Excellent candidates

The robust exterior masonry walls of the structures provide an excellent substrate for the support of overcladding systems. Combined with other energy saving measures, ovecladding can substantially cut their total energy requirements and significantly reduce their carbon emissions.

Overcladding refers to the installation of a new thermally effective “skin” installed over the existing façade of a building. The new skin is fabricated from high quality cladding materials. Typically an overcladding project also involves replacing the fenestration components. And because the buildings have a reduced energy demand their HVAC systems can be downsized.

Advantages of overcladding

Following are some of the benefits of overcladding:

• more financially and ecologically reasonable than demolition and reconstruction;

• does not require vacant possession; work can be carried out while the building is still in use with minimal impact on occupancy and with limited disruption to the fabric of the building.

• improves energy efficiency, thermal performance and air tightness;

• optimizes use of thermal mass and enables transfer of dew point outside structural wall elements;

• renews aging facades and improves appearance;

• reduces maintenance costs and allows upgrading of services;

• improves general comfort levels;

• increases life expectancy of the building;

• preserves the “embedded energy” contained within the existing structure.

Thermal overcladding has been accomplished in over 15 European countries with documented success. The European models involved interacting with both tenants and property managers with regard to health and safety issues, and the maintenance of what amounts to “new built” construction.cce

1 GRG Building Consultants’ PIEVC protocol-based Climate Change Vulnerability Assessment of a 16-story residential tower at 285 Shuter Street in Toronto is at www.pievc.ca/e/casedocs/Shuter/285_Shuter_Final_Report.pdf

2 See Tower Renewal Guidelines, http://www.daniels.utoronto.ca/trg