TORONTO, ON – The City of Toronto has initiated a program with Tridel Corporation to test the effectiveness of structural thermal breaks. The test will measure the degree to which structural thermal breaks save energy and maintain uniform temperature of the interior floor, as part of an effort to fine-tune the city’s sustainable design requirements for new construction.
The Toronto Green Standard is the city’s blueprint for sustainable design and is part of the overall urban plan to meet the pan-Canadian building standard of Net Zero Energy by 2030. Introduced in 2006 as a voluntary standard for new development, it has implemented increasingly rigorous “tiers” every four years to reduce building energy use and greenhouse gas emissions, improve air quality, and protect local waterways and ecology.
Tridel, one of the largest and earliest-born real estate developers in Ontario, is partnering with the City to test the effectiveness of thermal break solutions at the Bloorvista luxury condominium community. Bloorvista, a 35 storey tower, is part of the Islington Terrace master-planned community of residential, indoor and outdoor amenities and retail space. Schöck Isokorb® structural thermal breaks for balcony connections are being measured against another manufacturer’s thermal breaks, in a punctual solution arrangement, and a “do nothing” scenario.
Two kinds of Schöck thermal break products for concrete-to-concrete balcony connections were installed: one containing 80 mm of insulating material in the assembly, and one containing 120 mm of insulating material designed for higher thermal performance. The thermal breaks and temperature sensors were installed on the 32nd and 33rd floors in April of 2019.
On the 31st floor, the other manufacturer’s thermal break products were installed, providing a performance comparison by separate manufacturers of thermal break solutions.
Also being evaluated on the 34th floor is a punctual solution arrangement in which rigid insulation blocks between the interior floor and balcony slabs are placed alternately with lengths of uninsulated reinforced concrete. The intent is to measure heat escaping from the uninsulated areas to the outside.
A third-party independent company, AOMS Technologies, installed highly accurate and rugged sensors to measure the temperature of the concrete on the interior and exterior sides of the structural thermal breaks. Sensors were also installed on a floor without structural thermal breaks to create a baseline condition for comparison.
The testing continues over approximately 15 months to collect data for an entire seasonal cycle. Results are expected when the building is completed and heated during 2020 and 2021.
Thermal bridging occurs at penetrations through the insulated building envelope, creating an easy path for heat loss and weakening the thermal performance of the building envelope. In concrete structures, thermal bridging is commonly found at balconies where monolithic slab castings penetrate the insulated building envelope, allowing heat energy to travel through concrete and rebar into the cantilevered balcony. During low temperature conditions uninsulated balconies create a “cooling fin” effect.
In addition to wasting energy, uninsulated balconies chill adjacent interior surfaces, which can reach dew point in today's high-humidity buildings, promoting condensation and mould growth in stagnant wall and ceiling cavities.
Mould can become airborne years before becoming visible, exposing the owner to liability and remediation costs.
Positioned at the building envelope between the interior floor slab and cantilevered balcony slab, the longitudinal structural thermal break is fabricated of graphite-enhanced expanded polystyrene which is 2% as conductive as concrete, and stainless steel rebar which is one-third as conductive as carbon steel rebar. The structural rebar projects through the polystyrene and ties into conventional rebar of the interior floor and exterior balcony slabs prior to casting in concrete.
The resulting assembly provides the structural strength necessary to support loads, while reducing heat loss at the penetration by up to 90% and raising the temperature and comfort of interior floors. It also prevents condensation and mitigates the risk of mould growth, which can be the source of costly repairs, remediation and even lawsuits relating to the air quality and health of the building’s occupants.
The effectiveness of thermal breaks as revealed in the test may influence Toronto to include them in its sustainable design requirements for new construction.