Insulating buildings for green standard compliance

Photos courtesy Michael Muraz

By Tracy Dacko

Rising above Toronto’s Bayside community, a mixed-use neighbourhood on the shore of Lake Ontario, stands the 14-storey Aquabella condominium development. The 27,000 m2 (290,625 sf), 174-suite concrete building is the third of four planned condominiums in the area.

Its developers aim to achieve Leadership in Energy and Environmental Design (LEED) Platinum certification, as well as compliance with Toronto Green Standard (TGS) requirements. In effect since 2010, the TGS sets tiered energy, emissions, and sustainability benchmarks for new buildings, to support Toronto’s goal of reducing greenhouse gas emissions to net-zero by 2050.

Building envelope consultants have conducted energy modelling studies of the design. These studies verify the building meets its energy use intensity (EUI) efficiency target of 183 equivalent kilowatt hours per square metre (ekWh/m2) per year. As a result, it also satisfies the requirements of TGS Version 2 and the 2017 Ontario Building Code.

Aquabella is designed to be at least 35 per cent more energy efficient compared to a similar structure designed to the National Energy Code for Buildings (NECB), a Canadian government standard.

Aquabella is designed to be at least 35 per cent more energy efficient compared to a similar structure designed to the National Energy Code for Buildings (NECB). Image courtesy Tridel

Designing buildings for energy efficiency and esthetic requirements

The northwest corner of the L-shaped structure marks the tallest portion of the residence, which slopes downward towards its centre, then rises in height on the eastern flank. The condominium tower offers stepped, upper-level garden terraces with scenic views of Toronto and Lake Ontario.

To achieve the required energy targets, the project team pursued active strategies in the form of efficient mechanical systems, along with passive strategies which impact building performance—such as orientation, envelope materials, windows and daylighting, and natural ventilation.

Aquabella employs an electric-powered variable refrigerant flow (VRF) heating and cooling system with built-in heat recovery. Each suite includes an energy recovery ventilator (ERV), high-efficiency appliances and pumps, and low-flow water fixtures, among other LEED Platinum and TGS-approved features.

A high-performance building envelope was desired to passively reduce cooling and heating energy use, as well as resulting utility costs. The project team aimed for one-third of the insulation on the exterior and two-thirds on the interior. The building’s wall assemblies are comprised of 50 mm (1.9 in.) of semi-rigid insulation and 150 mm (5.9 in.) of thermal batt insulation. Its window wall systems are comprised of double glazing and have low-emissivity (low-e) coating to improve the insulating properties of the glass.

Eighty per cent of Aquabella’s suites have balconies, creating the potential for heat energy loss through thermal bridging.

Mitigating thermal bridging

Eighty per cent of Aquabella’s suites have balconies, creating the potential for heat energy loss through thermal bridging. Thermal bridges also allow cold surfaces in the interior space, negatively impacting occupant comfort and often resulting in condensation and mould issues. To minimize thermal bridging at the balconies and maintain a continuous insulated building envelope, structural thermal breaks were installed between the balconies and the interior floor slabs.

The development team had used these structural thermal breaks on a previous project. In April 2019, the City of Toronto and the developer launched a test at the 35-storey Bloorvista condominium. Balconies on four floors were fitted with these thermal breaks, as well as thermal breaks from a competitor. Temperature sensors were installed, and data was collected to determine the products’ effectiveness. While a final report has not been released, unofficial results were in favour of the desired thermal breaks.

Structural thermal breaks consist of an insulation module with stainless steel tension and shear bars running through the insulation for structural strength. The bars tie into the steel reinforcement bars of the building’s interior slab and cantilevered exterior penetrations. The module’s expanded foam is approximately 98 per cent less conductive than concrete, while its stainless steel rebar is approximately one-third as conductive as carbon steel rebar—reducing heat loss at balcony penetrations by up to 90 per cent, while preventing interior condensation and mould growth.

To minimize thermal bridging at the balconies and maintain a continuous insulated building envelope, structural thermal breaks were installed between the balconies and the interior floor slabs. Photos courtesy Schöck Canada

Installing structural thermal breaks at the building’s balconies

A total of 1066 m (3500 ft) of concrete-to-concrete thermal breaks were fitted on Aquabella’s balconies. These structural thermal breaks are manufactured in 1-m (3.2-ft) lengths and can be cut on-site to fit design conditions, ensuring easy handling and placement during installation. For installation in cast-in-place concrete, the thermal breaks are positioned between the rebar cages of the exterior balcony and the interior floor slab. Then, the steel reinforcement of the structural thermal break is tied off to the rebar cages to secure the thermal break in place. Finally, both the interior and exterior slabs are poured through.

Most of the building’s balconies featured sliding glass doors, which posed no issues for the project team in terms of installing the structural thermal breaks. The developers do not anticipate any thermal bridging issues at the balconies.

“By putting in the thermal breaks, we reduced thermal bridging and almost eliminated cold floors near the balconies, which is a common complaint,” says Howard Tuchman, architect and senior associate with Kirkor Architects and Planners, the project’s architects of record.

The building was completed in mid-2021, with occupancy soon following.

Tension and shear bars running through the insulation block tie into the steel reinforcement bars of the building’s interior slab and cantilevered exterior penetrations.

Implementing structural thermal breaks in other condominium projects

Two other Bayside condominiums from the developer feature similar energy-saving systems. A fourth residence is currently under construction. It was designed by the same architectural team and will also deploy structural thermal breaks at the balconies. The integration of these materials is consistent with the developers’ commitment to sustainability across all their Bayside projects.

“We’re looking forward to seeing the energy savings from the thermal breaks,” says Carlos Antunes, partner at Kirkor Architects and Planners. “Over the next couple of years, some monitoring will be taking place, followed by evaluation post-construction. We’re interested to see how well it performs and what it brings to the table.”

Author

Tracy Dacko is a building products strategic marketing expert and marketing manager for Schöck North America. She has more than 20 years of marketing and business experience, with dealings on all seven continents for both national and international companies. Dacko previously served as president of the Business Marketing Association—New Jersey chapter, a member on the board of trustees for the PeopleCare Center for Human Services, and an instructor at Raritan Valley Community College’s Small Business Development Center. She has also authored various articles, educational courses, and other published works.

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