At 52 stories, 3 Civic Plaza is the third tallest building in British Columbia. It houses the Civic Hotel, an urban campus for Kwantlen Polytechnic University (KPU), meeting rooms, a fitness center, a rooftop garden and 348 residential condominium units.
The design team, consisting of ZGF Cotter Architects, Fast + Epp structural engineers, and ITC Construction Group, paid close attention to energy saving measures at the building envelope to minimize costs and carbon footprint, and improve occupant comfort. Copious amounts of insulation were applied on the walls, roof and other areas. Mineral wool was placed in the window wall assemblies. Foamed plastic insulation was sprayed on the cast-in-place concrete exterior walls. Foamed plastic insulation board was applied at the roofs, and cellulose insulation was spray-applied at the slab soffits under occupied space in the underground parking.
However, 37 floors of condominium balconies posed a potential thermal bridging problem. If cast conventionally, as cantilevered extensions of interior floor slabs, balconies would conduct heat away from heated interiors and dissipate it into cold environments like cooling fins, wasting heat energy. Chilled floor slabs inside of the building envelope would cause discomfort for occupants. Condensation on cold adjacent interior surfaces would additionally support mold growth, an increasing problem in today’s air-tight, high-humidity buildings.
The design team studied options to prevent thermal bridging at the balconies, and ultimately decided to insulate them from the supporting slab using structural thermal breaks.
Structural thermal breaks consist of an insulation module with stainless steel rebar running through the insulation for tension and shear strength. Since stainless steel is roughly one-third as conductive as carbon steel, it minimizes heat transfer through the module. Structural thermal break modules are positioned in line with other building envelope insulation, and are tied into the rebar of the interior floor slab and the exterior balcony slab prior to casting both in concrete.
Starting on the 15th floor, the balconies range in size from 51 to 102 sq ft (4.7 to 9.5 sq m). To insulate and support them, the design team specified 1,755 Isokorb® modules from Schöck North America. In total, 6,325 linear ft (1,928 m) were installed, equating to 18 ft (5.5 m) per balcony on average.