Coal Harbour

Project Highlights

• Targeting LEED Gold and Passive House certifications, with the help of structural thermal breaks to help insulate the building envelope 
• Part of the second phase of the City of Vancouver's Coal Harbour Master Plan
• “As the general thermal envelope improves and the insulation levels increase in a Passive House, the relative impact of thermal bridging grows more significant on the energy balance,” said Cyril Vibert, thermal building engineer, A2M.
  
  

Passive House building rises on Vancouver waterfront 

The 11-storey Coal Harbour waterfront complex will complete the second phase of the City of Vancouver’s Coal Harbour Master Plan. The design team's creatively-engineered building envelope is on target to achieve LEED Gold and Passive House certification, thus meeting the city’s stringent building code. The code requires at least R-22 thermal performance in walls of multi-unit residential buildings, and calls for drastically reducing thermal bridging in the envelope.

The Passive House designation necessitates reducing a building’s space energy demands for heating and cooling to no more than 15 kWh per square meter per year (4.75 kBtu per square foot per year). 

The two-tiered building will integrate with the adjacent Community Centre (Coal Harbour Phase 1), which offers a range of programs and classes for all ages.

Phase 2’s lowest level contains bicycle storage and an elevator lobby. An atrium section rises from ground level one. Levels one through three will house Coal Harbour Elementary School, while childcare and an outdoor patio play area will occupy level four. The six upper levels provide 60 units of social housing with residential amenity space and a landscaped outdoor patio on the top level 11. A green roof will cap the building.

The project is being constructed by The Haebler Group, with Henriquez Partners Architects and Glotman Simpson Consulting Engineers (structural engineer), Belgium-based A2M as the Passive House consultant and RDH Building Science as the building envelope consultant. Project completion is expected by December 2024.      

Engineering the envelope

To mitigate heat loss through the building envelope, the design team specified a façade primarily composed of precast concrete sandwich panels – rated at R-39 with 20 cm (8 in.) of extruded polystyrene foam -- a triple-glazed fiberglass window wall system, and some 527 metres (1730 linear feet) of structural thermal breaks

The envelope, which extends below grade to a structural slab, is tied into a grade beam and connected to the walls using concrete-to-concrete structural thermal breaks. At the ground level, a layer of R-60 foam insulation is sandwiched between the lower slab and a grade-level slab.

Thermal integrity at the ground level is further achieved by isolating the curbs and upstands with vertically-oriented Schöck Isokorb^® structural concrete-to-concrete thermal breaks, combined with horizontally oriented concrete-to-concrete thermal breaks tying to the interior slab.

All floors employ the precast concrete sandwich panels. Fibreglass tabs connect the panels to the building structure and serve as thermal breaks due to their high insulation value. Fibreglass is also specified for all window frames as it reportedly offers 250% greater thermal performance than aluminum. 

The panels are craned into place with the inner foam layer sitting on the slab edge and acting as a thermal break with no contact between the outer and the inner walls, according to Christian Schimert, associate, Henriquez Partners Architects.

The rigid foam insulation on the project is environmentally friendly, Schimert adds. “Rigid insulation varies in its carbon footprint. There are now products on the market with a relatively low carbon footprint, which we specified. This is important since our aim is to reduce our carbon emissions as a whole.”

Role of structural thermal breaks

To mitigate thermal bridging and heat loss at all above-grade levels, the Phase 2 team specified vertically oriented concrete-to-concrete structural thermal breaks where curbs and upstands connect to the floor slabs.

The Isokorb® structural thermal breaks, designed for parapets and other vertical structures, consist of rigid foam insulation modules with stainless steel rebar running through for tension and shear strength. The reinforcement bars of the thermal breaks are tied horizontally to the slab rebar and vertically to the rebar of curbs and upstands. The structural thermal breaks transfer moment and shear forces from the vertical element to the concrete slab structure.

Structural thermal breaks are said to improve the R-value of the envelope at structural penetrations by up to 90 percent. “As the general thermal envelope improves and the insulation levels increase in a Passive House, the relative impact of thermal bridging grows more significant on the energy balance,” said Cyril Vibert, thermal building engineer, A2M. “Treating all thermal bridges is a key requirement of Passive House certification,” he adds. “If untreated, that area of concentrated heat loss can introduce a risk of condensation on the internal surfaces which is detrimental to the comfort of the users and can lead to mould growth.”

The six-storey residential portion of the building includes horizontal steel fins as a design feature, and as a mechanism to reduce solar heat gain by shading the upper portion of the windows. The fins are attached to the already thermally broken precast double-wall panels. Horizontally oriented thermal breaks are installed on the supports for the bow sprit ― a decorative architectural detail atop the front of the building facing the harbour.

“The project has hundreds of thermal breaks,” said Trevor Heide, project director, The Haebler Group, “most of which are designed for vertical elements. It's interesting because you have special ways to place and secure them.”

The potential for seismic activity in British Columbia necessitated additional structural thermal break modules designed for earthquake resistance. Used in combination with the standard Isokorb® concrete-to-concrete thermal breaks, they transfer earthquake forces parallel to the insulation layer as well as uplift forces.

Obviating fossil fuel

As a Passive House project, the building design significantly reduces energy consumption to eliminate reliance on fossil fuels. Schimert says that a correctly engineered Passive House can be heated using only sunlight and domestic hot water piping though most of the colder periods. Coal Harbour Phase 2 heats and cools using electric powered air-to-water heat pumps, while employing a centralized heat recovery ventilation system.

In addition to producing zero greenhouse gas emissions, the project targets a 40% reduction in embodied carbon to meet the city’s commitment to reducing carbon emissions during construction.

Expectations for the finish line

Phase 2 is a high-profile example of the Passive House concept sited on prized waterfront property. “It's challenging because it has very tight margins, but that's the nature of the beast,” said Schimert. “We have created a project that has a lot of architecture in it, which is unusual for Passive House.”

Trevor Heide adds that the Haebler Group's crews received the needed support from Schöck. “They have come in to train the guys on how to do the installation. They've answered questions, have been responsive, and their technical ability is very good. The manufacturer has been providing support, as everybody on the design team has been learning along the way.”