Oak Bay Passive House

Byng Residence Oak Bay, British Columbia

This 278-m2 single-family home achieves a seamless integration into its traditional neighbourhood by blending modern design with the familiarity of wood. The exterior material palette is defined by vertical cedar siding. Inside, local walnut brings warmth and texture to the space. The flat roof is prepared for PV panels, which will turn this house into a net-positive energy home.

Windows that extend from the floor to the ceiling of a two-storey great room allow natural daylight to suffuse the space and also provide a direct connection to the patio and rear yard. This west-facing glazing could have created overheating issues, but PHPP modelling showed that exterior shading, in combination with the large deciduous trees nearby, would address those potential issues. Skylights bring additional natural light to the middle of the house, further reducing lighting energy consumption during daylight hours. A punctuated overhang frames the view of the sky from the patio.

This project incorporates a wide range of Passive House features as fundamental components of its core sustainability concept. Its continuous blanket of insulation begins below the 15-cm concrete slab with 20 cm of a specialized EPS intended for geotechnical applications. Mineral wool fills the 2 x 6 wall assemblies, with a 15-cm layer of polyiso and an additional 38 mm of mineral wool exterior to the sheathing, creating a strong thermal break.

The roof assembly, topped with an SBS roofing product, has 30 cm of sloped insulation above the sheathing. The air-vapour membrane is placed over the plywood sheathing and creates a continuous overlap with the wall membranes, creating a very airtight building envelope.

With this envelope, the home’s comfort is assured with very little heating and no cooling. An HRV conserves the house’s heat while constantly filling it with fresh, filtered air. A heat pump water heater that uses CO2 as a refrigerant provides hot water for all uses, including heating the home when needed. A variable-speed mixing control pump siphons heated water from the storage tank and delivers it to hydronic piping snaking through the ground-level concrete floor. The thick slab functions here as a thermal buffer in both summer and winter seasons.

A thoughtful three-pronged strategy eliminated any need for mechanical cooling. Liberal use of exterior shading—a design element that Cascadia Architects takes very seriously—is this home’s first line of defense against summertime heat. Night flushing—setting the operable windows in the tilt position during the summer season—provides an exit pathway for excess warmth. Finally, setting the HRV to its summertime bypass mode enables it to draw in and circulate fresh air without conserving heat. Occupied since May 2017, the home has more than delivered on its promised comfort and outstanding air quality.

Team

Architect Cascadia Architects cascadiaarchitects.ca

Builder NZ Builders Ltd nzbuilders.com

Passive House Metrics

Heating demand 11 kWh/m2a

Cooling and dehumidification demand 0 kWh/m2a

Primary energy 43 kWh/m2a

Primary energy renewable demand 19 kWh/m2a

Air leakage 0.18 ACH50

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The Byng Street project is a blend of sleek design and craftsmen comfort, giving residents a livable stylish space. Cascadia Architects capitalized on natural light with a two-story open concept plan and skylights to take full advantage of natural light during the day. Liberal exterior shading is one aspect of Cascadia’s three-pronged approach to eliminating mechanical cooling and creating habitable outdoor space during the warmer months.