Net Zero Case Study
See how this century-old semi-detached home went from dark and drafty to a bright, modern, and energy-efficient oasis.
This amazing renovation project proves that any home – even one with tricky challenges – can become a Net-Zero haven. Learn how a step-by-step approach transformed this house into a comfortable, eco-friendly dream home.
Project Overview
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Project Name: Leslieville Net Zero
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Location: Toronto, Ontario, Canada
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Property Type: Semi-detached Home
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Square Footage: 1830ft2
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Year Built: early 1900s
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Renovation Completed: Phase 1: July 2022, Phase 2: Nov 2023, Phase 3: May 2024
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Motivation for Renovation: The home, suffering from a poorly done ‘flip’ reno was dark, drafty and poorly insulated.
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Architect: MOSS SUND architects
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Services: Climate Score, Net Zero Plan, Retrofit Co-ordination
Home Overview and Details
This project is a renovation and addition to a semi-detached home originally constructed in the early 1900s. The house, suffering from a poorly done ‘flip’ reno, was dark, drafty and poorly insulated.
The project took a stepped approach, with an end target of Net Zero, while also updating and modernizing home. The home now features an open plan layout, lots of light, an amazing kitchen and principal suite, as well as an efficient building envelope, large energy efficient windows and stack effect cooling. In Phase 2, the gas furnace was replaced with an air source heat pump and the gas on demand hot water with a highly efficient electric tank. Phase 3 added 9Kw of solar panels to make the home Net Positive.
The tight urban lot, shared party wall, and location on a flood plain regulated by the Toronto and Region Conservation Authority (TRCA) presented some challenges to the design. The lessons learned from this project will be used as a model for how existing urban homes can be retrofitted across Toronto in the years to come.
The goals of this project were equally to improve how the house looked and functioned as well as make it more energy efficient, comfortable and resilient. The stepped approach created a framework for upgrades with envelope upgrades completed first and equipment/generation added later.
As this is an east-west oriented semi-detached home on an urban lot, the design team was restricted in what could be altered. The back wall was removed to make way for a 2-storey (plus basement) rear addition that maximizes space and light. The roof of the addition was sloped to the south to allow for future solar panels. The existing structure was fully renovated to improve the layout, enlarge windows, replace a mish mash of outdated plumbing, wiring and ductwork, increase insulation levels and be more air-tight.
Performance and Impact:
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Pre-Renovation Energy Usage: 28,611 kWh
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Post-Renovation Net Energy Use: -4,702 kWh
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Energy Production: 10535kWh
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Energy Usage: 5,833 kWh
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Key Renovation Measures:
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Insulation Upgrade: The basement walls were insulated to achieve an R-value of 14 in the old part and R35 in the new. R10 sub slab insulation was installed in the new section. No insulation was added to the existing basement floor to avoid the embodied carbon of replacing the concrete slab. The above-grade walls were elevated from a spotty R11 to R38, and the cathedral roof’s were increased from R18 to R40. These insulation improvements brought about substantial enhancements in both the home's airtightness and mechanical performance.
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Window and Door Replacement: Double pane windows were replaced with high performance triple-glazed fibreglass units
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Air Tightness: A pre reno blower door test was not completed, however, based on similar projects, it was estimated at R15 or worse. Blower door tests were done through construction and the final reading was 3.37 ACH.
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Heating and Cooling System: The existing home had a relatively new gas furnace and no AC. The existing air handler was retained and a new indoor coil and outdoor heat pump unit were installed
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Hot Water: A new well insulated hot water tank was installed including a connection to run the existing in-floor heating.
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Solar: A 9 kW solar system was installed on the new roof and existing garage. Total output is expected to exceed the requirements of the home
Summary
This project is a shining example of what a committed homeowner can achieve. Not only has an existing home been saved and made ready for the next 100 years, the homeowner has a bright inviting space to live and emissions from the home have been reduced by 95%. Energy use and production will be monitored to see how it compares with the prediction of 111% Net Positive.
