Oshawa ADU — The Beginning
Why we're building a Passive House accessory dwelling unit in Oshawa, Ontario, and what we hope to prove with this project.
Every big project starts with a simple question. For us it was: can we build a truly high-performance home — built to the Passive House standard — as an ADU in the Durham Region, and document the entire process publicly?
The answer, we believe, is yes. And this journal is how we prove it.
Why an ADU?
An accessory dwelling unit is a self-contained home on the same lot as a primary residence. They’re practical solutions for aging parents, adult children, rental income, or multigenerational living. But most ADUs are afterthoughts — poorly insulated, undersized garden suites that cost a lot to heat and cool.
We wanted to show there’s a better way.
Why Passive House?
Passive House is one of the world’s most rigorous building energy standards. It’s not a style or a marketing term — it’s a building-science standard that requires:
- Super-insulation on every surface
- A continuous airtight envelope, verified by blower-door test
- Triple-glazed windows with thermally broken frames
- No thermal bridges at junctions and connections
- A Heat Recovery Ventilator (HRV) for continuous fresh air
The result: up to 90% less heating and cooling energy than a code-built home, with better air quality and near-total acoustic comfort.
The Oshawa site
Our first project is a Passive House ADU in Oshawa, Ontario, created for aging parents, adult children, and as a real-world demonstration of healthier, more comfortable, and energy-efficient living. Located in Durham Region, the project requires navigating local zoning, permitting, servicing, and inspection requirements. We are documenting every step of the process to develop a proven, repeatable system that will help future homeowners add high-performance living space with greater confidence and predictability.
What you’ll find in this journal
- Design decisions and trade-offs
- Permit process — what we submitted, how long it took, what came back
- Construction photos and notes at every stage
- Energy modelling results
- The final blower-door test result
We’re building this in public so the whole industry can learn from it. Follow along.