1.0
ACH@50Pa — Starlit standard
3.5
ACH@50Pa — Ontario code typical
60%
Energy savings vs. code minimum
If you're building a new home, there's one number that reveals more about its quality, comfort, and energy performance than any other: ACH@50Pa — air changes per hour at 50 Pascals of pressure. This metric, measured by a blower door test, quantifies how airtight your building envelope is. And it's the single best predictor of long-term energy costs, comfort consistency, and indoor air quality.
The Ontario Building Code requires a maximum of 3.5 ACH@50Pa for new homes. At Starlit, we build to 1.0 ACH@50Pa or better — more than three times tighter than code. Here's why this matters for your family, and how we achieve it.
Airtightness isn't about sealing your home in plastic. It's about controlling air movement — deciding where, when, and how much fresh air enters, rather than leaving it to chance.
What ACH@50Pa Actually Measures
A blower door test installs a calibrated fan in an exterior doorway and depressurizes the building to 50 Pascals (roughly equivalent to a 32 km/h wind hitting every surface simultaneously). The fan measures how much air flows through the building envelope to maintain that pressure — expressed as cubic feet per minute (CFM50).
ACH@50Pa converts that airflow into a rate: how many times per hour the entire volume of the building's air is replaced through uncontrolled leakage at the test pressure. A result of 3.5 ACH@50Pa means the building's air volume leaks out 3.5 times every hour at 50Pa — a staggering amount of uncontrolled air exchange.
NRCan's EnerGuide rating system uses blower door results as a primary input for home energy modelling. Homes achieving 1.0 ACH@50Pa consistently score in the top tier of the EnerGuide scale — approaching NetZero or Net Zero performance levels.
"Your builder should be able to tell you their average blower door test result. If they can't — or if they don't test — that tells you everything you need to know about their commitment to performance."
Why 1.0 ACH Matters: Energy, Comfort, and Health
The benefits of 1.0 ACH@50Pa compound across every dimension of home performance:
Energy Savings
Air leakage accounts for 25–40% of heating and cooling loads in conventional homes. Reducing from 3.5 to 1.0 ACH eliminates approximately 60% of that leakage-related energy waste — typically saving $1,200–$2,000 annually in Ontario's climate.
Comfort Consistency
Drafts are eliminated. Temperature differentials between rooms shrink from 3–5°C to less than 1°C. Cold spots near windows and exterior walls disappear because air isn't streaming through the envelope unchecked.
Noise Reduction
An airtight envelope is also a sound barrier. Homes at 1.0 ACH report 15–20 dB reductions in exterior noise transmission compared to code-minimum construction — transformative for homes near roads or urban environments.
Indoor Air Quality
Paradoxically, a tighter home has better air quality — because all fresh air enters through the ERV's MERV-13 filtration system, not through cracks that bypass filters entirely.
How We Achieve 1.0 ACH: The Air Barrier System
Airtightness at 1.0 ACH doesn't happen by accident. It requires a deliberate, continuous air barrier strategy that is designed before framing begins and verified through testing. At Starlit, our primary air barrier is the ZIP System structural sheathing — a panel with a factory-applied water-resistive and air barrier coating, sealed at all joints with ZIP tape.
But the sheathing is only one piece. Every penetration — electrical boxes, plumbing stacks, HVAC boots, window and door frames — must be individually sealed with appropriate materials: fluid-applied membranes at window rough openings, acoustical sealant at partition-to-exterior intersections, and proprietary gaskets at service penetrations.
This air barrier approach works in concert with our thermal bridge elimination strategy — the same continuous insulation layer that breaks thermal bridges also protects the air barrier from mechanical damage and temperature cycling, extending its service life.
The Passive House Institute has demonstrated that buildings achieving 0.6 ACH@50Pa (the Passive House standard) maintain their airtightness for 25+ years with zero maintenance. At 1.0 ACH, Starlit homes are well within the proven durability threshold.
"We perform mid-construction blower door tests — before drywall — so we can identify and fix any leakage paths while they're still accessible. The final test is a confirmation, not a discovery."
Airtight ≠ Sealed Shut: The Role of Mechanical Ventilation
The most common misconception about airtight homes is that they "can't breathe." In reality, an airtight home breathes better than a leaky one — because it breathes intentionally. Our ERV systems provide continuous, filtered, tempered fresh air at precisely controlled rates, regardless of wind speed, temperature, or season.
In a leaky home, ventilation is chaotic: too much on windy days, too little on calm days, and always through unfiltered pathways that admit pollen, dust, and soil gases. In a Starlit home, ventilation is consistent, efficient, and clean — every hour of every day.
Key Takeaways
ACH@50Pa measures how many times your home's air volume leaks per hour at test pressure — lower is better.
Ontario code allows 3.5 ACH@50Pa; Starlit builds to 1.0 ACH — over 3× tighter than code minimum.
Airtightness eliminates drafts, reduces energy costs by ~60%, and cuts exterior noise by 15–20 dB.
Controlled mechanical ventilation (ERV) replaces chaotic air leakage with filtered, tempered fresh air.
Mid-construction blower door testing identifies leaks while they're still accessible for repair.
Ask your builder for their average blower door result — it's the single most revealing quality metric.
