Compliance Status by Standard
Calculated Values
Full Calculation Summary
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How to Use the Airtightness Compliance Calculator
These figures come from the building drawings or the blower door test report itself, which typically calculates volume and envelope area automatically. Floor area and envelope area are used for normalized leakage calculations.
This is the headline number from your blower door test, typically reported directly by testing software such as TECTITE or Retrotec. It represents air changes per hour when the building is depressurized to 50 pascals.
Choose your applicable code path if your province or municipality has adopted a specific airtightness target beyond the national baseline, such as Ontario SB-12 or a specific BC Energy Step Code level.
The results show pass/fail status against NBC, Energy Star, and Net Zero thresholds simultaneously, along with your calculated natural infiltration rate and equivalent leakage area for a complete airtightness picture.
Understanding Airtightness Compliance in Canada
Airtightness testing has become a standard part of Canadian residential construction verification, driven by increasingly stringent building code energy requirements and voluntary certification programs. A blower door test provides an objective, repeatable measurement of how much uncontrolled air leaks through the building envelope, which directly affects heating and cooling energy use, comfort, and moisture management.
The ACH50 test procedure
A blower door test uses a calibrated fan mounted temporarily in an exterior doorway to either pressurize or depressurize the building relative to outdoors. The fan speed required to maintain a 50 pascal pressure difference — a standardized reference pressure roughly equivalent to a 32 km/h wind hitting all sides of the building simultaneously — indicates the total air leakage rate through the envelope. This airflow rate, divided by the building's interior volume, gives the ACH50 result: how many times per hour the entire volume of air in the building would need to be replaced to sustain that pressure difference. Lower ACH50 values indicate fewer leakage paths and a tighter envelope.
Canadian airtightness targets by program
The National Building Code of Canada's energy efficiency provisions establish 2.5 ACH50 as a common prescriptive target for residential construction, though this baseline has been tightening over successive code cycles and varies by climate zone and compliance path chosen. Energy Star for New Homes in Canada requires 1.5 ACH50 or better, a meaningfully tighter target that typically requires more careful air barrier detailing during construction, including continuous air barrier planning, sealed penetrations, and attention to typically leaky junctions like the rim joist and top plate. Net Zero and Net Zero Ready certification through the Canadian Home Builders' Association pushes further to 0.6 ACH50 or tighter, a passive-house-influenced target that generally requires a dedicated air barrier system, high-performance windows and doors, and meticulous construction sequencing.
Provincial and municipal overlays
Several provinces have adopted airtightness requirements tighter than the base national code through their own building codes or supplementary standards. Ontario's SB-12 has historically aligned close to the 2.5 ACH50 national baseline for most compliance paths. British Columbia's Energy Step Code creates a tiered system where Step 3 aligns near 2.5 ACH50, Step 4 tightens to approximately 1.5 ACH50, and Step 5 (the most stringent, often used for Net Zero Ready projects) requires 1.0 ACH50 or better. Many BC municipalities have adopted specific step code requirements ahead of the provincial schedule, so local requirements can be more stringent than what the provincial code alone specifies. Always verify the current requirement with your local building department, since these targets have been progressively tightening and vary significantly by municipality and building permit application date.
From ACH50 to natural infiltration rate
The 50 pascal test pressure is far higher than the pressure differences a building experiences under normal weather conditions from wind and the stack effect (warm air rising and escaping through upper leaks while cold air is drawn in through lower leaks). A widely used approximation, developed from empirical building science research, divides the ACH50 result by a factor typically between 15 and 25 to estimate the natural, unpressurized infiltration rate — the air exchange the building actually experiences day-to-day. A shorter, more sheltered building might use a higher divisor (20 to 25), while a taller or more wind-exposed building uses a lower divisor (15 to 17), since taller buildings experience greater stack-effect pressure differences that drive more natural infiltration for the same ACH50 test result.
The ventilation trade-off
As buildings become tighter, the natural infiltration that once provided incidental fresh air exchange diminishes, and mechanical ventilation becomes essential rather than optional for maintaining acceptable indoor air quality. This is why Canadian building codes pair airtightness requirements with corresponding mechanical ventilation requirements under provisions aligned with ASHRAE 62.2 principles. A building tested below roughly 3 to 4 ACH50 should have a properly sized and commissioned heat recovery ventilator or energy recovery ventilator to ensure occupants receive adequate fresh air without excessive energy penalty. Use the ventilation code calculator to confirm your mechanical ventilation sizing aligns with your measured airtightness level.
Frequently Asked Questions
ACH50 is the air changes per hour a building experiences when depressurized to 50 pascals by a blower door fan, a standardized test pressure that allows fair comparison between buildings of different sizes, shapes, and locations. A calibrated fan is temporarily installed in an exterior door, and the fan speed needed to maintain 50 Pa pressure difference indicates how much air is leaking through the building envelope. Lower ACH50 values indicate a tighter building envelope with less uncontrolled air leakage. Enter your test result into this calculator to check compliance against Canadian standards.
The National Building Code of Canada's energy efficiency requirements set a maximum airtightness of 2.5 ACH50 for most residential construction under the prescriptive compliance path, though several provinces have adopted more stringent requirements through their own building codes or supplementary standards. Ontario's SB-12, BC's Energy Step Code, and other provincial overlays often require tighter airtightness than the base national code, so always verify the specific requirement in your jurisdiction rather than relying on the national minimum alone. This calculator includes selectable overlays for common provincial programs.
Natural infiltration rate is the air leakage a building experiences under normal, unpressurized conditions from wind and stack effect, which is always lower than the ACH50 test result since 50 pascals is a much higher pressure than typical weather-driven pressures. A widely used approximation divides ACH50 by a factor between 15 and 20 (commonly 20 for a rule-of-thumb estimate) to estimate natural air changes per hour. This means a building tested at 2.5 ACH50 experiences roughly 0.125 natural air changes per hour under typical conditions, though the actual factor varies with building height, local wind exposure, and climate. This calculator computes both figures from your test result.
As airtightness improves, uncontrolled natural air leakage through cracks and gaps decreases, which reduces the fresh air that would otherwise dilute indoor pollutants, moisture, and carbon dioxide. Below approximately 3 to 4 ACH50, a building can no longer rely on natural infiltration alone to maintain acceptable indoor air quality, and mechanical ventilation such as an HRV or ERV becomes necessary to provide controlled fresh air exchange. This is why Canadian building codes typically pair minimum airtightness requirements with corresponding mechanical ventilation requirements. Use the ventilation code calculator to size your mechanical ventilation system correctly.
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