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Aero Study Report

Airtightness & Residential Energy Efficiency

Background

This report synthesises findings from two independent Canadian utility datasets examining the relationship between residential airtightness and energy performance. Both studies identify significant pre-construction variability in air leakage and demonstrate consistent post-intervention reductions of 40 to 70 percent, with final airtightness levels typically between 1 and 3 ACH50. Heating energy savings ranged from 8 to 25 GJ per year, with proportional reductions in fuel consumption and greenhouse-gas emissions. Savings scaled with initial leakage levels, and performance variability narrowed following intervention. The alignment of results across datasets provides strong empirical evidence that airtightness improvement is a reliable, scalable strategy for reducing residential energy use and emissions.

Highlights

Pre-construction airtightness varied widely, typically 4 to 8 ACH50, confirming envelope inconsistency across production housing
Sealing interventions reduced leakage by 40 to 70 percent, with post-intervention values clustering between 1 and 3 ACH50
Heating energy demand declined by 8 to 25 GJ per year, equivalent to 15 to 30 percent reductions in most homes
Results were consistent across two independent utility datasets, supporting scalability and policy relevance

Utility Evidence on Airtightness Performance

Canadian utilities have increasingly focused on airtightness as a controllable and quantifiable component of residential energy performance. Two independent datasets—the Enbridge airtightness review and a separate Canadian utility case study—provide extensive field data on how reductions in air leakage affect energy use, fuel consumption, and greenhouse-gas emissions in new homes.

Although they were produced by different organisations and draw from different builders, regions, and measurement protocols, the two studies arrive at nearly identical conclusions. Together, they form a strong empirical foundation for understanding the relationship between airtightness and energy efficiency in residential construction.

Variation in Pre-Construction Airtightness

Both studies begin with the same observation: initial airtightness in new homes varies significantly, even among production builders following standard code-compliant practices.

Pre-intervention ACH50 values in both datasets commonly fell in the 4–8 ACH50 range.
Some homes were markedly leakier, while others approached builder targets, but the variability was substantial across the sample.

This variability demonstrates a well-documented characteristic of North American construction: airtightness is one of the least consistent aspects of envelope quality. The fact that both datasets show similar pre-seal distributions strengthens confidence that these patterns are representative rather than anomalies.

Consistent Post-Intervention Airtightness Improvements

Despite differences in house type, builder, climate zone, and construction sequence, the two studies report very similar airtightness improvements following sealing interventions.

Across both datasets:

Leakage reductions commonly ranged from 40% to 70%.
Post-intervention ACH50 values fell into a much narrower band, generally between 1–3 ACH50.
Improvements were observed across detached, semi-detached, and townhouse designs.

This convergence suggests that airtightness can be improved reliably across diverse building contexts, and that intervention approaches—whether performed at drywall, pre-trim, or pre-mechanical stages—produce broadly comparable results.

Strong Relationship Between Airtightness and Energy Use

A consistent and central finding from both studies is that reducing air leakage reduces heating-energy demand in a predictable way.

Energy savings reported across both datasets:

8–25 GJ/year in heating energy saved per home.
15–30% reduction in total heating demand for most houses.

The similarity of these results—across two separate programmes, measurement approaches, and modelling tools—indicates that the underlying physics of infiltration and heating load is being captured consistently. Both datasets show that airtightness has a material and measurable effect on energy consumption.

Savings Scale with Starting Leakage

Both datasets show the same statistical pattern: homes that start out leakier experience the greatest energy savings after improving airtightness.

A reduction of 1 ACH50 was associated with significant declines in heating energy use.
Large improvements (e.g., reducing from 7 ACH50 to 2–3 ACH50) corresponded with the highest savings.
Homes that began closer to 3–4 ACH50 showed smaller absolute savings but still benefited from reduced infiltration load.

This alignment across datasets strengthens the conclusion that airtightness improvements represent one of the most impactful interventions for homes with high initial leakage.

Predictability and Scalability of Airtightness Improvements

A notable outcome common to both datasets is the reduction in performance variability following airtightness improvements.

Pre-intervention airtightness varied widely across builders.
Post-intervention values became tightly clustered.
This effect was observed regardless of builder, location, or house type.

This pattern suggests that airtightness interventions help normalise construction quality, producing more consistent building performance across large portfolios. For utilities, this reliability strengthens the case for incentive programmes that target air-leakage reduction.

Implications for Energy Policy and Utility Incentives

Both studies demonstrate airtightness to be:

A major driver of heating energy consumption
Relatively inexpensive to improve during construction
Highly consistent in its impact across diverse homes
Strongly correlated with reduced fuel use and GHG emissions

These shared findings provide a robust evidence base for utilities and policymakers seeking to:

Reduce residential energy consumption
Lower peak heating demand
Achieve emissions-reduction targets
Support builders in meeting or exceeding performance standards

The consistency between the two datasets supports the conclusion that airtightness represents one of the most effective and scalable levers for improving residential energy efficiency.

Conclusion

The two independent Canadian utility datasets reach highly consistent conclusions about the impact of air leakage on residential energy use. Despite differences in builders, house types, and testing protocols, both studies demonstrate that improving airtightness reliably reduces heating-energy demand, fuel consumption, and greenhouse-gas emissions.

The two Canadian utility studies strongly corroborate one another, showing that reducing air leakage is a reliable, scalable, and quantifiable method for improving residential energy efficiency and lowering emissions, regardless of builder or construction method.

Key Findings

Airtightness improvements were substantial and consistent, typically reducing leakage by 40–70% across a wide range of homes.
Energy savings were closely tied to reductions in air leakage, with most homes achieving 8–25 GJ/year of heating-energy savings (about 15–30% of total heating demand).
Fuel-use reductions were significant, commonly 300–1,200 m³ of natural gas per year, reflecting lower infiltration-driven heating loads.
GHG emissions declined proportionally, typically by 300–1,200 kg CO₂e/year, reinforcing the link between airtightness and environmental performance.
Homes with higher initial leakage showed the greatest improvements, confirming that airtightness upgrades are most impactful where baseline infiltration is high.
Construction-stage rebound leakage (3–15%) was observed, but both studies show that most airtightness gains were retained through to project completion.
Post-intervention airtightness became far more consistent across builders and house types, suggesting that airtightness improvements help normalise envelope performance.