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Design Considerations & Cost Optimisation

Airtightness isn’t just a detail—it’s a cornerstone of building performance

Why Airtightness Should Be Your First Design Specification

Airtightness has a greater impact on energy efficiency than walls, windows or attics.

Airtightness isn’t just a detail—it’s a performance multiplier.

Setting a low airtightness target (like ≤3.0 ACH50) early in design boosts the effectiveness of every other system that supports comfort, health, and energy efficiency.

Insulation performs to its full R-value, windows meet rated performance, ventilation runs more efficiently, and heating and cooling loads drop. In short, airtightness helps every part of the home work better.

Source: Based on IECC data from NEHERS presentation, ANSI/RESNET Conference, November 2023

Air leakage accounts for between 25 percent and 40 percent of the energy used for heating and cooling in a typical residence.

Start the Design Process by specifying Airtightness

Before specifying insulation, heating, or ventilation—start with specifying airtightness. A low air leakage rate sets the foundation for energy efficiency and cost-effective design

This approach:

Improves accuracy of energy modelling
Helps avoid unnecessary product upgrades
Delivers better performance at better value

Value Engineering Examples

Set a low airtightness target, and review the opportunities to reduce costs in other areas

System	Cost Benefit
Heat pump	Smaller unit required = lower upfront + running costs
Ventilation	Right-sized MVHR = less ducting, lower energy use
Insulation	Optimised levels = potential material savings
Glazing	May use high-performance double glazing instead of triple
Framing/Details	Simplified thermal breaks = easier, faster construction

“Don’t over-specify to compensate for a leaky home.”

Chris caiger, Director, aero

Sample Airtightness Specification Clause:

“The building envelope shall be constructed to achieve a verified air leakage rate of ≤3.0 ACH50 (insert desired ACH50 target). AeroBarrier air sealing technology shall be applied as part of the airtightness strategy to seal internal envelope leaks. AeroBarrier shall be installed by a certified applicator during the pre-lining phase (after services installation and before wall linings), with temporary masking of sensitive areas as required. A certificate of completion and test report confirming the final ACH50 value shall be provided as part of project close-out documentation.”

Design considerations

Achieving airtightness often requires time-consuming detailing around junctions, penetrations, and fixtures. AeroBarrier simplifies this by automatically sealing invisible leaks and bridging minor imperfections—helping builders hit airtightness targets like ≤3.0 ACH50 without changing standard construction methods.

Downlights: Use IC-F rated fittings with factory seals. Avoid oversized ceiling cutouts.
Flush Boxes: Avoid back-to-back boxes on intertenancy walls and boxes on exterior walls. Use standard steel flush boxes rather than open backed plastic flush boxes. For best results use airtight boxes.
Windows & Doors: Specify joinery tested to ≤ 0.75 m³/m²/hr at 50 Pa. Ensure airtight installation with perimeter seals, tapes, or gaskets.
Wraps: Preferably use high-quality air barrier wraps that are fixed securely and rated for airtightness—these will provide a more stable surface for air sealing sealing, particularly where flush boxes have been used on exterior walls.
Vents & Ducts: Use rigid ducts with airtight collars or gaskets. Include backdraft dampers to prevent unwanted airflow when systems are off.
Fireplaces: Avoid open fireplaces in airtight homes. If used, specify sealed, direct-vent gas fireplaces or airtight wood burners with external air supply. Ensure all flue and penetration junctions are sealed.

AeroBarrier makes airtightness practical for mainstream homes by sealing what’s hard to reach—streamlining construction while delivering measurable, certified results.

Certified Airtightness Results

When you set an airtightness level, you need to know it’s achievable—and provable. AeroBarrier gives you that certainty. It seals the invisible gaps that are almost impossible to catch manually, ensuring builders consistently meet the specified airtightness targets.

AeroBarrier provides a test certificate confirming the airtightness level achieved, so you can sign off with confidence.

Sample Energytight™ Solution Specification Clause

Energytight™ Air Sealing and Ventilation Install the Energytight™ system, combining automated air sealing using the AeroBarrier® process with mechanical ventilation as required.

Airtightness Target: Achieve ≤3.0 ACH50 or below, verified by blower door testing.

Installation Requirements: AeroBarrier® to be applied after rough-in and before linings by a certified applicator. Mask sensitive areas as needed. Blower door tests must be performed during and after sealing.

Certification: Provide a certified Energytight™ Airtightness Certificate confirming final test results.

Ventilation: Where airtightness is ≤3.0 ACH50 or below, install balanced mechanical ventilation with heat recovery (MVHR) or equivalent.

Coordination: Ensure penetrations, downlights, windows, and doors are sealed to support airtightness. Coordinate sequencing with all trades.ow when systems are off.