Airtightness Testing in Green Star Projects: Common Mistakes and How to Avoid Them
So you’re working on a Green Star project in New Zealand, the documentation’s piling up, and someone casually drops: “Have we booked the airtightness test yet?”
Cue the awkward silence.
Whether you’re an architect, project manager, ESD consultant, or builder, airtightness testing can be one of those things that gets pushed to the end — until it’s suddenly urgent. And by then, it’s often too late to fix the issues without blowing your timeline and budget.
This guide walks you through the most common mistakes made in Green Star airtightness testing — and how to dodge them like a pro.
Why Airtightness Testing Matters in Green Star NZ
Green Star Isn’t Guesswork — It’s Verified
Green Star NZ’s latest version puts strong emphasis on performance-based verification. That means airtightness is no longer an optional checkbox — it’s embedded into credits like:
✅ Credit 10.1.1 – Responsible Envelope
✅ Credit 2.2.2 – Verification and Handover
To claim these credits, you must test your building’s air permeability using ISO 9972 or ATTMA TSL2, report the results, and explain their context.
And testing isn’t just a formality. If you get it wrong, the ripple effects hit your compliance, certification, and credibility.
Top 9 Airtightness Testing Mistakes in Green Star Projects (and How to Avoid Them)
1. 🧠 Not Considering Airtightness in Design
The Mistake
Teams focus on insulation, glazing, and HVAC — but completely ignore airtightness strategy in the concept and schematic phases.
Why It Hurts
By the time you get to site, it’s too late to fix poor detailing at junctions, penetrations, and service cavities.
How to Avoid It
Engage an airtightness specialist (like BEO Buildingscience) early. Include an airtightness strategy in the Building Enclosure Commissioning Plan. Coordinate details with the architect and services engineers from day one.
2. 🔍 Vague or Missing Test Boundary Definitions
The Mistake
The “test boundary” isn’t clearly defined — no one knows what’s in, what’s out, or how big the volume is.
Why It Hurts
You can’t test what you can’t define. It also leads to disputes, delays, and inaccurate results.
How to Avoid It
Model the test boundary in 3D and confirm it matches site conditions. Include boundary diagrams in your test plan (a requirement in ATTMA TSL2). Get agreement from the team before construction starts.
3. 👷 Treating Airtightness as a “Services Problem”
The Mistake
Architects assume it’s the services contractors’ problem. Services assume it’s already sorted. Everyone assumes it’s someone else’s job.
Why It Hurts
Airtightness is about the entire envelope. No one owns the outcome, so it fails.
How to Avoid It
Assign responsibility clearly. Include airtightness in trade scopes. Do site inductions and toolbox talks. And don’t let mechanical chases become free-for-alls.
4. ⌛ Leaving Testing Too Late
The Mistake
Testing is booked the week before handover — when ceilings are closed, linings are on, and the building’s being cleaned for PC.
Why It Hurts
Too late to fix leaks. Too risky to fail. Too expensive to retest.
How to Avoid It
Schedule your test after the airtightness layer is complete — but before it’s covered. This means at the lock-up stage, not the finish line. Always plan for at least one test and one re-test window.
5. 🚫 Forgetting the Penetrations
The Mistake
Plumbers, electricians, HVAC — everyone punches holes in the airtight layer, then shrugs and moves on.
Why It Hurts
Each unsealed hole is a massive leak at 50 Pascals. Leaky cable trays and duct boots are the silent killers of q50 scores.
How to Avoid It
Use service sleeves and airtight grommets. Seal every penetration as it's installed — not later. Perform on-site QA with blower door and smoke pens while services are still accessible.
6. 💨 No Diagnostic Testing Before Final Submission
The Mistake
The first time the building sees a blower door is the day of the certification test.
Why It Hurts
Leaks are discovered too late. You’ve got no time to fix them, and everyone is under pressure.
How to Avoid It
Run a preliminary test (commissioning test) at lock-up. Use smoke, thermography, or pressure differential methods to identify issues early. Then re-test once resolved.
7. 🧾 Submitting Incomplete Documentation
The Mistake
Your test report is missing calibration records, volume verification, site photos, or tester credentials.
Why It Hurts
Green Star won’t accept it. You lose points, delay certification, or have to re-test.
How to Avoid It
Make sure your tester follows ATTMA L2 or ISO 9972 precisely. All documentation must be complete, including:
Boundary volume calculations
Fan calibration certificates
Weather conditions during test
Photos of test setup
Diagrams showing test boundary
8. 📉 Confusing q50 and n50
The Mistake
The project team quotes ACH @ 50 Pa (n50) instead of air permeability (q50) — or worse, tries to compare the two incorrectly.
Why It Hurts
Green Star NZ expects q50 (in m³/h/m²), not n50. You can’t compare results unless volume and envelope area are clearly defined.
How to Avoid It
Always report q50 for Green Star. If you want to express n50 too, include both — but explain the conversion clearly.
9. 🙈 Not Learning from Past Failures
The Mistake
Same team, same mistakes. No lessons carried over from previous projects.
Why It Hurts
You miss the opportunity to systematise airtightness QA and improve.
How to Avoid It
Do a post-project review. Record:
What worked
What failed
What to change next time
Use this as part of your continuous improvement process. If you work with BEO, we’ll give you a summary lessons-learned sheet you can reuse.
So, What’s the Ideal Airtightness Testing Workflow for Green Star?
Here’s what a successful airtightness testing process looks like in a typical Green Star project:
✅ Design Stage
Test boundary defined and documented
Airtightness strategy included in design coordination
Preliminary target (q50) set based on building type and use
ATTMA tester consulted and included in planning
✅ Pre-Construction Phase
Trade scopes updated with airtightness responsibilities
Toolbox talks for installers
Critical junctions reviewed and marked on drawings
✅ Lock-Up Stage
Preliminary blower door test booked
All penetrations sealed or sleeved
Diagnostics used to detect and fix issues
✅ Pre-Handover
Final test booked with ATTMA Level 2 tester
Site cleaned and intentional openings sealed
All documentation prepared (calibration, volume, boundary)
✅ Submission
Report submitted with q50 result
Photos, diagrams, and site notes included
Green Star points secured, no surprises
Don’t Let Airtightness Testing Be an Afterthought
Airtightness testing is one of the few metrics in Green Star that’s measurable, verifiable, and visible. It’s also one of the most misunderstood.
The difference between a smooth handover and a stressful retest often comes down to planning, coordination, and early involvement of your tester.
