What Is ATTMA L2 Testing and Why Green Star Projects Depend on It
If you're involved in a Green Star project in New Zealand, you've probably heard about ATTMA L2 testing. And if you haven’t, here’s your wake-up call: your airtightness strategy won’t go anywhere without it.
It’s not just a fancy acronym or another consultant’s box to tick. ATTMA Level 2 testing is the method that validates your building’s air leakage performance — and it’s now the industry standard for Green Star certification in large commercial and public buildings.
In this article, we’ll break down what ATTMA L2 testing is, why it matters, when you need it, and how to make sure your building passes with flying colours.
Why Airtightness Testing Is a Must-Have for Green Star NZ
Airtightness and Green Star Credits
Green Star NZ now requires airtightness testing to earn credits in two areas:
✅ Responsible Envelope (Credit 10.1.1)
✅ Verification & Handover (Credit 2.2.2)
To claim these, you must prove that the air barrier has been designed, tested, and performs according to standard. The test must follow ISO 9972 or an equivalent, which — in New Zealand — means ATTMA TSL2 for most commercial buildings.
So, What Is ATTMA L2 Testing?
ATTMA stands for the Air Tightness Testing & Measurement Association, a UK-origin standard now widely adopted in NZ. ATTMA Level 2 testing applies to buildings over 4000 m³ or more complex structures like hospitals, schools, and offices.
It’s more robust than Level 1 testing. It requires:
A qualified Level 2 tester
Strict test boundary documentation
Multi-point pressurisation testing
Calibrated equipment and traceable data
A full, certifier-friendly report for submission
ATTMA L2 testing isn’t just compliance — it’s proof that your building’s performance claims are real.
ATTMA L2 vs Level 1: What's the Difference?
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💡 Pro tip: Don’t guess your volume. Get your test boundary modelled early to avoid falling into the Level 2 category unprepared.
When Do You Need ATTMA L2 Testing?
You Need ATTMA L2 Testing If:
Your building is over 4000 m³ in volume
You’re pursuing Green Star NZ certification
You want to verify airtightness performance for commissioning or handover
Your client demands evidence of energy efficiency
You Should Test:
After the airtight layer is fully installed
Before it gets buried behind linings, claddings, or finishes
Ideally, once building pressure zones are separated and test boundaries are clearly established
The earlier you schedule testing, the more chances you have to resolve leaks before handover chaos begins.
How Does ATTMA L2 Testing Work?
Step-by-Step Overview
Design Phase Engagement
Pre-Test Preparation
On-Site Test Setup
Pressurisation/Depressurisation Testing
Diagnostic Work (Optional but Recommended)
Reporting and Certification
📎 What Green Star Assessors Want: A full test report that aligns with ATTMA TSL2 or ISO 9972, submitted during the commissioning phase.
What Does a Good Result Look Like?
Performance Targets for Green Star
Green Star NZ doesn't set a fixed airtightness threshold — and neither does ATTMA TSL2 in terms of compliance. Instead, airtightness results should be considered in context: paired with the building’s ventilation strategy and its intended use.
For example:
A hospital with critical air pressure zones will have different airtightness expectations than a warehouse.
A naturally ventilated school will have different requirements than a fully conditioned commercial office.
There’s no one-size-fits-all number. For exact targets, consult your ATTMA Level 2 tester early in the design phase. They’ll help set realistic, buildable airtightness goals that align with your project’s scope, services, and Green Star aspirations.
If You Fail? Don’t Panic
Blower door test failures happen — especially in fast-tracked builds. The key is having:
Diagnostic support to find leaks
A cooperative contractor ready to fix them
A test team who can return quickly for re-verification
That’s where our team at BEO shines.
How BEO Buildingscience Helps Your Project Pass
We don’t just show up with a fan. We work with your team from the early design phase all the way to submission. Our airtightness services for Green Star include:
✅ Design-phase strategy reviews
✅ Test boundary definition and documentation
✅ Site readiness inspections before testing
✅ ATTMA L2 blower door testing
✅ Smoke diagnostics and IR thermography
✅ Submission-ready reporting for Green Star assessors
We also train contractors and run toolbox talks so your build team knows what airtightness actually looks like on site (no foam guns in sight, please).
FAQs About ATTMA L2 and Green Star Testing
Can I Just Use a Level 1 Test?
Not if your building is over 4000 m³ — Green Star assessors expect ATTMA L2 or ISO 9972-compliant testing, and Level 1 doesn’t cut it for large or complex projects.
Do I Need to Seal All Internal Doors?
Only if they’re outside the test boundary. We help define what’s in or out — so you don’t waste time taping up irrelevant rooms.
Can We Test in Sections?
Yes — especially in staged construction or multi-tenancy buildings. We can test zone by zone, then extrapolate overall performance — but this must be planned from the outset.
Final Thoughts: Don’t Let Air Leakage Sink Your Green Star Score
ATTMA L2 testing isn’t just a compliance hurdle — it’s your proof of performance. If you design and build for airtightness, your test should confirm the quality of your envelope. If you don’t? You’ll be sealing leaks while the furniture is going in.
