Why Airtightness Testing Matters in Green Star Projects

What Is Airtightness Testing?

Airtightness testing measures how much uncontrolled air leaks through your building envelope. In tech speak, it quantifies air permeability — usually as q50 (m³/hr/m² at 50 Pa) or n50 (ACH at 50 Pa). In plain speak, it’s how “leaky” your building is under pressure.

Why Green Star Cares

Under the Green Star Buildings NZ tool, airtightness contributes to the Responsible Envelope credit and can support the Verification and Handover credit. It demonstrates that your shiny new building performs as designed — with reduced energy loss, better indoor comfort, and no mysterious drafts turning up in tenant complaints.

Spoiler: You don’t get Exceptional Performance without proven airtightness. And proving airtightness means testing.

Step 1: Understand the Test Before You Build

You Can't Test in a Spreadsheet

We see this all the time — teams focus heavily on thermal models, glazing specs, and ventilation systems... but forget the glue holding it all together: the air barrier.

Green Star projects must demonstrate continuity of the air barrier at design stage and verify performance during construction. If you’re skipping airtightness strategy until the final weeks? Brace for impact.

ATTMA L2 and ISO 9972: Your Testing Bibles

Green Star requires that blower door testing complies with ISO 9972 or a recognised equivalent — and in NZ, that means ATTMA TSL2 for large commercial buildings.

These standards define:

• Test procedures

• Equipment calibration

• How to define the test boundary

• Acceptable result reporting formats

💡 Pro tip: Work with a Level 2 ATTMA-accredited tester from day one (yes, we know someone).

Step 2: Design for Airtightness — Not Just Insulation

Airtightness ≠ Insulation

Insulation resists heat transfer. Airtightness resists air movement. Different but besties. Without airtightness, your insulation is like a puffer jacket with the zip undone.

Identify the Air Barrier Layer (Hint: It’s Not Always the Wrap)

Be clear in your documentation:

• Where is the primary air barrier?

• How does it connect at junctions (slab-to-wall, wall-to-roof)?

• What happens at windows and doors?

• How will services penetrate the barrier without ruining it?

Mark up your drawings. Coordinate with structure. Coordinate with services. Coordinate with reality.

🛠 “The details are where air gets in. Or doesn’t.”

Step 3: Communicate With the Contractor (Like, Actually Talk)

Good Builders Build to the Info They're Given

If airtightness expectations are buried on page 43 of a PDF, don’t expect miracles. Contractors need:

• Clear buildability notes

• On-site QA checklists

• Airtightness toolbox talks

Not to mention encouragement. Air barriers aren’t their usual jam.

At BEO, we provide:

• Contractor cheat sheets

• On-site briefings

• Photos of “what good looks like”

👷 “Builders aren’t the problem — unclear drawings are.”

Step 4: Get Ready to Test — Don't Wing It

When Should You Test?

The ideal time is when the airtightness layer is complete, but before linings and claddings cover everything. In Green Star terms: around the end of the structural enclosure phase.

This is your chance to:

• Verify performance

• Fix issues

• Avoid horrifying “post-handover discovery”

What's Included in the Test?

• Blower door setup using calibrated fans

• Measurement of airflow at various pressures

• Visual checks with smoke pens or fog machines (yes, they’re fun)

• Infrared scans to identify leakage points (aka air leak bingo)

We follow the ATTMA L2 protocol and prepare everything for Green Star documentation.

Step 5: Conduct the Test — And Keep Calm

What If It Fails?

First: Don’t panic. We’ve seen 20-storey towers hit great results… after they sealed a single riser.

Failures are just data. The real question is what you do next.

We help by:

• Diagnosing where leaks are coming from

• Providing remediation advice

• Coordinating a retest (if needed)

🛠 Common Culprits:

• Leaky curtain wall brackets

• Fire collars not sealed

• Lift shaft bypasses

• Roof membrane overlaps missed

👃 "If you can smell Subway through the wall, your air barrier isn’t working."

Step 6: Celebrate (or Seal and Repeat)

What Result Should You Aim For?

There’s no universal Green Star pass mark — but 1.5 to 3.0 m³/hr/m² @ 50Pa is typical for well-detailed projects. Exceptional Performance credits aim lower.

We’ll interpret your results, explain what they mean for certification, and give you:

• ATTMA TSL2-compliant reports

• Calibration certificates

• Boundary diagrams

• Leak location photos

📂 All formatted to satisfy Green Star documentation needs.

Step 7: Submit It Like a Pro

Once you’ve passed (cue slow clap), it’s time to submit. The Green Star assessor wants:

• Clear boundary definitions

• Confirmed test methodology

• Final test results with no surprises

We package everything for you, including:

• Methodology declaration

• Environmental conditions log

• Graphs and fan calibration data

✅ "Plug and play for your Green Star consultant."

FAQs About Airtightness and Green Star

Can’t We Just Skip the Test?

Under the Green Star Buildings NZ tool, airtightness testing is now mandatory if you want to claim credits like:

• ✅ Responsible Envelope

• ✅ Verification and Handover

These credits require a formal airtightness test — following ISO 9972 or ATTMA TSL2 — to confirm that your building performs as promised. You’ll need to provide evidence of testing as part of your commissioning process and submit a full report during certification.

So no — airtightness testing isn’t optional anymore if you’re chasing those performance points. It’s not a “nice to have.” It’s a non-negotiable requirement for ticking the boxes that actually boost your Green Star rating.

What If We're Already at Lining Stage?

Testing gets harder — not impossible. It may involve:

• Testing zones separately

• Using internal pressurisation techniques

• Some surgical smoke hunting

But yes, earlier is better.

What’s the ROI on Airtightness?

Lower HVAC load, better occupant comfort, moisture control, and fewer complaints. It’s also an easy win for sustainability cred without greenwashing.

Real Talk: Why Most Projects Fail Airtightness Testing

It’s rarely the big things. It’s the 500 small ones:

• The service duct someone forgot to seal

• The window installer who skipped one tape run

• The spec that said “Class 4 wrap” but didn’t define tape compatibility

Passing is about culture, not perfection. The teams who win are the ones who:

• Make airtightness visible

• Train their people

• Partner with the right testers (hey, that’s us)

Final Thoughts: Pass It the First Time — With BEO

At BEO Buildingscience, we’ve helped Green Star, Homestar, Passive House, and high-performance projects hit their airtightness targets. We’re not here to judge — we’re here to support.

From the first drawing markup to the last pressure reading, we walk with your team to:

• Clarify expectations

• Catch leaks before they become problems

• Deliver airtight buildings with real-world comfort and compliance