Designing for Airtightness: What Green Star NZ Requires and How to Deliver It

If you’re designing a building that’s aiming for a Green Star rating, here’s the unvarnished truth: your airtightness strategy will make or break your envelope credits.

Gone are the days of vague “air control layers” and last-minute sealing attempts. Green Star NZ now requires airtightness to be baked into your project — from the design stage all the way to blower door testing.

So if you want to stay on track, hit your credits, and hand over a building that actually performs, this guide is your cheat sheet.

Let’s unpack what Green Star NZ demands — and how you can actually deliver it.

Why Airtightness Is Non-Negotiable in Green Star NZ

Airtightness = Performance

Airtightness is the unsung hero of building performance. It reduces energy loss, prevents moisture damage, and boosts thermal comfort. Without it, even high-spec insulation and top-tier HVAC systems won’t deliver their full potential.

Where Airtightness Shows Up in Green Star

Airtightness is central to two key Green Star NZ credits:

1. Responsible Envelope (Credit 10.1.1)
   Requires a clearly defined, buildable air barrier strategy — plus evidence of airtightness performance via testing.

2. Verification and Handover (Credit 2.2.2)
   Involves commissioning of the air barrier as part of the overall building performance verification.

These credits don’t just ask for good intentions. They demand:

• Coordinated drawings

• Defined test boundaries

• ISO 9972 or ATTMA L2-compliant airtightness testing

• Commissioning reports

So yes — you really do need to design for airtightness from the start.

Step 1: Define the Airtightness Strategy Early

Start in Concept Design — Not Construction

Airtightness needs to be considered alongside structure, insulation, vapour control, and services — not tacked on after the builder asks, “Wait, what’s this Intello stuff?”

What a Good Airtightness Strategy Includes

• A continuous primary air barrier layer that runs through walls, floors, roofs, and junctions

• Clear, coordinated detailing at:

  • Roof-to-wall junctions

  • Slab edges

  • Window and door interfaces

  • Service penetrations

• Specific product selections (wraps, tapes, membranes) with compatibility

• Buildability notes — how it will be constructed, not just what it is

💡 Pro tip: Use colour-coded markup drawings to clearly show the air barrier path.

Step 2: Coordinate the Design Team Around Airtightness

Airtightness Is a Team Sport

Your architecture may be flawless, but if mechanical, structural, and fire services aren’t on the same page, you’ll end up with Swiss cheese.

Coordinate airtightness with:

• Mechanical: How are duct penetrations sealed?

• Fire engineering: Are collars and dampers airtight?

• Structure: Are bracing elements interrupting membranes?

• Façade: Curtain wall interfaces are notorious leak zones

This isn't just a documentation exercise. It’s damage prevention.

Step 3: Detail Junctions Like You Mean It

The Devil Is in the Junctions

A building’s overall airtightness performance is determined less by surface area, and more by the number of junctions, terminations, and penetrations.

For each junction:

• Show how materials change, and how continuity is maintained

• Include tape types, sizes, and overlap instructions

• Specify substrate preparation and sequencing

Don’t just write “tape to suit.” Be specific.

🛠 Example: “Pro Clima Tescon Vana tape, 100 mm wide, applied with a Pressfix tool to clean, primed OSB substrate.”

Step 4: Consider Airtightness in Construction Tolerances

Reality Check: It Has to Be Buildable

That beautiful isometric detail you drew? It won’t work if it requires the builder to levitate a membrane through a 10 mm cavity gap.

During the detail review:

• Consider what trades will install what — and when

• Minimise overlaps that depend on sequencing luck

• Provide mock-up guidance for tricky transitions

• Account for movement joints, tolerances, and rework

Airtightness doesn’t have to be fragile. But it does have to be practical.

Step 5: Document for Submission Success

The Green Star Assessor Wants Proof

To earn the Responsible Envelope credit, you’ll need to submit:

• Airtightness design strategy documentation

• Air barrier drawings and detail markups

• Construction QA checklists

• Final test reports from an ISO 9972 or ATTMA L2-compliant blower door test

In other words: if it’s not written down, it doesn’t count.

BEO provides all documentation you need — formatted for submission and backed by decades of experience on successful Green Star projects.

Common Mistakes That Tank Airtightness (And How to Avoid Them)

Mistake 1: Too Many Materials, Not Enough Clarity

Switching from wrap to membrane to concrete to plasterboard with no clear junction strategy? That’s a leakage nightmare.

✅ Solution: Minimise transitions and detail every change.

Mistake 2: Window and Door Details Are an Afterthought

Too often, window install methods are left to the supplier — and airtightness suffers. You end up with foam squirted somewhere near the frame and fingers crossed it holds.

✅ Solution: Draw the air barrier through the window perimeter. Loop membranes. Show taping. Provide insulation fill specs.

Mistake 3: Service Penetrations Are Uncontrolled

Nothing undermines airtightness faster than a half dozen tradies poking holes wherever they please.

✅ Solution: Define service routes early. Use standardised collars or sleeves. Assign responsibility for sealing.

How We Help You Deliver Airtight Design That Passes

At BEO Buildingscience, we offer airtightness consulting for Green Star projects that goes beyond compliance:

• Design reviews of envelope drawings and junctions

• Red-flag reports on potential leakage points

• Constructability advice for sequencing and trade coordination

• Site testing to validate your airtightness design

• Submission-ready documentation formatted to Green Star NZ requirements

We work with your architect, engineer, and main contractor to embed airtightness into the project DNA — not bolt it on at the end.

Final Thoughts: Design Airtight, Build Right, Certify Clean

If you’re serious about Green Star certification, airtightness isn’t the cherry on top — it’s part of the cake mix. And once you start designing for it, you’ll wonder why we ever didn’t.

✅ Less heat loss
✅ Fewer defects
✅ Happier clients
✅ Higher ratings

So do your future self a favour: treat airtightness as a design priority — not a compliance chore.

💬 What Our Clients Say

💬 What Our Clients Say

How would you describe your experience working with us on this project?

"Very enlightening, interesting and a pleasure to work with."

What aspects of our service stood out to you?

"Very knowledgable and experienced in the areas of airtightness and facades."

Would you recommend our services to others? Why or why not?

"Yes definitely, you should have been involved from the start of the design phase of the project."

Ready to Design Airtight From Day One?

Let’s review your project. We’ll help you:

• Meet Green Star airtightness requirements

• Avoid failure during testing

• Deliver airtight buildings that perform