We just achieved one of the best blower test results in New Zealand. Ever! An incredible 0.18 Air changes per hour - that’s up to 39x better than the average new NZ build, and even 3.6x better than Passive house certification level.


Testing was completed to ISO9972 by independent expert Nigel Murray of Seechangenz.

But, why does Airtightness matter? Imagine trying to fill a bathtub...

But there’s a hole in the bottom. Not just one hole - dozens of tiny leaks all around the sides and floor. You turn on the tap, water pours in, but it never fills up.
No matter how much hot water you add, it’s constantly draining away.

That’s what most New Zealand homes are like - even brand-new ones built to the current Building Code. They’re full of tiny air leaks that let precious warm air escape and cold, damp air sneak in. You’re paying to heat your home, but it’s leaking out faster than you realise.

Now picture a bathtub that’s sealed tight.
You fill it once, and it stays warm for ages. Efficient. Comfortable. Easy. That’s what living in an airtight home is like - and it’s what we build at Árbol using , high-performance framing, wraps, NZSIP panels and other low-energy design and manufacturing principles.

💨 Air Changes Per Hour: The Leaky Bucket Metric

Let’s get technical for a sec. Air Changes per Hour (ACH) is the measure of how many times all the air inside your home is replaced by outdoor air in one hour - due to leaks.

  • Standard NZ code home: 5–7 ACH at 50 pascals
    (Imagine trying to fill a bathtub that drains completely every 10 minutes.)
  • Arbol airtight home: 0.18–0.65 ACH (Better or equal to Passive House standard)
    (Now we’re talking - your heat stays in the tub.)

The fewer leaks, the better your home holds onto warmth. You spend less on heating, feel more comfortable, and enjoy better air quality all year round.

💧 Why Airtight Matters

✅ Keeps the Warmth In
You wouldn’t try to heat a leaky tent. So why live in a leaky house?

✅ Reduces Energy Use
Less heat escaping means less energy required to top it up. Like using a well-insulated thermos instead of a paper cup.

✅ Improves Health
An airtight home, combined with filtered mechanical ventilation (MVHR), means no cold draughts, no damp patches, and no mould spores lurking in the corners.

✅ More Comfortable
You don’t feel those sudden chills or stuffy rooms. Just clean, fresh, steady warmth - like a perfectly run bath.

✅ Future-Proof
As climate and energy standards rise, airtight homes are already ahead of the curve. Code-built homes? They'll need upgrades sooner than you'd think.

Your Home Shouldn’t Be a Sieve

So next time you hear someone say, “built to code,” remember this: the Building Code is the leakiest home you’re legally allowed to have.

At Árbol, we believe your home should be a sealed, high-performance envelope- warm, healthy, and built to last. 

🧠 FAQ: Common Questions About Airtight Homes

💬 Can I still open my windows?
Yes - absolutely! Airtight doesn’t mean locked shut. You can open your windows any time you like. The beauty of an airtight home is that you’re in control. You won’t need to open windows to get rid of stuffy air or moisture, because your MVHR (mechanical ventilation with heat recovery) system does that automatically and efficiently. But if you want a breeze or to hear the birds, open away.

💬 Won’t I run out of oxygen?
Nope. Airtight homes don’t mean airtight lungs. A well-designed MVHR system is constantly bringing in fresh, filtered air from outside and removing stale air - without losing the heat. It’s like your home is always breathing, but in a smart, efficient way. In fact, indoor air quality in a properly ventilated airtight home is much better than in a leaky, code-minimum one.

💬 Isn’t an MVHR expensive to run?
Not at all. Most MVHR systems use the same power as a standard light bulb - around 30 to 60 watts. That’s less than $1 per week for 24/7 fresh air and balanced humidity. And because it helps keep warmth in and moisture out, it actually reduces the need for heating, cooling, and dehumidifiers - saving you money overall.