Why Every New Home Should Have a Blower Door Test
Not just for Passive House. Here's the case for measuring airtightness on any new build — and what happens if you don't.
Blower door testing is often associated only with Passive House certification, where it’s mandatory. That association undersells it. Whether or not certification is on the table, a blower door test is one of the cheapest, most objective quality checks available for a new home — and one of the only ways to know, rather than assume, how the building actually performs.
10 min read
Key takeaways
- Being new construction doesn't guarantee airtightness — CSIRO's 2024 study of 233 new Australian homes found meaningful variation, with some homes leaking more than double the average.
- Air leakage directly affects energy bills, comfort and — critically, if ventilation isn't matched to it — moisture and mould risk.
- NCC 2022 uses airtightness as a ventilation trigger and offers a verification pathway using a measured result.
- MVHR and other mechanical ventilation systems are designed around an assumed airtightness level — testing confirms the assumption held.
- A blower door test is one of the only genuinely objective, third-party-measured indicators of build quality available on a new home.
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1. New construction doesn’t mean airtight
It’s a reasonable assumption that a brand-new home, built to current code, would be reliably airtight. CSIRO’s 2024 blower door study of 233 new Australian homes found otherwise: a national average of 6.86 m³/h/m², with some individual homes testing at more than double that. Being new is not the same as being tight — see how airtight is the average Australian home? for the full breakdown. The only way to know where a specific home actually sits is to measure it.
Energy performance
Uncontrolled air leakage is a direct, ongoing cost — heated or cooled air escaping and being replaced by outside air, working against your heating and cooling system every day the home is occupied.
Comfort
Draughts and cold spots are one of the most common comfort complaints in new homes, and they're almost always traceable to specific, findable leaks in the building envelope.
Moisture & mould risk
Airtight construction without matched ventilation is a known driver of condensation and mould. A test tells you exactly how airtight the home is, so ventilation can be sized correctly.
NCC compliance
NCC 2022 uses airtightness as a ventilation trigger and offers a verification pathway using a measured result — increasingly used by builders and assessors for compliance documentation.
MVHR performance
Mechanical ventilation with heat recovery is designed around an assumed airtightness level. A measured result confirms whether the system will actually perform as designed.
Verified build quality
A blower door result is one of the few genuinely objective, third-party-measured indicators of how well a home was actually built — not just how it looks.
2. Energy bills
Every cubic metre of conditioned air that leaks out has to be replaced by unconditioned outside air — and reheated or recooled. Insulation and glazing get most of the attention in energy discussions, but uncontrolled air leakage works against both, every hour the home is heated or cooled. A blower door test quantifies exactly how much of this is happening, rather than leaving it as an assumption baked into a NatHERS rating.
3. Comfort
Draughts, cold spots near skirtings and cornices, and rooms that never quite feel like the rest of the house are common complaints in new homes — and almost always traceable to specific, findable gaps in the building envelope. Smoke-pencil leak detection during a blower door test locates exactly where, rather than leaving occupants and builders guessing.
4. Moisture and mould risk
This is the reason airtightness testing matters most for health, not just comfort or cost. Modern construction methods and materials tend to produce tighter homes than older housing stock — which is a good thing for energy performance, but only if ventilation is matched to it. An airtight home with inadequate ventilation is a well-understood recipe for elevated humidity, condensation on cold surfaces, and mould.
A blower door test is what tells you — and your ventilation designer — exactly how airtight the home actually is, so mechanical ventilation can be sized correctly rather than assumed. See why airtight homes need ventilation and airtightness and mould for the full building science.
5. Ventilation compliance and performance
NCC 2022 uses a measured airtightness result as a ventilation trigger: homes testing at or below 5 ACH50 must provide mechanical ventilation meeting a minimum calculated airflow rate. It also offers an airtightness verification pathway for energy compliance, increasingly used by builders and assessors. See NCC 2022 ventilation requirements and the South Australian compliance guide.
Beyond compliance, MVHR and other mechanical ventilation systems are designed around an assumed airtightness level. If the as-built result is significantly leakier than the design assumption, the ventilation system won’t deliver the fresh air rates it was specified to. A test confirms whether that assumption held before it’s too late to do anything about it.
6. Build quality assurance
Airtightness is difficult to fake and hard to eyeball. A finished home can look immaculate and still leak substantially through junctions, penetrations and reveals that were never properly sealed during construction. A blower door result is one of the few genuinely objective, independently measured indicators of how carefully a home was actually built — not just how it presents at handover.
HiPer Haus field note
We regularly test new homes where the finish is excellent but the leak-hunting phase turns up several sealable gaps behind the plasterboard — see common air leaks found during blower door testing for real examples. Visual quality and measured airtightness are related, but they’re not the same thing.
7. A documented, verifiable result
A proper test report — ACH50 and q50 results, calibration records, leakage summary, photos — becomes a permanent, verifiable record of how the building performed at handover. It’s useful for certification, for NCC documentation, and simply as evidence for the homeowner that the building envelope was checked, not assumed.
8. When to test
Ideally, twice. A pre-lining test, before plasterboard conceals the air barrier, lets any leaks be found and sealed cheaply. A final test at completion documents the as-built result. See how to pass a blower door test for how to set up your project to get a good result at both stages.
Building new and want a real, measured result?
Get an instant quote →Frequently asked questions
Is a blower door test only relevant for Passive House?
No. It's mandatory for Passive House certification, but it's equally valuable for any new home — it verifies energy performance assumptions, supports NCC compliance, and confirms mechanical ventilation is correctly specified.
Isn't my new home automatically airtight because it's new?
No. CSIRO's 2024 study of 233 new Australian homes found an average of 6.86 m³/h/m², with meaningful variation between homes — some tested more than double the average. Being new doesn't guarantee being tight.
Does NCC 2022 require a blower door test?
NCC 2022 includes an airtightness verification pathway that can use a measured blower door result, and uses 5 ACH50 as a ventilation trigger. Whether a test is mandatory depends on which compliance pathway your project uses.
What does a blower door test actually protect me from?
Undetected air leakage that drives up heating and cooling bills, creates draughts and cold spots, and — critically — can contribute to condensation and mould risk if ventilation isn't matched to how airtight the home actually is.
Is it worth testing if I'm not aiming for Passive House?
Yes. Most homeowners and builders we test for aren't chasing certification — they simply want to know the building performs as intended and to catch expensive-to-fix issues while they're still accessible.
When in the build should testing happen?
Ideally twice: a pre-lining test while the air barrier is still exposed and cheap to fix, and a final test at completion to document the result.
Does testing help with MVHR or ventilation design?
Yes. Mechanical ventilation systems, including MVHR, are designed around an assumed airtightness level. A measured result confirms whether that assumption held, and whether the ventilation system will perform as designed.
Does a blower door test add resale value?
A documented result isn't a standard resale disclosure item in Australia, but a written report is genuine, verifiable evidence of build quality that a discerning buyer or their advisor may value.
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Building new? Get airtightness measured, not assumed
Book a blower door test with HiPer Haus for your new build, or get in touch to talk through timing and pricing for your project.
Written by
Jonathen HindryFounder of HiPer Haus. 25+ year plumber turned Certified Passive House Tradesperson — blower door testing, MVHR design and heat pump hot water across Adelaide and South Australia.
