Question 1

What is a blower door test?

Accepted Answer

A blower door test uses a calibrated fan sealed into an external doorway to pressurise or depressurise a home, measuring exactly how much air leaks through the building envelope. The result is expressed as ACH50 — air changes per hour at 50 Pascals — giving an objective, repeatable measure of how airtight the building actually is. We run a Retrotec system on every test, the same rig you'll see set up at our Nairne project.

Question 2

Why have a blower door test?

Accepted Answer

It's the only way to know how airtight a building actually is — visual inspection can't detect the air leakage that drives draughts, high energy bills, condensation and mould. Testing during construction (before linings go up) also lets leaks be fixed cheaply, rather than discovered and repaired after the home is finished.

Question 3

When should a blower door test be done?

Accepted Answer

Ideally at two stages: a mid-construction test once the air barrier is complete but before internal linings go up (so leaks can still be fixed easily), and a final test at practical completion for compliance or certification. Existing homes can be tested at any time — on our Thebarton and Nairne projects, we tested before the renovation started, purely to set a baseline.

Question 4

How long does a blower door test take?

Accepted Answer

Most homes are tested in 1–2 hours depending on size and complexity. Allowing for setup, pressurisation runs, smoke-pencil leak diagnostics and pack-down, plan for around 2–3 hours on site.

Question 5

What preparation is required before a blower door test?

Accepted Answer

Exhaust fans, range hood dampers and any deliberate vents need to be closed or taped, along with any incomplete penetrations. Internal doors are left open, external doors and windows closed. Our full checklist covers exactly what to do — and what not to touch — before we arrive.

Question 6

What does ACH50 mean?

Accepted Answer

ACH50 is “air changes per hour at 50 Pascals” — the number of times the entire volume of air in a home would be replaced through leaks in one hour, if the building were pressurised to a standard 50 Pascals. It's the universal metric blower door results are reported in, letting homes be compared on a level playing field.

Question 7

What is a good ACH50 result?

Accepted Answer

It depends on the target you're building to. NCC 2022 links ventilation requirements to a 5 ACH50 trigger; Passive House certification requires 0.6 ACH50 or better; many project specifications sit somewhere in between. There's no single “good” number — a good result is one that meets or beats your project's stated target.

Question 8

Can you fail a blower door test?

Accepted Answer

In most Australian residential projects there isn't a universal pass or fail result. The target depends on the project standard — NCC requirements, Passive House certification, or a builder's own specification — and the test's real value is identifying where air is leaking so those areas can be improved before the next test or handover. On our Willunga shouse conversion, the result was 3.556 ACH50, with the leakage traced mainly to the sliding doors and exhaust fans — a clear, fixable finding rather than a fail.

Question 9

What happens if my result doesn't meet target?

Accepted Answer

The test itself identifies where the leaks are, using smoke pencils and (where conditions allow) thermal imaging, so they can be targeted directly rather than guessed at. A good result is built through sequencing and detailing during construction, not achieved by chasing leaks after the fact — our guide covers the details that matter most.

Question 10

Can existing homes be tested?

Accepted Answer

Yes. Existing homes, renovations and shed conversions can all be blower door tested — it's often done before a renovation to establish a baseline, or afterwards to verify the airtightness work achieved its target. We've tested a shed-to-house conversion at Willunga and a pre-renovation home at Thebarton on exactly this basis.

Question 11

Do I need to leave the house during testing?

Accepted Answer

No. The test doesn't produce anything hazardous — you're welcome to stay and watch, and many homeowners find it genuinely interesting to see where the leaks in their own home are with a smoke pencil.

Question 12

Does blower door testing damage anything?

Accepted Answer

No. The equipment temporarily seals into a doorway using an adjustable frame and fabric panel, with no fixings into the building. Once testing is complete, the frame is removed and the doorway is left exactly as it was.

Question 13

Can a blower door test find where the leaks are?

Accepted Answer

Yes — while the building is pressurised or depressurised, a smoke pencil reveals exactly where air is moving through gaps, and thermal imaging (where conditions permit) can pinpoint hidden leaks behind linings. This diagnostic step is often more valuable than the ACH50 number itself. On our Thebarton test, it's exactly how we traced leaks to a cornice gap, a window frame junction and a ceiling access hatch.

Question 14

Is thermal imaging included?

Accepted Answer

Thermal imaging may be used where conditions permit, alongside smoke-pencil diagnostics, to help pinpoint hidden air leaks behind linings and finishes. It's a diagnostic tool used as part of the test, not a separate service.

Question 15

How much does a blower door test cost?

Accepted Answer

Cost depends on the size of the home, the number of tests required (mid-construction and final, for example) and location. Get in touch with your home's details and we'll provide a fixed quote.

Question 16

How airtight is the average Australian home?

Accepted Answer

CSIRO's 2024 study tested 233 new Australian homes with a blower door and found most performed well behind international airtightness standards, with wide variation between builders and building types. It's the most robust Australian-specific benchmark available, and useful context if you're wondering how your own result compares — on the tests we've completed so far, we've already seen results ranging from single digits to well over 10 ACH50 on the same street.

Question 17

What is airtightness?

Accepted Answer

Airtightness describes how well a building envelope resists uncontrolled air leakage through gaps, cracks and poorly sealed junctions — as distinct from insulation, which resists heat flow through materials. A continuous air barrier, wrapping the entire floor, wall and roof envelope, is what a blower door test actually measures.

Question 18

Is an airtight home healthy?

Accepted Answer

Yes — provided it's ventilated properly. Airtightness on its own just stops uncontrolled leakage; paired with mechanical ventilation (typically MVHR), it gives you continuous filtered fresh air, stable humidity and none of the draughts, dust and outdoor pollutants that leak in through a poorly sealed envelope.

Question 19

Can a home be too airtight?

Accepted Answer

Not in terms of the envelope itself — there's no such thing as “too airtight” for the building fabric. What matters is that ventilation is sized to match: the tighter the envelope, the more a home depends on mechanical ventilation, rather than gaps, to supply fresh air.

Question 20

Does airtightness stop mould?

Accepted Answer

Airtightness on its own doesn't stop mould — in fact, an airtight home with no planned ventilation is a common cause of it, because moisture that used to leak out through gaps now has nowhere to go. Airtightness plus properly sized ventilation is what actually controls the humidity that mould needs to grow.

Question 21

Does airtightness reduce heating and cooling costs?

Accepted Answer

Yes, substantially. Uncontrolled air leakage is one of the biggest drivers of heating and cooling load in a typical home — every gap is effectively a hole letting conditioned air out and outdoor air in. Sealing the envelope reduces that load significantly, which is why airtight homes can run smaller, cheaper heating and cooling systems.

Question 22

How does airtightness affect bushfire smoke?

Accepted Answer

A well-sealed envelope significantly reduces how much outdoor smoke infiltrates a home during a bushfire smoke event, provided doors and windows stay closed. MVHR systems fitted with appropriate filters can also be run on recirculate or paused, depending on the model, to further limit smoke entering the home.

Question 23

How does airtightness affect noise?

Accepted Answer

A continuous, well-sealed air barrier — including sealed penetrations, gaskets around windows and doors, and no gaps in the building fabric — noticeably reduces external noise transmission, since air gaps are also sound paths. It's a secondary benefit many owners notice before they notice the energy savings.

Question 24

Does insulation make a house airtight?

Accepted Answer

No — they're separate things that need to work together. Insulation slows heat transfer through materials; airtightness stops uncontrolled air movement through gaps. A house can be heavily insulated and still leak large volumes of air through unsealed penetrations, which is exactly what a blower door test reveals.

Question 25

What is an air barrier?

Accepted Answer

The air barrier is the continuous layer — membranes, tapes, sealants and airtight materials — that wraps a building's floor, walls and roof to stop uncontrolled air leakage. It has to be genuinely continuous: a single unsealed penetration, ceiling hatch or window junction can undo the benefit of an otherwise well-sealed envelope.

Question 26

What's the difference between airtightness and ventilation?

Accepted Answer

Airtightness stops uncontrolled, unplanned air leakage through the building envelope. Ventilation deliberately supplies fresh air and removes stale air, on purpose, in controlled quantities. They're complementary, not competing — a well-built high-performance home is airtight and ventilated, not just one or the other.

Question 27

What are the most common air leaks found during testing?

Accepted Answer

Field data from South Australian tests points to a consistent shortlist: sliding doors, exhaust fans, ceiling access hatches, downlights, service penetrations for plumbing and electrical, and junctions around windows and doors. Most are cheap to fix if caught mid-construction, and expensive to fix afterwards — see the box above for the specific leaks we've traced on real HiPer Haus tests.

Question 28

What air sealing details matter most during construction?

Accepted Answer

Service penetrations, top plates, window and door junctions and rangehood ducts are the details that are cheap and easy to seal properly during construction, but expensive — sometimes impossible — to fix once plaster is up. Getting these right the first time is the single biggest factor in a good blower door result.

Question 29

Does NCC 2022 require a blower door test?

Accepted Answer

NCC 2022 doesn't mandate blower door testing for every home, but SA's modern homes provisions (from 1 October 2024) link a home's ventilation requirements to its airtightness result, and testing is the only way to actually demonstrate that result. Many builders now test as standard practice for compliance and quality assurance.

Blower Door Testing & Airtightness