What Are the Disadvantages of a Passive House in Melbourne?

By Barbara Yerondais
Sep 24, 2026

What Are the Disadvantages of a Passive House in Melbourne?

Estimated reading time: 12 min read

A Passive House’s disadvantages in Melbourne are its demands: a whole-house airtightness test of 0.6 air changes an hour or less at 50 pascals, heat-recovery ventilation running continuously, a narrow and often imported window range, a certifier’s paperwork on top of your building permit, and the mould risk of a half-finished job.

A certified Passive House must test at 0.6 air changes an hour or less under a 50-pascal blower-door test, and it must run mechanical ventilation with heat recovery. EnerPHit, the renovation version, relaxes those targets only slightly, and you still inherit a narrow, often imported window catalogue and a certifier’s paperwork beside your building permit. At BY Projects Architecture we build sustainably and borrow the Passive House science without chasing the certificate, so the house performs, breathes, and counts its windows as part of the ventilation plan.

Someone has just told you Passive House is non-negotiable. The instinct behind that advice is a good one. A certificate arrives with its own rules, though, and a brief written around it signs you up to them before anyone has drawn what your site and household can actually take.

Lock that brief too early and the costs are real: an envelope and a ventilation system your household ends up fighting, or an airtightness number chased through rooms you never meant to touch. Worst is stopping halfway: Victoria’s building regulator links a house made tight without a designed way to breathe to trapped moisture, condensation and mould.

The decision is not whether the science is sound. It is whether you want the certificate’s rules, or the performance those rules are trying to buy.

Key Insights

  • A certified Passive House must test at 0.6 air changes an hour or less at 50 pascals; the average new Australian home tests at 15.4, and some older houses leak at more than 30.
  • Openable windows are still required, but fresh air is designed to come from mechanical heat-recovery ventilation running continuously.
  • Victoria does not ask for certification. New work and renovations are assessed against the National Construction Code (NCC) and Victoria’s Building Regulations.
  • Worth borrowing: orientation and shading, draught sealing, insulation where the fabric is opened, better glazing where windows are replaced, and a designed ventilation plan.
  • The riskiest path is the half-chase: a house made tight without a ventilation and moisture plan invites condensation.

Certified or borrowed: which path fits you

Question Choose certification when Choose to borrow the science when
Airtightness You want the 0.6 air-change test on the finished house, and you are ready to seal the whole envelope You want the worst leaks sealed first, and a blower-door test only if you want a number
Fresh air You are content for heat-recovery ventilation to run continuously, with openable windows still required You want mixed-mode: opening windows and cross-ventilation planned in, exhaust in wet areas, heat recovery where a tight new wing needs it
Windows and doors You will accept a narrow, often imported range of very well sealed, double or triple glazed units You will upgrade glazing where windows are being replaced anyway, chosen to suit the house
Thermal bridges You will design them out of the whole envelope You will design them out of new work, and treat them where existing fabric is opened
Proof You will fund the standard’s modelling, three-stage certifier checks and a final blower-door test, plus NCC compliance You will meet the NCC through your building permit, plus any testing you choose
Measure of success The certificate’s numbers Comfort, health, running costs and budget, with the numbers as a guide

Table of Contents

  • Six trade-offs to weigh before you lock the brief
  • Victoria asks for code compliance, not a certificate
  • The science worth borrowing comes in a budget-safe order
  • Price the performance before you lock the brief

Six trade-offs to weigh before you lock the brief

Passive House, or Passivhaus, is a performance-based design standard: it sets targets for comfort, energy use and airtightness without dictating products, and the Passive House Institute runs its certification, as the Australian Government’s YourHome guide explains. On an empty block those rules shape the design from the first line. On an existing house, every rule runs into something already built. Either way, read each rule as a decision you will live with, not as a feature list.

  • A steep airtightness target. 0.6 air changes an hour or less at 50 pascals, proven on site; YourHome puts the average new Australian home at 15.4 and some older houses above 30. Closing that gap means one continuous airtight layer through every junction. EnerPHit eases the targets only slightly.
  • No thermal bridges. Aluminium frames without a break, steel beams that run inside to out and uninsulated slab edges must go; an existing house already has them.
  • Continuous ventilation. Certification requires mechanical ventilation with heat recovery running continuously. Openable windows stay, but the design treats window ventilation as unreliable, and in a cool climate it significantly increases heating energy.
  • A narrower window range. Your window and door choices narrow to very well sealed, double or triple glazed units, often imported tilt-and-turn and lift-and-slide systems that can sit awkwardly with openings an existing house already has. Period fabric is covered in Passive House in a heritage home.
  • A second compliance story. You pay for the standard’s modelling, three-stage certifier checks and a final blower-door test, none of which replaces your building permit or translates directly into Nationwide House Energy Rating Scheme (NatHERS) stars.
  • Savings evidence from overseas. The Passive House Institute has found certified buildings generally cutting energy demand by 50 to 90 per cent against local code-minimum buildings in Europe, North America and China; YourHome notes that a similar analysis has not yet been undertaken in Australia.

The trap under all of this is stopping halfway. Victoria’s Building and Plumbing Commission notes that airtight construction combined with poor ventilation can trap water vapour in the building envelope, where condensation brings mould, structural failure and serious health problems. NCC 2025, which Victoria adopted on 1 May 2026, adds new condensation requirements for homes.

Victoria asks for code compliance, not a certificate

Passive House certification sits outside Victoria’s building approvals. Your project must meet the NCC as Victoria’s Building Act and Building Regulations apply it, and your building surveyor checks the design when issuing the building permit. The code is a minimum, and the Building and Plumbing Commission’s practice note on alterations to existing homes says its energy provisions do not preclude voluntary measures that go further.

The rule that catches renovators and extensions is regulation 233. If your alterations, plus any finished in the previous three years, exceed half the volume of the original building, the whole house must be brought into compliance. The surveyor can consent to partial compliance where full compliance is not reasonable. An extension larger than 25 per cent of the existing floor area, or 1,000 square metres if smaller, must comply in full itself.

The same practice note lists reasonable upgrades drawn from 2023 technical analysis for Victoria’s Department of Energy, Environment and Climate Action: ceiling insulation for flat or skillion roofs holding less than R2.5, wall insulation wherever cladding or linings come off, floor insulation in living areas where the subfloor can be reached, and argon-filled double glazing with high-solar-gain low-e coatings in living areas. The energy code even credits opening windows: as the practice note describes the NCC 2022 glazing calculator, the share of windows that open is used to calculate cross-ventilation, and the lower cooling load earns a higher summer target.

The science worth borrowing comes in a budget-safe order

We build sustainably, borrow the building science behind Passive House, and treat any standard as a guide rather than the goal. Houses need to breathe, so we design mixed-mode comfort: sealed and insulated for hard weather, with opening windows planned in for the days that allow it.

  1. Decide orientation, shading and thermal mass on paper. Where living rooms face, how summer sun is kept off the glass and where heavy materials sit are cheapest to change while they are still on paper.
  2. Seal the draughts. YourHome calls better airtightness one of the most cost-effective and easiest ways to improve comfort and reduce energy costs, citing CSIRO research that puts air leaks behind 15 to 25 per cent of winter heat loss.
  3. Insulate what the work opens. Ceilings and reachable subfloors first, walls whenever linings or cladding come off. Depending on location, the level a Passive House needs may be similar to the NCC’s or only slightly greater.
  4. Upgrade glazing where windows are being replaced, living areas first. On our Dudley Street apartment retrofit in West Melbourne, the thermal upgrade was the glazing: legacy single-pane windows out, high-performance double glazing in, inside a building envelope that could not change.
  5. Design the ventilation, then test. Once a house gets tight, fresh air has to be planned: YourHome records some consensus that below 3 to 7 air changes an hour at 50 pascals, mechanical ventilation is definitely required. A blower-door test tells you where you stand, and you can buy the test without buying the certificate.
  6. Detail rebuilt walls so they can dry. Research funded by Victoria’s building regulator found that more vapour-permeable wall membranes and a drained, ventilated cavity behind the cladding cut mould risk in new walls.

Price the performance before you lock the brief

The expensive mistake is writing certification into the brief before anyone has priced what your house can take. As renovation architects in Melbourne, we price the work at feasibility and fix the fee from day one.

Barbara’s method is staged design work that shows what your budget achieves beside what the full dream costs, with a shopping list between them so you choose the scope. Give each performance option its own line (a blower-door test, heat-recovery ventilation for a new wing, triple glazing, external shading) and weigh what each one buys. Before you sign a brief that names Passive House, check three things:

  • whether your works cross the regulation 233 thresholds and bring the whole house into compliance;
  • how your household will live with ventilation that runs continuously;
  • what the certificate buys beyond the upgrades on your list.

In one hour with Barbara Yerondais, FRAIA, in person or on Zoom, you’ll talk through your site, budget and planning timelines, and leave knowing what’s realistic and what your next step is. There’s no obligation to go further. Book a Feasibility Session.

Closing

Passive House is a rigorous standard and a generous teacher. Its disadvantages are the certificate’s demands: a whole-house airtightness test, a ventilation machine the house depends on, a narrow window catalogue and a second layer of paperwork. Borrow the physics that pays its way, design how the house breathes, and let comfort, health and running costs be the measure.

Frequently asked questions about Passive House trade-offs

Q: Can you open the windows in a Passive House?

A: Yes. The Australian Government’s YourHome guide says openable windows are still required in a certified Passive House. What changes is the design logic: fresh air comes from mechanical ventilation with heat recovery running continuously, and in a cool climate, ventilating through windows significantly increases the heating energy a home needs. We design mixed-mode instead, with cross-ventilation and opening windows planned from the start and mechanical ventilation where a tight new wing or a wet area needs it.

Q: Is Passive House certification required in Victoria?

A: No. A Victorian project must meet the National Construction Code as the Building Regulations apply it, and your building surveyor checks that when issuing the building permit. The code is a minimum and does not preclude going further. For renovations and extensions, scale is what matters: under regulation 233, if your alterations plus any in the previous three years exceed half the original building’s volume, the whole house must be brought into compliance, although the surveyor can consent to partial compliance.

Q: Is EnerPHit an easier way to certify an existing house?

A: Somewhat. EnerPHit is the Passive House Institute’s certification for retrofits and renovations, using the same principles and processes with slightly less stringent metrics, because high performance is harder to reach in existing buildings. You still commit to the standard’s modelling, a certifier’s checks and on-site testing, and to a design organised around the targets. For most existing houses we would rather spend that effort on the upgrades themselves, and measure them with a blower-door test if you want a number.

Q: What goes wrong if a renovation only goes halfway towards Passive House?

A: Moisture. A house made airtight without a designed way to ventilate can trap water vapour in the building envelope, and Victoria’s building regulator links the condensation that follows to mould, structural failure and serious health problems. If you tighten the envelope, plan the fresh air and detail rebuilt walls so they can dry, in the same job.

About BY Projects Architecture

BY Projects Architecture is a Melbourne practice led by Barbara Yerondais, FRAIA, who brings 35+ years in practice, and our team has delivered 400+ projects across Victoria. We design new homes, renovations and difficult sites on fixed fees, bringing site, soul, and structural intelligence to each one.

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About the Author

Barbara Yerondais, FRAIA, is the founder of BY Projects Architecture. With 35+ years of experience, she specializes in sustainable, community-focused design and heritage restoration. A dedicated mentor and rower, Barbara balances her high-impact Melbourne practice with a passion for social inclusion and passive, energy-saving design.

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