Energy-efficient living in Victoria: How Passive House design can cut your energy bills by up to 90 %
Key insights at a glance
In Victoria’s mild temperate climate, Passive House strategies can reduce heating and cooling energy by 50–90% compared with typical housing. The upper end applies mainly to older, leaky homes [1][2].
Airtightness is measurable. The average new Australian home sits around 15.4 ACH50. Passive House caps leakage at 0.6 ACH50, roughly 25 times tighter, which helps cut draughts and bills [1][2].
MVHR supplies filtered fresh air while recovering at least 75% of otherwise lost heat, using very low fan power [2][3].
Melbourne’s mix of cool winter nights, hot summer spikes and evening cool changes rewards good insulation, smart shading and night-purge design [4].
Quality double or triple glazing with the right frames can reduce window heat flow by up to six times compared with single glazing [1].
Victorian case studies show Passive House works locally, from student housing to inner-suburban homes [5][6][7].
Glossary
ACH50, air changes per hour at 50 pascals: The standard blower-door test result. It shows how many times the full volume of air in your home leaks out and is replaced each hour when the house is pressurised to 50 Pa. Lower is better. Passive House sets a maximum of 0.6 ACH50 [2].
MVHR, mechanical ventilation with heat recovery: A quiet system that brings in fresh outdoor air and removes stale indoor air through a heat exchanger so you keep warmth in winter and coolness in summer. Passive House requires high heat recovery efficiency and very low fan energy [2][3].
U-value: How easily heat flows through a building element. Lower numbers mean better insulation.
SHGC, solar heat-gain coefficient: How much of the sun’s heat a window lets through.
NCC and NatHERS: Australia’s building code framework and the national home energy-rating scheme.
BAL, Bushfire Attack Level: A rating of bushfire exposure that drives material and detailing choices.
What Passive House means for Victorian homes
Passive House, also known as Passivhaus, is a quality-assured building standard focused on five pillars: high insulation, extreme airtightness to 0.6 ACH50 or better, high-performance windows and doors, mechanical ventilation with heat recovery, and thermal-bridge-free construction. It also sets comfort limits for summer so homes remain pleasant during hot spells. In Melbourne’s climate, those pillars deliver a snug, quiet home in winter and a cooler, steadier home in summer, with tiny heating and cooling systems doing the work [2][3][4].
Why it suits Melbourne’s climate
Melbourne’s typical summer temperature sit in the mid-20s, with bursts over 30 to 40 °C, and winter nights often sit in the mid-single digits. Those cool nights and reliable cool changes make night purge, flushing the home with cool evening air, very effective when the building is designed for it. Good shading blocks harsh afternoon sun, and MVHR maintains healthy, filtered air during pollen or smoke days while keeping warmth or coolness inside [4].
Principle 1: Insulation that is continuous and climate-tuned
Think of insulation as a doona around the whole house. In Melbourne:
Roof and ceiling: aim roughly R5 to R6 continuous insulation to slow summer heat and winter losses
External walls: R3.5 to R4.5 plus is a sensible target using deeper studs or an external insulated sheathing
Slab edges and floors: insulate the slab perimeter and any exposed floors to avoid chilly floor edges and condensation in winter
Pair insulation with moisture control. Use a vapour-permeable external wrap for rain and wind, and a smart vapour retarder on the inside so winter moisture does not condense inside walls [2][3].
Principle 2: Airtightness you can measure and feel
Most homes leak air through gaps at frames, services and junctions. That leakage drives up bills and causes cold draughts. The average new Australian home sits around 15.4 ACH50, while Passive House caps at 0.6 ACH50 [1][2]. You get there by drawing a clear air barrier on the plans, sealing every junction and penetration, and testing with a blower-door before plaster so trades can fix leaks. The payoff is quieter rooms, no draughts and much smaller heaters and coolers.
Good to know: airtight does not mean you cannot open windows. You can open them any time. Fresh air is guaranteed even with windows closed because the MVHR provides a steady, filtered air exchange [2][3].
Principle 3: Windows and doors that work for you
Windows are often the weakest thermal link. Upgrading glass and frames pays off in winter and summer. The Australian Government’s Your Home guide notes that double or triple glazing can reduce heat flow by up to six times compared with single glazing, especially with thermally broken uPVC, timber or insulated aluminium frames [1].
Orientation tips
North, equator-facing: choose a higher SHGC to harvest winter sun and use eaves sized to block high summer sun
West and east: keep glass modest or use external blinds or screens to stop low-angle summer sun
South: focus on low U-values and airtight frames for comfort and condensation control
Install windows in the insulation plane, and tape to both the external weather-resistive barrier and the internal air barrier for a double line of defence [2].
Principle 4: Fresh air, filtered, with MVHR
MVHR continuously supplies fresh air to living areas and bedrooms, and extracts from kitchens and bathrooms. A high-efficiency heat exchanger typically recovers at least 75% of heat that would otherwise be lost, while certified units keep fan energy very low. Many units include a summer bypass so when the cool change arrives you can bring in cool night air without warming it through the exchanger [2][3].
Principle 5: Details that prevent mould and cold corners
Thermal bridges are paths where heat takes a shortcut, for example an uninsulated slab edge or a metal balcony connector. Passive House details wrap and break those paths so interior surfaces stay warm and dry in winter. That reduces condensation risk and the mould that can follow [2][3].
How much can you really save in Victoria
Global data and Australian guidance consistently show large reductions in heating and cooling energy from Passive House homes. Against older Victorian stock, savings can approach the headline up to 90 %. Compared with today’s better new builds the reduction is smaller yet still meaningful, and you gain comfort, air quality and resilience during heatwaves and smoke events [1][2][5][6][7][8].
Costs and payback in the real world
Local projects and guidance suggest a typical 5 to 10% construction premium for a detached Passive House, driven by better windows, membranes, tapes and MVHR. Victorian projects report that single-digit premiums are achievable with early planning and Passive House experienced teams. Energy savings plus smaller HVAC systems and comfort help close the gap over time [5][6][8].
Designing for Melbourne: comfort without over-cooling
Passive House certification limits overheating to no more than 10% of annual hours above 25 °C. In Melbourne you hit that by combining:
North-facing living with decent eaves
Modest or well-shaded west and east glazing
MVHR with summer bypass and ceiling fans
Night purge on cool evenings
A small, efficient split system for the rare 40 °C run
These measures keep you comfortable across seasons while keeping peak loads tiny [2][3][4].
Bushfire readiness, BAL, and Passive House
Passive House can be adapted to higher BAL ratings. There are Australian examples certified to BAL-FZ, which shows that with the right materials, window systems and detailing, you can combine an airtight, insulated envelope with bushfire requirements. For BAL-29 to BAL-40 sites around greater Melbourne, designers typically select BAL-rated windows and doors, include ember guards on vents and specify non-combustible claddings. Airtightness also helps reduce smoke infiltration on bad days [6][7][8].
Victorian case studies
Gillies Hall, Monash Peninsula, Frankston: A certified Passive House student residence that normalised airtightness and heat recovery at scale in Victoria [5][8].
Hütt 01, Coburg: A certified inner-Melbourne home on a tight site delivering year-round comfort through careful shading, glazing and airtightness [6].
Owl Woods, Trentham: A certified Passive House in Victoria’s cooler hinterland, with triple glazing and robust insulation, showing adaptability across the state [7].
Retrofits: EnerPHit for period and post-war homes
If you are renovating, EnerPHit is the Passive House retrofit pathway. It sets slightly relaxed targets, such as 1.0 ACH50 for airtightness, and focuses on deep insulation, high-performance windows and MVHR. Many Melbourne owners stage upgrades to spread costs. The big wins are comfort, healthier air and the end of winter draughts [2][3][8].
Step-by-step roadmap
Brief and budget. Ask your architect for Passive House performance. Aim for 0.6 ACH50 or better and model energy in PHPP from concept.
Site and layout. Put living spaces to the north, limit west glass, plan fixed eaves/shrouds or external blinds.
Envelope. Roof R5 to R6, walls R3.5 to R4.5 plus, insulated slab edge. Specify thermally broken frames and low-E double or triple glazing tuned for each facade.
Airtightness plan. Draw the air-barrier on every section. Use tapes, gaskets and airtight membranes. Include a blower-door test before plaster.
Ventilation. Choose a PHI-certified MVHR with high heat recovery, quiet ducts and a summer bypass. Fit filters suitable for pollen and smoke.
Commissioning. Balance the MVHR, test airtightness again, and hand over simple controls and a filter-change schedule.
FAQs
1) Can a Passive House in Melbourne really cut my energy bills by up to 90 %
Against older, single-glazed, leaky homes, yes for heating and cooling energy that level is possible. Compared with a new code-compliant home, expect a smaller but still significant reduction, plus a big comfort upgrade [1][2][8].
2) Will an airtight home feel stuffy
No. Airtightness controls where air moves so you do not lose conditioned air through gaps. MVHR brings in a steady supply of filtered fresh air and you can open windows whenever you like [2][3].
3) Do I need triple glazing in Melbourne
Not always. Many inner-Melbourne sites work well with high-spec double glazing if shading and frames are right. Cooler hills and fringe suburbs often justify triple glazing. Either way, modern glazing cuts heat flow dramatically compared with single glazing [1].
4) How does Passive House handle heatwaves and smoke
Overheating is limited by design to no more than 10% of hours above 25 °C. MVHR runs with good filters to maintain indoor air quality during smoke or pollen days, and a small split system covers extreme heat peaks [2][3][4].
5) What is the payback period
There is usually a 5 to 12% build premium. Many owners see a reasonable payback over time through much lower energy use, smaller HVAC systems and better comfort. Victorian projects show single-digit premiums are possible with early planning and experienced teams [5][6][8].
6) Can Passive House be built in bushfire-prone areas
Yes. With BAL-rated windows and ember-proof ventilation details, several Australian projects have met high BAL ratings, including BAL-FZ in one well documented case [6][8].
References
Australian Government, Department of Climate Change, Energy, the Environment and Water, Your Home: Windows and Glazing, Ventilation and Airtightness, Passive House, Canberra, updated 2025. Available at: https://www.yourhome.gov.au/
Passive House Institute, Passive House criteria and certification, airtightness, overheating and ventilation with heat recovery, Darmstadt, accessed 6 August 2025. Available at: https://passivehouse.com/ and https://passipedia.org/
International Passive House Association, Ventilation in Passive Houses and PHI component criteria, accessed 6 August 2025. Available at: https://passipedia.org/
Australian Government, Bureau of Meteorology, Melbourne climate information and historical summaries, accessed 7 August 2025. Available at: https://www.bom.gov.au/climate/
ArchitectureAU, Gillies Hall, Monash University Peninsula Campus, 21 September 2020, accessed 7 August 2025. Available at: https://architectureau.com/
Australian Passive House Association, Project register and case studies, including Hütt 01, Coburg, and bushfire rated projects, accessed 11 August 2025. Available at: https://passivehouseaustralia.org/
Blue Eco Homes, Sapphire Passive House, Blue Mountains, project information referencing BAL-FZ, accessed 8 August 2025. Available at: https://blueecohomes.com.au/
Sustainability Victoria and Monash University sources, Victorian Passive House case studies, performance and costs, accessed 7 August 2025. Available at: https://www.sustainability.vic.gov.au/ and https://www.monash.edu/
