Answering: Should you build a Melbourne heritage home to the Passive House standard, or borrow the parts that matter?
Estimated reading time: 9 min read
You can make a Melbourne heritage home genuinely comfortable year-round by borrowing the building science behind Passive House — deep insulation, draught control, good glazing, sound detailing, and clever orientation — without committing to the full certified standard. Building sustainably matters, and we design to it. But we are not Passive House purists, and on a heritage home we usually advise against chasing the certificate: a fully sealed, airtight envelope ventilated only by machine is the wrong fit for an old building that needs to breathe, and for the way people actually want to live. We design homes you can still open the windows in. Drawing on Barbara Yerondais’s roughly ten years lecturing Building Science at RMIT and the University of Melbourne, our approach is to take the performance that Passive House gets right and adapt it to the home and the climate — comfort and a connection to Melbourne’s seasons, not a stale box optimised to a number.
You bought a period home for its character — the deep skirtings, the leadlight, the proportions no project-home estate can fake. What you did not sign up for is a house that is freezing in July and stifling in February. So when sustainability comes up, the question is usually framed as: do we go all the way to Passive House?
Our honest answer is: borrow what works, leave the dogma. Passive House has taught the whole industry an enormous amount about how buildings keep warmth in and discomfort out. But a standard is a means, not the goal. The goal is a home that is warm, healthy, efficient and lovely to live in — one that adapts to its environment rather than shutting it out. Here is how that thinking lands in a heritage home.
Key Insights
- The building science behind Passive House — insulation, draught control, good glazing, thermal-bridge-free detailing, orientation — delivers most of the comfort, and you can apply it without certifying.
- Full Passive House on a heritage home means an airtight, sealed envelope ventilated only by machine (MVHR); we generally advise against it, because an old building needs to breathe and so do its occupants.
- A Heritage Overlay governs external change, so the protected front facade and original windows usually stay; performance is built internally, in the roof, and in a high-performing new addition.
- The aim is mixed-mode comfort — high performance you can rely on, plus windows you can throw open on a mild Melbourne evening — not a score on a certificate.
| Passive House principle | Worth borrowing for a heritage home? | How we adapt it |
|---|---|---|
| Continuous insulation | Yes — the biggest comfort lever | Roof and subfloor first; internal wall linings only where moisture risk is managed |
| Airtightness | In part — seal draughts, not the whole building | Close the gaps that waste heat; let solid old walls still manage moisture |
| High-performance glazing | Yes, where the overlay allows | Double glazing in the new addition; reversible secondary glazing behind heritage windows |
| Thermal-bridge-free detailing | Yes — at the new work | Detail the extension properly; you can’t re-detail a 120-year-old wall |
| Mechanical ventilation (MVHR) | Optional, not compulsory | We favour mixed-mode: good natural cross-ventilation plus openable windows |
| Orientation & shading | Yes — and it’s free | Plan living spaces to the north; shade summer sun; use the existing thermal mass |
Keep reading for full details below.
Table of Contents
- What Passive House Gets Right (and Worth Borrowing)
- Where We Part Ways With the Standard
- The Heritage Tension: What You Can and Can’t Touch
- Designing for Comfort, Not a Certificate
What Passive House Gets Right (and Worth Borrowing)
Before the reservations, the credit: Passive House (Passivhaus) has done the building industry an enormous service by proving, with hard numbers, where comfort actually comes from.
Its principles are sound building physics. Continuous insulation keeps heat where you want it. Controlling air leakage stops the warmth you have paid for escaping through gaps. High-performance glazing addresses the weakest part of most walls. Detailing out thermal bridges removes the cold spots where condensation and heat loss concentrate. None of that is fashion; it is the reason a well-built modern home stays comfortable on a fraction of the energy of an old one. Applied carefully, these moves can cut a home’s heating and cooling demand dramatically.
The good news for a heritage owner is that you can have most of this without certifying anything. Insulating the roof and subfloor, sealing the worst draughts, improving glazing where the overlay allows, and detailing a new addition properly will deliver the great majority of the comfort gain. This is where Barbara’s years lecturing Building Science earn their place in the studio: knowing which intervention buys the most comfort per dollar in a particular old house, and in what order to do them, rather than reaching for an off-the-shelf package.
Where We Part Ways With the Standard
Here is the honest part, and it is a view we hold deliberately: we do work towards Passive House performance, but we are not convinced that full certification belongs in most heritage homes. Two reasons, one technical and one human.
The technical reason is that an old building needs to breathe. The solid masonry and timber of a c.1900 home manage moisture by letting it move through the fabric. Wrap that fabric in a fully airtight, vapour-tight envelope, the way certification demands, and you can trap moisture against old materials and create the very problems — damp, decay, mould — that you were trying to avoid. Internal wall insulation on solid masonry, in particular, has to be designed with real care for exactly this reason.
The human reason matters just as much. A certified Passive House is sealed, and its fresh air comes from a mechanical ventilation system rather than a window. That is a legitimate way to build, and for some homes it is the right one. But many people — and we count ourselves among them — want to open a window on a mild Melbourne evening, feel the change of season, and live with the building rather than inside a controlled box. A home designed only to satisfy a standard can end up performing on paper while feeling lifeless to live in. We would rather design for comfort and quality of life, and let the number follow, than chase a number and hope the life follows.
The Heritage Tension: What You Can and Can’t Touch
Even if you wanted full Passive House, a heritage home would not let you, and understanding why reframes the whole project sensibly.
If your property is in a Heritage Overlay, a planning permit is generally required for external change, and the significant elements — the front facade, the original timber sash and casement windows, the roof form seen from the street — are protected. You cannot strip them out and rebuild to a continuous airtight line, and you should not want to. So the performance work naturally migrates to where it is both allowed and effective: the roof space, the subfloor, internal linings in non-significant rooms, draught sealing throughout, and above all the new addition, where you have a clean slate to build to a genuinely high standard.
This is why we treat the new wing of a heritage renovation as the thermal heart of the home. It can be insulated, glazed and detailed to near-Passive-House performance, and because it is usually where the day-to-day living happens, it carries the comfort for the whole house. The period rooms at the front, meanwhile, keep their character and their openable windows, gently improved rather than rebuilt. Across 59 heritage approvals, that division — conserve the front, perform at the rear — is one of the most reliable ways to reconcile comfort with the overlay.
Designing for Comfort, Not a Certificate
If certification is not the target, what is? A clear, honest definition of comfort, designed for from the first sketch.
The biggest levers cost the least. Orientation comes first: planning the main living spaces to the north so they take winter sun and can be shaded in summer is free at design stage and does more than any gadget. Using the existing thermal mass of solid masonry walls to even out temperature swings is a gift an old home gives you. Then comes the envelope — insulation and draught sealing in the right order — and only then the systems: an efficient, zoned, all-electric heat pump rather than an oversized one fighting a leaky house. Where mechanical ventilation genuinely helps, in a tight new wing or a wet area, we use it; but we design for natural cross-ventilation and openable windows so the house can run itself for much of Melbourne’s mild year.
The result is a home that adapts to its environment instead of shutting it out: warm and quiet when the weather is hard, open and breathing when it is kind. That is the point of the exercise — a heritage home that is genuinely sustainable and genuinely comfortable, built for living, not just for a rating. For a closer look at how we work through these decisions before design begins, visit our process page.
Closing
Passive House is a brilliant body of knowledge and a demanding standard, and a heritage home is the place to use the first without being ruled by the second. Borrow the building science — insulate, seal the draughts, glaze and detail the new work well, orient for the sun — and you will get the comfort. Hold the line on full certification, and you keep an old building breathing and a home you can actually open the windows in. Sustainable and alive are not opposites; good design is how you get both.
Frequently Asked Questions
Q: Can you build a heritage home to the full Passive House standard?
A: Rarely, and we usually advise against it. A Heritage Overlay protects the front facade and original windows, so you cannot achieve the continuous airtight envelope certification requires. More fundamentally, an old building needs to breathe to manage moisture, and full air-sealing can trap damp against original fabric. We work towards Passive House performance using its building science, without chasing the certificate.
Q: Will a more energy-efficient heritage home feel sealed and stuffy?
A: Not the way we design it. We use a mixed-mode approach: a well-insulated, draught-controlled home for the hard weather, plus natural cross-ventilation and openable windows for Melbourne’s many mild days. The goal is comfort and a connection to the seasons, not a hermetically sealed box. You should still be able to open a window whenever you like.
Q: What gives the biggest comfort improvement in an old home?
A: Usually orientation and the envelope, in that order. Planning living spaces to the north and shading summer sun is free at design stage and very effective. Then sealing draughts and insulating the roof and subfloor delivers the most comfort per dollar. Glazing and mechanical systems come after, once the basics are right. The exact order depends on your specific house, which is what we assess first.
Q: Do you ignore energy ratings altogether, then?
A: No — ratings and modelling are useful tools, and we use them to test decisions and meet the building code. We simply treat them as a guide, not the goal. A star rating measures one thing; a home that is comfortable, healthy, durable and a pleasure to live in is the real brief. We design for that, and let the performance numbers confirm it.
Want to Learn More?
With more than 35 years and a grounding in Building Science, BY Projects Architecture designs heritage homes that are warm, efficient and still alive to their surroundings. We borrow the best of every standard, and answer to none of them ahead of the people who live there.
Citations
- “Passive design” — YourHome (Australian Government). Sets out the building-science fundamentals of comfort — orientation, insulation, glazing, thermal mass, ventilation and shading — that underpin a low-energy home in the Australian climate. https://www.yourhome.gov.au/passive-design
- “Save energy in the home” — Sustainability Victoria. Confirms the practical sequence of efficiency improvements for an existing Victorian home — draught sealing, insulation, glazing and efficient heating and cooling. https://www.sustainability.vic.gov.au/energy-efficiency-and-reducing-emissions/save-energy-in-the-home
- “What is Passivhaus?” — Australian Passive House Association. Describes the five Passive House principles — insulation, airtightness, thermal-bridge-free detailing, high-performance windows and mechanical ventilation with heat recovery — that this article draws on selectively. https://passivehouseaustralia.org/APHA/About_Passivhaus/APHA/About-Passivhaus.aspx
- “Permits and approvals” — Heritage Victoria. Confirms that external change to a place in a Heritage Overlay or on the Victorian Heritage Register generally needs a permit, which is why performance work concentrates internally and at the rear. https://www.heritage.vic.gov.au/permits-and-approvals
These are the official Australian and Victorian sources behind a comfortable, sustainable heritage home: passive design fundamentals, the Victorian efficiency sequence, the Passive House principles we borrow from, and the heritage controls that shape where the work can go.
With 35-plus years and a Building Science foundation, our work is to make a heritage home genuinely comfortable and sustainable while keeping it a place you want to live — warm when it needs to be, open when it can be, and built for living, not just for a rating.
93%
Quality Verified
This content scored 93% in the Probably Genius Publication Readiness Assessment, meeting standards for direct answers, section depth, proof points, citation quality, and AI extractability.
