Why Is Retrofitting Melbourne's Homes So Important?

We can't demolish our way to better homes. Most of the houses Australians will be living in for the next fifty years are already standing, and most of them are cold, leaky and expensive to run. Knocking them all down and starting fresh is a fantasy, both financially and environmentally. Fixing the ones we've got is not.

Retrofitting matters because most Australian homes already exist and most perform badly. Over 70% were built before 2000, before airtightness or insulation were taken seriously. You can't rebuild the whole country, so upgrading the homes we already have is the biggest lever we have on comfort, bills, health and emissions.

Carland Proof Point: Our Retrofit Rifle EnerPHit in Williamstown proved it, taking a thirty year old home to certified standard at 0.43 ACH50 without knocking it down.

Why can't we just knock down old homes and build better ones?

Because there are far too many of them, and demolishing a house throws away everything that went into building it. Over 70% of Australian homes were built before 2000 (Australian Building Codes Board), which means the vast majority of the housing we'll live in for decades is already here, already built, and mostly built badly. We are not going to bulldoze three quarters of the country's homes and start again. It isn't affordable and it isn't sustainable.

There's a carbon argument too, and it's a big one. Every existing house has years of energy and material already locked into its concrete, its bricks, its frame. Knock it down and all of that goes to landfill, and the full environmental cost starts over from zero with the new build. Retrofitting keeps that existing structure working and pours the effort into making it perform, instead of throwing it away. The greenest home is very often the one that's already standing.

So the question isn't new versus old. It's whether we fix the enormous stock of poor homes we already have, or keep pretending we'll replace it. If we can't rebuild the country, what's the plan for the homes that are already here?

How bad are Australia's existing homes really?

Worse than most people who live in them realise, and the deeper problem is that almost none of them have ever been checked. The government's own Residential Efficiency Scorecard rates a home out of 10, and the average Australian home scores just 3 (Residential Efficiency Scorecard, homescorecard.gov.au). Go back further and the average home built before 2003 rates around 1.8 stars on the ten-star energy scale (CSIRO). Two different measuring sticks, the same verdict. The housing stock sits near the bottom of the range.

But the rating is only half the story. The bigger issue is that the vast majority of Australian homes have never been assessed or verified at all. Nobody tested them, nobody rated them, nobody ever checked whether they actually do what a home is meant to do. That's why the World Health Organisation ranks Australian homes among the coldest in the developed world relative to what it's doing outside (WHO Housing and Health Guidelines). We built to a minimum for decades, never verified the result, and sold the outcome to each other as normal.

This is the real opportunity in retrofitting. It isn't just warming up a cold house. It's finally measuring what a home does and holding it to a checked, verified standard, instead of hoping. If your house has never been rated or tested by anyone, how would you even know how badly it's performing?

Why does retrofitting matter for the cost of living?

Because a leaky home is a bill you pay every single winter, and retrofitting is how you stop paying it. In a cost of living crisis, the energy your house wastes isn't an abstract environmental problem, it's money leaving your account to heat air that escapes straight through the walls. The worse the house, the bigger the bill, and the older housing stock is full of the worst offenders.

A proper retrofit flips that. Seal the shell, insulate it, add heat recovery ventilation, and the home needs a fraction of the energy to stay comfortable. Our Retrofit Rifle EnerPHit took a thirty year old house down to a modelled heating demand of 31.5 kWh per square metre per year and, with solar, it now generates more energy across the year than it uses. That's not a small saving on the bill. That's the bill more or less disappearing, on a house that was an energy pig a year earlier.

Spending money to save money sounds like a slogan until you've watched a retrofit turn a brutal winter energy bill into almost nothing. If your house wastes money every winter, how much longer do you keep paying it rather than fixing it?

What does retrofitting do for the health of a home?

It turns a cold, damp house into a warm, dry one, and that's a health outcome, not just a comfort one. Cold and damp are not just unpleasant, they breed mould, and roughly 21% of confirmed asthma cases are linked to poor indoor air quality and mould (World Health Organisation and international respiratory health research). A huge share of the older housing stock sits cold and damp for months every year, quietly making the people inside it sicker.

Retrofitting properly, with the shell sealed, the walls kept dry and mechanical ventilation bringing in constant filtered fresh air, changes the air people actually breathe at home. Warm surfaces instead of condensation. Dry walls instead of mould. Filtered air instead of whatever drifts in through the gaps. For anyone with asthma, allergies or young kids, that isn't a luxury upgrade, it's the difference between a house that supports their health and one that undermines it.

We spend most of our lives indoors, most of that at home. If the home is cold and damp, that's not a minor issue, it's a daily one. What is the air in your house actually doing to the people breathing it?

Can an old Melbourne home really be brought up to standard?

Yes, and this is the part people don't believe until they see the numbers. The certified retrofit pathway, EnerPHit, exists precisely for old buildings, with targets set to be achievable on a house that already stands rather than one you design from scratch. It's not a watered-down badge. It's a rigorous standard adapted to the reality of working with existing bones.

Our Retrofit Rifle EnerPHit is the proof. A thirty year old volume home, the kind sitting on streets all over Melbourne, taken to certified EnerPHit standard. Tested airtightness of 0.43 air changes an hour, against a code-era home that would have leaked at around 19 (CSIRO and Australian Building Codes Board, 2016 airtightness study). Heat recovery ventilation. A modelled heating demand of 31.5 kWh per square metre per year. And with solar, generating more renewable energy across the year than it uses. That's not a display home built on a perfect block. That's an ordinary old house that was fixed properly.

It was a great test case, and it taught us a lot, so I'll be honest about the hard part. The trickiest bit of an old-home retrofit is the window installation details, getting new high-performance windows sealed and thermal-bridge free into walls that were never built for them. On Rifle Range that came down to the existing brickwork, and we're hitting the exact same challenge on a retrofit we're working on right now. That's the nature of retrofitting. Every old house fights you a little at the junctions, and the skill is solving them properly instead of papering over them and hoping.

If that can be done to a thirty year old volume home, it can be done to most of the housing stock in this city. So if the house you're in was never any good, why write it off when it could perform like that?

By Matthew Carland, certified Passive House builder and director of Carland Constructions. Five certified Passive House and EnerPHit projects in Melbourne, including a thirty year old home taken to certified retrofit standard.