The Hidden Danger in Every Old House

“Right now, we are building the retrofit projects of the future.”

Let’s stop tip-toeing around the reality of the Australian housing market. We are throwing up volume-built boxes and high-density apartments that are practically end-of-life before they’ve even seen their first winter. We sat down with Linden Thorley, architect, Passive House designer, and chair of the Australian Passive House Association Retrofit Committee. 

Linden isn't your typical architect rocking a pretentious turtleneck skivvy. His focus is on crafting resilient, healthy buildings using the Passive House Planning Package (PHPP) as a predictive tool rather than a playground for data nerds. After his own home was completely lost in a neighbouring fire, he went down the rabbit hole of building a new Passive House from scratch, putting himself through a hands-on masterclass in what it actually takes to deliver a high-performance envelope on site.

The Retrofit Revolution: You Can't Just Knock Them All Down

The conversation around building better in Australia usually turns into a lazy joke: "Just knock it down and start fresh." But when you look at the raw statistics, that argument completely collapses. There are 9.5 million existing houses in Australia, the vast majority of which were built entirely pre-energy efficiency provisions. We cannot build new homes fast enough to house the population, let alone cover the deficit.

The single biggest opportunity for designers, builders, and chippies over the next ten years isn't new custom builds, it’s retrofits. In fact, retrofits currently make up at least 80% of our direct project inquiries. But a true retrofit is vastly different from a simple aesthetic cosmetic renovation. It’s about radically altering the thermal performance, moisture management, and airflow of an existing fabric.

You can approach it two ways. You can strip the interior down to its bones and build a brand-new building inside the old shell, or you can perform an over-wrap on the exterior if you have the boundary space. But here is the critical catch: retrofitting is arguably the most dangerous type of construction because you have zero clue what you're getting into until the structure is ripped apart. Blocked weep holes, unrendered brickwork behind window reveals, mortar bridging the cavity - the site risks are massive.


Airtightness and Expectation Management: Scraping In Is Still Winning

When you step out of a predictable new build and into an EnerPHit or standard retrofit project, your target for airtightness changes from 0.6 air changes per hour (ACH) down to 1.0 ACH. If you have a continuous line of Pro Clima INTELLO running straight through a frame, hitting under 0.6 is easy. But if you're working with an old three-story walk-up or a double-brick terrace house, you are fighting a legacy fabric that was never intended to hold air.

As an architect managing these projects, early expectation setting with clients and builders is everything. Until that blower door test registers under 1.0 ACH, it is not a Passive House. But if you finish the project and hit an 8.0 or a 12.0 ACH down from an initial, unmeasurable 25+ ACH, that is not a failure.

If you applied all the core Passive House fundamentals - thermal-bridge-free details, high-performance windows, localised cavity fill, and a centralised Mechanical Ventilation with Heat Recovery (MVHR) system, you still have an incredibly capable, healthy, and durable building. Quantitatively, the energy difference between a certified 1.0 ACH house and an optimised 8.0 ACH home might literally equal the output of a single solar panel on the roof. It’s still an incredible building; it's just not a certified Passive House, and clients need to understand that value.


The Labour Crisis and the Battle Against Bureaucracy

Labour costs are driving the building industry to a breaking point. Retrofits are incredibly labour-intensive. Unlike standard custom builds where you can get away with standard pricing, a high-performance retrofit requires a meticulous amount of site hours. When you break down the numbers, a standard man-day on an Australian site costs anywhere from $600 to $800. By the time a builder accounts for WorkCover, payroll tax, QA systems, insurances, and a realistic profit margin to back up a long-term structural warranty, the budget stretches tight.

Instead of helping us solve the affordability puzzle, we are actively fighting outdated bureaucracy. Council planners and heritage advisors are consistently holding back energy efficiency standards. Planners will lose their minds over a 100mm height variance required to install above-sheathing roof ventilation on a heritage terrace house, simply telling you, "It's good enough for everyone else, why isn't it good enough for you?"

To survive this landscape, builders and architects must pull down the walls of isolation. We need an Early Contractor Involvement (ECI) framework where the builder is paid to be in the room during design, telling the architect exactly where their detailing is going to blow out site labour. We don't know everything, and sitting in an architectural ivory tower pretending site delivery isn't our problem is a recipe for a broken project.

The wave of the future isn't about chasing infinite square footage or building massive 300-square-meter homes just to satisfy a bank’s outdated risk profile. True sustainability is about understanding the concept of "enough" and maximising the performance of the space we already have. 

If you're a builder or a designer looking to lead the market over the next decade, stop treating retrofits like a standard extension. Shift your contracts to use provisional sums for airtightness layers, run your thermal modelling early, and collaborate before a single hammer is swung on site. The market is moving fast. 

You can keep building to the shittest code allowable by law, or you can step up, learn the science, and start fixing the millions of homes that actually need our help.

LINKS:

Connect with Linden Thorley:

Our Sponsors:

Pro Clima - https://mindful-builder.captivate.fm/proclima

MEGT - https://mindful-builder.captivate.fm/megt

CR Kennedy - https://www.crkennedy.com.au/


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Website:  www.yoursanctum.com.au/

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Instagram: @carlandconstructions

Website: www.carlandconstructions.com/

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The Builders Standing Up to a Broken Industry