Lessons from Our Fitzroy Passivhaus Retrofit 

Our Fitzroy retrofit is now certified to the Passivhaus Classic Plus standard, independently verifying the performance of the completed building.

One of the clearest lessons from the project is that successful retrofit starts before the design does.

Start with the existing building

Before we started designing Fitzroy, we met with the contractor, Hone Built, at the house to assess the existing building and discuss what could realistically be retained.

The 1950s house is a terrace built boundary to boundary. We had originally envisaged retaining more of the existing structure, but its condition meant we needed to reconsider that approach. We decided to carefully deconstruct more of the house, while retaining the front façade and boundary walls.

At Hone Built’s suggestion, bricks from the deconstruction were salvaged for reuse, along with the existing roof tiles. The reused bricks subsequently became a central element of the design.

Assessing the building with the contractor before we started designing changed our approach. The strategy needs to start with the building as it actually exists, rather than the building we expect to find.

Once it became clear that more of the house needed to be deconstructed, Hone Built also looked at how those materials could be reused or diverted from landfill.

At their initiative, 18.28 tonnes of material were directly reused or repurposed, and across demolition, excavation and construction, 91.1% of material by weight was diverted from landfill.

Retrofit is harder than new construction

These lessons informed my opening address at the Melbourne event for the Australian Passivhaus Association’s inaugural Retrofit Month in June.

One of the points I made that evening was that retrofit is harder than new construction.

With an existing building, we are working with incomplete information, unknown conditions, previous alterations and construction that may not behave in the way we expect.

A retrofit is not simply a renovation with more insulation.

Changes to one part of an existing building can affect the performance of another. Insulation cannot be considered without airtightness. Airtightness cannot be considered without ventilation. Changes to the building fabric can also alter moisture and condensation risk.

Retrofit is a whole-building systems exercise

This is why early input matters. What can be retained, how something can be deconstructed, what can be reused and how it will actually be built can all affect the design.

As I said during Retrofit Month, specialist input early is not an optional extra. It is risk management.

Taking the lessons into the next projects

One of the lessons we took from Fitzroy was the value of having the contractor involved before the design had developed. At Surrey Hills, we have taken that process a step further.

The project involves the retrofit and extension of an existing house and is targeting Passivhaus certification. At the very beginning of the design stage, we met on site with both the contractor and Passivhaus consultant to establish how we would approach the retrofit.

This is a change in our process. At Fitzroy we had the benefit of early contractor input. At Surrey Hills we deliberately brought the Passivhaus consultant into that discussion as well, before the design developed.

We have also carried the approach to material reuse into our Princes Hill project, which is targeting Passivhaus certification. Bricks from the deconstruction of the existing house are being salvaged and reused within the project.

I am currently completing the Passivhaus Retrofit Expert course, led by New Zealand Passivhaus certifier Jason Quinn. One of Jason’s observations during the course has stayed with me: “no two Passivhaus retrofit projects are the same.”

Passivhaus gives us a rigorous and measurable performance standard, but it does not prescribe a standard retrofit solution. The performance target may be consistent. The architectural and technical response cannot be.

The course is taking me further into the building physics behind these decisions, particularly moisture risk and the implications of insulating existing construction.

Why retrofit now?

New construction alone cannot address the performance of our existing housing stock.

If we are serious about reducing carbon, improving comfort and creating healthier homes, we need to improve the buildings we already have.

Existing buildings also contain carbon already invested in their materials and construction. Retaining and reusing what we can needs to be part of improving their performance.

Our starting point with an existing or heritage building has always been to understand what is already there before deciding what needs to change. What gives the building its character? What can be retained? What actually needs to change?

With heritage buildings, we need to respect the heritage significance while also improving the building’s performance.

Passivhaus retrofit asks us to apply the same discipline to performance. The challenge is not simply to improve thermal performance, but to understand how those interventions affect the existing building and what is important to retain.

Fitzroy has reinforced that good retrofit starts with understanding the building, understanding the risks and getting the right people involved early. Passivhaus gives us the rigour to test those decisions, with certification providing independent verification of the outcome.

With more than 70% of Australia’s existing residential buildings expected to still be standing in 2050, applying that rigour to the buildings we already have is becoming increasingly important.