Australia’s existing building stock — which accounts for approximately 90% of the buildings that will exist in 2050 — is increasingly in the spotlight as a critical lever for reducing emissions, improving health outcomes and delivering long-term economic value.

Writing exclusively for Architecture & Design, Dr Marcus Strang, director at Melbourne-based sustainable design consultancy HIP V. HYPE, makes the case for the Passivhaus EnerPHit standard as the framework to unlock a new era of high-performance retrofits across the country.

The scale of the problem

The average Australian home currently rates 1.7 stars under NatHERS. In winter, 80% of monitored indoor temperatures fall below the World Health Organisation’s minimum healthy threshold of 18°C — and cold indoor temperatures are associated with 6.5% of deaths in Australia, compared to 3.7% in Sweden.

Condensation and moisture defects affect approximately 40% of new and existing buildings, generating an estimated $4.2–5.6 billion in health costs annually. Extreme heat events, meanwhile, cause more fatalities than all other natural hazards combined.

“We keep treating performance metrics on energy, health and economic value as separate problems requiring separate solutions,” Dr Strang says. “EnerPHit is the Passivhaus retrofit standard — it offers a single framework that can address all three simultaneously.”

He draws on Donut Economics — Kate Raworth’s framework describing a ring-shaped space between a social foundation and an ecological ceiling – to frame the stakes. A well-executed EnerPHit retrofit, he argues, pushes a household above the social floor (adequate thermal comfort) and the building below the ecological ceiling (carbon emissions) at the same time.

What is EnerPHit?

EnerPHit acknowledges what every retrofit practitioner already knows: existing buildings cannot always meet the full Passivhaus new-build criteria. Rather than requiring demolition and rebuild, it offers two certification pathways — a heating and cooling demand pathway and a component-based pathway — with slightly relaxed thresholds to reflect real-world constraints, without compromising on methodology.

Five core principles must still be systematically addressed: superior insulation, high-performance windows and doors, thermal bridge minimisation, airtightness, and mechanical ventilation with heat recovery (MVHR). Moisture safety must also be demonstrated.

Three tools from the Passivhaus Institut support delivery: the Manufacturing Energy Evaluation Tool (MEET) for early-stage embodied and operational energy evaluation, the EnerPHit Step-by-Step Framework for sequencing retrofit interventions, and the PHI Photographic Checklist for on-site quality assurance. The key, Dr Strang notes, is adopting them early—they exist to record material decisions and keep projects tracking towards certification, avoiding late-stage remediation.

The Australian opportunity

Data from the Trajectory for Low Energy Buildings shows a substantial energy reduction benefit achievable by building new stock to the Passivhaus standard and retrofitting existing stock to EnerPHit over time — even at a 1 per cent annual retrofit rate.

Homes built before 1990 are disproportionately represented at the lower end of performance and disproportionately occupied by lower-income households for whom energy bills represent a significant share of disposable income.

Melbourne is particularly instructive. Its climate zone 6 conditions — meaningful cold winters and hot summers — mean a well-insulated, airtight envelope with MVHR delivers benefits in both directions. The city’s large concentrations of interwar brick homes, 1970s–1980s brick veneer estates, mid-century schools and older commercial buildings represent what Dr Strang describes as low-hanging fruit for EnerPHit intervention.

Social housing and publicly owned buildings are especially compelling — with unified ownership, large portfolios of structurally similar buildings and an explicit social mandate, the trifecta of reduced emissions, healthier living conditions and operational cost savings is difficult to ignore.

International examples demonstrate that Passivhaus at scale — particularly for multi-residential projects — can be delivered at or below the cost of traditional building methods. The incremental cost of achieving EnerPHit over a standard deep retrofit is currently estimated at around 10–15% in the Australian market, recoverable over time through energy savings and health-cost reductions.

The world’s largest EnerPHit certified residential retrofit, the Ken Soble Tower in Hamilton, Ontario, offers an achievable benchmark. Built in 1967 and 18 storeys tall, the social housing building was retrofitted to EnerPHit standard — modernising 146 units of affordable seniors’ housing, reinvigorating community spaces and planning for ageing-in-place living — at a fraction of the cost of a new build.

Realising the opportunity

Dr Strang argues technical frameworks alone cannot drive the EnerPHit agenda. Clients and developers must commit to certification as a project goal from the outset, lead with a long-term value mindset, and resist the cost management pressure that typically undermines performance targets.

Builders’ engagement is qualitatively different from a conventional project. The most effective approach is to begin with a pre-construction workshop involving the site supervisor, key trade subcontractors and the Passivhaus certifier — using annotated drawings, physical material samples and the photographic checklist to make the expected standard explicit. Builders who have completed one EnerPHit project, he notes, become the most valuable resource for subsequent projects.

Heritage officers, he adds, need not be treated as obstacles. Their primary concern — preservation of fabric and cultural significance — can be reconciled with EnerPHit’s requirements when solutions are presented early.

“Australia’s retrofit opportunity is enormous, but ambition without a standard is just good intention,” says Stalin Chakrabarty, CEO of the Australian Passivhaus Association (APA). “EnerPHit gives us the methodology to turn that ambition into measurable outcomes — healthier homes, lower emissions, and buildings that actually perform. The Passivhaus standard is the most rigorous, evidence-based framework we have, and it is precisely what Australia’s existing building stock needs.”

THRIVE 2026

Dr Marcus Strang (pictured) will be further exploring EnerPHit opportunities at the APA’s THRIVE 2026 conference in Melbourne, 25–26 June. Tickets are available via the APA website.

Architecture & Design Team

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