Mill Corner Longhaus
The Brief
Mill Corner Longhaus began with a clear and ambitious brief: to create a Certified Passivhaus — one of the most rigorous building performance standards in the world — in the foothills of Sheffield, Tasmania. The clients had spent years researching high-performance building and were determined to create a home that would be exceptionally energy-efficient, universally accessible, and designed to serve them well into retirement and beyond.
From the very first conversation, it was clear this would not be a conventional build. The Passivhaus standard demands meticulous attention to detail at every stage — from design and orientation through to the final blower door test. It requires a fundamentally different approach to construction, one where every thermal bridge is eliminated, every junction is airtight, and every material is selected for its long-term performance. For Davies, it was an opportunity to push the boundaries of what's possible in Tasmanian residential construction.
The site itself is nothing short of spectacular. Perched on an elevated rural block with commanding views of Mount Roland and the Badgers Range, the home needed to capture these vistas while responding to the specific microclimate of the Sheffield foothills — where winter temperatures regularly drop below zero and summer sun can be intense. The design team at Align Architecture worked closely with Davies to develop a linear 'longhaus' form that would maximise the northern aspect, frame the mountain views, and create a protected outdoor courtyard sheltered from the prevailing winds.
Sustainable Design & High Performance
Achieving Passivhaus certification requires a building to meet five key criteria simultaneously: space heating demand below 15 kWh/m²a, total primary energy demand below 120 kWh/m²a, airtightness below 0.6 air changes per hour at 50 Pascals, no thermal bridges, and adequate comfort in all seasons without conventional heating systems. Mill Corner Longhaus didn't just meet these targets — it exceeded them.
The home is strategically sited to maximise solar gain, with the long axis oriented due north. Ground-rock aggregate concrete floors serve as a thermal heat bank, absorbing the winter sun's warmth during the day and radiating it back through the evening hours. The building envelope is a masterclass in continuous insulation — a 150mm reinforced concrete slab sits on XPS underslab and edge insulation, while the 'hot roof' system features R6 insulation to prevent any heat escaping through the roof plane.
Perhaps the most impressive achievement is the airtightness result: 0.18 air changes per hour on the final blower door test — more than three times better than the Passivhaus requirement and among the tightest residential buildings ever tested in Australia. This level of airtightness means virtually no uncontrolled air leakage, which in turn means the Zehnder mechanical ventilation system with heat recovery can do its job perfectly — providing fresh, filtered air to every room while recovering up to 95% of the heat from outgoing stale air.
- •Continuous Insulation: 150mm reinforced concrete slab with XPS underslab and edge insulation, and a "hot roof" system featuring R6 insulation
- •Air Quality: Zehnder mechanical ventilation system with heat recovery provides fresh, filtered air while maintaining even, comfortable temperature year-round
- •Glazing: Thermally broken triple-glazed alu-clad timber windows from Ecosky frame the surrounding farmland while preventing heat loss
- •Airtight: Building envelope achieves 0.18 air changes per hour on final blower door test
- •No Thermal Bridges
Materiality & External Form
The exterior of Mill Corner Longhaus is a study in contrasts — sophisticated yet restrained, contemporary yet deeply connected to its rural setting. The primary skin is Colorbond Custom Orb in Monument, a sleek corrugated profile that wraps the building in a dark, protective envelope. Against the green pastures and the grey-blue of Mount Roland, this dark cladding gives the home a grounded, almost geological presence in the landscape.
Custom powder-coated window shrouds in a sand-tone finish punctuate the facade, creating a rhythmic pattern that draws the eye along the building's length. These shrouds serve a dual purpose: they provide solar shading for the triple-glazed windows while adding depth and shadow to the elevation. Blackbutt timber cladding and screens introduce organic texture, softening the transition from the double garage to the main residence via a covered walkway that doubles as an outdoor entertaining space.
The 'longhaus' form itself is a deliberate reference to both the Scandinavian building tradition and the long, low agricultural sheds that dot the Tasmanian landscape. At just one storey, the home sits low on the land, its roofline echoing the gentle slope of the paddock. From certain angles, the dark corrugated form almost disappears into the backdrop of trees, exactly as intended.
Interior
Step inside Mill Corner Longhaus and the warmth is immediate — not just in temperature (the home maintains a remarkably stable 20-22°C year-round without conventional heating), but in atmosphere. Tasmanian Oak raked ceilings soar overhead in the open-plan living area, creating a generous sense of volume that belies the home's modest footprint. The timber's honey tones are complemented by the polished concrete floors below, which serve as both a finished surface and a thermal mass store.
The floor plan follows a logical sequence: arriving through the covered entry, you pass through a mudroom and utility zone before emerging into the main living, dining, and kitchen space. This progression from compressed to expansive is deliberate — it amplifies the impact of the mountain views that flood through the north-facing glazing. To ensure the home is future-proof, accessible features have been integrated throughout: ramp access at the entry, zero thresholds at every doorway, wider hallways and doorways to accommodate a wheelchair, and reinforced walls in the bathroom ready for future grab-rail installation.
The kitchen is a masterclass in modern Australian design, balancing sleek, dark tones with the organic warmth of Tasmanian Oak. Clad in Porta Contours 'Riverine' panelling and topped with Polytec Xenolith benchtops in Marmo Di Torre, the three-metre-long kitchen island is the centrepiece of the home. It functions as preparation bench, breakfast bar, homework station, and gathering point — exactly the kind of multifunctional heart that a 'longhaus' demands.
Multi-Generational Living
Expanding the home's versatility is a 60m² self-contained accommodation wing, connected to the main residence by the covered walkway. Designed to the same rigorous Passivhaus standards as the primary dwelling, this wing includes its own bedroom, bathroom, kitchenette, and living area — making it ideal for multi-generational living, visiting family, or providing a premium 'Passivhaus experience' for BnB guests.
The decision to certify both the main home and the accommodation wing under the same Passivhaus umbrella was a deliberate one. It means that guests staying in the wing enjoy exactly the same level of comfort, air quality, and thermal stability as the homeowners — a consistent, even temperature with fresh filtered air, regardless of what's happening outside. For the clients, this wing represents both a practical investment and a philosophical statement: that high-performance building isn't a luxury add-on but a fundamental approach to creating spaces where people thrive.
Mill Corner Longhaus stands as proof that Passivhaus principles can be applied beautifully in the Tasmanian context. It demonstrates that a home can be simultaneously energy-efficient and architecturally striking, accessible and aspirational, rooted in its landscape and forward-looking in its technology. For Davies, it represents the kind of project that defines a career — a home where every detail, from the orientation of the building to the thickness of the window seals, has been considered, tested, and executed with precision.
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