MBAV Best Sustainable Home Award, Northern Region 2024

Located in the Strathbogie Ranges, two hours northeast of Melbourne, the clients wished to build a sustainable home and hobby farm, with the aim of transitioning from Melbourne to live a quiet and self-sufficient life. The home needed to be resilient, secure and protected from bushfire, responsive to a changing climate, made from ethical and responsible materials, and accessible for occupants as they aged. Connection to the landscape was also central to the brief, to celebrate the different seasons, and gaze at the vast skies and horizons of this isolated location. So, the challenge was set to develop a home which maximised northern solar-gain for passive-solar heating in winter, and embraced southern views, whilst achieving a net-zero-carbon, off-grid Passivhaus, built using bio-based materials.

The result is truly a testament to the innovation and craftsmanship of the design and build teams, with Huff ‘n’ Puff house being the first strawbale home in Australia to achieve Passivhaus Premium Level Certification – the highest level of Passive House Certification available. Generating more energy than it consumes, this unique off-grid home is a self-sustaining haven, which received the Best Sustainable Home Award in the MBAV Northern Regional Building Awards 2024.

Huff ‘n’ Puff house sits quietly in the landscape and is modest in size, yet feels spacious with biophilic connection to the horizon in every direction, and natural daylight throughout. A contemporary interpretation of a traditional strawbale farmhouse, the home zones the master bedroom wing at one end, with a common central living area, and the guest wing at the other end accessed via a screened external walkway, which also serves as a sheltered undercover outdoor living space. Bathrooms service both wings and a large mud room meets the functionality required for a working farm.

Whilst the traditional principles of solar passive design limit south-facing glazing due to heat loss from the home in winter and minimal solar gain, extensive thermal modeling undertaken in the design stage indicated that southern windows could be included without negatively impacting the internal comfort. The triple glazed Logitech window package is FSC certified for passive house design, with an aluminium external profile and internal pine from sustainably managed forests. The Tilt and Turn windows have been strategically placed to provide natural cross-ventilation for the home, and a Mechanical Ventilation with Heat Recovery system (MVHR) ensures the quality of air within the home is maintained at high levels. This balanced ventilation systems, actively expels and minimises pollutants, pollens and dust, and providing a constant supply of fresh air to create a healthy home. With the incorporation of this system extraction fans in the bathrooms and laundry weren’t required, minimising penetrations in the barrier of the home and preventing heat loss.

The key component to the construction of Huff ‘n’ Puff Haus was the use of a strawbale situp panel system. These panels were not only integral to the ethical material choices and structural integrity of the home, but also dramatically assisted the passive nature of the build. The 350mm strawbale situp panels have a very high insulative value of R7 – R9. By contrast, a typical code-compliant external wall in this climate would have R2.5 insulation. Straw is also very low in embodied-energy, meaning there is little energy use in its manufacturer as a building material, which greatly reduces the overall carbon emissions of this type of construction. A natural lime render was applied to the panels to form the internal air-tight layer.

The thermal envelope and airtightness were also key considerations, with continuous insulation to roof, walls and floor, and air-tight construction creating a high-quality building envelope which maximises efficiency. The orientation of the home and design of the roof and eaves allows for passive heating and cooling assistance at appropriate times of the year. Raised heel trusses create space for additional insulation and provide advantage for the solar panels. Insulation in the roof areas is R10, well over the R4 minimum code-requirement, and all pipework within the home is contained in lagging to minimise heat loss. The house also sits on a thermally broken concrete slab. A 100mm layer of insulation was placed continuously between the raft slab and the polished concrete screed, creating an airtight layer that minimises ground temperature effect.

Experienced in off-grid builds, Hedger Constructions ensured Huff ‘n’ Puff Haus was self-sufficient for power, water and disposal of bio-waste on site. The all-electric home has a solar PV system and batteries, incorporating 52 panels set at a 20-degree tilt angle. Mounted on the asymmetrical gable roof, the north-facing pitch is intentionally steeper to maximise the solar collection. The system also incorporates a diesel backup generator. With an estimated 78.3 kw/h of solar generation, reporting shows a 335 tonne potential reduction in CO2 output over 25 years. The home has also been pre-set as electric vehicle ready including full charging station. Huff ‘n’ Puff Haus is serviced by a 115,000-litre water tank with catchment from the house roof. A 315-litre heat pump is incorporated for hot water, assisting the off-grid requirements.

Building in a remote, bushfire prone area, the clients were acutely aware of the need to manage risk via careful material selection. With a preference for safe, healthy, natural and non-toxic materials, non-combustible Barestone cement-sheet was chosen for the external cladding, complemented by Colorbond Shale Grey Customorb metal roofing. The glazing package with aluminium-clad external frames was also selected for its low-maintenance and non-combustibility. These considered choices have delivered a resilient home, which exceeds the required BAL rating for the area.

Modelling suggests this industry leading Passivhaus provides up to 90% more heating efficiency than an average home, delivering long term environmental and economic benefits. But this home’s real beauty is more about what you can’t see. Its inner beauty is genuine ethical responsibility, proving you can achieve an efficient, sustainable low-carbon home, based on building science and responsible construction, that is healthier for people and the planet.