New build using the 3-bedroom Design For Place Banksia home plan, with additions of onsite renewable energy production, rainwater collection and waste management.
Photo: Harmony House
NatHERS thermal comfort rating
- Cross-flow ventilation
- Zoning for heating and cooling
- Thermally broken double glazed windows and sliding doors
- Partial reverse brick veneer
- Low-maintenance, ‘self-cleaning’ cladding
- Recycled composite decking
- Thermal heat exchange flooring
- Internal thermal mass including rammed earth walls
- Heat pump hot water system
- Far-infrared heating panels
- Split system heat pump
- LED lighting
- Onsite renewable energy production
- Rainwater harvesting with UV filtration system
- Recycled and renewable material use
- Worm farm septic waste management system
- Automatic and rechargeable lawn mower
Building type: Low density housing
NCC climate zone: 6 – mild temperate
House plan: Design for Place, Australian Government
Project manager: Self-managed by the owner
Project name: Harmony House
Builder: Combination of local builders and independent trades
Size of land: 1.5 acres
Cost: $300,000 to achieve the Design For Place home build; the owner added $100,000 worth of upgrades to achieve off-grid systems (power, water, sewage)
Site, block orientation, location and climate
The house is located approximately 1.5 hours from Melbourne in South Gippsland, near the town of Inverloch. The property is located in a mild temperate climate zone.
Winters can be cold and wet with hot periods in summer. The north-facing aspect of the house enables the passive solar design features to keep the inside temperature stable despite the large temperature range outside.
Photo: Harmony House
The owners wanted to build a house on a moderate budget using passive design features to reduce the family’s overall environmental footprint.
The owners’ objective was to create a home that could heat and cool itself, produce its own energy, collect its own water, process its own waste and also grow food on the surrounding land. In addition to adopting these sustainability features, the owners chose materials and systems that had a long life and were low maintenance. They were strongly motivated to rely solely on onsite electricity generation in the day-to-day running of the house.
After exploring a range of options, the owners discovered the Design For Place plans. The owners used the plans and specifications that suited their climate zone, exceeding some insulation and glazing specifications (where budget allowed). They flipped the plan east–west to cater for the property’s driveway from the east. The owners also made modifications to the bathrooms to include a self-enclosed toilet cubicle.
The resulting home – Harmony House –uses passive solar design elements such as internal thermal mass, cross-flow ventilation and window placement to create a bright living environment with comfortably stable internal temperatures year round.
The design’s use of common building materials and methods, as well as the money saved on design fees with the free plans, meant the project stayed within budget.
The house is clad in designer-finished fibre cement boards with a wood look. The cladding has a long lifespan and suits the aesthetics the owners wanted.
The finished boards minimise the maintenance that wood panels and painted surfaces require. In addition, the boards have a ‘self-cleaning’ coating in which silica particles absorb water molecules from the air to form a protective film on the surface of the panel. This prevents dirt in the air from attaching directly to the panel, so that when it rains, dirt is washed away.
Passive heating and cooling
Thermal mass in a home absorbs and releases heat to help stabilise internal temperatures and ensure the home maintains a comfortable temperature throughout the year.
The house incorporates internal thermal mass through:
- reverse brick veneer walls in the side bedrooms
- rammed earth walls in the living room and brick walls in the adjoining bedrooms
- concrete floors throughout the house.
The owners added to these elements by insulating the concrete slab and adding stone and hardwood floor panels. This maintains thermal conductivity while giving the look and feel of wooden floors. The owner also upgraded the living room walls from brick to rammed earth for slightly denser thermal mass and an aesthetic feature.
In winter, the sun enters the house through the northern windows to heat up the internal thermal mass. In summer, the eaves block the sun. The placement of openable windows allows cross-flow ventilation overnight to remove build-up of indirect summer heat. Thermally broken double-glazed windows and sliding doors help to reduce internal temperature changes in both summer and winter.
Photo: Harmony House
Active heating and cooling
For backup active heating, the owner opted for a split system heat pump and far-infrared heating panels. The heat pump split system has a COP (co-efficient of performance) that allows 1 unit of electrical energy to be converted to up to 7 units of heat energy. The owners say it can raise the temperature of the main body of the house by a few degrees in around 30 minutes.
The far-infrared heating panels are an alternative that supply direct radiant warmth. They have the advantage of warming objects rather than air. This works well in a passive solar house with internal thermal mass, as the far-infrared rays are absorbed and re-emitted by the thermal mass.
In summer when overnight temperatures are warm, the heat pump split system is also an energy-efficient air-conditioner.
The house produces its own electricity using an off-grid 14kW photovoltaic system and battery bank. The main components include an inverter/charger (7.5kW continuous delivery), 24 sealed gel batteries (1600Ah = 76.8kWh @C100), and 48 290W polycrystalline solar panels.
Sunshine is experienced most of the year in the region, which allows for sufficient solar energy generation. The owners find the energy production in winter is ample for household needs and production over summer far exceeds what is currently used.
The system is also large enough that, if needed in the future, a charging station for an electric vehicle could be installed. Depending on driving needs, the owners predict that on-site energy production could cater for an electric vehicle during all but the winter months (at which point in-transit community charge-points could be used more often).
The owners initially wanted to opt for an evacuated tube system. With further research, they decided to install a heat pump hot water system after reading findings that in the Victorian climate a heat pump above a certain COP (co-efficient of performance) would use less energy over the course of a year than an evacuated tube system.
The house was designed to let in natural light throughout, which saves on energy use for lighting. No downlights were used, to avoid compromising ceiling insulation. Energy-efficient LED lighting is used throughout the house.
Photo: Harmony House
The annual rainfall of 920mm is spread out during the year. The owners chose to use rainwater collection to meet all the household and property water needs. The house features 2 x 27,000L water tanks to provide all water requirements without the need to connect to town water.
Stainless steel tanks were chosen as they are long lasting and have nonreactive material characteristics. According to the owners, the material has cost benefits over the lifetime of the material compared with other cheaper (and less healthy) materials.
The owner implemented a number of features to improve the end quality of collected water:
- First-flush diverters discard an initial amount of rainwater from the roof, adjustable to either 0, 100 or 200 litres of water. This means that dirt and pollution from the roof is not washed into the tank.
- The outlet system on the tank itself is designed to take water from the cleanest level near the top.
- Auto-vac overflow systems automatically suck out any collected sediment from the bottom of the tanks during an overflow event.
- A UV filtration system is installed just before the water line enters the house, comprising a 20um filter, a 1um filter, and a UV lamp.
All household wastewater is processed by a worm farm septic system. This provides a chemical-free and easy-to-maintain method for processing all sewage, black and grey water. The worms process many times their own body weight in solids each day, while the liquid component drains through the porous upper platform to lower levels where microbial processing occurs. The resultant treated liquid is like a liquid fertiliser, which is pumped to dispersal trench lines where it enriches the soil.
The property features a water reticulation system that uses the rainwater and renewable energy to maintain garden beds, vegetable beds, and a future small orchard area.
The lawns are maintained with an auto mower that has an ongoing mowing regime and recharges itself from the solar PV system as needed.
The owner and family have been impressed by the free Design for Place plans, finding their home a beautiful and comfortable place to live.
They have found that active heating and cooking systems are used only occasionally, usually a few times in mid-winter. The owners are pleased that these systems are all supported with energy generated by renewable sources.
The overall objective – to create an environmentally friendly and sustainable lifestyle for the family’s children to grow up in and learn from first hand – has been well achieved, and will benefit the family for decades to come.
Acknowledgements and further reading
Harmony House: Sustainable Living in a Modern World www.harmonyhouse.com.au
Geoworks Imagery 2018
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- Learn how to use the Design For Place free house plans
- Explore the Materials for ideas on methods and materials for building a home in a tropical climate