Inverloch, Victoria - Case Study

New build using the 3 bedroom Design for Place home plan, with additions of on-site renewable energy production, rain water collection and waste management.

Low density housing.

National Construction Code (NCC) climate zone 6 – mild temperate.

wooden house and garden
Photo: Harmony House
Harmony House is clad in designer-finished fibre cement boards that have a ‘self-cleaning’ coating to prevent the build-up of dirt

Topics

  • Passive design
  • Reducing water demand
  • Embodied energy
  • Renewable energy
  • Waste minimisation
  • Landscaping and garden design
  • The healthy home
  • Adapting to climate change
  • The liveable and adaptable house
  • Rainwater

Thermal comfort rating

Nationwide House Energy Rating Scheme (NatHERS): 8.2 Stars

Heating: 47.9 MJ/m2/year

Cooling: 10 MJ/m2/year

Total: 57.9 MJ/m2/year

Sustainability features

  • North facing design
  • Cross-flow ventilation
  • Zoning for heating and cooling
  • Thermally broken double glazed windows and sliding doors
  • Recycled composite decking
  • Partial reverse brick veneer
  • Low-maintenance, ‘self-cleaning’ cladding
  • 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
  • On-site renewable energy production
  • Rainwater harvesting with UV filtration system
  • Worm farm septic waste management system
  • Food production
  • Automatic and rechargeable battery-operated lawn mower

Project details

House plan: Design For Place, Commonwealth Government

Project manager: Self-managed by the owner

Project name: Harmony House

Builder: Combination of local builders and independent trades

Size: 194m²

Size of land: 1.5 acres

Cost: $300,000 to achieve the Design For Place home build.

The owner added $100,000 for a drive way and 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 and has a range of weather conditions during a given year.

Winters can be cold and wet with hot spells in summer. The north-facing aspect of the house enables the various passive solar design features to keep the inside temperature stable, despite the large temperature range outside. Sunshine is experienced most of the year, albeit to a lesser degree in winter, which allows for sufficient solar heat gain to warm the house in winter and for generating energy all year round.

The annual rainfall of 920mm is spread out during the year. The home owner chose to use rainwater collection to meet all the household and property water needs.

Sunset outside a house
Photo: Harmony House
Views of the sunset to the north west.

Design brief

The owners wanted to build a house on a moderate budget and use modern, passive design features to reduce the family’s overall environmental footprint. They were strongly motivated to solely rely on on-site renewable energy and not use fossil fuel energy from the grid in the day-to-day running of the house.

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 owner chose materials and systems that had a long life and were low maintenance

Design response

After exploring a range of options, the owner discovered the Design For Place plans.

The home owner used the Design For Place 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 drive way from the east. The owner also made modifications to the bathrooms to maintain a self-enclosed toilet cubicle.

The resulting home - Harmony House - makes use of passive solar design elements, such as internal thermal mass, cross-flow ventilation and window placement to create a bright and nurturing living environment. This rewards the family with comfortably stable internal temperatures, year round.

The design’s implementation of common building materials and methods, as well as the money saved on design fees with the free plans, all meant the project could stay within budget.

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 be value-adding for the family for decades to come.

Passive heating and cooling

Internal thermal mass is a major element in passive heating and cooling. The house absorbs and releases heat to help stabilise internal temperatures and ensure it maintains a comfortable temperature that is warmer in winter and cooler in summer.

The house incorporates internal thermal mass through:

  • Reverse brick veneer in the east and west external bedroom walls
  • Rammed earth walls between the living room and bedroom 1 and 2
  • Concrete floors throughout the house

The owner added to these design features by insulating the concrete slab and adding special stone/hardwood floor panels. This maintains thermal conductivity whilst 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 low-arcing sun enters the house through the northern windows, to charge the internal thermal mass with slow-release heat. In summer the eaves block the high-arcing sun from any direct access into the house. The specific placement of openable windows allows cross-flow ventilation overnight, to remove the build-up of indirect summer heat. Thermally broken double-glazed windows and sliding doors help to stop heat or cold transfer from inside to outside in both summer and winter.

Active heating and cooling

For backup active heating, the owner opted for a split system heat pump and far-infrared heating panels. It turns out these are used only occasionally - just a handful of times a year in the depth of winter.

The heat pump split system has a COP (co-efficient of performance) that allows one unit of electrical energy to be converted to up to seven units of heat energy. The owners say it can raise the temperature of the main part of the house by a few degrees in around half an hour.

The far-infrared heating panels supply direct radiant warmth (akin to sunlight rays without the UV). 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. The owners prefer this form of heat over the “blow-heat” of the split system.

In summer when overnight temperatures are warm, the heat pump split system is also an energy efficient air conditioner.

The owners are pleased that these systems are only occasionally used and when used they are all supported with energy generated by renewable energy.

living room of a large house with windows
Photo: Harmony House
The house’s design applies passive design principles to maximise winter heat gain. The living areas have a northerly orientation to maximise sunlight combined with appropriately sized glazing. 

Renewable energy production

The house produces its own electricity using an off-grid 14 kW photovoltaic system and battery bank. The main components include an inverter/charger (7.5kW continuous delivery), twenty-four sealed gel maintenance free batteries (1600Ah = 76.8kWh @C100), and forty-eight 290W polycrystalline solar panels.

The home owners find the energy production in winter ample for household needs and energy production over summer far exceeds what is currently used. The system is large enough that, if needed in the future, a charging station for an electric vehicle could be installed. Depending on driving needs, the owner predicts 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).

Rainwater collection

The house features two 27,000 litre water tanks to provide all water requirements, without a need to connect to town water.

Stainless steel tanks were chosen, as they are long-lasting and have non-reactive material characteristics. According to the owner, the stainless steel material has cost benefits over the lifetime of the material compared to other cheaper (and less healthy) materials.

The owner implemented a number of features to improve the end quality of collected water.

Immediately prior to the tank inlets are two custom-made first-flush diverters. The flush diverters discard an initial amount of rainwater from the roof, adjustable to either 0, 100 or 200 litres of water.

The outlet system on the tank itself is designed to take water from the cleanest strata of water near the top, and auto-vac overflow systems automatically suck out any collected sediment from the bottom of the tanks during an overflow event.

Last in the set-up, just before the water line enters the house, is a UV filtration system comprising of a 20um filter, a 1um filter, and a UV lamp. The resultant whole-house water supply is clean and healthy, without the use of chemicals or additives to treat the water.

Waste water processing

All household waste water 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 (akin to liquid fertiliser) is then pumped to dispersal trench lines where it enriches the soil.

Hot water system

The owner’s initial tendency was to opt for an evacuated tube hot water system that used sunlight directly. With further research they decided to install a modern heat pump hot water system, as they found that a heat pump hot water system above a certain COP (co-efficient of performance) would use less energy in the Victorian climate over the course of a year, than an evacuated tube hot water system.

Energy efficient lighting

The house was designed to promote natural light throughout, which saves on energy usage. No downlights were used, to avoid compromising ceiling insulation. Energy efficient LED lighting is used throughout the house.

Photo: Harmony House
Rammed earth walls in the living room are one of the internal thermal mass elements that provide a slow release of heat to maintain a comfortable internal temperature without the need for active heating.

Cladding

The cladding is low maintenance, has a long life and suits the aesthetics the owner was after.

The house is clad in designer-finished fibre cement boards with a very convincing wood-look. The finished boards also minimise the maintenance that wood panels and painted surfaces require.

In addition, the fibre cement boards have a ‘self-cleaning’ coating, in which silica particles in the finish 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.

Sustainable landscaping

The property features a water reticulation system, which uses the rainwater and on-site renewable energy production to maintain garden beds, veggie beds, and a future small orchard area.

The lawns are maintained without any hours behind the mower from the owners. An auto mower that recharges itself from the on-site renewable energy system as needed, maintains the lawns on an ongoing mowing regime.

floor plans
Plans: Floor plan for Harmony House, Victoria house design

Evaluation

The owner and family have been more than impressed by the Design For Place plans, finding their home a beautiful and nurturing place to live - full of sunlight, warmth and open spaces.

It suits their family of four down to the ground, and has provided the backbone to an on-going creative exercise in living a sustainable low-footprint lifestyle.

Acknowledgements and further reading

Harmony House: Sustainable Living in a Modern World www.harmonyhouse.com.au

Geoworks Imagery 2018

Author

Commonwealth, 2020.

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Next chapter - Perth, Western Australia