Josh's House

Josh’s House is an innovative housing-scale sustainable design and construction project based in Hilton WA, led by environmental scientist and national media personality Dr Josh Byrne in conjunction with Curtin University and the CRC for Low Carbon Living.

Consisting of two dwellings, the project aims to demonstrate that high performance water sensitive and energy efficient homes can be built at a comparable cost and timeframe to regular houses.

The homes have achieved a 10 Star NatHERS rating, they are net energy exporters and they optimise the collection and recycling of water. The landscaping for the property includes food production, shading and play spaces. The interiors incorporate ‘Healthy Homes’ (indoor air quality) and ‘Liveable Homes’ (universal access) principles. The dwellings also achieved HIA GreenSmart accreditation.

• Resource efficient homes are an available and viable option: Josh’s House set out to prove that resource efficient homes can be built at a comparable per square metre cost and timeframe to regular Perth houses.
• There are significant mains water savings to be had at the residential scale through a greater understanding of water supply and use: Using an integrated approach to alternative water supply and water use optimisation, the Josh’s House project aimed to use less than one third of the typical Perth household mains water consumption.
• How a more sensitive approach to residential subdivision can improve both sustainability and liveability:  Landscaping that includes natural shading, children’s play spaces and local food production can result in important health and lifestyle benefits.

• Rainwater tanks: Rainwater tanks for each home are used to supply all internal use with connections to mains water providing a back up during dry periods. The front house is fitted with a 12kL tank, and the rear is fitted with a 20kL tank. These tanks meet the demand for internal purposes for approximately eight months of the year. When the tanks run dry, water supply automatically switches to mains water via a mains water backup valve. There are multiple features in the rainwater supply system to ensure potable water standard, including diversion valves, filter meshes, cartridge filters and UV disinfection.
• Rainwater overflow soak wells and diversion valves: The rainwater tanks are fitted with diversion valves and overflow valves to discharge water into soakwells below the driveway to divert the first rains of the season (first flush) and to discharge excess water when the tanks are full.
• Water efficiency fixtures and toilet: The houses are fitted with high efficiency shower heads and tapware, as well as low volume dual flush toilets with integrated hand basins that use basin water to fill the cistern.
• Direct diversion greywater systems: Both houses have direct diversion greywater systems to provide irrigation to selected areas.
• Bore water supply: The productive gardens are watered from a shared bore into the shallow aquifer to supplement the rainwater and greywater, minimising any imported potable water. Bore water makes up 36% of the total annual water use for the houses with abstraction levels based on a sustainable site recharge water balance. (For further detail on bore suitability see section on Transferability).
• Water efficient garden, landscape design and irrigation systems: The outdoor spaces are strategically designed to minimise water demands. Elements include ‘hydrozoning’ (the system of grouping plants based on their common water and
  management requirements), substrata surface driplines (to minimise evaporative losses), soil conditioners and water efficient mulch to improve moisture retention of sandy soil. The productive gardens use a state of the art centrally controlled irrigation system that incorporates both soil moisture monitoring and weather monitoring to maximise water efficiency.
• Permeable pavements: Gravel pathways and driveways are used in the landscape to allow localised stormwater infiltration. The driveway used a lightweight recycled plastic drainage cell which is covered with coarse gravel.
• ‘Native dampland’: A raingarden/infiltration sink (common to Western Australia coastal sandy plains) is installed in the garden of the front house. The raingarden features native plants in a depressed zone, to ‘make the most of stormwater’. The water from the carport and from veranda downpipes is directed to this feature, which is depressed 600mm from the surface, with free draining sand and subsoil drainage.

• Sustainable homes do not have to cost more, or use non-standard materials: The build cost for Josh’s house was comparable with conventional modern houses and used common building materials. Cost of living expenses are reduced through savings on utility bills.
• Rainwater tanks can be used to provide a large proportion of water supply: The on-site rainwater harvesting system was able to provide most of the water needs of the household, including potable water needs, from April to December.

Most features of Josh’s House are highly transferable to other Australian houses. Design plans and factsheets are available on the website to aid others in replicating the sustainable features on other projects. Elements such as rainwater tanks, greywater system, permeable paving and water sensitive landscape design are all globally replicable lot-scale solutions. The integrated water management components are replicated most easily on new house constructions, where dual pipe systems can be cost-effectively installed. Retrofits are possible, but more expensive.

However, the integrated water management strategy for Josh’s House relies on bore water (36% of water use), which irrigates productive gardens. There are many areas across Australia (and elsewhere) where the use of bore water isn’t appropriate (either due to overuse of the bores, or because superficial aquifers are not present at the site). Decisionmakers should check with local and state government departments of environment/land/water to determine whether bores are likely to be suitable for a given site.