Clockwise from above: The north facing deck and living area; plantings along the driveway; and Josh Byrne. Photos by Brendan Hutchens
Josh Byrne, presenter on ABC TV’s Gardening Australia, and his wife Kellie Maher began construction of their remarkable 10-star rated house in Hilton, near Fremantle, in November 2012. Construction of two dwellings on a little over a ‘quarter-acre’ (1012 m2) block was completed in June 2013. Josh, Kellie and their children Oliver and Caitlin live in the rear house, while another family lives in the front house. Both houses achieved a ten star Nationwide House Energy Rating Scheme (NatHERS) rating, mainly due to their thermal performance, efficient power generation and use, and the largely self-sufficient water supply.
The minimum standard for all new houses built in WA, since May 2011, is six stars. Ratings are calculated considering the climate zone, location, dimensions of the dwelling and occupancy. A ten star rating is difficult to achieve. Besides maintaining a comfortable temperature all year round, without the need for air conditioning or additional heating, the construction is required to feature efficient insulation, as well as thermal mass, to hold heat and thus moderate variable temperatures often experienced in Australian houses. Window placement is another necessary consideration, to enable cooling breezes to enter when required, using windows that act like vents to extract warm air to surrounding areas.
Both dwellings on the site generate more electricity than they use, with the sun powering the roof-mounted, grid-connected three kilowatt photovoltaic array. A combination of reverse brick veneer and double brick walls has been used to increase internal thermal mass where it was needed. Where this wasn’t required, timber framed walls were used, as they have less embodied energy and, therefore, a lower carbon footprint. Windows are double glazed, and doors and windows are fitted with seals that reduce loss of heat in winter, and limit heat gained from ambient conditions in summer.
Water harvesting technologies include a greywater diversion device and an irrigation system. A 20000 litre rainwater tank collects eight months supply of water for the family to use inside; and the front house uses water from a 12 000 litre tank.
Bore water is used to irrigate the vegetable garden, trees and native plantings and while this ground water is being extracted, it is also being replenished by storm water, via soakwells located under the driveway. Impermeable surfaces have also been kept to a minimum, with gravel being used for the driveway to allow rain to penetrate the sandy soil below.
As well as using passive solar design, rainwater harvesting, greywater reuse on gardens and grid-connected solar panels, both houses have water and energy-efficient appliances and fixtures, LED and compact fluorescent lighting and gas-boosted solar hot water systems.
Clockwise from above: The thriving garden powered by greywater; battery unit; and Josh’s kids with their garden harvest.
Other features of the houses include: low-emissivity glazing and argon-filled double glazed windows; low VOC (volatile organic compounds) paints and finishes; a fire pit; solar tubes for additional winter lighting; outdoor kitchen; insulated walls; and extensive use of recycled and salvaged materials used for decking, fences, garden beds and other structures. Some of these materials were repurposed from the original house from the site, demolished to make way for the new constructions.
A solar energy storage system, using new generation lithium iron phosphate (LiFePO4 or LFP) batteries has since been installed, to test how effective solar energy storage can be in reducing grid dependence. The system is able to store excess energy for use when supply is needed, such as during the night and on days when sunlight is reduced. Along with their solar panel system, Josh believes that in the future their house will only use the grid for about three per cent of their electricity needs, while current rates of reliance are at fifty- six per cent. This LFP system is one of very few installed in WA, and is being researched and closely monitored by Curtin University’s Sustainability Policy Institute, through the Cooperative Research Centre for Low Carbon Living.
Detailed monitoring (there are around seventy channels of data logging) is being undertaken at Josh’s house to assess the performance of the various design features and technologies in place. There are sensors to monitor local weather conditions, internal room temperatures (including concrete slab, ceiling, roof cavity and roof surface temperatures), metering of all water sources (mains, rainwater, greywater and bore), and extensive metering of gas and electrical supply (mains, grid and rooftop photovoltaic system). This will enable a detailed thermal and operational energy footprint to be determined for the complete site, so that the performance of this best practice, sustainable design can be analysed and the information made available to all.
A sustainability assessment, carried out following the completion of the building, found that the family save $2000 a year in energy costs, compared to a standard new Australian house. The property also uses just under half the water that a typical house in Perth would use, largely due to the water harvesting and recycling technology on site. The assessment also found that the houses only use around ten per cent of the energy, and emit less than ten per cent of the greenhouse gases, of a typical new house. Josh’s house produces nearly double the electricity used over the year, making it comfortably ‘net zero energy’. Real-time performance of this new system can be found on the Josh’s House website.
The garden areas include composting and earthworm farming, poultry, integrated gardens to shade and cool walls, and a large variety of edible and other useful plants. The small garden space means that fruit trees are either trellised or grown in pots that can be moved around, some garden beds are grown vertically, and productive vegetable beds are compact and intense. Josh says that, ‘We have maximised effective garden area around the houses to allow for natural shading, children’s play spaces and local food production – important health and lifestyle benefits that are rapidly disappearing from our suburbs’.
You can examine real-time data online for Josh’s house at www.joshshouse.com.au/ (there is also a Facebook page) and visit the property, as part of the metropolitan tour, after APC13 in October 2016. (See noticeboard.)
Greywater system specifications:
Grey Flow by Advanced Wastewater Systems fitted with sump and dual interceptor unit, followed by installation of pump, self-cleaning mechanism and irrigation pipework. Applied to fruit trees and shrubs at a maximum rate of 10 mm of water per day over an area of 40 m2 of garden.
Solar system specifications:
3 kW solar array
REC 250 w poly silicon panels
8 kWh solar energy storage system
Solar hot water system:
Chromagen PKT OOO 300 litre thermosiphon
‘open loop’ panel
Rainwater storage: 20 000L
Scheme water usage: 12% of total water used
Comparisons with Perth average use:
– 92% less scheme water used
– 89% less gas used
– 72% less carbon dioxide emitted
Savings on electricity bills per year: $1543.61
Power exported to the grid per year: 3551kWh
Annual rebate for power exported: $314.41
Average internal temperature: 25 degrees
Highest internal temperature: 29.2 degrees
Lowest internal temperature: 15.8 degrees
Annual savings on gas usage: $566.08
Annual savings on water usage: $560.15