By Tina Perinotto and Andrew Starc
30 September 2010 – When Mirvac launched its Harmony 9 zero-carbon house in Melbourne, the idea wasn’t to make it the basis for the next tranche of housing product the company would release to the market but more as a prototype – a bit like a concept car that can capture the imgination and show what’s possible, perhaps just around the corner, according to national practice director Peter Cotton.
“It’s the concept car approach to sustainable housing,” Mr Cotton said this week. “It’ s not necessarily applicable now. Some things are costly; manufacturing has not got there with the economies of scale. So that’s how we looked at it.”
Mr Cotton said said some elements in the house were included now in projects but others could well be rolled out in other projects as the costs of manufacturing and construction gained economies of scale. Especially with elements such as the reverse brick construction, which places the greatest thermal mass on the inside of the house in order to stablise temperatures.
“It’s a non-standard approach, not just in the technology but in the building techniques. There needs to be a shift in the housing industry in terms of non standard techniques.”
Some techniques such as creating vents in roofs to allow heat to escape are relatively easy -but only where there are roof voids to allow this to happen.
The other issue is of course, what the market is willing to pay.
“Some of the things we are rolling out with the market [now] is smart metering.”
This allows residents to view their electricity use and inform them of the tariffs being charged which vary during the time of day, and therefore chose when to run dishwashers or laundry equipment for instance.
Green switches are another innvation that Mr Cotton said Mirvac may soon offer in its product.
These allow an entire circuit that to be switched off, preventing appliances with stand by-power to continue to suck energy even when the appliances are not in use.
Consumers were also starting to become interested in solar energy.
“With all the subsidies and grants you can gets… it is starting to be more affordable,” Mr Cotton said.
Certainly at the Waverley Park site office where Harmony 9 is located there is a range of sustainabiltiy features on offer that Mr Cotton said were priced competitively because of the buying buyer of his company. These included solar power, solar gas hot water systems and larger than standard water tanks.
Meanwhile Harmony 9 will remain as a site office “for quite some time.”
Following are some of the key features of Harmony 9
Design and construction
The house has a highly flexible design, to allow the house to meet the changing needs of modern occupants. The ground floor, for instance, allows a future main bedroom and ensuite to be added, and internal glass panels provide privacy and separation in the living spaces when desired. First floor bedrooms can also be joined to create informal living spaces.
The house can passively regulate its temperature – using sunshine, shading and cross ventilation so effectively that it requires almost no additional heating or cooling. The small amount of energy required by the home will be less than or equal to the amount generated by solar panels mounted on the roof.
Construction started with a 100 per cent recycled concrete slab, which underwent a six month curing period. The unique recycled concrete slab was the first of its kind in Australia and was another pioneering feature of this innovative home, Mirvac said.
There is very high wall and ceiling insulation.
A “reverse brick veneer” construction with bricks on the inside and the timber frame on the outside – the heavy-weight materials inside the home create internal mass and stabilise the core temperature
North facing living zones and skylights maximise natural light internally. Windows with correct shading and locations maximises cross ventilation.
The spine of bluestone wall acts as a thermal battery. During summer it is protected from direct sunlight and helps maintain a comfortable house temperature. In winter the same thermal mass can store the heat from the sun or heating to release it at night helping the home stay warm.
Highly insulated external walls using R 5.0 batts and R 8.0 Glass wool in the roof space. Internal walls consist of R 2.5 Glass wool insulation
Computer modelling shows the house will use no more than 27 megajoules a square metre annually, compared with a 5 Star home which uses 165 megajoules/sq m a year. It rates 9.2 Stars, with forecast energy use of only 21.9 megajoules/sq m a year.
Eco-Vision electronic smart metering system indicates water, electricity and gas usage providing the occupants with feedback about their consumption patterns.
Hot water Service is supplied by a Rheem solar hot water system 80 per cent efficient, gas boosted.
LED (light emitting diodes) or compact fluorescent light fittings are used throughout the home to ensure minimum electricity use for lighting output.
Solar Cells 3.6kw system, located on the roof and the façade as sun shading devices.
A study modelling household energy and water use conducted using the Moreland Council STEPS rating tool indicated the Harmony 9 home will achieve cost reductions when compared to the average Victorian home, of $1,200 per year on energy bills and a saving in mains water use of 125,000 litres per year. The house has been designed so that there will be no net greenhouse gas emissions from energy use in the home, saving an estimated 12.047 tonnes of carbon dioxide per year.
One of the most important elements in ensuring the correct performance of the Harmony 9 home is the smart energy meter, Mirvac said. “It is now very important to start changing user behaviour so we can live in these energy efficient homes to reap the maximum benefits,” the company said in a media statement. “If ‘driven’ poorly, a 9 Star home could use as much energy as a conventional 5 Star home. Our Smart Energy Meter is a major initiative in this area – it gives real time feedback to the occupants about energy, water and gas usage, and carbon emissions.”
Externally, Harmony 9 home features specific shading design to control solar energy, adjustable louvers on east-facing windows, lightweight cladding, recycled timber for garden decking and locally made pavers. The landscaping takes advantage of the supply of rain or recycled water and also provides a “rain garden” to clean the driveway water run off.
Other features include:
- A Nubian Class “A” recycled water system treats grey water from the showers, basins and the bath.
- A 20,000 litre tank is located under the driveway which stores all roof storm water (120 square metres) and the class “A” recycled water.
- Water from this tank is available for use irrigating the garden, flushing toilets and use in the laundry.
- High Water Effciency Labelling and Standard (WELS) rated fittings – taps 6 Star, shower heads 3 Star, toilet Systems 4 Star.
- All external hard-scape areas are permeable (except the driveway).
- Driveway stormwater runoff is directed to a rain garden to clean the water before discharging into the street system.
- Slab Boral Envirocrete was used, a unique recycled concrete slab floor incorporating 100 per cent recycled aggregates and 60 per cent cement substitutes.
- Recycled timbers of various species for the external cladding, pergolas and sun screens. Mixed species & sizes for the cladding is a result of using the off cuts and “left overs” from the supplier.
- Recycled/reclaimed bricks from various construction sites are used to form reverse brick veneer wall construction and used partly as an artistic composition internally.
- All walls are Boral 13 mm recycled plasterboard Good Environmental Choice Australia Certified.
- Internal paint is Wattyl ID low Volatile organic Compound (VoC) paint.
- No carpet has been used to minimise VoC emissions.
- Clear finishing timber cladding/window frames use a natural oil to seal.
- Plantation Hoop Pine Eco Ply is used in the kitchen joinery, which is locally sourced from managed forests, while low formaldehyde content glues were used to bond the materials.
- No composite boards or carpets used internally in order to reduce the amount of VOCs produced. Boral Silkwood timber flooring was sourced locally from Australian species and is Australian Forestry Standard Certifed. Timber flooring uses a type of adhesive that has effectively zero formaldehyde emissions. Flooring also consists of extremely Low VOC content UV cured acrylic coating.