Stockland’s new Zero Net Carbon home
Objective
In 2019, Stockland joined Sustainability Victoria’s Zero Net Carbon Homes (ZNC) program to get support for the design, construction and marketing of high-efficiency, low-emission homes. By 2020, the company finished its first ZNC home, Apollo, a three-bedroom town home that is part of Stockland’s Orion development in Braybrook.
Outcomes
- The project showed that medium-density housing can achieve ZNC status, even if it’s one home and not an entire development stage.
- Further, that improved energy efficiency leading to homeowners’ savings makes a strong value proposition. The National Construction Code requires a 6-star NatHERs rating and the ZNC program requires 6.5 stars.
Home snapshot
Name of the home: Apollo
Estate: Orion
Address: Braybrook VIC
Home Builder: Creation Homes
Land Developer: Stockland
Size: 126.2 m2
NatHERS energy rating: 7 stars
Carbon status: Net Zero Carbon
Introduction
Australian property group Stockland is creating thriving communities that reduce waste, encourage healthy living and contribute to a sustainable future.
General manager of Built Form Communities Ben Cantwell said, “There are some people who want to do the right thing for the environment by going for sustainable homes. But there are also many people who will take up these options to help them reduce their cost of living.”
CEO of Sustainability Victoria, Claire Ferres Miles said: “The ZNC Homes program has provided technical and marketing expertise to Australia’s leading residential builders to facilitate the development, marketing and sales of higher quality more comfortable homes that contribute to Victoria’s goal to achieve zero net emissions by 2050.
“We look forward to continuing working with Stockland to accelerate the construction of more ZNC homes,” she added.
Home design and build
Stockland decided to aim for 7 stars, which reduces the heating and cooling loads by 30% compared to a standard home.
Sustainability Victoria worked with Stockland to find ways to increase the energy efficiency rating of the original home design through different measures.
Modelling data shows that four people living in the home rather than a standard home can:
- enjoy lower heating and cooling loads
- enjoy 50% lower energy bills (about $1000 per year)
- produce no net emissions from the energy use in the home
- reduce gas emissions by about 4.7 tonnes per year.
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An orientation enabling the main living areas to face North was chosen so the house could make the best use of sunlight.
People living in the house will be more comfortable throughout all seasons. As they will need less heating, cooling and lighting, they can save on living costs.
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The townhouse’s walls were thickened to allow for more insulation. The insulation in the external walls increased to an R-value of 2.5 from the original 2.0; the shared townhouse walls increased to R5 from R2.5.
This reduces outside noises and keeps the home warmer in winter and cooler in summer, further reducing energy bills. The roof was fitted with anti-con blankets, adding an extra R1.5.
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Insulation was added to internal walls in all wet areas, reducing noise pollution.
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Additional draught-proofing was done, including sealing gaps between windows, walls and floors.
This reduces draughts throughout the house, enabling maximum comfort and reducing heating and cooling costs.
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The original home design had a mix of single and double glazing. Low-e double-glazing was applied to windows in the kitchen and living areas, making all windows double-glazed.
Double glazing cuts down winter heat loss by as much as 50% and reduces noise pollution.
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An adjustable external shading was installed for the ground floor’s North facing windows. The shading’s retractable arm awning has a horizontal depth of 1.5m to shade the windows on a hot, sunny day.
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An energy-efficient reverse-cycle heating and cooling system and solar gas-boosted hot water services help to lower energy bills further.
All lighting used IC-4-rated LED bulbs. LED bulbs require much less wattage and are more durable than fittings such as fluorescent lamps. The IC-4-rating is important because insulation can be installed next to downlights with lower fire risks. Lighting density decreased from the National Construction Code’s required 5 W/m2 to 2.6 W/m2.
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A small and inexpensive battery-ready 3.3kW solar array was installed on the roof.
This enables the home to produce enough renewable energy to completely offset its annual greenhouse gas emissions.
Orientation analysis
This table shows the difference orientation makes to the efficiency of the home, with North as the most favourable orientation and West the least favourable, for this property.
| Living area orientation | Azimuth (°) | Heating load (MJ/m2) | Cooling load (MJ/m2) | Total energy loads (MJ/m2) | NatHERS rating (stars) |
|---|---|---|---|---|---|
| North | 0 | 81.9 | 13.7 | 95.6 | 7.1 |
| Northwest | 45 | 83.6 | 23.5 | 107.1 | 6.7 |
| West | 90 | 84.8 | 32.6 | 117.4 | 6.4 |
| Southwest | 135 | 86.9 | 15.7 | 102.6 | 6.9 |
| South | 180 | 87.9 | 10.1 | 98 | 7 |
| Southeast | 225 | 88.2 | 13.8 | 102 | 6.9 |
| East | 270 | 80.3 | 21.6 | 102 | 6.9 |
| Northeast | 315 | 77.7 | 15.9 | 93.6 | 7.2 |
As-built verification
A blower door test and a thermal camera were used to check if the insulation was installed properly. Results showed that the home was draught-proof with only 4.3 air-changes per hour.
Air-tightness and insulation integrity results
The townhouse exceeded the requirements for air-tightness and insultation testing.
| Requirement | Target | Achieved | Value result |
|---|---|---|---|
| Air-permeability in m3/m2.hr @50 Pa | max 6.00 | 4.36 | Passed |
| Insulation non-coverage walls | max 5% | 0% | Passed |
| Insulation non-coverage ceiling | max 5% | 0.25% | Passed |
| Insulation non-coverage floors | max 5% | 0% | Passed |
Conclusion
- It’s important to consider energy efficiency in the design phase before the project starts. Retrofitting energy efficiency into the design during construction phase can increase costs by 100%.
- When planning a sustainable development on a large scale, orientation is a relatively low-cost way to increase the NatHERS rating. The right orientation can add 0.8 NatHERS rating without costing anything extra .
- Sustainable design is more about good building practices than innovative technologies.
"We see energy-efficient homes as the future of residential building. Thanks to the ZNC program, we are upskilling our sales teams to demystify the complexities and sell the benefits of sustainable home design."