White Gum Valley, Western Australia
Two new apartments that use passive solar design principles, solar and water technologies, and smart home systems on a small suburban infill block.
The two apartments, commissioned by friends, are located within a development with high environmental standards.
Photo: Monique Manolini (© Monique Manolini, Crib Creative)
NatHERS thermal comfort rating
Overall average: 7.5 Stars
Heating: 12.4MJ/m²/year
Cooling: 10.1MJ/m²/year
Total: 22.5MJ/m²/year
Apartment A: 7.7 Stars
Heating: 12.4MJ/m²/year
Cooling: 10.1MJ/m²/year
Total: 22.5MJ/m²/year
Apartment B: 7.3 Stars
Heating: 20.7MJ/m²/year
Cooling: 6.2MJ/m²/year
Total: 26.9MJ/m²/year
Sustainability features
- Passive solar design
- Thermal mass
- Stabilised rammed earth
- Reuse of construction and demolition waste materials in walls and concrete slab
- Lightweight construction
- Double glazing
- Solar photovoltaic (PV) system
- Renewable energy production
- 3-in-1 heat pump (hydronic heating, hot water and air-conditioning)
- Smart home wiring preinstalled
- Sub-metering to trade electricity and water across a mini grid
- Energy-efficient appliances and lighting
- Water treatment on site
- Reducing stormwater runoff
- Greywater recycling
- Productive garden
Project details
Building type: multi-residential housing
NCC climate zone: 5 – warm temperate
Designer: Richard Hammond Architect
Builder: Ecovision Homes
Size: 145m² (Apartment A: 63m²; Apartment B: 80m²)
Size of land: 274m²
Cost:$570,000 for the build only (the land cost was $375,000)
Site, block orientation, location and climate
This 274m² corner block is located in a newly planned infill development in Fremantle. Fremantle enjoys a Mediterranean climate, which ranges from hot and dry summers to cold and wet winters. It experiences predictable afternoon sea breezes from the south-west throughout the year.
The longest side of the house faces the street to the north, suiting passive solar design.
Design brief
This development of 2 strata-titled apartments was commissioned by friends who purchased the land together. They engaged a local architect to design 2 separate homes that share resources and amenities.
The owners selected a block within a new development in the suburb of White Gum Valley, which has strong environmental credentials including One Planet Living certification. One Planet Living sets out 10 sustainable development principles, including sustainable water, local and sustainable food, sustainable materials, sustainable transport, zero waste and zero carbon energy.
In keeping with these principles, the owners wanted to build comfortable and efficient homes that capitalised on the north-facing orientation and district views. The design also needed to overcome the small land size.
The owners wanted the apartments to share several technologies, resources and amenities to save on upfront installation costs, realise operational costs over time, and maximise the space available for productive gardens.
The building is located on the site’s southern boundary with zero setback, which maximises the northern exposure.
Photo: Monique Manolini (© Monique Manolini, Crib Creative)
Design response
This micro development on a small lot contains 2 apartments – a 2-bedroom with a study, and a 1-bedroom. The building is located on the site’s southern boundary with zero setback, which maximises the northern exposure.
A double garage sits on the site’s western edge, where it provides a buffer against hot afternoon sun. This reduces the heat load on the main building in summer.
The 2 apartments share the double garage, the roof terrace above the garage, a laundry with 2 washing machines, an outdoor shower and toilet, and large productive gardens.
The building complies with the White Gum Valley design guidelines and the City of Fremantle’s sustainability policy.
On the ground level, the apartments were constructed using a combination of stabilised rammed earth (SRE) walls and concrete floors, chosen to provide thermal mass for stable indoor air temperatures. The SRE walls contained 50% construction waste from the site, and the concrete floors were made using a combination of cement and a waste by-product to minimise its environmental impact.
On the upper level, well-insulated, lightweight construction materials combine with roof ventilation to reduce heat build-up and passively purge warm air. Hot air is pushed out the top of the building by cooler air entering below.
Rammed earth provides thermal mass for stable temperatures.
Photo: Monique Manolini (© Monique Manolini, Crib Creative)
Cladding
The upper-level walls and roof were constructed using lightweight materials, specifically 90mm insulated stud framing and corrugated steel cladding.
The roof was angled to the south to avoid overshadowing the neighbouring house.
Windows
Double-glazed windows and doors help to reduce noise transfer from outside, and maintain stable indoor temperatures during the extremes of summer and winter. They can be opened at night to release hot air.
All windows and doors are also sealed to increase the efficiency of space heating and cooling. A blower door test was carried out to determine the building’s airtightness. A score of 4.8 air changes per hour (ACH) was achieved, which compares favourably to the average result for new Australian homes (15.4 ACH, according to a CSIRO study).
Being within the range of 3 to 7 ACH means the house is regarded as tightly sealed against leaks that increase heating and cooling costs, without compromising air quality. The house does not have a mechanical ventilation system – the owner has found that opening the windows a small amount can provide ventilation when needed.
Upstairs, operable skylights are used to vent hot air in warmer weather using the chimney effect. At other times they are left open a little for ventilation.
Heating and cooling
A 3-in-1 heat pump provides space heating and cooling to both apartments. This is achieved using hydronic tubes in the ground floor concrete slab, and a single fan coil unit upstairs in each apartment. The heat pump is controlled by a separate thermostat in each apartment, and separate valves allow different amounts of heated or chilled water to be supplied to each unit.
Living rooms and bedrooms are also fitted with ceiling fans to generate air movement in summer. The apartment to the west has windows on the south-west corner to capture the regular afternoon sea breeze.
The solar heat pump system has smart controls that allow it to be operated by solar-generated electricity throughout the day. The hydronic tubes in the ground floor concrete slab provide cooling in summer and warmth in winter, if there is sufficient solar power to do so. This increases the passive heating and cooling properties of those spaces.
A bedroom with a ceiling fan and roof window for cross ventilation.
Photo: Monique Manolini (© Monique Manolini, Crib Creative)
Insulation and sealing
The ground floor walls are 300mm-thick rammed earth with an insulation value of approximately R0.3–R0.5. Additional insulation within the external cladding (polyester R2.0) increases the overall value to approximately R2.4.
On the first floor, the wall and roof insulation is R4.0 with an R1.5 foil-faced insulation blanket, which is designed for temperature and noise control in buildings with metal roofs.
During construction, the builder chose to make several modifications to the proposed design, such as changing the roof structure from structural insulated panels (SIPs) to stud frame and cladding. The owners also requested external insulated cladding be added to the south wall to improve thermal performance, and fibreglass insulation was installed throughout the upper floor wall studs and ceiling during the build.
Lighting
Several window and door openings to the north, east and west allow both apartments to receive abundant daylight on sunny days. Skylights and clerestory windows introduce additional daylighting to the first floor.
LED fixtures were used to reduce energy consumption. Indoor and outdoor lighting was also designed for ambience, task and utility, with appropriate lamps selected for each effect.
Appliances
The apartments have been wired to be smart home ready so they can operate as connected, intelligent, responsive homes. As technology advances to real-time environmental monitoring, the operation of appliances and management of energy and water will be further optimised.
Some of these smart home systems are already in place.
The thermostat in each apartment is wired back to the controller in the heat pump room. The controller is connected by wi-fi to a web app, where residents can adjust the temperature and duration of heating and cooling in each apartment. The system can also be programmed to warm or cool the floor if there is sufficient power being generated by the rooftop photovoltaic system.
The irrigation controller, which serves 4 zones within the garden, is connected by wi-fi to a weather station. This ensures the garden is not watered when it is raining.
In addition to the standard utility meters and communication networks, there are sub-meters installed in each apartment. These calculate how costs are divided for shared systems, such as the heat pump and solar power. The use of sub-meters will enable electricity and water to be traded with secure peer-to-peer partners – both within the White Gum Valley precinct and beyond – in the future.
Concrete slab floor and rammed earth walls on the ground floor make this space comfortable all year round.
Photo: Monique Manolini (© Monique Manolini, Crib Creative)
Renewable energy
A shared 5kW solar photovoltaic system provides electricity to both apartments to reduce reliance on grid energy.
The energy generated by the solar panels is controlled by smart home systems, which allow excess electricity to be used where needed. This includes operating washing machines and the heat pump for hydronic heating.
The owners may choose to install a battery system in the future, to store solar electricity. The shared double garage can then have a charger for electric vehicles.
Energy-efficient design, smart home control, and the selection of energy-efficient appliances reduce grid electricity consumption in these apartments. The result is significant financial savings and decreased greenhouse gas emissions.
Hot water
The shared 3-in-1 heat pump provides hot water, and space heating and cooling, to both apartments. It is largely powered by the photovoltaic system on the roof, so saves on electricity costs and greenhouse gas emissions.
This integrated system is expected to cost approximately 20% less to run than a traditional hot water solution.
Water
The apartments are connected to mains water but have additional water collection, storage and treatment systems.
Rainwater is used for flushing toilets and washing clothes. Greywater from the shared laundry is used for subsurface irrigation, while further irrigation water is sourced from the shared White Gum Valley community bore.
Together, these measures reduce mains water consumption by more than 50%.
Waste
Research has found that the construction of a new home in Perth produces an average of 40 tonnes of waste to landfill, and there are more than 15,000 new homes built there each year.
This development aimed to reduce the level of construction and demolition waste in landfill by diverting some of it into the stabilised rammed earth walls, which were made from 50% waste.
The build team implemented other strategies to reduce construction waste, such as using separate bins for different types of waste generated on site and employing a contractor that maximised recycling after collection.
Embodied energy
The design included materials like concrete, which has high embodied energy, to create thermal mass in the ground floor areas and provide passive heating and cooling. However, low-energy substitutes were used instead, such as an environmentally friendlier concrete that contains up to 65% less cement than traditional mixes.
The outdoor areas include landscaped gardens, timber decking, and soft bark for circulation paths, reducing the amount of embodied energy when compared to concrete and pavers.
Floor plan of White Gum Valley house design.
Plans: Richard Hammond (© Richard Hammond)
Additional information
The landscape forms an integral part of the overall design, with edible plants including fruit trees, vegetables and herbs planted in the front gardens and across the council verge. These productive permaculture gardens benefit from organic waste composting onsite – household food scraps are sorted into 2 bin types so that all organic waste returns to the garden, closing the waste cycle.
An additional roof garden on part of the garage increases the permeable area of the site, which helps reduce stormwater run-off. It also enhances local biodiversity and satisfies council by-laws regarding the obstruction of views and overshadowing of screen walls.
While the apartment residents experiment with their own sub-metering system, they are optimistic about the broader potential of sub-metering across the White Gum Valley precinct. The wider installation of sub-meters will allow solar power and water to be shared across the site.
Evaluation
During the design phase, this development was rated using a lifecycle assessment tool and achieved a gold rating. Total emissions per occupant per year were estimated to be 823kg of carbon dioxide equivalent (CO2e); the average Australian household generates around 7 tonnes of greenhouse gas emissions per year.
These apartments are fitted with sensors, monitors and hardwiring that run the heating and cooling systems and appliances in an intelligent way. They also enable data to be easily collected so that energy consumption and thermal performance can be measured over time. The benefit of this, according to one owner, is that they can be assured their home is performing well ahead of average Perth housing across nearly all environmental indicators.
The project delivers significant comfort and liveability dividends. Living spaces are cool in summer and warm in winter, lit naturally and open to the environment, and require very little grid electricity for their operation.
In addition, the productive garden means the owners can harvest their own food, reducing food transport miles and packaging.
Author
Renew, 2020
Learn more
- Next case study - Freshwater, Sydney, NSW
- Read Thermal mass to understand how to make your concrete slab or rammed earth walls work effectively in your climate
- See Buying an apartment to find out more about increasing the energy efficiency of shared communal spaces
- Explore the Energy and Water sections for tips on saving energy and water in your home
