Northcote, Victoria
Family home built on existing foundations using passive solar principles, local materials and high-density insulation.
The new home was built on the slab of the previous house using passive solar principles.
Photo: Tatjana Plitt (© Tatjana Plitt Photography)
NatHERS thermal comfort rating
7.9 Stars
Heating: 27.1MJ/m² per year
Cooling: 28.5MJ/m² per year
Total: 55.6MJ/m² per year
Sustainability features
- Used existing foundations and concrete slab
- Rammed earth walls
- Engineered set lengths of cladding
- High-density bulk insulation
- Effectively sealed airtight building
- Double-glazed low-emissivity (low-E) multipoint locking windows
- Openable clerestory windows
- Solar photovoltaic (PV) panels
- Heat recovery ventilation system
- Heat pump hot water system
- LED lighting
- Energy-efficient appliances
- Adaptable design
- Rainwater tanks
- Food production
Project details
Building type: Medium density housing
NCC Climate zone: 6 – mild temperate
Designer and builder: Luke Middleton, EME Design
Size: 196m²
Size of land: 525m²
Site, block orientation, location and climate
The house is on a long, thin, east–west-facing block of 525m2 in Northcote, an inner suburb of Melbourne. The climate is mild temperate, with cold, damp winters and hot, dry summers.
A nearby creek creates a variable microclimate around the property, lowering the average temperature in winter and increasing it in summer.
Design brief
The owner initially wanted to renovate the house to make it more liveable for his family, but after a year decided a renovation would not be adequate – the property was poorly insulated, overshadowed by a house to the north, and had an inefficient layout that was difficult to reconfigure.
The owner wanted a house that would be comfortable and adaptable. It also needed to be constructed using materials with low embodied energy, and have the potential to be self-sufficient with rainwater, greywater, solar panels and food production.
The house design would use a mix of passive solar and ‘Passive House’ design principles to reduce running costs. The goal was to reduce or eliminate the need for mechanical heating and cooling.
The asymmetrical gable form is taller on the northern side with windows positioned to capture winter sunlight, views and ventilation.
Photo: Tatjana Plitt (© Tatjana Plitt Photography)
Design response
The new 2-storey house design was based on the existing footprint, orientation and streetscape. Passive House principles were employed to make the house airtight. Passive solar design elements were used to heat and cool the home.
The existing strip foundations and 40m2 concrete slab informed the footprint of the house. This saved money and embodied energy. Additional foundations were poured to support the walls of the improved configuration.
The front gable frames the verandah, carport, and recreation and storage areas. There are 2 bedrooms and a multipurpose room on the ground floor, while the master bedroom and a second adaptable space are upstairs. These rooms can be converted into second living areas or additional bedrooms to cater for changing family circumstances. The bathrooms are mobility-friendly.
A side courtyard garden opposite the kitchen brings in northern light and an outdoor connection to the middle of the house, and the north and south walls of the living area are rammed earth. The kitchen island doubles as a dining table and desk, and furniture in the living area can be rearranged depending on seasonal light.
A rear deck steps down to the garden, and a bungalow at the back of the property serves as a multi-functional space. It will be refurbished in the future with a green, productive roof.
Cladding
Natural materials are used on the home’s interior and exterior, and there is no plasterboard used in the house. The interior is lined with radiata pine plywood with a whitewash. The owner made this choice because of aesthetics, the robustness of the material compared with plasterboard, and its potential to be recycled.
The external cladding is yellow stringybark shiplap, the floors are blackbutt, the hallway and kitchen ceilings are wormy chestnut shiplap, and the kitchen joinery is birch plywood with a laminate pre-finish.
The kitchen island doubles as a dining table and desk. All appliance are efficient electric to run on solar-generated electricity.
Photo: Tatjana Plitt (© Tatjana Plitt Photography)
Windows and doors
The windows are positioned to allow more sunlight and ventilation into the home in winter. Their placement was informed by seasonal sun movement, as an adjacent single-storey home was found to cast significant shadows in the cooler months.
High clerestory windows on the northern wall allow for passive solar gain in winter, as warmth from the winter sun is stored in the southern rammed earth wall. During summer, low openable windows on the southern side of the house work in conjunction with a fernery zone to purge hot air. External blinds shade west-facing sliding glass doors and windows.
Particular attention was paid to window selection to minimise heat loss and gain. The windows are double-glazed and have a low-E coating, reducing outside noise and improving thermal comfort. Multipoint-locking windows, where the locks press the sash into the frame for a tighter seal, keep the house secure and airtight.
A courtyard garden brings northern light and an outdoor connection to the middle of the house.
Photo: Tatjana Plitt (© Tatjana Plitt Photography)
Heating and cooling
A heat recovery ventilation system provides fresh air throughout the day and night while also extracting stale air. Heat transfer ducts move air from warmer spaces to cooler spaces, such as from the living area and upstairs rooms to the front bedrooms downstairs.
There are 2 air-conditioners from the original house contained within secret bulkheads in the walls. They are used very rarely.
A small slow-combustion wood heater in the living room provides heating in winter and uses approximately 800 to 1000kg of locally sourced firewood per year. The high-efficiency unit draws in external air and has low particulate and heat output, using very small quantities of wood per hour. It is a compact model as a larger unit would overheat the home.
Pipes have been installed in the walls for the provision of hydronic heating if needed in the future.
Insulation and sealing
Passive House methods for airtightness have been employed in the design and construction to maintain stable indoor temperatures and reduce heating and cooling use. These methods include:
- high levels of insulation
- wrapping the structure in an internal membrane
- selecting multipoint-locking windows to minimise airflow and draughts.
The roof has been insulated with high-density bulk insulation and a roof blanket (R6.5), and the walls and floor both have high-density bulk insulation (R5).
The induction cooktop has downdraft recirculating extraction, which pulls stale air down into a duct. This means there is no ceiling or wall penetration for the exhaust fan, which keeps the internal building airtight.
As this is a highly sealed building, a heat recovery ventilation system was installed. This keeps air quality high by removing stale air, and reduces humidity. These systems are common in buildings built to Passive House standards as they limit the need to open windows, which can compromise the stable temperature within the home.
Natural materials are used on the interior including rammed earth walls on the north and south walls as well as shiplap plywood.
Photo: Tatjana Plitt (© Tatjana Plitt Photography)
Lighting
The side courtyard garden and northern windows allow sunlight to enter the home, minimising the need for artificial light during the day.
LED lighting is positioned for indirect light. This reflects light off surfaces such as walls and ceilings, instead of directly illuminating objects. Dimmers allow the intensity of light to be modulated.
Appliances
All appliances are new, except for the 2 air-conditioners from the original house. The appliances are energy-efficient, and include an induction cooktop, 5-star oven and 3.5-star fridge.
Renewable energy
A 5kW solar PV system allows the household to run all electric appliances. The system produces an annual average of 24kWh per day. In summer it can generate up to 40kWh per day, and in winter it generates around 8 to 14kWh per day.
The average daily energy consumption for the family of 4 is approximately 12kWh. The excess – more than 3500kWh annually – is returned to the grid.
Hot Water
A high-efficiency heat pump was chosen to provide hot water. These are very efficient electric hot water systems that can operate on surplus solar electricity.
Highlight windows bring daylight into the home and allow for passive solar gain in winter. The windows are double-glazed, which helps to reduce noise from the nearby train line.
Photo: Tatjana Plitt (© Tatjana Plitt Photography)
Water
There are 5 low-profile rainwater tanks installed under the deck that provide 11,000L of storage capacity. The family currently consumes an average of 55L of water per person per day.
The owner plans to use greywater in the future and reserve the rainwater tanks for garden use during summer. Greywater will be collected from the bathroom and laundry basins, the shower, bath and washing machine.
Waste
Timber boards engineered to set lengths were used during construction to reduce waste. The boards were made from offcuts and ordered to the required length. According to the owner, the waste bin for the construction of the house was approximately half that of other equivalent homes.
The pattern and layout of the internal plywood lining worked closely with standard sheet sizes to reduce waste. Reusing the existing foundations and concrete slab also decreased waste from demolition.
The pattern and layout of the internal plywood lining worked closely with standard sheet sizes to reduce waste.
Photo: Tatjana Plitt (© Tatjana Plitt Photography)
Embodied energy
The design retained the existing foundations and 40m2 concrete slab to preserve the embodied energy of the concrete and steel. Steel beams from the original house were also reused in the subfloor framing and in the retaining walls of a large vegetable garden wicking bed. Construction materials were sourced locally.
The 200mm-thick rammed earth walls have low embodied energy in their production and high thermal mass. The sustainable timber and lightweight timber framework have low embodied energy, and the minimisation of waste reduces embodied energy.
The flexibility of the house to adapt and evolve will extend the lifespan of the structure, saving embodied energy over the long term.
Additional information
The family has developed an indigenous garden at the front, back, and along the north side of the property, and integrated a productive garden on the south side of the backyard where it receives the most sun.
The owner has designed and built custom multifunctional furniture for the house, rather than choosing rigid built-in furniture settings.
Floor plan of Northcote house design.
Plans: Luke Middleton (© Luke Middleton, EME Design)
Evaluation
By combining solar access, insulation, airtightness and air quality, the house has fresh air and comfortable temperatures year-round with minimal heating or cooling. On a September morning when it is 1.2°C outside, the house is 20°C inside without heating.
The owner says the house performs well and is beautiful to live in. During winter, only minimal heating is required through a fireplace using locally sourced firewood. Throughout summer, the house is effective at lowering the temperature passively through shading, insulation, natural ventilation, the heat recovery ventilation system and thermal mass.
The owner calculated that a 2.5kW solar system would be sufficient to cover the home’s energy consumption. It currently has a 5kW solar array and therefore operates energy positive, generating almost twice the energy it consumes.
The owner views the house as an ongoing experiment and has installed 15 sensors to monitor temperature, air quality, humidity and carbon dioxide levels. They now have a better understanding of the strengths and weaknesses within the home, such as which spaces work better and remain more comfortable. This data will inform the design and construction of future projects.
Graph showing the results of temperature sensors between 19 August - 27 August 2020 in Melbourne, VIC.
Source: Luke Middleton (© Luke Middleton, EME Design)
Author
Renew, 2020.
Learn more
- Next case study - Birkenhead, SA
- Read Designing a home for ideas when designing an energy-efficient home
- Explore Design for climate and Thermal mass to discover how to make sure your home suits the climate in your region
- Look at Photovoltaic systems to learn about solar PV systems for your home
