Passive Solar Design Balcatta


As concerns about climate change and energy use continue to increase, client demand for more energy efficient residences is rapidly growing, motivating the building industry to provide more innovative and effective ways of saving energy.

Exemplifying this trend, our recent 8.8 energy rated home in Hazelmere employs a number of highly innovative design solutions to dramatically reduce the building’s energy consumption.

Having bought a north-facing block of land the clients intended to build their home with the main living area as much to the north as possible. This was achieved in their passive home design by angling the living area to the north. To obtain cross ventilation through the house a central hallway was created with windows at both ends that could be opened.

As windows play a crucial role in passive design, the choice was made to use thermally broken aluminium windows with double glazing. The north facing windows were chosen with a high solar gain to bring in the winter sun, while the east and west facing windows have a lower solar heat gain to minimise summer morning and afternoon heating. All the glazing is double glazed, with a low-e coating and argon gas inside.

Beneficial shading was achieved by planting a deciduous plum tree on the west elevation, which is a natural way to stop afternoon sun when it is not wanted in the summer. Also incorporated in the design is a wisteria growing on a trellis located at the eastern elevation of the home.

A 1.8m roof overhang was built on the north side to keep the summer sun away from the windows. A removable shade sail has been placed over a ‘secret garden’ which gives the master bedroom winter morning sun while providing shade on summer mornings. The ‘secret garden’ contains tropical plants that also benefit from the summer shading.

In order to achieve a higher R rating for the external walls, the choice was made to use 140mm timber framing with R3 insulation batts to the external walls and selected internal walls, with reverse brick veneer to utilise as much thermal mass as possible. To further increase the thermal mass in the house, all internal walls were constructed with brickwork. Large ceiling fans were placed throughout to circulate air around as much as possible.

The clients’ intention was to ensure non-renewable energy sources were not used. To this end, there is no gas connection and all cooking and water heating is electrical. All lighting is energy efficient LED lamps, and efficient ceiling fans are used throughout the house thereby eliminating the need for air-conditioning. A heat pump inverter hot water system, which is the most efficient way of heating water, has been installed.

A dedicated area on the roof is reserved for solar panels and while there are currently no solar panels installed, all conduits are in place and ready, terminating at a storeroom next to the carport. The inverter is also to be installed there as well as a future battery back-up system. This room was chosen because it is next to the carport, thus ensuring ease of installation of any charging equipment for future electric cars. Light colouring has been used throughout to minimize heat gain in the summer as per the energy consultant’s recommendations. The roof sheets are ‘Surfmist’ white.

According to the clients, the home is extremely comfortable to live in, with little to no need for thick jumpers and slippers in the early hours of the morning or into the evening. The large ceiling-to-floor windows provide an open, airy feeling with abundant light even on a dull day. The clients say the ‘secret garden’ of the master ensuite is a unique and welcoming feature to wake up to.

The other bedrooms in the home have been designed away from the sun so that the occupants can stay comfortable well into the late morning if desired. The central kitchen, dining and living area sit next to large stacker doors and a decked patio, making an easy transition from one space to the other and allowing easy supervision of children playing in the garden. An automated window system was designed as part of the cross ventilation to deal with Perth’s high summer temperatures. There are five temperature sensors and one anemometer (wind speed sensor) installed in the house to keep track of environmental factors which may influence the ventilation.

The automation system is unique to this home with nothing like it in Perth. The system allows the windows on the east and west side of the home to open up automatically, based on the setting and temperature. On the ‘summer’ setting the windows will open when the average temperature internally is higher than the average temperature externally. In Perth’s summer, this usually happens in the early hours of the morning when the occupier is sleeping.

On the ‘winter’ setting, the windows will operate the opposite way in that they open when the temperature inside is lower than the temperature outside. In Perth’s winter, this would happen in the early afternoon. The anemometer is used to override the system should it be too windy. This system needed to be designed into the layout of the house as the windows had to be under cover to ensure there is no flooding during wetter weather, and also for reasons of security.

For any questions about this home or passive solar design, get in touch with us today.