Gabao (Keith Cockburn)
South-east Queensland’s sub-tropical climate with its marked diurnal (day into night) temperature movements is ideal for a passive design which harnesses thermal changes to stabilise temperatures in a home to within a comfortable range.
This family home in Pullenvale, 15 kilometres from the Brisbane CBD, exploits the four pillars of passive design
– orientation, ventilation, insulation and thermal mass
– to create an environment that does not rely on artificial heating and cooling.
Despite its relative closeness to Brisbane, Pullenvale is a semi-rural area with large houses on even larger blocks. The owners of this property lived next to their new site for over ten years. They were looking for a home that could separately accommodate their two young-adult sons and frequent overseas visitors, while bringing the family together for meals.
Their new home sits in a natural clearing straddling the top of a ridge. The one-hectare greenfield site has a stunning northerly aspect. “It’s perfect,” enthuses architect Karen Ognibene of Arkhefield, “You couldn’t ask for better. There are beautiful views over the surrounding hills and from certain points in Pullenvale you can see right down to the border ranges between Queensland and New South Wales.”
Despite having previously lived in a classic timber Queenslander, the owners, originally from South Africa, didn’t want their new house to “touch the ground lightly,” Karen explains. “They wanted it to feel like it had grown out of the ground, quite the opposite to a Queenslander!” Aside from the accommodation requirements, this was top of their brief.
That’s not surprising, as South Africa has a strong heritage of building in brick, stone and concrete. However the selection of brick was not a foregone conclusion. “We tossed around various materials but in the end came back to brick because of its richness,” says Karen. “Stone can also be rich but structurally it has to be fixed to concrete block or the like and all of a sudden it starts to lose its integrity.”
The spine of the house is a massive brick wall travelling 40 metres along the southern elevation and rising to an average of about four metres. Behind the wall is a circulation corridor allowing access to the linear room programming. Joinery is also built into the brickwork, including wine storage and part of the kitchen.
Two more cavity brick walls bookend the house, running at right angles to the southern wall.A fireplace is built into each of these flanking walls, indoor to the east servicing the living area, outdoor to the west warming a terrace.These two walls and the southerly spine wall enclose the entertaining space.
Unusually (for south-east Queensland at least) these walls are constructed in cavity brickwork and finished as face brickwork, internally and externally.
We asked Karen why she and her clients chose internal face brickwork.“Brick is such a rich material,” she considers. “The balance of the interior has quite a crisp, clean modernist aesthetic with white walls, a lot of glass facing north and nice polished floors. Brick was just a way of bringing the landscape into the house and it gave an enhanced texture without adding another material to the palette.”
Two brick types were chosen from the Daniel Robertson range of premium quality clay bricks: Hawthorn Black and London Blend. These were expertly blended to create a distinct visual aspect for this project. “They look rich, quite rustic, like they have been dug out of the ground,” Karen contends.
This was taken a step further by laying a course of Roman (50mm high) bricks for every four courses of standard height (76mm) bricks. The resultant banding is a subtle disturbance from the expected regular pattern of brickwork.
Not satisfied with that, the decision was made to lightly rake (recess) the horizontal mortar joints and flush finish the vertical joints. “So when you look down the wall you read the horizontal nature of the brickwork rather than the individual brick form.”
There’s a lot of steel in the structure, partly due to the lightweight upper level which cantilevers off the underlying structure. It carries the master bedroom, ensuite and one of the two studies in the house.
Steel posts support the superstructure including the considerable roof, a hipped design with a two degree pitch that precluded trusses. These supports rise through the brickwork cavity, performing double duty by bracing the tall walls. This structural design also allows the highlight windows lining the upper level of the southern wall to be recessed about a metre from the outer edge of the brickwork.
Not surprisingly, sustainability was to the fore. The site has 45,000 litres of rainwater storage for topping up the swimming pool and as a firefighting reserve. Extensive use is made of ceiling fans while air-conditioning is limited to bedrooms and studies. There is no central heating, just the two fireplaces and reverse cycle heating. Deep eaves shade the interior from the high summer sun, while allowing the lower winter sun to penetrate and warm the internal thermal mass of brickwork and concrete floor slab.
An unexpected bonus is that all Daniel Robertson bricks are now certified as Carbon Neutral under the Australian Government’s National Carbon Offset Standard. This is largely due to their manufacturing process which uses waste sawdust as the primary firing material instead of natural gas. Incremental improvements were also made to other aspects of the manufacturing and associated processes, and the relatively small residual CO2 emissions are offset by purchasing carbon credits that assist in projects such as tree planting under the Forests Alive program (forestsalive.com).
Even the carbon expended in transporting the bricks to the customer – anywhere in the world! – is fully offset. All Daniel Robertson bricks are certified Carbon Neutral from raw material excavation through to delivery of the finished products to the work site.
This is on top of the life-cycle advantages of clay bricks such as their longevity, contribution to thermal mass, and the fact that they don’t require expensive, energy-hungry finishes such as paint or render to maintain their good looks and durability. The Pullenvale home achieved six stars on the BERS Pro housing energy rating scheme.
Building in a bushfire-prone area required a number of concessions. The site was already largely clear, minimising the tree removal required to create a buffer zone.The degree of threat varies from highest near the garage to lowest on the long northern elevation. Fire-resistant timber species such as kwila and black butt were specified for window and door frames, decks and to clad the lightweight upper level.
Brickwork is naturally immune to fire but the horizontal mortar joints were required to be raked to minimise the formation of ledges that could catch embers. Alternatively, the joints could have been finished as ironed (half-round) or a weather-struck, which slopes upwards and inwards from the edge of the lower brick.
Bushfire resistant. High thermal mass. Rich colours and textures. Long life. Low maintenance. And now certified Carbon Neutral. Building with Daniel Robertson bricks is the perfect answer for a sustainable, attractive, liveable home … wherever you are in Australia.
Highly valued for their character, earthy appeal and individual charm, all Daniel Robertson bricks are now certified Carbon Neutral.
Colour: Hawthorn Black, London Blend
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