Less, not excess
A small, smart Sydney renovation uses energy modelling to fine-tune the design and make the most of limited space.
Having lived in their dark, cold two-bedroom brick cottage on a tiny block in the Sydney suburb of Alexandria for two years, Abi and Oliver were keen to improve its thermal comfort, energy efficiency and natural light. They engaged Anderson Architecture to design a modest extension that would create more space while retaining as much of the original house as possible. With a limited budget and a determined focus on sustainability, the couple chose to prioritise their spending on features that would add to the home’s performance and energy efficiency, opting for cost-effective finishes and fixtures to balance the budget.
Simon Anderson and his team developed a two-storey solution that respects the local heritage conservation area and works within the existing footprint of the house. The front two bedrooms and living room were left as is and merely refurbished (with one new window), and at the rear are a new kitchen, dining, bathroom and laundry, sitting between the retained brick side walls. The end wall has been opened up and glazed for sunlight, ventilation and a connection to the courtyard, which is paved with the bricks that were removed. Upstairs is a new bedroom, bathroom and walk-in robe. Even with space at a premium, care was taken to maximise northern sun with the staircase climbing across a large new north-east window downstairs and light borrowed across the stairwell upstairs.
The design team used thermal modelling to fine-tune the design and product specification. “Through the modelling of various possible improvements, we optimised the thermal efficiency of the home, reducing the active heating and cooling needed throughout the year,” says Simon. “We found that double glazing, insulation under the concrete floor and increasing the R values of the other insulation had a marked impact on the thermal efficiency, achieving a 7.2 Star energy efficiency rating.”
Retaining the cottage, reusing the bricks and specifying products with low embodied energy reduced the environmental impact of the build. Simon’s calculations show that the embodied energy is approximately 70 per cent lower than the Australian average for a new home, and the global warming potential (emission of greenhouse gases) is around 3.5 per cent of the Australian average. Oliver and Abi chose natural and low-VOC products, and sourced tiles and other fittings from small, local businesses where possible.
The pitch of the addition’s roof has been designed to reduce its visual impact, and the ridgeline is in keeping with nearby houses. “Our solar studies ensured this form would enable the house to operate efficiently without compromising the neighbours’ amenity,” says contributing designer Alexandra Woods. The sloped roof will also accommodate the planned 2.3 kilowatt solar system that will cover much of the household’s daily energy demand.
Inside, the use of exposed laminated veneer lumber (LVL) beams instead of a ceiling to the ground floor increases the perceived height and reduced required construction materials. The kitchen bench extends along the southern wall, and a compact family bathroom is tucked behind the pantry cupboard. All windows and doors are double-glazed and timber-framed for improved thermal efficiency.
The laundry is fitted into a neat corner cupboard – “It didn’t need its own room,” says Abi – and in a build where no space is wasted, an alcove under the stairs admits light and provides a cosy place to sit. The upstairs bedroom has two large windows for light and views, and two openable high-level bathroom windows help air the house via stack ventilation and provide natural light for Abi’s orchids to flourish.
Extending beyond the ground floor, the new bedroom creates a deep eave to block summer sun while allowing winter sun to warm the thermal mass of the concrete slab floor, which also houses the hydronic heating pipes. The design team specified 3 Star Green Star concrete with fly ash cement replacement as it has less embodied energy than regular concrete, and the floor features imprints of gum leaves that fell from nearby trees when the concrete was being poured. “Rather than removing these imprints through polishing, our clients opted to keep them, adding another unique touch to this less-is-more house,” Simon says.
Insulation beneath and around the edges of the concrete slab reduces heat loss, and three efficient heat pumps provide hot water and run the hydronic heating in the slab and via wall radiators in the front rooms. The couple say they enjoy the comfort of the heating system with the even heat it emits, and its cost-effectiveness.
Investment in the energy-efficient heating, double glazing and high levels of insulation was offset by choosing economical paints and finishes. “We encourage all our clients to take this approach when budgeting for a home, stressing the incomparable benefit of prioritising sustainable features and systems over spending on ‘fashionable’ aesthetic choices,” Simon says.