Starting with a clean site, the design brief for the beach house project was to be a model and test case for various sustainability measures. Those measures were aimed at demonstrating active and passive sustainable initiatives whilst accommodating a coastal lifestyle.
The project is situated on the south side of Mona Vale Headland in Sydney. The south facing aspect and the narrow site proportions limited the passive design potential.
Architect John Choi worked around the site constraints by opening up the roof at the centre of the house with a large north-facing skylight to allow win ter sun into the south facing living areas. This also traps and holds the warmth of the winter sun using the thermal mass of the structure.
“The house is of reverse veneer con struction. It utilises low embodied ener gy and low thermal mass timber cladding to the outside and heavier thermal mass of concrete and blockwork to the inside,” Choi says. The house’s ‘zoning’ into three separate areas also assists in the retention of heat in winter.
The front living area ventilates through a series of louvres in a bank of high level clerestory. Bedrooms also have cross ventilation via fanlight win dows above doors. Other sustainability initiatives include a 15,000 litre rainwater storage tank, the use of evacuated tubes for infloor heating and hot water supply, and photovoltaic solar panels to provide electricity back to the grid — 1.4 kW grid sized for an upgrade to 3.0 kW.
Both Choi and builder Paul Gray agree the most innovative aspect of the home is the front living pavilion, which is comprised of three large portal frames of steel, with all the timber walls infill walls. “So when the skeleton of the building went up, it was quite amazing because the roof is held up by nine little sections of steel that were only 50 mm x 50 mm,” Gray says.
Timber and steel were prominently used in the home. “By using steel, we could keep the structural members down to a minimal size. This was critical in achieving the lightly framed expres sion to the front pavilion and the 'float ing' roof,” Choi says.
“We used UC columns over rectangu lar hollow sections for two reasons. Firstly, the UC allows us to insulate and infill with timber. Secondly, the UC has strongly defined edges which provide a precise and fine appearance.”
With the property so close to the coast, all materials were well considered to ensure products would stand up to the elements. For example, windows had to be able to withstand strong wind gusts. “We were 90 per cent done on the project and we had a horrific storm and there were over 100 km an hour winds. So we had to build thinking about that happening,” Gray says, with the chosen windows tested in wind tunnels.
With so much timber used in the proj ect, Gray says it was difficult to find large sections of spotted gum, the main timber species used, for the exterior sliding windows on the eastern side of the building. “Ninety per cent of the timber is spotted gum, but there is a lit tle bit of blackbutt around the place, which to the naked eye wouldn’t be visi ble,” Gray says.
Most of the timber came from a tim ber yard in Mona Vale — Hardwoods Australia — and a small amount from Australian Architectural Hardwoods in Kempsey. To protect the timber, it was coated with an oil prior to installation and once erected, was coated three times. The steel was also galvanized and had four coats of paint to protect it.
The working relationship between Choi, Gray and the client was a close one where each person was “constant ly” talking to one other on the phone daily, via e-mail and weekly site meet ings. There was also particularly close involvement from the client, who had considerable knowledge about ESD and sustainability products.
The home’s environmental perform ance will be measured, with thermal performance, energy use and water consumption tracked over the year.
Stephanie McDonald
