Skipless—Lego-Like Passivhaus in Perth’s Swan River
Mesh façade in winter – letting the light in. Clever planting sends hops up to the roof in summer.
This staircase was 100% created off site – it arrived in one piece and was dropped into place.
Loving the spaces they had lived in in Japan, Siew-Fung and Reto were keen to create room for traditional ‘lying around and reading’.
Simple, neutral features in the kitchen belie clever solutions that will stand the test of time.
Despite the small footprint of this house, every space is matched to a lovely considered requirement. Space and loft in the entry marks coming home.
The powerful trifecta of Passivhaus design, off-site construction and a heavy reliance on one material result in a paragon of efficiency and elegance.
A nest of Lego-like shapes, this house near the Swan River in Perth seems perfectly simple at first glance, its lovely lines creating defined and easy living spaces that fit together like a puzzle. It is cozy, snug and friendly with an unfussy feel – a bit like a cabin in the woods somewhere – but, as is so frequently the case with good design, all this ease and simplicity belies the extensive considerations and engineering that is behind its construction. The house was designed by architect Siew-Fung Then, associate of Ewert Leaf, for her family; partner Reto Hofman and their two daughters.
Siew-Fung’s first step in her process was to employ a certified German Passivhaus builder and certifier to make sure her plans adhered to the five principles of Passivhaus design and met various other super strict requirements. Not only that, she also designed the house to be almost completely prefabricated off-site. The house truly is a network of prefab pieces, meticulously designed to the millimetre to perfectly fit within the confines of Passivhaus certification – some feat! In her initial discussions with the builder, Siew-Fung was thinking of plywood for the internal finishes.
“When I told him that we wanted plywood, not plasterboard, he suggested cross-laminated timber. I love the look of ply, not so into plasterboard, so when he suggested CLT I thought, yes, that’s really good!” says Siew-Fung. They then determined that each panel could be constructed entirely of pre-insulated timber. Almost all the pre-cut panels in the house are made from laminated Australian and New Zealand pine, with a minimum of three layers. Externally, rockwool insulation and cladding in silvered Victorian ash and shell grey metal is then added to adhere to the Passivhaus principles, depending on the orientation and openings of each side of the house.
The engineering is a masterpiece. “When we did the design, we had to know exactly what the sizes were…and exactly where the metal connections are,” says Siew-Fung. “So the engineers, in Melbourne, did all the structural design…and then they were cut in the factory with a waterproof membrane already applied externally. It was assembled in four and a half days. We didn’t need a skip bin at the front of the site! There was no waste.”
The house is three storeys but only uses 35 per cent of the block. The first floor contains the main living spaces, with defined separations determining their uses. A two-storey void in the entry creates an immediate sense of space which then narrows into a hall and staircase with a view to an adjacent internal courtyard. The family bathroom and laundry are on the other side of the hallway.
The house opens again into a living and dining area and kitchen tucked around the side. A raised tearoom off the living area and along the other side of the courtyard reminds the couple of the years they lived in Japan. Tatami mats create a space to lie around and listen to the growing trunks of black bamboo clank together. First floor is the girls’ bedrooms at the front and Siew-Fung and Reto’s at the back with a gorgeous eastern view to the river. A screen at the front of the house has been cleverly planted with potted hops that rampage up the screens in summer to create shade and screening, but then completely die off to let in the western winter light to the girls’ bedrooms.
The third floor is Reto’s library/study and a roof deck with longer views of the river. The couple have installed a heat recovery ventilation system, with two openings to the wall. One takes the stale air out and the other brings fresh air in, which circulates via ducts throughout the house. PVC-framed triple-glazed windows with warm edge spacers between the panes keep the temperature within the house around 20 degrees, year-round. Of course, all the windows and doors can also be opened to let in Western Australia’s famous sea breezes. Reto and Siew-Fung consciously kept the footprint of the house as compact as possible to allow room for a rambling backyard. The design, by Annghi Tran Landscape Architecture Studio, includes many edible plants and, after a year and a bit – including one of Perth’s hottest summers – is looking well on its way to creating the final touch to this incredible house.
“We didn’t need a skip bin at the front of the site! There was no waste.”
Specs
ARCHITECT
Ewert Leaf
BUILDER
Evans Builds
ENGINEERS
Vistek
LANDSCAPE DESIGN
Annghi Tran Landscape Architecture Studio
LOCATION
Noongar Country / Nedlands / WA
PASSIVE ENERGY DESIGN
Built on a vacant long and narrow subdivided block with a 1.8-metre slope, the certified German Passivhaus is oriented to the north-west (street façade) and south-east with views to the Swan River and Perth Hills. The front façade receives a lot of sunlight throughout the day and so has an expanded metal screen with deciduous hops growing to shelter the balconies and bedrooms at the front. The winter sun from this façade helps to keep the house warm, requiring no further heating. All windows and doors are positioned for effective hot air purges at night during the summer months. The internal courtyard lightens up the space significantly without heavy use of artificial lighting during the day. Because Perth’s climate is mild, thermal insulation is added around the ground floor concrete slab edge, walls and roof in various R-values and thicknesses depending on the orientation. Each area is meticulously calculated by Passive Analytics and insulation is added accordingly. The design provides comfortable living with low energy use year-round.
MASS TIMBER
Constructed mainly from cross-laminated timber (CLT), manufactured by XLAM Australia and certified as Red List Free. With a total of 134 CLT panels serving as both structure as well as finishes for floors, walls and ceiling, most panels are left exposed internally with natural timber knots and imperfections remaining visible. CLT is also used for the roof, floors, walls, stair and balustrade. On the external side it is covered with waterproof membranes from Rothoblaas. External finishes limited to Victoria ash timber cladding, untreated, and prefinished aluminum cassette metal panel in shale grey. Internally all floors, walls and ceiling are painted with hardwax oil in a satin finish. Minimal plasterboard lining is painted with Dulux low-VOC paint. By using CLT, the all-electric home has sequestered 68 tonnes of CO2 from the atmosphere.
MATERIALS
Internal materials include Japanese mosaic wall tiles and Italian porcelain tiles from Original Ceramic. Kitchen benchtops are Mont Blanc quartzite slab from Lusso Group with Laminex products for all kitchen, bedrooms and bathroom joinery. The rest of the joinery is in plywood. All kitchen appliances are V-Zug, with kitchen sink and mixer by Franke.
FLOORING
The ground level has a burnished clear-sealed concrete slab with insulation to perimeter for improved thermal mass. All upper-level floors and stairs are built from solid CLT and painted with two coats of hardwax oil in satin finish. The tearoom has a Japanese straw mat (tatami) floor.
GLAZING
All windows (tilt and turn, lift and slide or hopper) are thermally broken uPVC Deceuninck frames in timber-look walnut finish with argon gas-filled low-E triple glazing and warm edge spacers between panes supplied and installed by Arco Windows.
HEATING AND COOLING
With such a high-performance house, the final blower door test reading was 0.4kPa, which satisfies the German Passivhaus requirement. A mechanical heat recovery ventilation (MHRV) unit is installed to provide fresh air intake and stale air exhaust. The unit (Zehnder “ComfoAir”) uses very low energy and runs continuously. This allows for consistently good indoor air quality and saves energy for heating and cooling. Two sets of Daikin multi-head air conditioning systems are installed to provide cooling and heating, though to date the heating function has not been needed. On hot summer nights, two sets of portable Vornado fans are used in bedrooms.
HOT WATER SYSTEM
Reclaim heat pump hot water system.
LIGHTING
The house uses low energy LED lighting from Unios and features light fittings from Volker Haug and Noguchi Akari lanterns throughout.
ENERGY
A total of 5.8kW grid-connected solar power system by Solar Edge has been installed with provision for future battery installation and panel expansion.
