Mary Henning’s house in the Sydney suburb of Clovelly is a model of water efficiency.

Since renovations to her three-bedroom semi were completed in 2004, the building’s environmental strategies, particularly with water, have won it numerous awards and provided a leading case study for the New South Wales Government’s Building Sustainability Index (BASIX) modelling.

The house has also attracted attention internationally, appearing on Britain’s World Architecture News website and Canada’s Slow Home website and featuring in US Dwell magazine.

It was presented at the 2006 national conference of the Royal Australian Institute of Architects and tours of the house have been organised.

Renovations were designed by architects Kennedy Associates in conjunction with environmental engineers ENVDS.

On an infill site of just 234 sq m, they shoehorned in an extension to the original house, a 9000-litre in-ground pool, a courtyard, off-street parking and a water harvesting and recycling system that reduces the household’s town water usage by a staggering 75 per cent.

This is nearly double the BASIX requirement of a 40 per cent reduction to water use and greenhouse gas emissions for “alts and adds” greater than AU$50,000. The plans were approved by Randwick City Council before BASIX was introduced.

“I think you need to do things that spark debate in the community about conserving our resources,” says Henning.

“Water and energy are two major resources we use daily, so their impacts continue week after week. We went for really big reductions in water use, because you can buy green energy but you can’t buy green water.”

SUSTAINABLE DESIGN

The front of the semi was retained in its original format, with a two-storey addition grafted onto the rear. The new section houses the living and service areas, home office and main bedroom, with a void at the rear to channel light deep into the interior.

It has solar hot water and pool heating, provision for solar power generation, external louvres to temper the western sun at the rear, skylights, a thermal chimney, cross-ventilation, LED lighting and ceiling fans instead of airconditioning.

“We set out to design a beautiful house as well as a sustainable one,” says principal architect Steve Kennedy. “Sustainability should be integral to design, not an adjunct, and the drought has been an important wake-up call – people increasingly are looking for high-end architecture that performs.”

At the heart of the water system are three rainwater tanks, each holding 3000 litres of runoff from the 100 square metre roof. The tanks were custom made, because at the time their size (2.1m high by 90cm wide) wasn’t standard. Now such options are readily available, partly because of the success of this project.

The showers, bath and hand basins are all fed from the tanks, as are the garden irrigation and plunge pool. Wastewater from the bathrooms or laundry (it’s interchangeable) is recycled in a three-tiered “green wall” opposite the tanks.

Pumped to the top of the three-tiered vertical garden, the grey water percolates down through the layers of plants in hydroponic gravel, sand and charcoal, which polishes it to an almost potable (drinking) quality – according to regular tests by ENVDS. The water

is then held in an underground tank that supplies water to the toilets and washing machine.

The only direct town water connection is to the kitchen sink and the hot water system. There’s also a top-up valve in case the tanks run low, but it’s never been used.

“The tanks have never run dry, though they’ve gotten low at times,” says Henning, a long-time advocate of environmental awareness. Her two-person household uses less than 100 litres of town water a day.

“I love the fact that my clothes are washed in water recycled from shower and bath water,” Henning says. “It’s marvellous. And I know the pool is a luxury, but it’s not a drain on community resources. I’m providing for it with the tanks, so I feel very good about having it.”

VERTICAL WETLAND

Sydneysiders in general have buckled down with their water use since the drought began to bite. Sydney Water estimates usage per person has dropped by 32 per cent, from 500 litres a day in 1991 to around 340 litres a day.

Imagine the savings if more homes – and businesses, for that matter – were hardwired like Henning’s.

Sydney Water was initially sceptical about Henning’s recycling system, understandably perhaps, given the lack of precedent – it’s a first for Australia and possibly the world. But the science isn’t new.

According to environmental engineer Toby Gray of ENVDS, “It’s like using a wetlands garden to clean and polish the water – like the one in Michael Mobbs’ house.” (Mobbs designed the systems for and lives in the Sustainable House, a renovated 19th-century inner-city terrace house in Sydney that has provided for all its own water, sewerage and energy needs since 1996.)

“But space is the perennial problem in urban settings. This backyard had to squeeze in parking, a pool and water recycling, so we started toying with the idea of a vertical wetland, which is essentially what it is,” Gray says.

Randwick City Council applauds the lateral approach: “Apart from its role as a grey water filter, it changes the way we view and use small courtyards, which is particularly important as urban densities increase and private open space decreases. In this case, the vertical garden triples the garden area.”

Kennedy likes the system’s circularity. “The beauty is, apart from black water [from toilets], all water from the site is retained and used on site. The rainwater tanks supply most of the taps where the grey water comes from, so you’re recycling water you got for free.” Now that’s making every drop count!

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Materials

• zero-VOC paints
• timber floors sealed with vegetable-based oils
• minimal use of off-gassing materials
• minimal copper plumbing
• water-efficient shower heads
• pool cover

Landscape

• native plants to reduce the need for watering
• green wall uses bio-systems and plantings to clean grey water

Thermal

• thermal chimneys and skylights for heating rooms
• insulation of internal walls and ceilings
• adjustable external louvres on western face

Power/lighting

• provision for solar power generation
• low-watt lights
• solar hot water and pool heating

GREEN WALL FACTS

Water savings: 75 per cent (minimum) reduction in town water usage, saving 115,000 litres a year.

Size: 6m long x 2.1m high x 3.5m wide.

Cost: AU$20,000, or 5 per cent of renovation budget.

Note: This was a prototype and the science for the system has progressed. ENVDS plans to launch a modular version of the water wall for sale later this year. Environmental engineer Toby Gray says it will be considerably smaller because it uses a new filtering medium of woven polyethylene instead of sand and charcoal.

“It's a more open medium so you can process more water in a much smaller space. We estimate you’ll need a 1m length of water wall, still three tiers, for every bedroom in the house. So a two-bedroom house would need a 2m unit,” he says. Costs are still being determined.

INTERVIEW with architect Steve Kennedy

Q: Was it easy to get builders and plumbers interested in the project?

Kennedy: Builders were interested, if a bit daunted. The plumbers had some difficulty with the ideas. During the project we changed plumbers to one who was committed to sustainability principles – one of the few in Sydney.

Q: Was special plumbing required?

Kennedy: Yes. The house has a three-pipe reticulation system, all in polypropylene pipe with almost no copper – part of the overall sustainability of the house. The additional plumbing added around AU$2000 to the project.

Q: Are special soaps or chemicals required in the system?

Kennedy: No. The occupants use normal soaps and shampoos, however, the less chemicals put into the system, the longer the filter mediums work effectively before needing to be replenished.

Q: Is the rainwater drinkable?

Kennedy: Our analysis suggests it is, but it is not used here for drinking, as both Sydney Water and NSW Health do not support the use of rainwater as potable.

Q: How frequently will the filter materials need replacing?

Kennedy: We anticipate between five and 10 years, but as this is a first we’re not sure. We monitor it regularly.

CLOVELLY HOUSE - AWARDS

2004 Green Buildings Awards Gold Medal

2004 National YBE (Year of the Built Environment) “Best Practice House”

2005 RAIA Environmentally Sustainable Architecture Award

2005 DIPNR (NSW Department of Infrastructure Planning and Natural Resources) leading case study for BASIX

2006 Randwick City Council Urban Design Awards: Alterations and Additions to a Single Dwelling, and Sustainable Development