Sustainability built in

By Andy Kenworthy

Photo: Ted BaghurstThe solar array on the roof of this home in Kupe Street, Orakei is expected to produce around $775 worth of electricity per year and has a 7 Star Homestar rating.
Photo: Ted BaghurstThe solar array on the roof of this home in Kupe Street, Orakei is expected to produce around $775 worth of electricity per year and has a 7 Star Homestar rating.

Architecture & design: The new home of Stu Selby, Erika Whittome and their baby daughter Rosanna is a great example. It was completed in February on a tight, 350-square-meter section in Orakei, Auckland, after a six-month build. Its compact three-bedroom, two-story layout was designed by architect Frans Kamermans and constructed by Harris Built Ltd, and is packed with a combination of clever design thinking and cutting edge technology.

First and foremost, the home applies 'passive solar' design to make the most of available sunlight for free heat and light. It has large windows orientated north, with eaves that allow in winter sunlight but restrict the summer sun to avoid overheating. There is a tiled concrete floor on the ground floor and an insulated block wall, both of which absorb heat during the day to radiate that warmth back through the extremely well-insulated interior of the home as outside temperatures fall. This is augmented with underfloor heating, running from a high-efficiency heat pump, and low energy LED lighting.

The mains electricity supply is supplemented with $14,000 worth of electricity-producing photovoltaic solar panels on the roof. A smart meter even allows the family to sell additional power back to the grid when the panels are producing more than they need, contributing to a projected pay-back time on the system of just seven years.

Hot water is provided by another heat pump, and rainwater is collected from the roof and stored in a tank under the deck, to be used in the toilets, garden, and washing machine.

Around the rest of the home every other detail of sustainable living has been considered. The carpets are pure wool, the wood used is all sourced from certified sustainable sources, the taps are all low flow to reduce water use and the washing line is outside under cover, to reduce damp in the home and let the sunshine do the work of a drier. A worm farm was even been installed in the garden.

Stu said the finished home is the result of two years of inspiration and investigation, followed by a six-month planning process prior to the build. "We wanted to be as sustainable as we could," he said. "There needs to be a big push to build smarter, more energy efficient homes that you can heat more effectively."

The success of the design has earned it seven out of ten stars under the Homestar home performance rating scheme - when an average home in New Zealand would gain a maximum of five. Homestar is a joint venture partnership between BRANZ and the New Zealand Green Building Council. It also has the Ministry of Business, Innovation and Employment, the energy Efficiency and Conservation Authority and many of the big players in the building and home design industries on board. As well as guidelines on materials and design, the Homestar scheme promotes recycling during the build.

Stu says: "Going through the Homestar rating provided a focus. It wasn't hard in terms of cost, but you have got to collate all the evidence, and keep all your documents and receipts."

The build cost came to around $3,500 per square metre, putting it at the top end of a conventional home build. However, the financial pay-off comes in electricity bills of just $60 a month, and the knowledge that the home should hold its value because of the quality of the materials and the increasing popularity of homes with sustainability built in.

"I love the place, and ten years down the track it is still going to look attractive, we are going to have paid off our investments and our energy consumption is going to be really low."

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Built in
The insulation in this home is Pink Batts with ceilings rated R5. All remaining external/internal walls and mid floor are R2.6.

Solarcity installed the 2.3kWp array of solar panels. It is expected to generate in a typical year 3100kWh/a, with a retail value of around $775, where no more than 150kWh are exported to the national grid per month.

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