Let's deal with the difficult bit first.
What is sustainability? Once the preserve of those perceived as "greenies", the term sustainability has become a buzz word particularly well-used by teachers and politicians.
It can mean different things in different contexts, but a useful layman's definition is this: sustainability is putting as much back into the environment as you take out - in other words, meeting the needs of the present without compromising the ability of future generations to meet their needs.
For Tim Bishop, the Sustainable Habitat Challenge - cutely known as SHAC - is all about coming up with innovative ways New Zealanders can live well while being free from reliance on expensive resources.
That means houses which are better insulated, cost less to heat, use the most efficient building methods possible, and are not too expensive to construct.
It is also about collaborations, where teams tap into the expertise of others in this country and overseas and explore what is practical and possible to build today, Mr Bishop says.
"It is fantastic to see people working together already . . . discovering ideas which will work and ones which can't yet.
For example, one team wanted to install a grey water system in their house which would reuse water but found it was too expensive to do today. [However,] they are discovering what it will take to be able to install such a system in the future."
One of the aims of the challenge is to promote business opportunities, as designers worked with New Zealand suppliers and manufacturers to source or make products unavailable in this country as yet.
One team doing just that is Team Waikato, a collaboration between the Waikato Institute of Technology (Wintec), a private businessman and the Hamilton City Council's eco adviser.
It will use two products new to New Zealand in its 60sq m transportable cottage.
The walls will be constructed of panels consisting of soy-based foam sandwiched between sheets of plywood, while the exterior cladding will be Australian-made weatherboards manufactured from waste eucalyptus bark.
The businessman behind the panels has been trying to introduce the system to New Zealand for many years, lead designer Rod Yeoman says.
The panels, which would use plywood made of New Zealand pine, were lighter, stiffer, had much better insulation qualities and were much quicker to put together than a traditional timber-framed house.
But because the system is untested in this country, no building code is available and it had proved time-consuming to obtain consent to use it.
"It's been a really interesting roller-coaster ride.
Because of the multilayered approach we have adopted for construction, institutions and local authorities have found the consent process complicated.
It has been hard to make the project real, even if the engineers say the design makes sense."
But now the difficulties are ironed out, Mr Yeoman says.
The house is all set to be built next year by Wintec trades students, either under cover in the polytechnic's huge warehouse facility, or possibly as a "quick build" during the two-day Hamilton home show.
Mr Yeoman says the time and energy which has gone into obtaining consent for the panels will assist the businessman, who hopes to begin manufacturing the panels commercially for the New Zealand market, and manufacture the Team Waikato cottage for sale as a sleep-out or granny flat.
The Auckland-based zero.plus team is also looking internationally to complete its project, New Zealand's first zero-energy, or passive, house.
While most of the team members are staff or students at the University of Auckland, the team is also working with urban sustainability experts from the Technische Universitat Berlin, Germany, the Institut fur Architektur und Raumentwicklung Hochschule, Liechtenstein, and the Politecnico di Milano, Italy.
A passive house is one in which the indoor temperatures remain above the World Health Organisation (WHO) recommended minimum of 18degC year round, without active heating or cooling systems.
Research shows only 50% of New Zealand houses reach temperatures above that level in winter, with the temperature in an estimated 30% of homes dropping below the WHO recommended minimum temperature of 16degC.
Another team is sticking much closer to home with its project.
Whareuku, which involves students and staff from the University of Auckland, Maori landowners and a private builder, is using rammed earth as the main construction method for its two-bedroom house.
Whareuku is the only team which has already completed its project, building its house on Maori land on the banks of Lake Rotoiti, near Rotorua.
The walls have been made from locally sourced materials - 90% soil, 2% dried flax fibre and 8% cement - which is inserted between timber struts.
Project spokeswoman Gabrielle Chin says a major advantage of the system is its simplicity, enabling houses to be built by homeowners with minimal professional assistance.
Many people had worked on the Whareuku house and shared a collective ownership and pride in the building.
"During construction, many locals have approached the team, inquiring about the house.
Educating the community through pamphlet drops and presentations has [also] been discussed."
Earth is an under-appreciated and under-utilised building material, Ms Chin says.
"Earth is readily available, as cheap if not cheaper than most other materials, and has better thermal qualities than a conventional house, so it is warmer in winter and cooler in summer.
Some of the other projects are equally as interesting.
The Bach 101 team plans to use only recycled materials to renovate and extend a historic holiday home on Rangitoto Island, and also plans to install new water and sewerage systems for the house.
The Plant Room team plans to add "clip-on" rooms to the exterior of an existing Wellington high-rise building.
As well as providing additional living spaces, the rooms will collect rainwater, which will be used to nourish gardens.
Team Housewise is designing an insulation upgrade package for 1950s state houses, plus a software package giving tenants tips on more sustainable living.
Team Dunedin, led by Otago Polytechnic staff, plans to create the most efficient transportable house it can, using cost-effective, sustainable and environmentally friendly products readily accessible in Otago.
Much planning work has gone in already, polytechnic executive projects co-ordinator D'Arcy Dalzell says.
University energy studies student Maria Callau and Dunedin City Council energy manager Neville Auton have provided advice and assistance on the house's energy needs, while others have recommended and sourced construction materials.
These include "thermally broken" double-glazed windows, where plastic spacers are used to ensure there is no connection between the two aluminium frames, thus stopping heat transfer through the glass, and room sensors which automatically turn lights off when no movement is detected.
The house will be built by trades students next year and auctioned for charity.
Judge Dave Cull is impressed by the projects and the variety of construction methods being attempted.
"Reading about their ideas has been absolutely fascinating. The range of ideas is extraordinary.
"They are not just building new whizz-bang houses but doing things like using entirely recycled materials."
He describes sustainable housing as "future-proofing" - building the best house possible to ensure a long-lasting product.
"There is much more awareness of sustainable housing now. I think awareness has been growing over the past decade or so.
"The leaky home saga was about people wanting more bang for their buck and going for bigger rooms at the expense of things like eaves, which we know now are very efficient at keeping the water out.
"Now we are getting back to incorporating better design and perhaps a little more cost up front to ensure a better life-cycle costing."
Mr Cull says he has not yet been told how the judging will be carried out or whether it will require visits to each of the home sites, but says he is looking forward to the judging process.
"It will be difficult. How do you choose a winner when the projects are all so different? But I am sure it will be great fun."
Mr Bishop says while the challenge - New Zealand's first - is officially a competition, only small prizes will be awarded.
"The ultimate aim is to generate publicity about the projects and to raise awareness of the many possibilities which already exist for more sustainable housing."
The Sustainable Habitat Challenge '09
What?
A competition sponsored by the Ministry for the Environment for which teams design, develop and build sustainable, low carbon and environmentally-friendly housing in their own communities.
Why?
To get people thinking about sustainable housing, and to encourage collaboration between architects, researchers, product designers and tradespeople.
Who?
Otago Polytechnic won the bid to organise the competition. The national co-ordinator is Tim Bishop.
How many?
Ten teams have entered design and construction projects for the 2009 event.
When?
Entries will be judged in October 2009.
Who are the judges?
Robert Vale (sustainable housing researcher, Victoria University), Nick Collins (general manager for sustainable housing consultancy Beacons Pathway), Maggie Lawton (owner of Braidwood Research and Consulting), Dave Cull (self-employed building contractor, television presenter and Dunedin city councillor), Nigel Isaacs (energy researcher, Building Research Association of New Zealand).
