Walk into Matt and Julie's rural Wairarapa home and the first thing you notice is the sense of space and light.

Its design uses natural colours, recycled swamp totara and macrocarpa detailing, and rock features to create a visual connection to Wairarapa's rugged topography, which can be seen through large windows from most areas of the house. While other homes have indoor-outdoor flow, in Matt and Julie's it's almost as if the landscape has been brought inside.

"Visitors tend to feel instantly comfortable here," says Julie. "Children really enjoy being able to run around while still be a part of what's going on. They react to the variety of textures and colours, and especially like the rocks."

The home is 2 and half storeys tall, the 'half'; being a turret that adds character and provides 360-degree views and an additional living area to relax in. At 186 square metres, with three bedrooms and two bathrooms, it is a moderately sized family home.

Apart from living areas and the kitchen, Julie and Matt have a bathroom and bedroom on the ground floor as they wanted the house to be accessible for people with limited mobility and to build adaptability into the design. The ground floor bedroom doubles as a library and accessible guest room.

Warmth and comfort

While the home's feeling of space and harmony with its surroundings is its most noticeable feature, it is also designed to for energy efficient heating and cooling.

They used an architect who was experienced at building energy efficient homes. "He was very enthusiastic about the project," says Julie. "A lot of his designs are based around passive solar using orientation and window placement to get as much sun usefully into the house as possible."

Though the home has extensive views, the main glazing - including windows and glazed doors from the living area ‑ faces north to make best use of the sun. To maximise heat gain, the living area is on an east-west axis.

Eaves and windows are designed to let the sun in during winter but provide shading in summer.

Insulation

Matt and Julie originally wanted a straw bale house, but they realised that, given the wet and windy climate, straw bales weren't suitable for the north-facing wall. Instead they built a timber-framed house, clad in pre-painted steel, with a single straw bale wall on the south side. This wall gives additional insulation, particularly in winter when the southerly blows. Using this area as their pantry means food is kept at a nice constant temperature and vegetables stay fresher for longer.

On the other three walls, Julie says: "We used at least double the insulation that the Building Code requires. Everything - the walls, ceilings, floor, and between floors and internal walls ‑ is insulated."

Heating and cooling with thermal mass

Julie and Matt's home is built on an insulated concrete pad. In the north-facing living areas, porcelain floor tiles help the slab to catch and absorb solar energy, which then radiates into the home when the temperature drops.

Rocks in a wrought iron cage beneath a north-facing windowseat add to thermal mass. Rocks around the woodburner heat up when it's in use and continue to radiate heat well into the next day.

A rock feature wall inside the main entrance wasn't placed for sun, but provides summer cooling by absorbing heat from the surrounding air.

Ventilation

To allow air to circulate and heat to travel to the upstairs area, Matt and Julie incorporated vents at the top of the downstairs walls. These can be opened to allow heat to the upstairs bedrooms.

Supplementary heating, cooling and insulation

The only active space heating is from a woodburner. They currently have a low-cost source of firewood and have planted trees to burn in the future.

Water heating

Matt and Julie's house has a solar hot water system under the roof. The system's 4.8 square metres of panels feeds a 300-litre hot water cylinder. Although two people live in the house most of the time, they regularly have visitors and the system is designed for a six-person household.

Solar energy meets all of the household's water heating needs for nine months of the year. For the other three months, supplementary heating is provided by a wetback connected to the woodburner, and by an electric booster.

"The booster can be set to operate automatically but we tend to manage it manually so we can reduce how often we use it," Says Julie.

Having solar water heating has changed the way Matt and Julie manage their water. Julie says they're much more conscious of when to turn on the hot tap. A temperature controller lets them know how much hot water they have.

Julie has estimated that 75-80% of the household's annual water heating needs are met through solar energy.

Energy efficient lighting

As well as using passive solar design to maximise natural light, Julie and Matt use compact fluorescent light bulbs in all areas except where light is only on for short periods.

Water and wastewater

Living in a rural setting means Julie and Matt had to opt for water-saving features and an on-site sewage system.

They collect rainwater for household use in a 31,000-litre tank. They chose pre-painted steel roof cladding because it is safe for water collection. They treat their water with chlorine after testing for micro-organisms, and also use an under-bench water filter for drinking water. "I think it's a myth that rainwater doesn't need treating," says Julie. "It's as simple as adding a cup or two of bleach to the tank every four to six weeks.

To keep water use down, they have low-flow fittings on their taps and showerheads and low-water toilets. Being conscious of water use and conserving hot water means they haven't run out of water since they started living on the property four years ago.

Sewage is treated on-site with a multi-chamber treatment system which discharges wastewater into a soakage field in a grove of kanuka on their six hectare property. An engineer's report helped them decide on the site for the soakage area.

Choice of materials

While Julie and Matt's choices of interior materials played a vital role in the ambience of their home, it also served another purpose: ensuring the air was healthy to breathe.

“We were determined to keep toxicity levels as low as possible," says Julie. Natural paints were used in the bedrooms and living areas, and water-based enamel was used in wet areas such as the kitchen. Natural oils were also used extensively and have proven very durable. The macrocarpa floor was sealed with a Swedish one-pot water-based epoxy - Julie explains that it was chosen because it added durability but did not contain isocyanates (which cause respiratory and skin conditions).

Hemp curtains and wooden blinds have been used on windows.

"Even in the middle of summer, while we were painting and oiling, there were no fumes," says Julie.

The design and construction process

Julie and Matt began planning their home in 2002, building a sleep-out first so they could test out the concepts before building the main house. This was particularly important for testing straw bale in the local climate. The sleep-out now doubles as accommodation for visitors and a workspace as both Matt and Julie work from home.

Building the sleep-out first also allowed them to live on-site while the main house was being built. This enabled them to keep an eye on the building process ‑ their experience with tradespeople was very positive. "Everyone really got on board and saw it as a new challenge."

They wrote into their contract with the builder that they wanted to keep on-site waste to a minimum, and returned unused materials to suppliers. This led to cost savings. Local building firms combined excellent workmanship with an understanding of local conditions to translate the design into reality.

Costs and benefits

Julie says that the house didn't cost as much as people might expect. "It was more than a kitset house but no more than the average house in this area. We had a budget, and stuck to it. We saved in some areas and spent more in others. People often think that because it looks a bit different, it must have cost a lot more to build but that's not true."

She say the upfront costs of additional insulation, double glazing and solar water heating are balanced by ongoing cost savings. Power bills for 2005 averaged $75 a month. Matt and Julie's overall electricity usage was around 2400kWh in 2005, the average New Zealand household uses about 6700kWh.

Was it worth it? "Absolutely!" says Julie, "we wanted the house to be energy efficient to see how we could use building design to cut down our cost of living. It was really interesting working through the whole design process. Doing a few things differently at the beginning meant we got some really big benefits… It's an incredibly easy place to live in."