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The interior of this house has a Scandinavian feel but the bush-clad setting is quintessential New Zealand. Kim Dungey reports.

The owners of this house were initially looking for a section that was on the flat and away from sea breezes.

They ended up on a precipitous site overlooking Otago Harbour.

Mattias Salomonsson and Annika Bokor say they instantly fell in love with the plot, despite it ticking none of their boxes.

Its position in a bay meant it was protected from southerlies, there was plenty of bush in which their two boys could run around and the view was "awesome": "You feel like you’re in the middle of nowhere, but you’re still only 10 minutes from town."

Located in St Leonards, the certified passive house provides a large amount of amenity space on a challenging section. Despite its appearance from the road, it is actually two storeys with the entry, main living area and master bedroom on the upper floor, and a family room and three further bedrooms on the lower level.

Always having been keen to build a warm, energy-efficient home, the couple looked at various concepts and even came across a "house within a glasshouse" in their native Sweden. However, their desire for minimal energy costs and a healthy, comfortable interior eventually led to them to passive houses. The voluntary standard has tools that can accurately model how a building will perform, even before construction has started.

Temperatures in Sweden drop as low as -30degC but once the houses are warmed up, the heat stays inside, Mr Salomonsson says. They had never heard of electric blankets or hot water bottles until moving to New Zealand in the early 2000s.

"It was definitely a shock realising that people here just heat up the living room they’re in and keep the doors closed to everything else and it’s only 12 degrees in the bedrooms."

Their 220sq m home was the first timber-framed, foam-free passive house designed by Architype Ltd and the reason structural insulated panels were not used is surprising.

"It’s because of me," Dr Bokor says, laughing. "I wanted thicker walls so we could have deep window sills and put decor and plants on them."

The exterior walls are 235mm, which is made up of 190mm of wall and a 45mm service cavity on the inside, and insulation is well above the minimum in the building code. Triple glazing was imported from Germany. Solar panels enable them to be off grid in summer and provide 30% of their total energy usage in the height of winter, which includes charging their electric vehicle every second day.

If there has been no sun during the day, a couple of freestanding panel heaters go on for short bursts during the night downstairs. But in June it cost only $100 to keep the entire house around 20degC, run appliances and charge their electric car.

"It’s nice having a uniform warmth," Mr Salomonsson says. "You don’t walk into a room and feel it’s cold or you don’t walk close to a window and feel a draught."

The building is more or less airtight, so a ventilation system ensures a constant supply of fresh air. Up to 95% of the heat from the extracted air is transferred to the fresh air supply, saving energy.

Energy efficiency, however, was only one part of the detailed brief presented to the architects.

The couple had already chosen colours, fixtures and fittings and Mr Salomonsson had even drawn up a concept for the house using a CAD programme.

Designed as their "forever home", it is wheelchair accessible, has a separate area for their sons to "grow into" and features they were used to back home, including a dedicated laundry room.

"Something that’s really common in Sweden is having a fully glazed conservatory out on your deck, which was a hard concept to get past everyone ... Another thing we wanted, which is a Swedish thing, is a cloakroom next to the entry."

Despite the cost, the wraparound deck was another must-have and not just to take in the views.

"There’s a 10m drop from one corner of the house down to the ground, so [without it] it would have been very hard to wash the windows or even clean out the guttering."

Given the height from the ground, the exterior was also designed to be low maintenance. The window frames are uPVC, rather than timber, with aluminium clip-on strips on the outside to protect the plastic from ultraviolet light. The corrugated iron cladding will not have to be scaffolded and repainted every few years; it is also lightweight so particularly suited to a house on poles.

Passive houses are more expensive to build than conventional homes, but their budget was modest, says Dr Bokor, a professional practice fellow in the biochemistry department at the University of Otago.

The rectangular shape is the easiest, cheapest option when building, and energy efficient because it minimises the number of corners that can leak air.

The two big-ticket components were the triple glazing, which was 10%-15% of the total costs, and the ventilation system. Many of the other items, including lights, were bought on sale. She made curtains and comforters. Mr Salomonsson — an infrastructure architect at Port Otago — programmed the home automation system himself and drove to Christchurch with a trailer to pick up a free comms rack.

"Smart homes can be something as trivial as remote controlling an appliance using an app on your phone, but we’ve gone down the route of automation — the house should know what we want it to do and do it automatically for us without us needing to push any buttons or use any apps," he explains.

"There’s a hub that controls the whole house and various sensors in all the rooms."

This means, for example, that the motorised blinds will drop when a certain temperature is reached and the sun is in a particular position, then retract when the sun’s angle changes. Lights dim and change colour as night approaches, signalling to the brain that it is time to unwind. The system even controls the lights, heater and pump in son Max’s fish tank, lets them know when it is time to empty the dishwasher and plays one of six humorous messages when someone rings the front door bell.

Good planning made the project stress-free but their "‘extraordinary" builder, Wayne Dyet, also played a part, Mr Salomonsson says.

"He’s very detail-orientated and he puts that down to having been an air force engineer, where everything comes down to parts of millimetres."

Nine months after moving in, the couple are delighted to have a home designed specifically for them.

"Taking in breathtaking views while having breakfast, or listening to the native birds chirping while we’re lounging on the deck, is very relaxing and peaceful," they say. "We enjoy the quiet area and our friendly neighbours and we love living in the treetops whilst still being so close to the city."