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A two-storey house with timber cladding on a very steep site

It’s not every day that you see a helicopter flying in a digger to a residential building site – but you might not be surprised it happened in Wellington. This was how Karl Wakelin of Wakelin Builders’ started the build of his dream green house in the city’s north suburb Wadestown in February 2016. “No one had been mad enough to build on the site in 25 years, since it was subdivided. You had to walk down 100 stairs to get to the property so of course that’s why we had to drop in the digger to get cracking,” he laughs.

Interestingly, getting the digger in by helicopter wasn’t the hard part, it was carting materials down 100 flights of steps that was the biggest challenge.

“We were lucky to be able to use the neighbour’s driveway and then we only had 50 steps to contend with. I had two workers taking reinforced steel and sheets of plywood down these steps. It was dangerous and hard work, but worth it in the end!” Wakelin and his father built the two-storey three bedroom, 140sqm, passive, low energy house on the 7000sqm site over the next two and a half years, finishing last September.

A two-story sustainable house with timber panelling on a hillside

The house and the story behind its build was so appealing that it featured on Three’s Grand Designs show in October. “My wife Amélie thought we should apply for the show, and then I thought if I can get on and educate the nation about how to build sustainable housing, then it’s worth it.”“ She wrote a very convincing application to the show and a few weeks later I was having a Skype call with the producer.”

The application revealed how Karl was building the house with his Dad, who lives 950km away and that this was the last house he would build before retirement. As well as the helicopter mention of course. Karl and his architect friend Ben Mitchell-Anyon drew up plans for the house based on the German certification standard known as Passive Haus, which essentially results in a very low energy building that requires little energy for heating or cooling.

To conserve as much energy as possible, Karl spent the most in money and time on the building envelope (walls, floor, and windows). The internal timber walls were heavily insulated, with two layers of insulation and an airtightness layer. He built a concrete wall on the southern side of the house where it’s closest to the bank of the hill and insulated with 80mm of rigid foam insulation on the outside to reduce the loss of energy.

Rear view of a two-story sustainable house on a hillside with misty outlook

To improve energy efficiency, Karl installed a heat recovery ventilator which recovers over 90% of the heat in exhaust air and brings in fresh air to the house. This system provides continuous fresh air all year round, all but eliminating the need for additional heating. The window joinery is thermally broken, argon filled and includes a low emissivity coating which limits the solar gain into the house in summer and reduces the amount of heat lost through the glass in winter.

The end result was a comfortable, healthy and energy efficient home for Karl, Amélie and their three year old daughter Claudie. “We’ve been living in the house for five months and it is great! We hardly notice when the temperature drops suddenly in a southerly, and it has been nice and cold through summer. We spend about $60-75 a month on power and I doubt that will go up much in winter.”

Bunnings Account Manager Steve Boyles helped Karl by supplying the core materials and put him in touch with other suppliers. “It was the first time I’ve worked with a green house builder so it was a great experience. A lot of guys are increasing insulation and double glazing windows – but this was a whole other level,” he said.

Karl’s top tips for building a sustainable home:

  • Invest in a good building envelope that will ensure your home is well insulated and airtight
  • Install a heat recovery system for continuous ventilation
  • Beware of putting much glass in your house (especially east and west) – this can heat up the house too much.
  • Use sustainable & local materials where you can.