Sustainable Foundations in Shotover, New Zealand

Posted October 4, 2023

Location: 74 Risinghurst Terrace, Shotover Country, Queenstown

Builder:  Evolution – division of Rilean Construction

Client: Annabelle and Gen Numaguchi

The Brief

Our goal was to build a home that was warm, sustainable, and of course, affordable. We immigrated to Queenstown from Utah, USA with our two children in 2010, so while we were accustomed to feeling cold outside, we were not used to cold houses inside. We were determined to build a home with centralised heating that could easily maintain a constant, comfortable temperature whilst being sustainable and energy-efficient (under 50kwh/m2/a). On a fixed budget of $400,000 for all build costs, we had to make the most of what was available to avoid ridiculous power bills during colder months. 

We initially wanted to buy an Evolution home that was on the market but unfortunately missed out. Because of this, we decided to build the same floor plan with the same company, Rilean Construction. Being able to visit the other Evolution homes and visualise the space with our possessions was a real game-changer. Having the opportunity to ask about the concept plan’s performance made the process a lot easier. I (Annabelle Numaguchi) was so excited that a company was committed to building energy-efficient homes, that I joined the company as Marketing Manager!

The Challenges 

Because we used pre-existing plans and completed research into energy efficiency, including using the NZGBC Homestar rating tool to guide us we thankfully didn’t face any challenges. Evolution and MAXRaft® were perfect for this project and definitely made things smooth for us. 

The Results

Evolution used a holistic system to create a thermal envelope and MAXRaft® was chosen as the insulation for the foundation. The installation took barely a week. The Evolution team was used to installing MAXRaft® as it’s their first pick, which made installation a breeze. The polystyrene and steel was laid out within a week, and then the concrete poured within a day. Perimeter edge insulation is one way of combating thermal bridging and losing precious heat to the outside in winter, and if I’m correct, MAXRaft® was the first system in New Zealand that included this.

We ended up on a centralised ducted heat pump to heat the home when necessary. We have timber-engineered flooring made by Haro in the living areas and often guests think we have underfloor heating!  This is simply an effect of the solar gain being radiated back into the home at the end of the day.

Life After Construction

We ended up with exactly what we wanted. It’s a very comfortable home, year-round. It also earned a 6 Homestar built rating.  The home takes care of us without us having to do much to take care of it. The internal temperature doesn’t fluctuate much, always hovering around 20-degrees celsius. This was achieved by creating a complete, high-performing thermal envelope – of which MAXRaft® was an integral element. The 100mm of concrete slab insulation and perimeter insulation benefits the home by keeping ground moisture out and retaining thermal gains achieved in the winter. In other words, the sun heats the floor during the day and that warmth is radiated back into the house at night.

We have a laser thermometer that we use regularly around the house, mostly to record temperature differences at junctures like wall-to-ceiling or wall-to-floor. The exterior edge of our floor is never more than 2-degrees lower than the rest of the home. That difference is really important because mould and moisture damage occur as warm air moves to cold and the water held in that warm air starts to condense. Cold spots in the house can lead to these serious problems that harm your health and the integrity of the home. Our floor has performed consistently well over the past four years, with no cold areas around the wall-to-floor perimeter. We’re very grateful for finding MAXRaft® and look forward to living here for years to come.


  • Proclima Intello and Solitex Extasana (vapour check membranes)
  • Haro flooring
  • Knauff Earthwool insulation

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