Solar at the Zero Energy House

Zero Energy House

Solar's contribution to the Zero Energy goal

<p>The average Auckland house uses 7,970 kWh of electricity from the grid each year<sup>1</sup>, with 30% of the electricity used for heating. The Zero Energy House has been designed and built so that its building envelope (framing, insulation, and glazing) eliminates the need for heating, effectively getting its owners, Shay Brazier and Jo Woods, 30% of the way towards their Zero Energy goal.</p>

Although the house relies on the grid for power at night and on overcast winter days, over the course of a year solar energy provides the remaining 70% that a typical house would normally need. A solar water heating system (SHW) contributes 25% by providing almost all of the house’s water heating needs. The last 45% is met by solar photovoltaic (PV) panels, which generate enough electricity to power all of the appliances and lights in the house, and run the hot water cylinder for the remaining water heating needs.

Why go solar?

<p>For Shay and Jo, the choice to go solar was tightly linked with the goals they set at the beginning of their project and with the reasons why they chose to pursue Zero Energy. Building a house like this protects two things they care about:</p>

<p><ol><li><strong>Better for the environment.</strong> Most of New Zealand’s electricity supply comes from hydroelectric power, with a portion coming from coal-powered plants. Coal pollutes the atmosphere and hydroelectric power requires infrastructure that infringes on the natural environment. And, regardless of the source, electricity gets shifted all around the country on a massive transmission grid that costs money to maintain and results in energy loss. Generating electricity via solar on-site is clean, efficient and, as Shay and Jo believe, also elegant.</li>
<li><strong>Better for family finances.</strong> When long-term electricity costs are factored in, solar energy makes financial sense. In 2010, the average Auckland home paid $2,000 a year in electricity bills<sup>2</sup>, equating to $50,000 over a 25-year period. That is without taking into account energy price increases. Since 2000, inflation-adjusted prices have risen by 3% per year<sup>3</sup>. If they continue to do so the average home could face $80,000 in electricity bills over a 25-year period; the Zero Energy House’s solar system cost a fraction of that.</li></ol></p>

Designing for solar

On a typical house the roof is there simply for protection from the elements, but Shay and Jo decided to make the roof of their house work for them. During the design stage, they worked with their architects to integrate the requirements of the solar system into the architecture in order to have an aesthetically pleasing result and optimise the performance of the systems. Together they:

  • Pre-sized the solar systems based on the energy budget created by Shay and Jo to understand how much energy they would use in their new house. 
  • Defined the roof size, shape, and pitch (along with orientation and placement of the entire building) to make sure it could capture the amount of solar energy they needed to achieve the Zero Energy goal.
  • Chose a product that replaced the traditional roofing material with photovoltaic tiles and worked in the Building Consent documents to get it approved.
  • Reiterated the energy model and budget to make sure the final solar design had enough capacity to satisfy the house’s electricity and hot water needs.

What the solar roof looks like

As a result of this process, the entire north-facing side of the roof is covered in energy-generating panels that avoid the need for roof cladding and blend seamlessly with the architecture. Eight solar hot water (SHW) panels are lined up in a row along the ridge-line, and an array of eighty-eight photovoltaic (PV) roof tiles cover the remainder of the roof. Using both systems helps the family meet all of their energy needs.

Design rendering showing the north-facing roof's solar water heating and photovoltaic panels.

For Shay and Jo choosing solar energy for their home was an easy decision, as this technology aligned with their initial project goals and provided the renewable energy they needed to achieve the Zero Energy goal. The couple worked with the design team not only to integrate the solar requirements into the design of the house, but also to optimise the building’s passive performance so that the amount of energy needed was reduced in the first place. The resulting solar system fits perfectly into the roof where it is placed, is elegant and discreet, and, most importantly, performs in a highly efficient way that allows the house to be Zero Energy.

Finished roof showing the ridgeline row of solar water heating panels with the solar array below.
Footnotes
  1. Building Research Association New Zealand (BRANZ). (2006). Energy use in New Zealand households: Report on the year 10 analysis for the household energy end-use project (HEEP). p18.
  2. This is based on the 2010 rate of 25.5c per kWh in, Ministry of Economic Development. (2011). New Zealand energy data file: 2010 calendar year edition. p130-131.
  3. Based on calculations from data in the MED report above. The non-adjusted average annual increase is 7%, as we state in the video.

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