Green is the colour

…of the future. Here are some ideas we think those looking to build should consider

FOR YEARS NEW Zealanders, who seem born with the she’ll be right attitude to pull on an extra jumper when the weather turns chill, have put up with living at less-than-ideal temperatures. But times they are a-changing and the decision to build sustainably is no longer about energy prices, but about being responsible about the planet’s finite resources.

At David Reid Homes, we think our little corner of Earth is pretty damn fine – and we’d rather not imagine a time when melting ice floes, burning forests and general meteorological mayhem gets the better of Godzone. So, in our houses, we advocate for sustainable choices that put energy efficiency in the spotlight. When building, the 10 ideas overleaf will ensure more in-moment comfort and an ever-hopeful horizon. F

LEFT Orient the house plan for optimum solar gain and that’s half the energy-efficiency battle won.

1. Best face forward

Design for the correct orientation to the sun to ensure optimum solar gain and the battle is half won. Simple fact. No explanation needed.

2. Energy returns

By all means go solar now (Lorde would approve) but don’t expect payback anytime soon, says David Reid Homes franchisee Chris Leith. A $25,000 solar system helps offset energy bills and ticks the sustainability box, but you won’t recoup costs within five years. Eventually the batteries will need to be replaced but the technology is always advancing. One way or another, solar is set to be a bigger part of all our tomorrows.

3. Pump up the volume

If you don’t invest in superior insulation, you’ll pay the price – forever. The message here is: aim higher than the stipulations of the NZ Building Code. It’s not a goldstandard benchmark. In the US, says David Reid Homes franchisee Fraser Mackenzie, 90 per cent of homes use a rigid air barrier of plywood or chipboard beneath the cladding. This not only gives the building more bracing (against earthquakes or landslides) but it stops draughts. Use this, mask all the joins and seal around it, and you’re away laughing. Also, maximise the volume of all batts, particularly on exterior walls. “We use thicker 140mm framing compared to the traditional 90mm which means we can put the thicker ceiling batts into the walls,” says Fraser. The R Value (a measure to indicate a material’s ability to resist the transfer of heat) is R3.2 to 3.6, which is significantly higher than code at R2.6 to 2.8. More insulation makes it easier to keep heat in for the winter months and to keep hot air out in summer.

ABOVE Solar-energy technologies are ever advancing and a clear part of a sustainable strategy, but it’s a long-term planet-friendly commitment as it takes many years to recoup the costs of the system purchase.

4. Horses for courses

The Building Research Association of New Zealand divides our long, skinny land into three climate zones which it uses to set the thermal-performance requirements of the Building Code. Fraser MacKenzie advises that, whichever zone you live in, code is not enough. For energy efficiency, build in more insulation and better heating systems. Heatpumps cut it in much of the North Island, but in places like Central Otago, sub-zero temperatures mean they can struggle to work, with units freezing and fans blowing up. He advises a central-heating system that combines in-slab heat and radiators. These can be run on gas (expensive, as it comes from the North Island) or diesel. “While the slab heating warms up slowly and keeps you snug from the bottom up, diesel radiators give really quick heat.”

5. See the wood, and the trees

Clients with an eye on sustainability may prefer cladding that goes the extra mile – or doesn’t, for that matter. “Importing eucalyptus from Australia is far shorter haul than cedar from North America,” points out Chris Leith, “a smaller carbon footprint.” Although cedar is favoured, it’s not planet-friendly and its cost per lineal metre has tripled in the past six years. The eco-conscious should also factor in the maintenance aspects of timber cladding. Cedar needs to be oiled every three to six years, unless you like the weathered look. And, while engineered timbers such as Abodo Vulcan cladding (made from pine) appear more sustainable and are locally sourced, how it’s produced might take a lot of energy. “You need to consider the product’s life from cradle to grave.” F

BELOW Concrete floors act as a solar sink but can also incorporate sub-floor heating systems and, while heatpumps get top marks for energy efficiency in North Island climes, some may fail in the sub-zero temperatures down south.

6. Plan for the planet

When planning your dream home, install an electric socket or two in the garage or carport for charging the car. Standard AC sockets take 8-10 hours to fully charge so if you want to cater for a fast-charge DC option, you’ll need higher-rated circuits and connections.

7. As rare as air?

Homeowners often forget about ventilation but airflow circulation, with clean, fresh air coming in and stale, damp air going out, reduces moisture. A damp home is more difficult and costly to heat. While there are good mechanical systems that operate heat-exchange technologies, don’t forget the basics. Windows with double-tongue latches for venting are an easy fix and louvres provide cross-ventilation. While extractor fans in bathrooms and laundries, and rangehood fans in kitchens, are part of the building code, opening a window makes all the difference to air quality, and can prevent mould.

8. Foundation station

Fraser Mackenzie operates the David Reid Homes franchise in Queenstown and has seen the results of houses without the correct foundation: weeping windows and shivering owners. In alpine areas, he’d opt for a fully insulated, thermally broken Maxraft slab system as a foundation any day of the week. A reinforced concrete slab with polystyrene insulation underneath it, including around the perimeter, is an efficient thermal break between floor and ground. It’s the perfect solid base for concrete floors, which act as a heat sink to capture the sun’s warmth and slowly release it. “I remember the days when they used silver paper as underfloor insulation – 25 years ago. No wonder I was so cold!” says Fraser.

ABOVE Any new-build will benefit from a fast-charge DC electrical socket in the garage or carport to charge the EV.

9. H2Go with the flow

Water is precious and efficient tapware, shower fixtures and loos are better for the Earth, and the monthly bill. When choosing plumbing fixtures, don’t just amp for aesthetics, think about money down the drain. “Look for a good WELS [water efficiency labelling scheme] star rating,” advises Tim Sunderland of David Reid Homes Wellington and Kapiti. In showers, the highest WELS rating achievable is 3 stars. It likely means the showerhead has a built-in flow limiter. Apart from putting an egg timer in the shower to cut down on time spent (thinking teenagers), it’s the only way to reduce water use. It reduces flow, not pressure. “Don’t worry, you’ll still be able to have an enjoyable shower,” says Tim. With loos, target dual flush – a 4-star WELS rating means the average flush will use no more than 3.5 litres (when compared with more than 6 litres for toilets with no star rating at all). Finally, when it comes heating water, consider your situation. If it’s a holiday home that gets used by a lot of people, infrequently, over a short period of time, instantaneous gas heating will be better (no waiting for the hot water cylinder to heat up) but in a busy household, the gold star for water heating is a system driven by an electric heatpump. “Since it takes warmth from the air, you get more bang for your buck,” says Tim, “although the units do commonly need to be installed outside.” To make a gas instantaneous heater even more efficient, use an electronic controller to heat the water to just the temperature you need for a shower.

BELOW Install flow limiters on taps to save water. RIGHT Instantaneous gas water heating may be better for a holiday home but a hot-water system driven by an electric heatpump is a prime everyday option.

10. An invisible sandwich

Although the building code stipulates double-glazing as an energy-efficient baseline, at David Reid Homes we like to take this up a notch. Windows account for 10% of heat lost in a home so opting for higher spec makes a real difference. Argon gas (it’s inert, don’t worry) between the panes works because it is denser than air and thus slows the transfer of heat. Think of it like an invisible blanket. Low-emissivity glass effectively has an invisible coating which reflects heat back into the room instead of escaping, and heat out into space when the sun is beating down on your windows. Finally, if you are choosing aluminium joinery, opt for a product with a thermal break. No, that’s not a holiday in the islands, it means a nylon barrier has been sandwiched between the frames to keep warm and cold areas separated. P