Trends magazine article

12 February 2007

Energetic design from New Home Trends volume 2006

With recurring energy shortages in New Zealand over the last few years, saving energy in the home has become a popular topic.

While there is ongoing debate about how best to meet the country’s increasing demand for electricity, there are things you can do to reduce your electricity use, without compromising your lifestyle. You’ll also be mitigating the effects of climate change by reducing greenhouse gas emissions.

Using energy efficiently does not mean restricting yourself to short showers or shivering through winter. Through good design and the thoughtful selection of building materials and appliances, you’ll be able to heat your home during winter, cool it in the summer and have hot showers without wasting energy.

So how does this work? From the very beginning of your building project, talk energy efficiency with your architect. There’s a lot that can be achieved early on.

When selecting a site, choose a north-facing position to maximise solar energy, says Robert Tromop of the Energy Efficiency Conservation Authority.

“The sun is the most powerful source of energy we have, and it’s free to use,” he says. “By orienting your glazing to the sun, you will passively heat your home. This means you won’t need to use other forms of heating as often, or as long.”

Thoughtful selection of construction materials will provide significant energy savings. Any extra expenditure now, will be recouped over time.

Concrete is one such material. It has a high thermal mass, which means it absorbs and retains heat. As the day cools, it slowly releases the heat back into the air.

A concrete slab foundation is a good starting point, and a concrete or brick wall on the sunny side of the house will operate like a night store heater, warming your home after the sun has gone down.

You will need to insulate your concrete walls though. There are several options to choose from, a polystyrene layer over the wall, concrete filled polystyrene building blocks, or a polystyrene biscuit fitted inside the concrete block, says Tromop.

“Choose either a masonry or hard plaster finish on the wall to make the most of the energy efficient properties of the concrete,” he says.
Concrete also works well in the summer, absorbing heat to keep your home cool.
When building with wood, you should use plenty of insulation. The building code specifies the minimum amount of insulation required, however you should definitely use a higher level of insulation than the minimum, says Hamish Handley of the Building Industry Authority.

“A well insulated home is warmer, drier and cheaper to heat and cool,” he says.
The optimum amount of insulation to use for your region is set out in Better Best Standard, produced by Standards New Zealand. Ask your architect to refer to it when specifying insulation for your new home.
Another insulator to consider is double glazing. Currently 70% of new homes in the South Island are double glazed, says Handley. The warmer climate in the North Island leads many people to believe double glazing is unnecessary.

In Auckland, for example, double glazing provides the same amount of energy retention as regular glass with curtains. However, if you were to install double glazing, you immediately negate the need to close your curtains in the evening.
“It’s a great idea for homes that overlook the harbour, or the city. You can enjoy the view without wasting any energy,” says Handley.
“For those in the very cold regions of the country, triple glazing is a sensible option to maximise heat retention,” he says.
Sunshine and good insulation aside, you do still need to consider heating your home when it gets very cold.
Your options include heat pumps and highly efficient gas flued heaters.

Up to 300% efficient, a heat pump will produce up to three units of heating or cooling for each unit of energy used.
Using gas as an alternative energy fuel should also be considered, given it’s efficiency and cost effectiveness, says Stacey Tibbetts, gas distribution channel manager at Vector, the country’s largest multi-utility network owner.

“Gas is three times more efficient than electricity when used as a direct fuel,” says Tibbetts. “When gas is used to generate electricity, three times more gas is required to boil a kettle than when gas is used directly,” she explains.
Most parts of the North Island have natural gas pipes in the street, making it easy to connect. For those who don’t live in the network area, LPG can be considered as an alternative.

“Another advantage of gas is the wide range of heating options available. You can choose a flame effect fire for ambience, portable heaters for convenience, or ducted gas heating to warm your entire home,” says Tibbetts.
For most homes that use electricity as their sole energy source, heating and maintaining a hot water supply is the largest component of their electricity bill.

In addition to cost-effectiveness, a gas continuous hot water system only heats the water you use. This means there’s no need to heat a whole tank of water, and unlike a hot water cylinder, the hot water never runs out.
You don’t have to compromise the standard of living you enjoy in a bid to save power. By making energy-wise decisions when designing and building, your new home will cost less to run, while providing all the warmth, comfort and hot water you need.

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