Homes need the right ingredients to withstand cold New Zealand winters, discovers Joanna Mathers.
Power bills over the colder months reflect this — it’s not uncommon for households to be paying $300-plus a month in electricity costs.
Insulation and heat pumps do some good, but don’t address the problems caused by cold air coming through cracks in the window frames and under doors.
For homes to be truly energy efficient they need to be designed accordingly.
Natalia Harrington from Hybrid Homes (who specialises in energy-efficient eco homes) likens good design to cooking.
She says that the ingredients need to be right if you are to strike the perfect balance.
“Too much of one thing and not enough of the other can spoil the end result. Preparation is key — so orientation and design are at the top of the list,” she says.
She says that a correctly oriented house will let sun in during the winter, and keep it out in the summer — this way you will at least use nature’s free resource.
Long hallways and open spaces can be problematic; she encourages people to opt for quality rather than quantity when it comes to space.
“Thereafter you can layer it with building product choices that will meet your budget and end goal of how far you would like to take your energy efficient home.”
Darren Jessop from Jessop Architects agrees that for a home to be energy efficient, it needs to be designed as such.
Older homes. while character-filled and charming, can never be truly energy efficient
“There are between 17 and 22 air changes an hour in an old building,” he explains.
“You can bring the houses up to a relatively comfortable state, but you can never make an old house truly energy efficient.”
Jessop Architects are responsible for the design and project management of the first house to be certified “passive” in Australasia.
It’s a house that can heat and cool itself without any other devices —representing an extremely low level of energy consumption.
Jessop also developed a range of energy efficient homes called Cool Houses — these are modular homes that use passive house innovations and sustainable technology to create homes that are extremely kind to the environment.
He says that air tight homes are becoming more popular In New Zealand and represent the highest level of efficiency.
Very common in Europe where temperatures regularly drop below freezing, air tight homes are created through sealing of any gaps and the use of HRV systems to reticulate the air.
The upshot of this is a regular temperature and a huge reduction in power bills.
“One of the clients we created an energy efficient, air tight home for has power bills of around $20 a month in winter,” says Jessop.
Air tight homes use what Jessop calls “a kind of building paper that doesn’t breathe” – no heat escapes and there is no need to regulate temperature with heaters or cooling devices.
These homes have no dust – therefore no dust mites – and they are ideal for people who suffer from asthma or allergies.
He says that another key element that needs to be addressed when designing an energy-efficient home is the issue of thermal bridging.
Thermal bridging refers to an object having much higher heat transfer than the materials that adjoin it; this leads to the reduction of thermal insulation through the entire space.
This is rectified by thermal breaks: materials with low thermal conductivity that are placed between materials such as panes of glass to reduce the flow of energy.
Jessop says his company utilised a unique thermal break in a home he designed in St Heliers.
“The home was designed so it didn’t touch the earth,” he says.
“Polystyrene was used as a base, with file piles penetrating. While there was a little leakage, the energy transfer was minimal.”
Thermal breaks can also be used in joinery, windows and between framing and cladding.
Tilt and turn windows are an excellent example of how clever design can reduce heat loss and allow for good ventilation. Conceptualised in Germany, they have a multipoint locking system and their design allows air to circulate without a draft.
They “tilt” or “turn” according to your requirements; if they are tilted fresh air can flow in and hot air at ceiling height can flow out, if they are turned, air comes in freely and you can maximise any views.
Solar panels and other forms of heating that use natural resources can also be used to reduce the cost of electricity over the cold months.
If you are generating your own electricity you can also sell the extra energy back to the grid and make money from your investment. There are other options as well for people who live in rural areas.
“While solar is a very popular choice, especially in urban environments, wind and hydro can be used if there is a bit of land available,” says Harrington.
People are often put off energy-efficient homes because of what is seen as prohibitive costs.
Jessop estimates that a truly energy-efficient build will cost 20 per cent more than a conventional home.
He says that some people find this off-putting, but his advice is “just make your home 20 per cent smaller”.
There is also the option of making only part of your home fully energy efficient.
“We designed a home recently that had energy efficient bedrooms and bathrooms, but the rest of the home wasn’t,” he says.
While New Zealand is a bit behind the times, when it comes to truly energy-efficient homes, both Harrington and Jessop say times are changing.
Harrington enthuses: “We have been building for over 10 years, and it has been an incredible journey while also having the privilege to be a part of the movement towards energy-efficient, sustainable homes.”