Good Design Vital to Securing a More Energy-Efficient House

Going off grid has become a consumerist Holy Grail, encapsulating freedom from energy bills and the guilt of carbon-emitting power generation.

And with storms seemingly cutting off more people every year, those moving to the country are taking a serious look at alternative power generation.

To find out the best way to go off grid we talked to Dean Buckeridge and Ray Hawthorne, two of the three directors behind “Zero Energy Home” architectural designers 3 Architecture, which designs scores of lifestyle blocks for clients every year.

House size

“Up to 70 per cent of the life-cycle energy usage of a new home is determined in the first 1% of the project, so getting those initial things right are critical to the life-cycle cost of a house,” Buckeridge says.

Key to this is realising that bigger is not always better. “The motivation for large houses is to make them special. Currently we think that bigger is better, but when people examine their motivation they will often realise that a more space-efficient but better designed house that is warmer, dryer and more cost effective to live in is a better choice.”

Orientation

“The most critical factor is the orientation of the house – siting it for the sun – and planning the layout of the house so you get the sun into the rooms as you use them during the day,” Buckeridge says.

“So, if I am working on an energy- efficient design, I will always have the sun coming into the kitchen first thing in the morning.

“The family room will be on the north side and get sun all day, and then the formal lounge, which will use the sun late in the day, will be situated more to the west.

“Shading is important in the summer, along with natural ventilation to minimise overheating.

“You can then arrange the bedrooms as you want them. But with lifestyle properties the big advantage is you have the space to spread out and optimise the orientation of the house.”

Creating thermal mass

Next, you’ve got to start thinking about building material choices for insulation, with concrete highly recommended.

“The concrete block house does have generally a higher cost than other materials, but it is the ultimate option for creating thermal mass when used in conjunction with adequate insulation,” Hawthorne says.

“However, a lot of the material choice is determined by the client, in terms of what their perception of the house is. We can advise them on the relative cost of each material.”

The thicker the walls and floors are made the better. “If you are getting good sun in there, for the cost of an extra cubic metre or two of concrete you get a huge amount back in terms of useful thermal mass,” Buckeridge says.

“It’s a similar principle to a wine cellar. You put a wine cellar underground and you’ve got a lot of earth around it which keeps a constant temperature there.”

With window frames being a major insulation weak point, 3 Architecture recommends investing in thermally- broken suites, which provide a blocking layer of rubber insulation within aluminium window frames, and staying away from recessed down lights that create a hole in the insulation envelope.

“This is no different to buying a top quality sleeping bag and then cutting holes in it before you use it,” Buckeridge says.

Smart wiring

We all know the consequences of a light or heater being left on unintentionally, so investing in a smart wiring system like C-Bus to automate usage can have a massive effect on efficiency.

“But what we can do is structure these so that when you leave the house you press the ‘away’ button and it will shut down power to all of your phantom loads, all the stand-by power.

To facing page

From facing page “It will leave the fridge going, it will leave the alarm going, and it can leave the answer machine going but everything else gets shut down,” Buckeridge says.

“You can also use smart wiring systems to naturally ventilate your house. Hot air rises, in a properly- designed house you’d have a thermal chimney or a high point in the house where hot air can rise to with a thermostat at the top, and if the temperature goes above a preset level the system opens a window so it doesn’t overheat.

“You could also have lighting on sensors in hallways, meaning the light only stays on for a minute as you pass through and then turns off.”

Power source choices

The stereotypical image of “going off grid” normally involves a large wind turbine spinning against a strong Nor’wester, but realising that image may still be some way off.

For a start, wind turbines work best at height and, obviously, in the clear path of wind, two facts which clash immediately with residential height by-laws and the need for shelter belts on the plains.

They are also still largely uneconomic to use, unless you can claim to live in an area with 100 per cent year- round gusts, known for their noise levels and are generally unpopular with other residents who have to live in eyesight or earshot of them.

While the costs of wind turbines are coming down and designers are tackling the height and noise issues with success, 3 Architecture are not generally recommending them for clients just yet – although rural situations are definitely more suitable.

For a more economic and practical investment the architectural designers often incorporate photovoltaic cells (solar power) and geothermal energy into their designs.

With a combination of these two power sources, 3 Architecture says it is possible today to create a 100% zero energy home which doesn’t require connection to the grid, but they still recommend a significant battery storage system and a back-up generation system be put in place.

However, if the homeowners have balanced their power consumption and generation needs well, they may just want to hold off before cutting all ties to the big power companies.

“What we are likely to do for most situations is still be connected to the grid, so the excess energy you collect during the day can be sold back. You can be ‘grid connected’ now.

“Then later in the day, when you need electricity, you can draw it back,” Buckeridge says. “So the ideal situation is to minimise your energy requirements through good design and solar water heating and then balance the amount of energy you need and put it on the same amount of generation capacity.”

Buckeridge points to the Energy Efficiency and Conservation Authority’s (EECA) assertion that every home in New Zealand receives 20 to 30 times the amount of energy it needs in solar radiation from the sun every year.

And while installing solar panels do come with their own consent conditions (such as a sub-division covenant or a zone-specific council rule on visual impact) in regards to being seen from the street, these conditions are often irrelevant on a quarter acre lifestyle block.

“Photovoltaic cells are coming down in price – they used to be $10,000 a kilowatt and they are now down to about $6500 a kilowatt.

“I was told recently by a distributor that they are working closer with roofing manufacturers and the future is going to be roofing materials which are photovoltaic in nature,” Buckeridge says.

“Solar panel technology is moving very fast.

“There are flexible photovoltaic materials available now and there is a lot of work being done on photovoltaic paint.”

Hawthorne is a particular advocate of geothermal energy, which sees lengths of piping put into the ground at about 700-800mm below the surface to source free heat from the soil.

Like solar, it requires an initial investment, but once it is in the ground there could be no limit to its longevity.

“This is something I have been talking to clients about a lot,” he says. “It takes the heat from out of the ground and then recycles that through the house. That works particularly well on a country site because the more land you have got the more pipes you can put in the ground.

“We’re talking about a quarter of an acre of lawn, that most lifestyle blocks would have anyway.

“I think geothermal energy is the way of the future – it’s out of the way and, other than the refrigeration pump units, they are presumably maintenance-free because nothing can happen to it under the ground. Once again, there is a cost involved, but once you’ve got it in there it should last a lifetime.”

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