Michael Green

Writer and producer

Solar thermal heating and cooling

In Architecture and building on

HEATING and cooling churns through nearly 40 per cent of Australian household energy use. Energy prices are set to hit ever-higher levels, so the more efficient a temperature control system is, the more attractive it looks – almost day-by-day.

There’s a growing industry selling units that use the sun’s free energy to ventilate, warm and even cool your home. They can also improve indoor air quality by reducing humidity, moisture build up and mould. Broadly, the systems fall under the banner of ‘solar thermal air heating and cooling’.

So what’s commercially available and how well do they work?


Roof space systems

These units work by moving the air in our roof cavities. When the sun strikes the roof, it warms the air below – just as cars get stuffy on clear days even if it’s chilly outside. For heating in wintry weather, roof space systems pump that warmer air inside the home. To help with cooling in summer, some units can extract the hot air from the roof during the day, and also, blow cooler outside air into the house overnight – useful if you’re worried about security or the noise of open windows.

There are two types of roof space solar collectors. One kind, sold here by businesses such as HRV, Solectair and Smart Roof, uses the whole roof cavity as a collector. The intake is near the top of the space, where the warm air rises. A fan sucks the air through a filter and ducts it into the home.

The second kind of technology, offered by Smart Roof in its Smart Breeze system, is suitable for metal roofs. It captures heat in the gap between the roof sheet and a layer of insulating foil or sarking underneath. The warm air rises to the apex of the roof cavity, where it’s nabbed and whisked into the home (using a solar-powered fan). “The ribs act as ducts and we seal the ridge so the air can’t escape,” says Smart Roof CEO Robert Semmel.

He says that the system can significantly reduce bills, but won’t do away with other sources of temperature control. “Our aim is to reduce heating and cooling by up to 40 per cent, not to replace it. If you’ve got a miserable, wet day there’s no radiant heat and on really hot nights there won’t be any cool air to bring in. But those are extremes.

“If the sun is out on a 15 degree day, we get temperatures up to 40 degrees [in the roof]. When cloud cover comes over, we get 30 degrees. There’s a lot of wasted energy we can use,” Semmel says.

According to energy efficiency expert, Adjunct Professor Alan Pears from RMIT University, the catch is that our roofs aren’t very good solar heat collectors. “A roof space can be described as an unglazed, very leaky solar collector, with a substantial proportion of its area facing the wrong direction,” he says. “So in that sense it’s not very efficient.”

But all is not lost. “On the other hand, it’s a very large area, so you can collect quite a lot of useful heat, especially in mild seasons,” Pears says. Light-coloured roofs with insulation directly underneath will collect much less warmth than a dark roof without insulation. Similarly, the roofing material will influence the way the systems function. Metal roofs heat up (and cool down) quickly, whereas the thermal mass in tile roofs means they take longer to warm, but stay hotter for longer in the evening.

If you’ve ever crawled into your roof space, the idea of pumping that air into your home might make you splutter. But Pears argues the air near the top of the roof space is likely to be no worse than other sources of ventilation in our homes. “The air coming through windows or under doors is unfiltered and often highly polluted,” he says. “In any case, most roof space systems offer a filter. The filtration systems available are very impressive, as long as you buy a good one and maintain it properly.”

Solar air collectors

A solar air collector consists of a clear plastic or glass-fronted panel that uses solar radiation to heat air, like the way a solar hot water unit heats water. The panel is mounted outside the house, either on the roof or a wall. A fan (usually solar-powered) blows the warmed air into the house. For cooling at night during summer, it may also blow cooler outside air into the home.

In Australia, a variety of solar air collectors are available, including products from SolaMate, Solar Breeze, Sun Lizard and Solar Venti.

Arne Hachmann’s business, Global Eco and Environmental Solutions, sells Solar Venti units. If you want to ventilate your home, he advises that a 3 square-metre panel will suffice for an energy-efficient 250 square-metre home. If heat gain is your priority, he recommends one unit of that size per 100 square metres of floor space.

He says the Solar Venti warms air to about 35 degrees above the outside ambient temperature. “If you have a sunny 15-degree day, you would expect to get 50-degree air ducted into your house for free, at a rate of about 200 cubic metres per hour.”

Pears has a SolaMate prototype solar air collector installed on his Melbourne house. The panel is three square metres and feeds into his hallway and living room. “In reasonably sunny winter weather, it’s enough to make a significant difference to the temperature of my fairly small and well-insulated home,” he says. “It makes a bigger difference in spring and autumn when the house cools down a lot overnight but the weather outside is pleasant.”

He warns that householders should buy big units if they want to collect a lot of heat. “Most systems are not very large, so they may not collect a lot of energy, especially on cloudy days. Also, if they’re single glazed, their efficiency may not be very good in colder weather.”

He says that solar air heaters work better in winter if they’re steeply sloped to face the low sun. “It may also be preferable to angle them slightly east of north, so they warm up the house more in the morning when air temperatures are lower and the building interior is colder.”

Cost and benefit

According to the Solar Thermal Air Heating and Cooling Association, both kinds of systems start from about $2,500 installed, with an average price of $4,500 installed. It estimates that the return on investment will vary from two to ten years, depending on the house and the habits of the householders.

Dr Bob Fuller, a low-temperature solar thermal researcher from Deakin University, is not yet convinced of the effectiveness of the systems. When it comes to heating, “there’s a big mismatch – the resource is low in winter when the demand is high,” he says.

Another problem is that there is no Australian Standard for this technology. “There needs to be some independent modelling and testing,” Fuller says. He maintains that as a first step, householders are best served by improving energy efficiency in other ways. “I would spend the money on conservation – on better insulation, curtains, and shading in summer.”

Certainly, these products should not be considered as a replacement for appropriate solar passive design, either when building from scratch or retrofitting. Semmel, from Smart Roof, says that if sun is pouring through a bank of west-facing windows, a ventilation system can only do so much. “In that situation, stopping heat getting in from the ceiling is not your major concern.”

For heating and cooling, the systems are most useful in a well-designed and insulated building. Where a home has thermal mass, the heavy materials will store the extra warmth and ‘coolth’ provided by the units. In a well-sealed house, the systems not only provide fresh air securely and noiselessly, but also, less of the airflow will escape through gaps.

Both Fuller and Pears note that there is a trade-off between the temperature and the volume of the air coming into the home. That is, the systems take time to heat the air, but if the fan runs too slowly, then not enough will enter the home to make any difference. “In some cases, because of other heat losses or gains, to maintain a temperature you might need enough volume for up to ten air changes per hour,” Fuller says.

Pears says it’s vital that solar air collectors include a high-capacity, variable-speed fan that can adjust flow rates according to the heat of the air in the panel. Likewise, the ducting on both kinds of systems should be good quality, and as short and straight as possible, so as not to reduce airflow.

Some systems, complete with clever thermostats, can adjust and make the tricky decisions for you. Set to function automatically, they will sense the temperatures in the collector, as well as inside and outside the home, and heat or ventilate as required.

But even the best designed systems, says Fuller, will not always be able to provide enough warmth and airflow to maintain the temperature inside the home. So it’s important not to expect miracles. These are supplementary systems – they won’t do the job all by themselves. 

Published in Sanctuary Magazine

Asylum

In Culture, The Big Issue on

In a small room at Oregon State Hospital, in Salem, north-western USA, hundreds of shiny copper urns line up like cans on a supermarket shelf. Dating from 1920s and earlier, they contain the unclaimed ashes of the asylum’s former residents.

The image comes from a new book of photography by Chris Payne, Asylum: Inside the Closed World of State Mental Hospitals. It is a room guarding burnt bodies and souls. Who were these people? How did they live? And why are they here, like this?

These themes fascinated the architect-turned-photographer for six years as he documented 70 decaying mental hospitals across 30 US states.

“I fell in love with the buildings and the places – the communities that the hospitals had been,” he says, “and with thinking about the thousands of people who had lived, worked and died there.”

Asylum is a grand, melancholy tribute to the lives spent in the institutions and to the astonishing scale and quality of the buildings themselves.

In 2002, when Payne needed a new project, a friend suggested he visit abandoned mental hospitals. The New York-based photographer drove to Pilgrim State Hospital on Long Island. Opened in 1931, it was the largest hospital ever built in the world – at its peak, it housed over 14,000 patients. “I was amazed to find this abandoned city just sitting there,” he says. “I quickly learned it wasn’t isolated to one hospital or one area. It was all over the country.”

From the mid-19th to the early-20th century in the US, nearly 300 institutions were built for the insane – often designed by prominent architects and always set in spacious grounds. The facilities were intended to offer calm and comfort, to treat inhabitants by means of fresh air and beautiful surrounds. The hospitals functioned as self-sufficient communities, including farms, workshops and auditoriums, and in some cases, even cafés and bowling alleys.

But care diminished as hospitals became overcrowded and pressed by tight budgets. Then, as treatment came to encompass extreme methods such as electro-shock therapy, ‘asylum’ became a by-word for squalor and abuse.

Payne’s elegiac photos, with flaking colour and tender light, show beauty in places we least expect. “Every society has its asylums, but I think there is a misconception that the buildings are bad and should be torn down. In a way, the stigma of mental illness has been passed onto the architecture of the buildings,” he says.

His previous book documented abandoned substations that had powered the New York subway. His photography shows the architecture of an optimistic era, a time when industrialism promised human progress. “I’m fascinated with buildings that really had purpose. We don’t build like that anymore,” Payne says. “And I think it represents a shift in the way we function as a society. It’s sad we’ve lost that faith in building.”

Windows

In Architecture and building on

Windows might be transparent, but they’re complex. Good windows well placed will help keep your home comfortable all year round. Bad windows in the wrong place will cost you dearly.

In a typical insulated house, they cause more heat gain or loss than any other part of the building fabric. While they’re expensive up front, they’re also an investment in the resale value and day-to-day comfort of your home.

So which windows should you choose? There are hundreds of products and combinations to consider, from the glazing, frames and coatings, to the size, shape and location. The Window Energy Rating Scheme website lists detailed ratings of over 40,000 products.

Two years ago, Alan Kerlin designed his sustainable home in Canberra. Afterwards, he established a consultancy, Solar Flair, to help pass on what he found out. When he was researching windows, he found good advice hard to come by. “It’s a difficult area, but it’s easier if you understand some of the basics behind the science,” he says.

Heat transfers in different ways – for windows, you’ll need to consider conduction and radiation. Conduction refers to the ambient warmth that passes through the glass and the frame. A window’s conduction is measured by its U-value. The lower the U-value, the better its insulating qualities, and the better for your electricity bill.

Radiation, in contrast, refers to heat transferred when sunlight passes through the glass, hits something and warms it up. It is measured by the window’s Solar Heat Gain Coefficient (SHGC); the higher the SHGC, the more radiant heat it lets through.

Passive solar design

Armed with this knowledge, you need to consider the weather where you live and the design of your home. Most Australians live in climates where we want to draw in extra warmth during the cold months and shut it out throughout the hot months. With careful consideration, your windows can help this happen – together other elements of passive solar design, such as shading and orientation.

In Canberra, Kerlin designed his home with a bank of glass to the north – the sun streams in throughout winter, but eaves and shading block the direct rays in summer. Small windows to the south, east and west help reduce the solar access when the sun is low in the sky and passes below the awnings. “But remember: it all depends on where you are living,” he says. “In northern Australia, you never want sun hitting your glass at all.”

Insulating glazing units (IGUs)

No matter your location, there is one constant: double glazing is always preferable to single. For now, nearly every Australian home has single-glazed windows. “They’re like a thermal wound in the building envelope,” says Gary Smith, from the Australian Window Association.

Double and triple glazed windows – known as IGUs – help heal the wound. “Standard double glazing can reduce conducted heat transfer by about half,” Smith says. Triple glazing is common in Europe and North America, but rare here. The window units weigh and cost more, but provide extremely low U-values and excellent sound proofing.

Within an IGU’s frame, the panes of glass are held apart by a spacer. A wider gap gives better insulation – 12 mm is regarded as the best. Likewise, an IGU will prevent even more heat transfer if the cavity is filled with an inert gas, such as argon, rather than air. “With argon, you get about a 15 per cent improvement in U-value,” Smith says.

IGUs also perform strongly in bushfire attack conditions. “Double glazing works really well in the bushfire tests because the insulation barrier stops the radiant heat coming through the glass,” he says. This year, all states and territories will introduce a new standard for windows and doors in bushfire prone areas. So far, few products have been tested to the top levels.

Smith says the extra cost between single and double glazing can be between 50 and 100 per cent, depending on the company and the product. Householders can spend from a few thousand, to tens of thousands of dollars extra. “There’s a huge variance. The best bet is to shop around – there are good deals and really good products out there.”

Glazing

Glass is no longer just plain old glass. It now comes in a dazzling range of coatings and tints that will help keep your energy bills down.

Low emissivity (low-e) glass has a transparent metallic coating that reduces the pane’s U-value. “Low-e glass can significantly reduce the amount of heat that travels through your windows, keeping your house more comfortable in both summer and winter,” says Jamie Rice, vice-president of the Australian Glass and Glazing Association. It can also curtail UV light and reduce fading in furnishings.

Single-glazed low-e coated glass is a good option for people who want a step up from standard glass but can’t stretch their budgets to double glazing. However, it’s far more effective when placed inside an IGU – it can reduce the U-value of a double glazed window by half again.

Tinted glass cuts the heat transmitted into the home from direct sunlight. Available in a range of colours, tints are especially suited to west-facing windows that receive direct, summer afternoon sun. “The problem with standard tints has been that to improve the performance you end up cutting out light,” says Rice. “But there’s now a more sophisticated product, called spectrally selective tinted glass, which significantly increases solar control and only slightly decreases light transmission.”

Low-e coatings and tints can be used in combination. Together, they reduce both the U-value and the SHGC, making for a window that’s ideal for keeping out the heat.

Frames

Most window frames in Australia are made from aluminium. They’re cheap and versatile, but conduct heat very easily, which means they slice the insulating performance by up to 30 per cent. Thermally broken aluminium or composite frames offer better insulation, but they’re much more costly and, for the time being, not widely available.

Timber frames also have significantly lower U-values than aluminium. Edith Paarhammer, from Victorian window manufacturer Paarhammer, argues that although timber is more expensive, it performs better than any other framing material.

She recommends that eco-conscious buyers choose products made from either plantation timber or Forest Stewardship Council certified timber. “It’s also very important that the frames are substantial, not flimsy,” she says. “And make sure they have seals all around, so there are no draughts.”

Another high performing frame is uPVC. Only recently introduced into this country, it has a comparable thermal performance to timber, but is cheaper. Warren Miles from Ecovue says a double glazed uPVC window can cost just 25 per cent more than equivalent single glazed aluminium.

Miles says it’s crucial that buyers look for frames that minimise air leakage. “You need a complete seal between the window and the frame, and also between the frame and the structure of the building. If you can’t achieve that you may as well not worry so much about the glazing.”

Miles says it’s crucial that buyers look for frames that accommodate double glazing while also minimising air leakage. “You need a complete seal between the window and the frame, and also between the frame and the structure of the building. Reducing air infiltration is a significant part of energy efficiency.”

Few businesses are specialist window installers, although some manufacturers can also do the job. You can find them listed on the Australian Window Association website.

Retrofitting

If you’re in an existing house and want to improve your windows, you have several options. The most effective and expensive way is to remove and replace the entire window units. In some systems you can replace the glass alone.

It’s also possible to retrofit double glazing, either with glass secondary window systems or cheaper acrylic panes that attach to your window frame using magnets. Cheaper still (but less effective) is Clear Comfort, a membrane that you tape to the window frame and make taut by shrinking with a hairdryer (a 10-metre kit costs only $180).

Films are an efficient way to cut solar heat gain on existing windows. They range from almost transparent to dark grey and cost between $60 and $100 per square metre, installed. They also come with low-e coatings.

Glossary of terms

U-value: the measure of a window’s heat conduction. High insulating windows have U-values from about 3.5 down to 1.4 (the lower the better).

SHGC: Solar Heat Gain Coefficient. The measure of the heat transmitted through the window when the sun strikes it directly; 0.8 is high, 0.2 is very low.

IGU: Insulating Glazing Unit. Double or triple glazed window systems, which have sealed cavities between the glass layers.

Low-e glass: glass with a low-emissivity, metallic coating that improves its insulating qualities. Some low-e coatings also reduce the SHGC.

Spectrally selective glass: glass that allows lots of light in, while cutting out unwanted UV and solar heat gain.

Read this article in Sanctuary Magazine.

See related article: Window coverings and retrofitted double-glazing

Meet your neighbours

In Environment, The Age on

From backstreets to the big end of town, there’s reason for neighbours to become good friends.

Last year, my neighbour and I leafleted houses in the streets nearby. We proposed something unusual. On our flyer, we wrote, “…we’d like to set up a system to share some of our resources and build a friendly local community”, and then we promised all manner of neighbourly fun, including street parties, movie nights, swap meets and veggie sharing.

And now, our block in Carlton moonlights as a ‘sharehood’.

The Sharehood is a social networking website that shows you everyone with a profile who lives within 400 metres of you. It includes lists of things to borrow and lend and a forum for upcoming events. The first one was set up in Northcote in 2008, but it works no matter where in the world you live.

The Sharehood’s creator, website developer Theo Kitchener, says connecting online can help meeting face-to-face. “It’s all about encouraging neighbours to get to know each other in real life – all kinds of good things can come from that.”

So, aside from a sensible impulse to borrow a circular saw rather than shell out for one of my own, what’s behind my wish to know my neighbours?

Associate professor Kathleen Hulse, from Swinburne University’s Institute for Social Research, says knowing our neighbours not only makes us feel safer, but also meets our deep need for a sense of place. “Being connected locally is strongly associated with a sense of belonging, and we all need to belong somewhere. It’s a profound thing – that is what a home is about.”

According to Gilbert Rochecouste, from placemaking consultants Village Well, there’s been renewed interest in “caring for place”. Governments, councils and property developers are all aiming to strengthen local communities. “People are changing their priorities,” he says. “We’re seeing that with developers building ‘neighbourliness capital’ into projects.”

Mr Rochecouste points to Delfin’s Laurimar estate, past Epping in Melbourne’s north, which includes a town centre lined with local stores within walking distance of all the homes. “People meet in main streets, that’s where the heart is,” he says.

Also at Laurimar, a community worker is employed to organise activities. “In greenfields developments like that one, we’re starting to see place managers who coordinate community gardens, events and food swaps,” Mr Rochecouste says. “To build citizenship you’ve got to invest in it.”

The trend isn’t limited to the urban fringe. Sue West from the McCaughey Centre at the University of Melbourne says that over the last decade, state and local governments have supported more and more initiatives to build community resilience. Now, about eight in ten local councils say they fund projects of that kind, be they community gardens, local action plans or activities to bring different cultures together.

“There’s been growing interest in programs that involve communities in getting to know each other,” Ms West says. “The research was showing that a country or a community can be doing really well economically, but people’s wellbeing is beyond just money and the economic measures. It’s about the connections people have with each other.”

Ms West coordinates Community Indicators Victoria, a set of measures gauging social, economic, environmental, democratic and cultural wellbeing in local council areas. “Feeling connected to neighbours does contribute to wellbeing. It can be really important in difficult times, like the one we’ve just been through with the financial crisis, and the ones we continue to go through because of climate change and drought,” Ms West says.

Improved neighbourliness also goes hand-in-hand with environmental gains. As well as The Sharehood, there are a large number eco-friendly neighbourhood groups across our suburbs, such as Sustainability Street (a group training program in eco-living) and community gardens. There were 75 community gardens in Melbourne at last count, in 2006, and interest has been flourishing since then.

Transition Towns is another grassroots eco-development movement. The people in each location determine what they’ll do, but generally speaking, the goal is to live better with less – to re-make your area into a food producing, low-energy, low-emission, tight-knit community. It was founded in England in late 2006 and there are already over similar 250 initiatives worldwide. In Australia, 27 groups have officially signed on and dozens more are joining up, including seven in suburban Melbourne.

Razia Ross is convenor of Transition Town Boroondara, which traverses inner-eastern suburbs from Kew East to Ashburton. She says the threats posed by climate change and peak oil will change our relationships with people nearby. “It seems to me that we really need our neighbours in a way we didn’t before.” For now, her group is scheming for community gardens, orchards and guerrilla gardening.

The good news, according to housing researcher Dr Hulse, is that we have a strong base of neighbourliness to build on. “I think that the connections in suburbs are underestimated. Special initiatives like community gardens are important, but they wouldn’t work if there wasn’t already a fabric there,” she says.

It’s true in my block. At our sharehood events, long-term residents pass on local folklore to newcomers – yarning, for example, about the old Maltese man who built a boat in his backyard (too big for the yard, it jutted over the footpath) then set sail for Malta. It’s all part of the sharing.

A new nature strip

Depending on how you look at it, Gilbert Rochecouste and his partner Amadis Lacheta have either taken their work home, or their home to work. They run Village Well, a placemaking consultancy that works on relocalisation and civic renewal.

And on the nature strip outside their house in North Coburg, they’ve planted a community herb garden and installed a seat, among other things. “The old ladies who get off the bus pause and sit down and we’ve gotten to know them,” Mr Rochecouste says. “They’re so appreciative – sometimes they drop over pickles.”

He says neighbourliness turns a street into a meeting place. “There are eyes on the street. It helps breaks down the fear culture – you feel comfortable to knock on someone’s door and meet together. And it’s much more fun.”

Read this article on the Age website.

Village Well’s 10 ways to be neighbourly:

1.     Say hello to your neighbours when you pass.

2.     Organise a potluck lunch, dinner or picnic and invite people in your street.

3.     Plant a community herb garden on your nature strip

4.     Organise a neighbourhood swap – share and exchange clothes, garden produce, plants, books or skills.

5.     Organise a neighbourhood ‘salon’ – share music, food, poetry or stories.

6.     Install a seat on your nature strip for neighbours to sit and chat.

7.     Organise a yearly street party.

8.     Do some street beautification or community art.

9.     Create a community garden or green area.

10.  Put a free table on your nature strip and give away food, books, furniture and bric-a-brac.

Six-star homes

In Architecture and building, Environment, The Age on

Higher star ratings will add little extra cost.

The energy efficiency of our homes is on the rise again. Last year, state and federal governments agreed to lift the residential standard from five to six stars. The changes will come into the national building code from this May, and then the states must bring them into effect by May 2011, at the latest.

In Victoria, the new rules are the first major increase since the introduction of the five-star regulations in 2004. So what difference does a star make?

It’s only a small rise in cost for a cushy lift in comfort, according to the CEO of VicUrban, Pru Sanderson. With its builder partners, the state land development agency has been offering six-star homes for years. “They’ve become VicUrban’s base standard,” she says. “We’ve proven to the market that it is doable, at scale, for a very, very small price tag.”

VicUrban estimates that the better performing homes will cost $5000 extra at the most, but much less – under $2000 – if the planning, subdivision and orientation of the blocks is done carefully. “In terms of the cost of a home, it’s a very small outlay for a long-term benefit,” Ms Sanderson says. “We estimate that a six-star house uses about 15 per cent less energy in heating and cooling compared with a five-star house.”

Matt Fisher, from the Association of Building Sustainability Assessors, says the price tag could be even lower. “We did some studies that looked at real world [plans] and found that they could be increased from five to six stars for about $500,” he says.

The last jump in energy efficiency rules forced the industry to improve the building fabric and insulation. Mr Fisher says that this time around, the changes will summon designs that better suit the climate and location of the house.

David Hallett, from Archicentre, the building advisory service of the Australian Institute of Architects, agrees. He argues that the house plans and the site of the land must always be considered together. “Most of our homes are designed in isolation and plonked on a block, depending on which floor plan the client happens to like. Sometimes it works well, and sometimes, really badly.”

Poorly oriented homes may still be able to reach six stars, but they’ll need top-notch windows and insulation. It will be much cheaper for new homes to meet the higher standard if they are well-suited to their block – with features such as smaller windows to the west and south, living areas to the north, and eaves calculated to shade over summer and let in sun over winter.

The ideal way to address local conditions is with a custom design that fits your land. But Ms Sanderson maintains that big builders and developers can also offer well-oriented houses at scale – though the industry will first have to invest in expanding the range of its products. “At VicUrban we already have sophisticated guidelines about typical building configurations for different kinds of blocks,” she says.

Although Ms Sanderson approves of the higher standard, she’s also quick to point out that the new regulations don’t mean we’ll consume less energy. “The improved performance is being offset by the ever-increasing size of new houses,” she says. “The average new house is 40 per cent larger now compared with the 1970s.” Bigger homes not only chew through more energy, but also more construction materials and waste.

Likewise, the way we live in the house has a drastic effect on the amount of energy we consume. “We’re wasting our time doing all of this if we don’t help educate people about how to live in a more environmentally attuned way,” Ms Sanderson says. “We want the six-star lifestyle to go with the six-star house.”

Renovating with the stars

The six-star regulations will also apply to extensions. Retrofitting energy efficiency is more difficult than starting from scratch, but Anthony Wright, building designer at Sunpower Design, says the higher standard is well within reach. “We generally aim for seven stars or better – six stars is a minimum.”

The new rules are slated to work the same way as the current five-star renovation system, which applies only to projects that require a building permit and varies depending on the size of the alteration. For larger additions the whole house must comply, while for smaller changes only the new part must adhere to the rules. “You’re not required to do the impossible,” Mr Wright says.

To make the grade, he says designers will need to incorporate solar passive design techniques, including smart orientation to get sun in winter and exclude it in summer. That task can be tricky for additions to the shady south. “Sometimes it requires more thought, but there are lots of ways to get northerly sun in a southern extension, such as using roof glazing or setting the extension back.”

Mr Wright has two main tips for would-be renovators. “Do a preliminary energy rating at the sketch design stage to see whether the designer is coming close. It might cost a few hundred dollars, but could save you a lot of grief down the track,” he says. “And be realistic about the amount of glazing you put into the house and the direction it faces. Think strategically about it, rather than having expanses of glass.”