After the bushfires, many people are opting to re-build sustainably.

ANTHONY Smith’s Kinglake home burned down in the Black Saturday fires. “I heard the fire coming,” he says, “and it sounded like hundreds of helicopters droning together in the near distance.

“Once the house started to shake and vibrate with the noise, I thought: ‘I’m out of here’.”

He left, but the home he’d lived in for 24 years was reduced to a few charred stumps. When he set about rebuilding, he decided to do it differently: he wanted a passive solar design, one that would need little power and incur few bills. The home is still under construction, but based on the plans, it will achieve a 9-star energy rating.

Mr Smith is one of a number of residents in the area who are sharing their stories on the Build It Back Green website, coordinated by Green Cross Australia.

Mara Bún, CEO of Green Cross Australia, says personal experiences such as these can propel a wave of change, and not only among those rebuilding from the fires.

“The Black Saturday bushfires captured the hearts and minds of Australians in a deep way, and so we think these stories will inspire people to make changes in their own lives,” she says. “The information on the website about green building is very practical and applicable to everyone in the state.”

The Build It Back Green movement began in New Orleans after Hurricane Katrina devastated the city in 2006. “Now it’s happening all around the world where natural disasters occur and communities want to recover in a sustainable and resilient way,” Ms Bún says.

“The way we rebuild can either refuel the cycle by being very emissions intensive, or it can begin to break the cycle altogether.”

She says the website is a hub of information on low cost, sustainable and resilient building. It includes a guide developed by the Alternative Technology Association, containing tips on green materials and building techniques, together with lists of products and suppliers.

The website also features videos and profiles of people rebuilding from the fires, and details of local events.

“We’re really stressing community participation,” Ms Bún says. “Getting to know your neighbours is a hugely important factor as we confront these threats, especially in Victoria, which has so much risk from climate change.”

Mr Smith, a woodcutter and sawmiller, took time completing the design for his new home. He observed the sun’s path throughout the year before staking the orientation along an east-west axis, with a slight twist towards the sun on winter afternoons. “Kinglake is pretty cold, so I wanted to get maximum sun on the windows during the cooler months,” he says.

He sketched out a three-bedroom house just over 6 metres wide and 28 metres long. “It’s narrow, with a low pitching height,” he says, “so the rooms are very manageable sizes for the sun to warm up.”

The post-and-beam dwelling will have Hebel (Autoclaved Aerated Concrete) block walls and insulated slab floor, with stone paving to provide thermal mass near the north facing, double-glazed windows.

Mr Smith is also using recycled materials wherever he can, including reclaimed timber and bricks from a neighbour’s demolished home. “I felled trees on my block and milled the structural timbers,” he says, “so I’ll have my own floorboards and timber for the roof.”

Hobby beekeepers create the land of food and honey.

LOUISE Davey’s backyard in Coburg is lined with well-tended vegie patches. Chooks cluck in their coop under the fig tree. But the most important residents – the queens of the food garden – live next to the olive tree in the middle of the yard.

Ms Davey has been an amateur apiarist for two years. “I just love watching the bees and getting the honey,” she says. “The people who live around my area love getting it too. I’m keeping quite a few families in honey from my two hives.”

Her bounty, now about 60 kilograms a year, has grown with each harvest. “Because I’m in the suburbs, the honey tastes slightly different every time. It reflects the plants the bees collected the nectar and pollen from,” she says.

There are about 2200 beekeepers registered with the Victorian Department of Primary Industries and around 1800 of those are hobbyists, according to apiary inspector Daniel Martin.

Although each local council has its own bylaws, backyard beekeepers are usually allowed to keep one or two hives, under the state’s Apiary Code of Practice. It is compulsory, however, to register with the department ($15 per year). “Bees are classed as livestock,” Mr Martin says. “Registered beekeepers have access to a honey testing program to help with early detection of an endemic honeybee brood disease.”

He says beekeeping is not only a way to source your own sweet bliss, but also provides an important ecosystem service. “Many people don’t realise that one in every three mouthfuls of food is dependent on honeybee pollination. By keeping bees you’re contributing to your neighbourhood’s food production.”

If you do it well, it’s also good for the bees. “Suburban hives are often really strong because they’re stationary and they’ve got access to nectar and pollen all year round,” Mr Martin says. “Many commercially run hives are migrated around the country and the bees often need supplementary feeding for extra nutrition.”

The DPI website has a series of useful how-to guides on beekeeping and safe management practices.

Beehives must be set back from your fence and should be placed in a sunny, sheltered spot with access to water. It’s best if they don’t face directly towards the street – the bees’ flight path must not cross low over the footpath. As a beekeeper, you’ll need safety equipment, including light-coloured clothing, gloves, a veil, a hive tool and a smoker to distract the bees while you harvest the honey.

Mr Martin says that if you care for your bees responsibly, they’ll happily go about their own beesness.

“Bees are like every animal – if they’re neglected they become unhappy,” he says. “Beekeeping isn’t a skill that comes overnight, so I highly recommend joining or liaising with a local beekeeping club.”

Ms Davey honed her skills with the beekeepers at Collingwood Children’s Farm and CERES in Brunswick. She suggests that newcomers get hands-on experience before they strike out on their own.

“Although bees are fairly low maintenance, it’s a little daunting the first time you open up your hives and you’ve got hundreds of bees flying all around you,” she says.

While she’s suffered her “fair share” of stings, they usually come when a bee inadvertently falls into her slippers. “Bees aren’t aggressive – they’ll only sting if they think they’re being mistreated.”

A new project takes the waste out of wastewater.

WHILE it may seem polite to keep the lid on toilet talk, if you’re pursuing household sustainability, you can’t ignore your sewer.

Rita Narangala, engineer at Yarra Valley Water, explains that our sewerage system not only consumes buckets of potable water, but also demands electricity for pumping and treating.

“It’s something a lot of people don’t immediately think about, but sewage is actually quite energy intensive to collect and treat,” she says. “When you install efficient fittings, it’s a real double-whammy in terms of the savings in water and in the energy for supplying the water and treating the sewage.”

In Kinglake West, Yarra Valley Water is building a research project that changes the way the company deals with our pipes. It undertook a life cycle assessment of wastewater options for the environmentally sensitive area, which is bordered by national park.

When the plumbing and infrastructure is complete, up to 90 homes will have an alternative sewerage service, comprising urine diverting toilets, greywater treatment and reuse systems, and a pressure sewer.

The measures are expected to halve wastewater discharge, slash nutrient discharge by about 80 per cent, and cut greenhouse gas emissions by one-third compared with a conventional sewer.

One element of the approach in Kinglake West is a switch from “nutrient removal” to “nutrient recovery”; that is, turning the problem into a solution.

Presently, the high-nutrient content in effluent can cause pollution in our waterways and bays. It’s a problem that must be overcome by extensive and expensive treatment. At the same time, however, our farmers buy in artificial fertilisers in a quest to boost their soil fertility.

“Urine is rich in phosphorus and nitrogen, so diverting it is an easy way to capture a small fraction of the wastewater, which is nutrient-rich and relatively low in bacteria and pathogens as well,” Ms Narangala says.

Yarra Valley Water will work with a local farmer to trial the use of urine as a fertiliser replacement (most likely on a non-food crop, such as turf). Projects of this kind are well advanced overseas, especially in Scandinavia.

“Phosphorus is an essential plant nutrient – there’s really no replacement for it,” Ms Narangala says. “But there’s a view amongst scientists that reserves could run out in the next few generations. The peak level of production, after which demand outstrips supply, could occur much sooner.

“We need to find alternative nutrient sources – human waste is one, as well as efficiency gains in the way it’s mined and the way we produce food.”

While the solutions adopted by Yarra Valley Water in its Kinglake West project are specifically designed to suit local conditions, they’re a sign of changes in the pipeline elsewhere.

In sewered suburbs it’s more difficult to retrofit large-scale greywater and nutrient recycling all at once. But as urban infill and infrastructure upgrades continue, the utilities will seek out solutions that cut water and energy use, and turn nutrient pollution into a resource.

Ms Narangala says decentralised treatment and recycling may become more common. “Our infrastructure is in the ground already, but we’re looking at alternatives to simply replacing parts when necessary. Water companies recognise that we’re in a unique position to recover and reuse nutrients. The industry is assessing the best ways to build a sustainable sewage system.”

Read this article on the Age website.

For more information on peak phosphorus, see Phosphorus Futures, founded by researchers from the Institute for Sustainable Futures at the University of Technology Sydney. 

Transition initiatives are spreading throughout our cities and regions.

IN Northcote, by the railway line, there’s a grand old apple tree. It had long since been neglected, until local artist Cat Wilson began photographing it through the seasons, and volunteers from Transition Darebin held working bees to clean up the site.

“Now we’ve put seats there and had lots of picnics,” says Sally MacAdams from Transition Darebin. “It’s become a lovely community area.”

It might not sound like much, but this small act of civic engagement is part of a big movement buzzing through the western world and beyond.

Transition Darebin is a member of the thriving international Transition Network. The first transition town – Totnes, in Devon, England – was launched in late 2006. Now there are over 600 active groups around the world, 60 of which are in Australia.

“We want to prepare our community for a turbulent time ahead,” Ms MacAdams says. “The government is talking about climate change, but not doing much, and it doesn’t seem like they’re considering it together with the prospect of rising oil prices.”

She says that as oil becomes more difficult to extract, the cost of food and transport could climb steeply. “We have to change the way we live. The approach transition towns takes is that we can change in a way that makes our lives better. We can improve the connectedness and resilience of our communities, mostly through doing and making things more locally,” she says.

The details change from place to place, but broadly, transition groups seek to remake their streets into food producing, low-energy, low-emission, tight-knit neighbourhoods.

In Darebin, which traverses suburbs from Alphington to Reservoir, the residents have turned their minds to their pantries. Among other things, they’ve formed a vegie and dry goods co-op, visited local growers and sellers, held a forum on food security in Preston and begun planning urban orchards with the council.

Australia’s first transition town was the Sunshine Coast. This year, residents there presented an Energy Descent Action Plan to their council. The plan sketches the region in an energy-constrained future, spanning issues from household efficiency through to transportation and the economy.

That kind of preparation is also being championed by the Municipal Association of Victoria. The association has created a program for local governments, called ‘Councils And Communities in Transition’, which includes energy descent planning. So far, 20 Victorian councils are taking part; the association is aiming for every council to be inducted by 2012.

Janet Millington, from Transition Sunshine Coast, says that while councils have a role to play in educating and supporting their residents, it’s important that local people fast track change themselves.

“We can’t wait for government – it’s going to be too slow,” she says. “We can’t do it individually – it’s not going to be enough. But if we work together in communities, it might be enough and it might be in time.”

Ms Millington says the scale of the challenge before us depends on the speed and severity of both climate change and the decline of non-renewable resources.

“Transition initiatives are about getting people to think, ‘Hey, what do we do when all these things hit?’” she says. “We’re all living on the same finite, self-regulating system. If we push it too far, it’s going to regulate us right out of the picture.”

Read this on The Age website. 

Fans and ventilation will take the heat out of your bills.

Our electricity consumption spikes on hot summer days. But with utility bills soaring and climate change pressing, it’s time to turn off the air conditioner. There are cheaper ways to keep your home cool.

Andreas Sederof, from sustainable housing design firm Sunpower Design, says carefully planned cross-ventilation is a vital part of a well functioning home. It’ll help you harness each cool change on a stifling day and every fresh breeze in the evening.

If you’re planning to build or renovate, Mr Sederof’s first tip is that all windows are not equal. “To be effective, your windows must be sufficiently openable,” he says.

For example, awning windows, which hinge at the top, don’t allow as much breeze as casement windows, which hinge at the side like a door.

“Casements expose the whole opening of the window to ventilation,” he says. “In Melbourne, most cool changes come from the south and southwest. You can get the windows to act like chutes for the cooling breezes to enter the house.”

Mr Sederof’s second principle is to give the wind a free run of your home. “The building’s spaces should be organised in such a way that it allows cross-flow ventilation. It’s best to have the ventilating doors and windows opposite one another – like a good aerodynamicist, you need the air flow to be as unrestricted as possible,” he says.

According to Sustainability Victoria’s Air Movement guide, providing an outlet for the wind, as well as an inlet, creates wind speeds up to eleven times greater than only opening an inlet window. Larger outlet spaces to the north allow a greater volume of air to enter from the south.

Even if the southerly change hasn’t yet arrived, you can still passively cool your home each evening by venting the day’s heat.

“In summertime we often get still, clammy nights,” Mr Sederof says. “That’s when openable roof glazing, highlight windows or thermal chimneys can be very effective. Hot air rises, so it’s easy to evacuate. Cooling towers like those have been around for centuries in the Middle-East.”

When you open both a low window and a roof window (once the temperature has fallen outside) hot air will flow out and cooler air will enter. “If you’ve got low windows opposite small fern gardens or vegetation, you’ll replace that hot air with slightly colder air from the plants’ transpiration,” he says.

Ceiling or roof-mounted exhaust fans work on the same principle as high windows. They’ll extract hotter air from high in the room and draw fresh air through open windows. They can be either powered or passively operated. Make sure you choose models that have covers or dampers, or seal automatically if they’re not being used, so you don’t lose warmth in winter.

If your home doesn’t have good cross-ventilation, and you can’t retrofit it, ceiling fans are the next best bet. In hot weather, fans can make you feel a few degrees cooler. Mr Sederof recommends one fan for every 10 to 12 square metres.

“Fans rely on evaporative cooling. The air moving over your skin is what makes you feel cool,” he says. “But you have to buy decent quality ones – if you’re spending less than $200, they’re probably not good enough.”

During No Impact November, you can look at your lifestyle anew.

MARA Chambers has decided to change the way she shops – and she’s starting with a weeklong challenge. From November 11 to 18, Ms Chambers, from Altona, will skip the supermarket altogether.

“I’ll buy what I need from organic shops or farmers markets,” she says. “I’ll also have to nut out what to do if I need things like toilet paper or washing liquid. I’m hoping to change my habits for the long-term, so I need to look for something else that’s achievable.”

She’s avoiding the well-trodden aisles as a part of No Impact November, run by the Ethical Consumer Group.

In the lead up to the challenge, participants have been meeting to devise their individual goals. The ideas for action range from switching off electronic gadgets to using a composting toilet.

Ms Chambers chose a supermarket-free week because she’s become increasingly dissatisfied with the lack of transparency in the provenance of house brands in the large chain store where she’s been shopping. “I feel like there’s a lot of greenwashing with their organic produce, and they don’t seem to stock many smaller suppliers anymore,” she says.

“I’m really conscious that my power is where I spend my dollar. There are lots of things I can’t control, but I do have freedom over where I spend my money.”

No Impact November is the third annual household action challenge run by the Ethical Consumer Group. In previous years, the participants sought to eat from within one hundred miles, and to produce no waste for a week.

Nick Ray, from the group, says the hard work of changing habits is made easier by doing it together. The people taking part are planning to gather for a meal at the start and end of the week to share their experiences.

“We all have impacts in our everyday life,” he says. “Often people are unable to minimise them because they feel overwhelmed, or because they’ve tried and burnt out. The idea of our household action challenge is to choose something that’s manageable. It pushes us hard for a week, but then we can digest it.”

This year, Mr Ray and his family have come up with a three-pronged challenge: to bake their own sourdough bread, to forgo driving their car, and to cut their electricity consumption by one-third.

“The average Australian citizen consumes an amount of energy equivalent to nearly 50 people pedalling bicycles non-stop, day and night,” he says. “That statistic makes me think twice about our energy use. Do we want to be dependent on oil, or on slaves when oil runs out? Or is there another way?

“We need to really pioneer new ways of living that aren’t fossil-fuel dependent, and that’s why we’re not going to get into the car for the week,” he says.

If you’d prefer to start with a shorter challenge, November 27 is Buy Nothing Day, an international day of protest against over-consumption.

Alternatively, to find out the facts behind your regular buys, check out the Ethical Consumer Group’s Guide to Ethical Supermarket Shopping. The fourth edition will be available shortly, as both a booklet ($6) and an iPhone application ($4).

“It’s great for people who are looking for something with an ethical edge for Christmas stockings or to buy for their friends,” Mr Ray says.

Better planning controls can add to household sustainability.

From next May, new houses and renovations must reach six stars. Even so, our building standards will still be full of gaps, according to Alan March, senior lecturer from the Melbourne School of Design at University of Melbourne.

“The current star rating system measures the performance of buildings. That’s good – it means they don’t let heat pass through windows or walls as badly as in the past. But there’s a whole range of opportunities to make them perform even better,” he says.

In a forthcoming research paper, co-authored with Christina Collia, Dr March found that the building code skips over bigger picture concerns, including the location and materials used in the home, as well as waste production and links with public transport and bicycle paths.

Even simple things, such as clotheslines, are left out in the cold. “If people want to dry clothes outside, it’s no good if the backyard or the balcony never gets sunlight. They’ll buy an electric dryer instead, and all the building technology goes out the window very quickly when you start using electricity from Hazelwood Power Station,” Dr March says.

He believes it would be simple to peg extra features onto existing planning controls. Those guidelines could encompass native habitat, rainwater tanks, fixed heating and cooling systems, lighting and daylighting, and even food growing and composting areas.

“We could go beyond a technological view of individual houses and start to create whole communities,” he says.

The Moreland City Council is already hoisting homes above the average with STEPS, a web-based tool that assesses residential sustainability. It covers five areas: greenhouse emissions from operating energy, peak energy use, water use, stormwater and building materials. The program also considers bike storage and space for waste and recycling.

Shannon Best, from Moreland City Council, says STEPS predicts household energy use more accurately than the star ratings. “If you install a lot of lights or an inefficient hot water service and air conditioner in a five-star house, you can end up with a much worse result than an existing home. It’s important to look at the whole product, not just the thermal efficiency.”

A group of 14 Victorian councils – the Council Alliance for a Sustainable Built Environment – is now promoting STEPS as a voluntary measure for residents submitting planning applications.

Mr Best says the tool’s key benefit is to begin conversations about sustainable design. “If you’re going to build a house, ask your architect or designer to put it through STEPS to see how it performs,” he says.

“Last year alone, we calculated that the savings were equivalent to one-third of council’s greenhouse emissions and water use. That comes from getting people to talk about sustainability initiatives in their buildings – people can and do learn.”

Dr March says that while STEPS opens up a path to greener homes, a more comprehensive, compulsory scheme would be easier for local governments to enforce. “It’s a simpler and better outcome if the process is standardised across Victoria,” he says.

“Whether it’s sooner or later, we will do these things – and we as a community will be better off. People will be happy not to have to switch on their lights. Developers will enjoy the certainty that it provides, and they’ll have a better product to sell.”

A place making conference draws a new map for the city’s public life.

WHAT makes a “good” place? It could be a street where kids can safely chalk their hopscotch squares, a neighbourhood where you walk to the locally owned baker, or a public square that fizzes with action.

According to Gilbert Rochecouste, from Village Well, vibrant places such as these often connect high quality of life with low environmental impacts. They’re likely to reduce private transport and consumption, and encourage food production, green building and socially responsible business practices.

“The biggest thing we can do to reduce our carbon footprint is to create affordable, accessible, amazing places,” he says.

The Melbourne Place Making Series conference will be held from Wednesday 27 to Friday 29 October. It is hosted by VicUrban, together with Village Well, Fed Square, City of Melbourne and the Department of Planning and Community Development.

The series has been running six months, including online discussions and forums for developers, financiers and the community sector. It aims to engage government, industry, planners and international experts on how we can make our city and our suburbs better places to be.

Mr Rochecouste says development too often focuses on hard infrastructure, such as roads, buildings and utilities, at the exclusion of less obvious necessities.

“Place making brings in the soft infrastructure, like the gathering places, the culture, the walk-ability and the daily rituals of living,” he says. “All the things that we yearn for and take for granted when we visit great places, like Europe.

“But we don’t get them here. We’ve taken our model from America and delivered it to disconnected places. We’ve separated living, working and entertaining. Place making brings it all together,” he says.

VicUrban CEO Pru Sanderson says the idea differs from normal urban design in its scope and holistic vision. “Place making cuts across a whole range of disciplines. It is about more than just design,” she says.

“It’s about creating places that are resilient and can grow and respond in a climate-challenged future. We want this to be the mindset for new developments and for revitalising older areas in Melbourne.”

The agency has brought a place-based approach to its Revitalising Central Dandenong initiative. It is transforming the main road, Lonsdale Street, into a pedestrian-friendly boulevard and creating areas for people to congregate. It’s also running community arts programs with the local council. “It is about nurturing the economy, culture and physical place all at once,” Ms Sanderson says.

Mr Rochecouste says the best changes are resident-driven, rather than design-driven. “We run participatory democracy sessions, so people are deeply engaged in the process. When you do it well, you get much better places – you get the x-factor,” he says. “People say what they want and how they want it, and we end up with a much more informed and inspired citizenry.”

In that forthright spirit, he says we shouldn’t wait for good places to fall upon us: place making begins at home. “The first physical structure is our household, and then our footpath, street and local shops. All these things are our daily narratives – the more beautiful they are, the more connected, the more people feel like they can say hello to their neighbour. They feel safer,” he says.

“Neighbourhood renewal, street parties and celebrations. All these details add to people’s quality of life. That’s place making.”

Community-ownership could herald a gust of green power.

CONSTRUCTION is about to begin on Australia’s first community-owned wind farm. The Hepburn Community Wind Park Co-operative held its official groundbreaking ceremony last week at Leonards Hill, 10 kilometres south of Daylesford.

Vicki Horrigan, a director of Hepburn Wind, says the turbines should be ready and rotating by mid-2011. “It’s over five years since the local community here had the idea. And now we’re building a project worth just under $13 million.”

The wind farm comprises two turbines with a combined capacity of 4.1 megawatts. They’ll be built by German company REpower Systems AG and connected to the grid.

“The turbines are estimated to produce about 12,200 megawatt hours each year,” Ms Horrigan says. “That’s enough to power 2300 homes, which is more than the number of households here in Daylesford and Hepburn Springs.”

Hepburn Wind was set up as a co-operative. Membership is open to all Victorians, but there’s a lower minimum investment threshold for locals. All members get one vote, regardless of the size of their shareholding. Once they’re whirling, the turbines will generate a return for members and contribute funding for local projects.

“The structure has been a real bonus for engaging the local community, because they can see the idea came from here and they can participate in it easily,” Ms Horrigan says. “It’s a good financial model, but it’s also a good philosophical model – it’s socially responsible investment.

“People often feel powerless about climate change on a global scale. This project shows that local communities can set up systems that really go towards making ourselves sustainable.”

Precinct-scale power generation can also be much more efficient than a house-by-house approach. The Hepburn Wind turbines will cost far less per household in the area than a comparable roll out of rooftop solar photovoltaic panels.

The group’s success has turned heads. “We get a couple of requests every week from other communities wanting to find out about what we’re doing and how they could start something similar,” Ms Horrigan says.

There’s a lot of advice to pass on – among the thorniest impediments have been raising the capital, estimating costs and gaining planning approval.

For this reason, a spin-off organisation, called Embark, has been founded to support other communities through the process.

Embark’s executive director Mary Dougherty says the organisation is already in contact with about ten groups, including some working on proposals for mini-hydro and solar schemes, as well as wind turbines.

“We’re trying to break down the steps involved and provide practical advice and templates, like business plans, financial models and landholder lease agreements. It’s much easier than starting with a blank slate.”

There are scores of articles on Embark website, covering everything from the ins-and-outs of the energy market, to how to run effective public meetings, together with case studies from both here and abroad.

In Denmark, co-operatives own over a quarter of the country’s wind farms. “In the European countries where these community projects started out, they have a far greater uptake of renewable energy overall. These small projects lead to large ones,” Ms Dougherty says.

“In ten years, we’d love to have started 100 projects. Through all the investors, that translates to about a million people who are exposed to the benefits of renewable energy first hand. That’s really powerful.”

When you’re building or paving, put concrete alternatives into the mix.

IT’S hard to get away from concrete. According to Dr Peter Duxson, from eco-concrete company Zeobond, it’s the second most used commodity in the world, behind only water. It also accounts for about five per cent of global carbon dioxide emissions.

“Wherever there is human activity, there is concrete. It’s versatile and cheap,” Dr Duxson says. “It just turns out that the base ingredient that makes concrete go hard is bad for the environment.

Conventional concrete is made up of sand, rock and water, bound together with Portland cement. Although the cement comprises only 10 to 15 per cent of the substance, it accounts for about 70 per cent of its carbon footprint.

The high greenhouse gas emissions come from burning limestone to create lime – from both the energy required to heat the kilns and the chemical reaction in which limestone releases carbon dioxide. “One kilo of carbon dioxide is emitted per kilo of cement,” Dr Duxson says. “So every concrete truck equals about two tonnes of CO².”

Among the material’s plusses are its extremely long lifespan and usefulness as thermal mass in appropriate solar passive design – it can help to even out day and night time temperatures.

For example, an exposed concrete slab floor, positioned by the window in a north-facing living room, will receive direct sun in winter. It absorbs heat and warms the house into the night. With appropriate shading, the sun won’t hit the slab over summer, so the chill of the concrete will help the home stay cool.

Even so, you can significantly reduce the emissions caused by concrete in your home by opting for lower-carbon concrete and choosing other materials where you can, especially outside.

Look for products with reduced Portland cement content, such as TecEco’s magnesia-based Eco-Cement, Boral’s Envirocrete or Independent Cement’s Ecoblend. Up to 30 per cent of the cement in conventional concrete can be directly replaced by fly ash and slag (by-products of burning coal and smelting iron ore, respectively) without compromising quality. “Once you get beyond that, it starts to take longer to go hard,” Dr Duxson says.

There are also many products that use recycled crushed aggregate. Be aware that although it’s a good way to save virgin resources, it doesn’t significantly reduce the carbon dioxide emissions of the product.

Dr Duxson’s business, Zeobond, makes Ecrete, a kind of concrete that completely replaces Portland cement with fly ash and slag. Known as a geopolymer or alkali-activated concrete, Ecrete produces two-thirds fewer carbon dioxide emissions than the conventional product. It uses other chemicals to kick-start the binding process and ensure the curing time is fast.

The first Ecrete supplier is located in Epping, in Melbourne’s north-east. Zeobond also manufactures pre-cast panels and pavers. “The cost premium on Ecrete is about ten per cent, but as we get to scale, we expect that price to come down quite significantly,” he says.

The other alternative is to minimise your use of concrete altogether. Inside the home, there are other materials that can provide thermal mass, such as earth or brick. Outside the home, the sustainable design guide Your Home recommends only paving where you sit, stand and walk. Too much paving will make your house and garden hotter and reduce the amount of rainwater that soaks into your soil.