Guide to sustainable building materials and practices 

Timber is a renewable resource and can be readily sourced from sustainably managed forests and plantations. It’s light and easy to work with for builders and requires minimal specialist equipment beyond standard carpentry tools. It also has a very low environmental impact when it comes to the energy used to turn it into a usable material (known as embodied energy).

The major drawbacks are that it deteriorates over time (particularly timber exposed to the outside elements, such as decks or balconies) if not carefully maintained by oiling or painting, which takes time, effort and money.²

Additionally, most weatherboard homes built before 1990 don’t have insulated walls, meaning they can get very cold in winter and hot in summer.³ Of course, you can add insulation to a timber home when renovating or building a new home.

Bricks come from a non-renewable source, as clay is dug out of large pits and fired into bricks, while the components for concrete bricks are also mined in various ways. However, they are reusable; should a building be demolished, the bricks can be cleaned and reused as new building material or paving.

The longevity of brick buildings is much greater than timber. But there are some issues with the thermal properties of brick veneer (single layer brick wall) buildings in summer during extended heat waves, due to the heat building up in the walls.⁴ To stay warm in winter, these homes may also need to be draught proofed.

It’s worth considering roof tiles such as terracotta, clay or even slate (cut stone). As some tiles can use a lot of energy in their creation, consider looking for locally made tiles with fewer plastic components or recycled roof tiles.

Old tiles and bricks can also be repurposed; you could make pathways, garden features (e.g. fire pits, garden bed edging) and craft projects that can add a fun touch to your home.

A classic sustainable building material that’s been around for thousands of years, mud bricks can be a cost-effective material for building a home.

The low energy inputs for material transport and construction make mud bricks an attractive option for those wanting a sustainable building material, as they’re formed and dried using only natural energy from the sun.

However, as mud brick has low levels of natural insulation, buildings may need additional insulation to be compliant with the National Construction Code in Australia.⁵

A variation on mud bricks, rammed earth uses onsite soil mixed with gravel, silt and sand that is poured into a wooden or metal temporary frame (the ‘formwork’) and pounded into solid walls. Once set, the formwork can be taken away.

It may, however, need to also consist of cement (5-10% of the mixture) in a process known as cement stabilisation to make the walls sturdy and more capable of bearing weight; this does make it a less environmentally friendly material.⁶

Like the name says, straw bale construction uses bales of hay or giant, straw-like bricks to build walls. The walls are then covered with a render to prevent moisture from entering and rotting away the straw. This also stops potential fire hazards and keeps vermin out of the straw where they could otherwise nest and cause structural integrity problems.

Straw is a waste product of hay, and as much of it is usually burned, using it in construction instead lowers air pollution and stores carbon.⁷ It’s also a good insulating material.

Concrete can be purchased in bulk and is simple, versatile and durable, making it an attractive building option. A common way to use these materials is by pouring concrete around steel reinforcing mesh in a frame. This may be done onsite, or prefabricated concrete panels can be transported from a manufacturing plant. In addition, you can use reclaimed or recycled steel for the frame.

Precast concrete blocks are also an option if you want to expend less energy on the construction site. While their embodied energy is relatively high compared to other sustainable building materials, you can choose to have the blocks made from recycled aggregate and steel. This keeps waste products from being sent to a landfill and makes the material eco-friendlier.⁸

Steel and concrete are also commonly used for roofing, with concrete tiles and metal sheet roofing being popular choices. Metal roofing is less environmentally friendly than clay tiles, but not by a lot. This is because the thin size of the metal compared to thicker clay tiles means you need less material to cover the same amount of area.

Similar to regular concrete, hempcrete (also known as hemp masonry and hemp-lime composite) is a more economical and environmentally friendly alternative. It’s made by combining the centre wood part of hemp stems with water, lime binder and occasionally sand.⁹

The move towards hempcrete as a building material is based on its minimal environmental impact, and the combination of being a natural insulator with high breathability. Hemp fibre crops have low water needs, and as a natural resource are fast-growing, so there can potentially be multiple harvests in a single year.⁹ In addition, the material is naturally resistant to mould growth, fire and potential pests.

However, it’s a heavier material and requires a timber frame, which acts as the weight-bearing frame allowing hempcrete to be built around it. Hempcrete is also at risk of cracking if built too thin, so all walls should be thick and solid. It’s not often used for roofing due to the heavy weight of the material; however, in recent years, a lighter weight version is increasingly being used for roof insulation.

As Australia grows more environmentally conscious, there are a number of new and emerging sustainable building materials and an increasing demand of less common ones.

Numerous specific building products are available, including specially-designed materials that behave like brick or concrete but have enhanced thermal insulation properties. They include materials manufactured using wood waste, plastic waste, recycled glass bottles, polystyrene or even aerated concrete, manufactured using various industrial processes. This gives new life to many old materials that would otherwise be sent to landfill.

There’s also a growing interest in new materials such as mycelium, a thread-like fungi structure. Mycelium is an extremely sustainable and eco-friendly source of material that is biodegradable, has high density and is low in cost to produce.¹⁰

The sustainability of these building materials varies, so each material should be considered individually. However, choosing a material with good insulation may save you on electricity later if your home requires less heating or cooling.

Beyond the construction of a sustainable home, there are ways to continue to support the environment and reduce greenhouse gas emissions even after you’ve turned the lights on. By choosing a clean energy plan, or one that has a high percentage of GreenPower, you can help increase the amount of renewable energy added to the electricity grid.

By comparing energy plans from a range of providers, you can search for ones that are part of the GreenPower program. But keep in mind these plans may be costlier than a regular electricity plan.

In Australia, our summers can be sweltering hot, especially if you can’t escape the sun. Before you start building, taking the seasons into account can help alleviate some of the burden electricity has on heating or cooling your house. There are a range of building design choices that can help keep your home at a comfortable temperature year-round, including:

• Have smaller windows with shaded blinds on the east and west of the house to help protect against the hot summer sun.
• Zone your most used rooms to the north as that part of the house will be the most comfortable year-round, and lesser-used rooms such as garages and bathrooms to the west.
• Bigger north-facing windows allow low-angle winter sun in to warm the house, though shades might be necessary for summertime.¹¹

Your location within Australia can make a difference too, based on the angle of the sun and general temperature experienced across the four seasons. Also, you might have natural breezes that you can take advantage of in the summer months.¹²

Good insulation is crucial for anyone wanting to limit their energy consumption to heat or cool their home. Insulation provides a barrier that keeps heat from escaping your house in winter and from entering in summer, and reduces your reliance on air-conditioning and other heating and cooling appliances. It works best when combined with a design that promotes passive heating and cooling.

Choosing an insulation material that is eco-friendly can help reduce your energy carbon footprint.

Bulk insulation materials considered to be more environmentally friendly include natural wool, cellulose fibre and polyester.¹³ Cellulose insulation is usually made from at least 82% to 85% recycled materials.¹⁴

Before deciding on an insulation type, consider both the insulation level (known as the R value) of the material and your local climate.¹³ Not all insulation materials are suited to humid or dry climates, so be sure to choose one that will be effective in your environment.

Photovoltaic (PV) solar panels and batteries or solar hot water systems can significantly reduce reliance on non-renewable energy sources. The initial cost for solar panels may be relatively high, but solar systems will pay for themselves over time. A good solar system can potentially save you money, particularly if you store solar during the day in a battery for use at night.

Harvesting rainwater in tanks can save you some expense in the long term, reduce your reliance on the water supplied by the city and provide a backup water source during emergencies.

However, it’s important to ensure that your gutters and tank are well-maintained, and if you plan to use the water for consumption, that you make the appropriate health and safety considerations.¹⁴

Green walls and roofs refer to gardens covering the roofs and walls of your building. Green walls have a range of benefits, including:

• Cooling the air
• Providing insulation
• Blocking out sound
• Creating additional gardening space
• Helping improve the efficiency of solar panels
• Reducing local flooding by capturing rain.¹⁵

Growing your own vegetables at home can further improve your home’s sustainability if you have a ‘green thumb’ and love to garden (or even if you don’t!). You put the soil to use and become more self-reliant, meaning you don’t need to buy as much food from the supermarket.

Not only does this help save you money, but growing your own veggies can help reduce your family’s impact on the environment. This is because there is a lot of long-distance shipping involved in supplying supermarkets with fresh produce, which often involves fossil fuels.