When it comes to constructing a new home, many of us want to reduce any impact to the environment as much as we can.
By building with sustainably sourced materials and taking sustainable design principles into consideration, you can build harmoniously with nature and add value to your home.
Happily, there’s a variety of sustainable building materials to choose from if you want to go down this path. In this guide, we’ll cover options both ancient and modern options for you to explore so that you can build a more sustainable home for the future.
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).2
The major drawbacks are that it deteriorates over time if not carefully maintained by staining, oiling or painting (which takes time, effort and money).3 Additionally, sustainability Victoria notes that most weatherboard homes built before 1990 don’t have insulated walls – this means they can get very cold in winter, and hot in summer.4
Of course, you can add insulation to a timber home after the fact when renovating, and when building a new home, it’s easy to include insulation when building.
Timber can also be used for edging parts of the garden path, roofing, retaining walls, footpaths and other aspects of the home. Depending on the specific element of the home, you may be able to use reclaimed wood and recycle materials from a previous building – further reducing any environmental impact from your 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. While there are some issues with the thermal properties of brick veneer buildings in summer, double brick or ‘cavity brick’ buildings have excellent insulating properties during winter.5
It’s also worth considering roof tiles such as terracotta or clay or even slate (cut stone). Slate is heavy, relatively fragile and often imported. Even clay tiles have a considerable amount of energy involved in their creation and they may have plastics mixed-in.
However, you may be able to recycle roof tiles or look for locally made tiles with as few plastic components involved as possible.
A classic sustainable building material that’s been around for thousands of years, mud bricks are generally constructed onsite using available soil. This style of home is also known as ‘Adobe’ in some parts of the world.
The low energy inputs for material transport and construction make mud bricks an attractive option for those wanting sustainable building material, as they’re formed and dried using only natural energy from the sun and wind.
However, mud brick (and earth walls) have a more complicated building approval process as the Building Code of Australia is undergoing an update and the current version no longer mentions earth wall construction. The South Australian Government encourages anyone interested in using mud brick to contact a structural engineer or expert builder for advice.6
A variation on mud bricks, rammed earth uses onsite soil mixed with gravel, sand that is poured into a wooden or metal temporary frame, known as the ‘formwork’, and pounded into solid walls. Once set the formwork can be taken away.
The Earth Building Association of Australia notes that it is easy to mould and shape, with the only limit being the formwork frame.7
Another type of rammed earth construction is known as cob construction. It uses straw as well as soil, gravel and sand, but no formwork frame. The use of straw helps improve insulation, but the lack of a frame means the walls are typically smaller and less dense.8
Like the name says, straw bale construction uses bales of hay or straw-like giant 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 bale buildings generally have good thermal insulation. The bales of straw themselves can be load bearing, but in places that receive snow or extreme weather, the home can be built on stronger supports and use the straw bales to fill in the walls and provide insulation.9
One key downside is that the plaster which protects the straw can crack and will need to be maintained to prevent mildew, pests damage and to ensure the home is resistant to fire.
Straw can even be used to make thatched roofs, though this is very rare in Australia due to the risk of bushfires, mould, and pests making themselves at home in the roof.
You’re more likely to see grass roofing on small gazebos and huts by the pool to add a ‘tropical feel’ to a home, rather than as a roofing material.
The increasing use of steel and concrete in construction is primarily an economic one. Materials can be purchased in bulk and used on any project of pretty much any size.
The most common way to use these materials is by pouring concrete around steel reinforcing mesh in a frame, then attaching the formed walls to a steel framework. This may be done onsite, or prefabricated concrete panels can be transported from a manufacturing plant.
Concrete is really good at retaining heat from daylight. While this will be good in winter and cool nights, it can be an issue if you have a concrete floor exposed to the sun in summer. Sustainability Victoria recommends using concrete floors in homes that are north-facing, as this orientation naturally reduces the harsh impact of summer sun while keeping the house well-lit and warm in winter.10
Steel and concrete are also commonly used for roofing with concrete tiles and metal sheet roofing. 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.
There are numerous specific building products available, including specially designed materials that behave like brick or concrete but have enhanced thermal insulation properties. They include materials manufactured using wood waste, recycled glass bottles, polystyrene, or even aerated concrete, manufactured using various industrial processes.
The sustainability of these building materials varies, so each material should be considered individually.
It’s also worth noting that the type of material you use can affect the value of your home, which in turn affects the cost of your home and contents insurance.
During summer the sun shines down from east to west at a higher angle, beating down below.11 For this reason, the city council of Joondalup in Western Australia notes that there are a range of building designs choices that can be built-in to make a difference:
Your location within Australia can make a difference 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.13
Photovoltaic panels (PV) solar panels and batteries or solar hot water systems can significantly reduce reliance on non-renewable energy sources. The initial outlay for solar panels may be relatively high, but solar systems will pay for themselves over time. A good solar hot water system can save energy too by heating water when the sun is available, and storing it in a battery pack for use later on.
Harvesting rainwater can be beneficial, especially if you use it to water a vegetable garden. It can save you some expense in the long term and reduce your reliance on the water supplied by the city, and provide a backup source of water during emergency situations.
There are various sizes and options to choose from, but there are some common maintenance tips as noted by the Brisbane city council:
Water storage does have drawbacks – all water catchment needs to be accounted for.
For example, storm water drains are calculated to operate with a certain flow-through of water each year, with a particular peak flow that cleans them out once in a while.15 If water is taken out of the system before it reaches the storm drains, cleaning them out may mean someone has to get in there and do it.
In some cases, water companies will continue to charge fees for this kind of service even if you don’t buy your water from them. It’s worth checking into with water supply companies and city councils in your local area.
Green walls and roofs refer to gardens covering the roofs and walls of your building. The NSW Department of Planning, Industry and Environment notes that green walls have a range of benefits:
Also known as ground source heat pumps, geothermal heat pumps offer a more environmentally friendly heating option that reduces energy usage, making the home more sustainable. Geothermal heat pumps work by harnessing the heat underground through pipes connected to the heat pump that draws heat up from below the earth’s surface.17
Geothermal heat pumps can also be used to help cool the home too by using colder temperatures under the ground during hot days.
While they do cost more to install than other heating and cooling systems, geothermal heat pumps can help reduce electricity usage and have lower ongoing maintenance costs.
If you have a ‘green thumb’ and love to garden (or even if you don’t), growing your own vegetables at home can further improve your home’s sustainability. You put the soil to use and become more self-reliant and need to buy less 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 involves fossil fuels.