Last Updated Feb 14, 2013 · Written by Craig Gibson
Brick veneer isn’t necessarily the most eco-friendly building material for your home. Making bricks requires a lot of energy, and brick veneer provides poor insulation, meaning more energy, to heat and cool your home. Bricks can also be difficult to recycle. This article introduces some alternative, more eco-friendly building materials. The most appropriate choice for your home will depend on your block, location and climate. For instance, lightweight materials cost less to transport to remote locations and make more sense for an elevated home on a sloping block, while heavier materials can provide better insulation. An architect, building designer or builder can help you decide on a building material that will work for your home and for the environment.
The key points are whether the material came from a sustainable source, such as timber from a sustainably managed plantation, and how much energy was used to make it (its “embodied energy"). For instance, steel needs a lot of energy to manufacture while mud brick need none. Transport fuel is part of a product’s embodied energy so for remote locations, lightweight materials may be more eco-friendly.
Materials with good insulation properties are more eco-friendly because less energy will be needed to heat and cool your home.
The longer-lasting it is, the better for the environment – and for you
4. Disposal and recycling
Is the material easy to dispose of in an environmentally friendly way? Better still, can it be recycled?
Mud bricks are made by mixing clay earth with water and sometimes straw (which helps stop the bricks cracking), then placing the mixture into moulds to dry in the sun. Mud bricks are joined with a mortar, made from a similar clay-water mix as the bricks themselves. They need to be protected from driving rain by paint, linseed oil or turpentine.
Mudbrick is one of the oldest building techniques, and one of the most eco-friendly. The only energy needed is sunshine and all the materials are natural. If you have suitable clay on your property or nearby, little or no transport is needed. With maintenance, it is very durable – mudbrick buildings have stood for centuries. And at the end of the building’s lifetime, the bricks will break down to earth again.
Because mud bricks are simple to make, they are a good choice for owner builders. However, making the bricks, while technically simple, is hard physical work and mudbrick is not a particularly good insulator.
Rammed earth - also known as pise - walls consist of a mix of sand, silt, gravel and clay poured between two flat panels (called formwork) and compressed. Stabilised rammed earth is the same with a small amount of cement added to the mix. Rammed earth is usually, although not always, coated with a breathable sealant for added protection. Rammed earth requires relatively little energy to manufacture and can be made using local material if available. However, like mudbrick, it is labour intensive and does not provide particularly good insulation.
Strawbale consists of straw bound with mud and compressed into blocks by wires. Strawbale walls are normally rendered with a smooth layer of cement or earth. Strawbale is surprisingly durable, and provides excellent insulation (and sound insulation). Straw is a renewable natural material which absorbs carbon dioxide (CO2) while growing. Straw for building often comes from farming waste that would otherwise be burnt off, releasing the CO2; instead, strawbale locks the CO2 into your building’s walls. It can also be mulched after use. Again, however, making strawbale is labour intensive.
While it takes a lot of energy to make steel, it is very long-lasting – a house with steel walls could be expected to last a couple of hundred years. And it can be easily recycled or reused and is lightweight, making it cheaper to transport. Currently, about 60 per cent of steel used in Australia is recycled. These features make steel a potentially eco-friendly option. Steel gives a home a striking, modern look and some of Australia’s finest architects, such as Glenn Murcutt, have built homes using steel.
Like strawbale, wood is a renewable plant-based material that can actually reduce greenhouse gas emissions, because growing trees absorb CO2, which is then stored in the timber. Timber can be reused, or even composted, after use. The main thing to look out for is whether your timber comes from a sustainable source, such as a sustainable plantation, and not from old-growth forests or endangered tropical hardwoods.
Lightweight panel systems made of straw or recycled paper have low embodied energy, are easy to transport and recycle, and insulate well. Autoclaved Aerated Concrete (AAC) is concrete with a lot of air pockets, making it about a fifth the weight of concrete. It is long-lasting and provides good insulation and thermal mass and its embodied energy is much less than normal concrete, making it a relatively environmentally friendly choice.
Covering your roof with a layer of earth with a living lawn (think Parliament House in Canberra) or other plants can provide excellent insulation – and you could even use it to grow food.
Finally, a great way to reduce the environmental impact of your home, and give it a touch of character and uniqueness, is to use salvaged building materials. The embodied energy of salvaged materials is negligible as the material has already been made. You can find a wide range of salvaged materials including bricks, steel and timber.
Why not browse your local building supplies outlet for any of the above?