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Make an informed choice

Every building project involves many decisions, both big and small, on the materials to be used. This can be complex, as every material has an impact on our natural environment and our society in terms of its production, use and disposal. This needs to be weighed up along with the material’s expected contribution to the energy efficiency and comfort of the house, and its financial cost.

Environmental and social considerations for selecting materials include:

  • Embodied energy (the energy consumed by all the processes associated with the production of a material, from the mining and processing of natural resources to manufacturing, transport and product delivery)
  • Renewability of the raw material
  • Recyclability
  • Durability, longevity and maintenance requirements
  • Toxicity of the manufacturing process and the material itself
  • Health impacts (for more information, see our Healthy Homes ebook)
  • Waste minimisation during production and installation

We recommend Your Home for an excellent overview of the issues involved in materials selection. For more detail, the book How to Rethink Building Materials is an invaluable resource.

For extra guidance on specifying building products, see our Sanctuary article Material benefit. And for inspiration on building with minimal waste, read our article on building without skip bins.

Read on for an overview of some common materials in sustainable homes.

This impressive table at Peter McKay’s Passive House in the ACT is made from re-milled timber Peter reclaimed from a series of footbridges which were being replaced in the park across the road.
Earth building and regenerative materials

Humans have been building with earth in its various forms for tens of thousands of years. The term is used to refer to buildings made of earth-based materials other than stone, and not fired like clay bricks. In Australia, contemporary earth building materials are usually rammed earth or mud brick; other techniques include light earth and cob. Rammed earth walls are made with a mix of gravel, sand and clay, commonly mixed with about five per cent cement. Minimal extra water is added, and the mix is set within timber or steel forms and manually or pneumatically tamped down. Mud bricks are generally made in moulds from wet plastic clay, and dried on the ground. Many practitioners add fibres to the mix to reduce cracking during the drying process. For more on earth building, read our Sanctuary article From the ground up.

Also in the natural building materials category, regenerative materials are readily renewable and include bamboo, straw (in strawbale form) and hemp.

Lightweight and with the tensile weight-for-weight strength of mild steel, bamboo is a grass rather than a timber. In the right conditions it can grow up to 30cm a day, and can be harvested without destroying the original plant. These qualities make bamboo one of the world’s most sustainable building materials. Laminated bamboo products are used widely for flooring. Read more about bamboo for building.

Rendered strawbales offer fire resistance, are more resistant to vermin and rot than most timber, and provide insulation values that comfortably exceed the most stringent demands of the building code. And as a sustainability bonus, when the building’s life is over, most of its walls can be turned into mulch. Strawbales can be used as infill in timber or steel framed structures, or (less commonly) can be built as load-bearing walls. Read more about building with strawbale and how to learn the skills you’ll need.

Hemp masonry is gaining recognition as a high-performance, low-impact and contemporary building product. It has benefits for the performance and liveability of the building, it is kind to the world in its processing, and it is one of the super-crops that are part of the regenerative farming revolution. It can be used in several ways in building, and goes by several names, such as ‘hemp-lime composite’, ‘hemp masonry’, ‘hempcrete’, and simply ‘in situ hemp’. Read more on building with hemp in Sanctuary magazine.

Concrete

Concrete, most commonly in the form of floor slabs, is a standard way to embed thermal mass in passive design. However, conventional concrete has high embodied energy and is responsible for high greenhouse gas emissions, mostly from the production of Portland cement and the mining of raw materials. This impact can be significantly reduced through the use of eco-concrete that replaces some of the cement content with alternatives like fly ash. To help decide whether a cement floor is right for you, read our Sanctuary article When is a concrete floor the right choice?

Beyond Zero Emissions’ publication Rethinking Cement is an excellent resource for those interested in the future of zero carbon cement in Australia.

Timber

Timber is a versatile and attractive material that is often a top choice for flooring and decks, structural framing, exposed roof beams, detailing like architraves, and cabinetry. It’s a renewable resource, but it can come with huge environmental costs. To avoid contributing to illegal and unsustainable forestry operations, make sure you’re choosing timber with a sustainability certification: FSC (Forestry Stewardship Council) has the most robust requirements. Better still, use recycled timber if you can; read more about the things to consider in our Sanctuary article.

Brickwork and blockwork

Components of masonry construction, bricks and blocks are high mass materials that can be made from fired clay, stone, manufactured stone, concrete and glass. When insulated on the outside as part of a reverse brick/block veneer or insulated cavity masonry wall, these materials provide excellent thermal mass benefit, stabilising the internal temperature and improving the thermal comfort of the house. Read our Renew article on thermal mass and how to include it in your home design, and our Sanctuary article on greener building blocks.

Engineered and prefabricated materials

There is an increasing range of engineered and composite materials available for building, including cross laminated timber (CLT), plywood, structural insulated panels (SIPs), fibre cement composite products and many options for prefabricated panels and other building components. These can offer a range of benefits from waste minimisation to increased strength and longevity.

SIPs provide a strong, efficient and lightweight prefabricated alternative for walls, roofs, and floors. The high performance composite building material is a load-bearing structural system usually consisting of an expanded polystyrene (EPS) insulating foam core sandwiched between two outer engineered skins, typically oriented strand board (OSB), but which may also be magnesium oxide, plywood, sheet metal or fibre cement. Read more in our article Composite benefits: When are SIPs the right choice?

Prefabricated or off-site construction is taking off in Australia. It falls into two main construction categories – modular and panelised – but within these a huge range of different products is on offer. The prefab approach offers efficiencies in build time, waste minimisation, and options for high building energy star ratings, renewable materials and cost-effective production. We look at the latest developments in the prefab industry in Sanctuary.

Steel and sheet metal

Metal in beam and sheet form – most commonly steel and aluminium, and occasionally zinc and copper – is a common choice for structural framing, roofing and wall cladding, and window frames. Very durable and requiring little maintenance, it’s a material that is also extremely recyclable, although the embodied energy is high.

Materials options for different parts of your house: roofs, walls, floors and fences
Roofs

There are many different roofing materials to choose from, but what are the advantages and disadvantages of each, and how sustainable are they? We survey the market in our article A roof over your head.

Walls

There are many different approaches used for building the walls of a home, but which one is ideal for your build? We take you on a quick tour of the different systems, materials and their sustainability credentials in our article Bricks, blocks and panels: What’s in a wall.

Floors

When building, you may put a lot of thought into the floor coverings, but what about the sub-floor structure? Both are important to ensure a sustainable result. We survey the options in our article The right floor for your build.

Fences

Contemporary architecture is inspiring many of us to think more creatively about house design. With a little extra planning, you can push the boundaries of your fence design as well. Read about fencing design and materials in our article Pushing the boundaries.

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