The types of materials selected at the design stage of building a home will impact fundamentally on its longer-term sustainability. These choices have implications for saving energy, improving bushfire resilience and improving comfort.
Building materials typically considered to be ‘green’ include renewable plant materials like straw and mud brick, timber from forests certified to be sustainably managed, recycled materials and other products that are non-toxic, reusable and renewable.
Concrete is an excellent material for creating thermal mass in a passive solar designed home. In temperate and cool climates thermal mass helps regulate a home’s temperature and keep it warm in winter and cool in summer.
These are a relatively new building system that started in Australia with thermacell blocks. Generally, these systems consist of a range of wall blocks and corner blocks that are assembled onto a solid foundation, such as concrete slab or footings, to make a complete wall.
Timber is probably the most commonly used building material there is. It is strong, flexible, readily available and providing it is sourced properly, is a renewable resource. It is an easy material to work with and requires relatively basic skills, making it ideal for owner-builders
Mudbricks are pretty much what they sound like – bricks made of mud. Often, they are made on site from local soil, providing there is enough clay content.
The soil is mixed with water and reinforcing materials such as straw and even cement and then pressed into wooden forms and allowed to set.
The forms are removed and the bricks set aside to dry for up to several weeks. As they are made from natural materials they are a sustainable, recyclable, non-toxic and healthy form of building construction.
Strawbale building like mudbrick is a good sustainable choice as it is made from natural materials they are a sustainable, recyclable, non-toxic and healthy form of building construction.
Rectangular strawbales are stacked up to form walls, fixed in place with metal or wooden pins, and then trimmed and shaped (often using a chainsaw!) before being rendered with mud or cement based renders.
Timbercrete is an interesting material, being a combination of timber waste (sawdust) from various sources and concrete. This results in a material that is lighter than solid concrete, but of greater strength and with better insulating capabilities.
Some Timbercrete products can produce walls with R ratings of 3.7, which is higher than most other materials except strawbale.
Rapidwall is a load-bearing wall construction system that uses large prefabricated panels to assemble both inner and outer walls in one go.
The panels are made of fibreglass reinforced water resistant gypsum plaster which is moulded to the required size.
Panels are available up to 12 metres long and 3 metres high, so entire walls can be prefabricated and then installed onsite using a crane.
Common clay house bricks as a building material have the advantage of high thermal mass, so they can be used to store or absorb heat to help provide temperature stability inside a home.
However, to do this, they must be on the inside of a home, not on the outside.
Not to be confused with mud brick, rammed earth is a precisely controlled mixture of gravel, clay, sand, cement, and sometimes lime or waterproofing additives.
The contents are carefully proportioned and mixed, and then machine-compacted in removable formwork to yield a stone-like wall that is massive, water resistant, load bearing and long lasting.