Energy efficient construction

There are a range of sustainable building materials that are both Earth friendly and elegant at the same time. Mud brick and poured Earth construction techniques are just a few of the options available for earth friendly construction. Building with alternative materials can be a challenging but ultimately rewarding adventure.

Below you'll find some some tips, advice and information to consider if you're thinking about embarking on a energy efficient building project that involves sustainable building materials.

Earth Building

Mudbrick, also referred to by the Spanish name of 'Adobe' which means mud or puddled earth, generally refers to the technique of building with sun-dried mud blocks in either load bearing or non load bearing construction. Mudbricks are becoming increasingly commercially available in a range of stabilised and non stabilised bricks.

Mudbrick has several advantages over conventional fired clay or concrete masonry. The advantages include:

  • Low in embodied energy
  • Utilisation of natural resources and minimal use of manufactured products
  • Good sound absorption characteristics
  • High thermal mass
  • A claimed ability to "breath"
  • Suited to a wide range of soils
  • Easily manufactured and worked
  • Flexibility in design/colour/surface finishes
  • Insulation properties similar to those of concrete or brickwork

Mudbricks are typically 250 mm wide x 125 mm high x 375 mm long and normally made from earth with a clay content of 50 to 80% with the remainder comprising a grading of sand, silt or gravel. Kaolin clays are the preferred clay types due to their non expansion characteristics. Stabilising the mudbrick with straw or other fibres is sometimes employed where the soil mix displays excessive shrinkage behaviour. Cement and bitumen stabilising is also used with the latter particularly effective in waterproofing.

From an engineering viewpoint, mudbricks typically have compressive strengths of around 1 to 2 MPa and need to posses a demonstrated resistance to erosion and cracking before being accepted for construction. Mortar for mudbrick laying is either a traditional sand/cement mortar or a fine aggregate soil mortar preferably made from the same parent material as the mudbrick units.

Finishing of mudbrick walls can be undertaken with a variety of techniques ranging from as constructed to a simple "bagged" finish to a full set earth render. Linseed oil is commonly used to seal the exterior of as constructed mudbrick.

Cast Earth (Poured Earth) Construction

Also called, rammed Earth construction, cast earth is a modified and now patented building material which uses a composite which is is made up with soil as its bulk component. Generally it is mixed with calcined gymsum (plaster) instead of cement. Generally it can be used to form solid walls without reinforcement. Forms are typically set up and then filled (or poured) with the cast earth. The forms are removed once the mix has set.

Other Earth Friendly Building Materials

Where possible sustainable buildings should be manufactured off site - this approach helps to reduce wastage and helps to maximise recycling (because it can be done on site). Building materials which might also be considered "sustainable" also include green lumber from certified growers. Recycled stone, recycled metal (and other recyclable products, including tiles, glass and even tyres) can be used.

If you're not sure where to start, or what materials might be appropriate for your building, you should discuss your requirements with a a building planner who has had experience creating ecologically friendly designs in the materials you may be considering for your project.

For further information please visit the GBCA website - http://www.gbca.org.au/green-star/ and check out their green building case studies for ideas about your own projects.