Performance

Overview

Different building materials are good for different things.  Some are great for capturing and storing heat whilst others have fantastic insulation properties, all of which can help make your home more comfortable.

So how does it work

The pros and cons of different building materials

  • Insulation value

Like insulation and windows, some building materials have an R value which describes their insulation properties, or how much they inhibit the transfer of heat..  The Australian Institute of Energy has calculated these values for common building materials  

  • Fire rating

Depending on where you live, your property will be rated according to the potential Bushfire Attack Level.   This has implications for the types of building materials that you will be able to use. Resources below will assist you with planning and building for bushfire protection:

  1. Building a home: Is your house situated and constructed or modified to withstand a bushfire? A guide to retrofit your home for better protection from a bushfire
  2. Building in a Bushfire Management Overlay
  •  Recyclable/renewable- life cycle approach
  • Appearance

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Here is some samples of non standard bricks

Geopolymer Brick

Made from a very cheap material available in great quantity: lateritic clay earth. This special and abundant earth, mixed with a simple geopolymer binder is compressed to give the shape of a brick then heated in a furnace. Heated at 85°C, LTGS brick is water stable and has enough compressive strength to build a wall.  Compared to a traditional brick fired at 1000°C in a kiln, the LTGS brick needs about eight times less energy for an equivalent strength.

Geobrick

Geobrick is a clay/gravel and cement stabilized composite brick (rammed earth brick), manufactured under extremely high pressures (30 tonne) through a ‘state of the art’ dry press process atBealiba,Victoria. Geobricks use at least 2-6 tonnes less carbon dioxide emissions (CO2) on every new home compared to kiln fired solid bricks.

Timbercrete Brick

Timbercrete is made from discarded timber a waste product (containing carbon) which is sequestered in a cementitious tomb. This process offsets the carbon gas emissions of thousands of cars per year. This product is light weight (2.5 times lighter than concrete or clay) and can be nailed and screwed just like timber.

Timbercrete has an improved fire rating compared to concrete, clay, timber or steel, FRL240/240/240 (at 190mm thick), exceeding the highest possible fire rating. It has a lower embodied energy; because it takes vastly less energy to produce compared to traditional clay fired bricks.

Hebel

Hebel is a lightweight building material constructed from Autoclaved Aerated Concrete that is formed into blocks and panels for a wide range of both load bearing and framed construction applications. It is manufactured from sand, cement, recycled material, lime, gypsum and an aerating agent, aluminium paste. A 75mm Hebel® panel has up to 5 times the R-Value of a 110mm house brick .

Many Hebel® systems achieve a four-hour fire rating (the maximum under Australian Standards), more than twice that achieved by traditional materials such as bricks.

Mudbrick

Mudbricks are made by mixing soil, straw water and small stones in a mould.  The small stones or aggregate are added to increase the strength of the bricks. Mud brick buildings generally have thick walls (approximately 300 mm) and high thermal mass. When outside temperatures fluctuate above and below comfort temperatures, the high thermal mass of mud bricks considerably reduces heat transfer, although this works better in the summer than in the winter, where houses tend to lose heat more quickly.  To improve winter performance, rendering the bricks is recommended.

Mud brick walls have a fairly low R-value of 0.4 meaning that heat will transfer through the brick over time. Mudbricks have good fire resistance – a standard 350mm Mudbrick has a 4 hour fire rating meaning that it takes 4 hours for the heat of a fire to transfer through the brick. This type of brick has very low embodied energy as they are sun dried, not kiln dried.

Rammed Earth

Rammed earth walls are constructed by ramming a mixture of selected aggregates, including gravel, sand, silt and a small amount of clay, into place between flat panels called formwork.  Composed of selected aggregates bound with cementitious material, this is an extremely flexible method of construction and a large range of shapes, colours, and finishes can be achieved.

The high energy-efficiency of a Rammed Earth home is not due to its R-Value, because rammed earth actually has a very low R-Value. The high energy efficiency of a well-designed rammed earth home is due instead to its high thermal mass. In tests by the CSIRO a 150mm thick Cinva-rammed earth block wall (similar to rammed earth) achieved a near four hour fire resistance rating. The embodied energy of rammed earth is low to moderate.

Reverse Brick Veneer

Reverse brick veneer is a method of construction where the bricks are placed on the inside of the structural framing.  The outside of the home has some form of cladding, and there is a layer of insulation between the cladding and the brickwork on the inside.

Reverse brick veneer construction is a preferred form of construction as the thermal mass is inside the building, not outside. In traditional brick veneer, the bricks are on the outside and they contribute very little to heating and cooling efficiency.  When the bricks are on the inside combined with insulation, the heat and cold from the outdoors is not transmitted into the home, as the bricks are protected from the external weather conditions.

Straw Bale Construction

Straw-bale construction is a building method that uses bales of straw (commonly wheat, rice, rye and oats straw) as structural elements, building insulation or both. This construction method is commonly used in natural building or “green” construction projects. Advantages of straw-bale construction over conventional building systems include the renewable nature of straw, cost, easy availability, and high insulation value. Disadvantages include high space requirements for the straw itself. Surprisingly straw bale construction has good fire resistance. The ASTM E-119 fire resistance test for plastered straw-bale wall assemblies in 1993 passed for a 2 hour fire-wall assembly. In this test a gas flame blows on one side of the wall at approximately 2000 degree Fahrenheit (1100 degrees Celsius) while the temperature of the other side of the wall is continuously measured. The results of this test had no burn-through and a maximum temperature rise of 60 degrees Fahrenheit (33.3 degrees Celsius).

Straw bale is an extremely good insulator. A standard straw bale is 450mm thick with an R-value in excess of 4.8 and up to R9 for a standard bale.

Your Home technical manual has a section on Straw bale construction.

 

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