Thermal performance of different materials

Thermal performance of different materials 
Building materials have their own insulative properties, which contribute towards the overall R values for your home.

How do different materials affect insulation needs?

When choosing your building materials, it's important to note that each different type will have its own thermal qualities which will either increase or decrease the effectiveness of your insulation. The thicknesses of the material will probably play the greatest role in determining how effective it is, although the density and thermal mass of the chosen material will also factor in.

For example, a solid brick veneer wall has a high thermal mass and will retain heat in summer, releasing it long into the night. In winter, the same wall is likely to remain cold and absorb the heat from your house. For that reason, it's very important to ensure that the wall is properly insulated so that your home has a tight thermal envelope.



Overall R values for different parts of your home

Choosing what sorts of materials you will use to build your house will make all the difference when it comes to insulating your home. Thermal mass properties, the thickness of the material and the method of construction will change the R-values of your walls and roof. There are minimum R-value requirements for these parts of your home specified under the Building Code of Australia (BCA) - and dictated to by the state and climate zone in which you live. Your structural and cladding materials, along with your insulation, will contribute to the overall R values of these parts of your home.


Structural materials with insulation properties

Some building materials are specially chosen for the fact that they already incorporate insulation into their design. These include structural insulation panels (SIPs), straw bales and autoclaved aerated concrete (AAC) blocks. The primary advantage in using these types of materials is that there is no need for separate insulation to be installed, which saves you the cost and hassle of doing this.

Another key advantage is that these materials don’t require a standard housing frame, eliminating any possibility of thermal bridging and making them very effective and uncomplicated in practical terms. Most of the time these materials will require some additional facing to protect them from the elements though, so plan ahead for this.


R values for different wall materials

Below is a table to give you a rough idea of the various inherent R values of different wall materials:

Wall material Overall R value
Weatherboard 0.55
Brick veneer 0.51
Cavity brick 0.53
Solid brick (230mm thick) 0.44
Solid concrete (100mm thick) 0.23
Solid concrete (200mm thick) 0.30
Aerated concrete (100mm block) 0.78
Aerated concrete (200mm block) 1.54
Mud brick (300mm block) 0.40
Source: Sustainability Victoria - Insulation types INFO fact sheet