There has been a lot of talk lately about the energy efficiency of various building materials, with terms like R-value and thermal mass being bandied about. This is because the government has introduced a new Australian Standard for Energy Efficient Housing to help reduce Greenhouse emissions. All new housing will be required to meet this standard, which is good news. What does this all mean to you and how does it relate to an energy efficient home?

What is R-Value?
The R-value of a material is its ability to resist changes in temperature, or in simpler terms, how good of an insulator it is. (Polystyrene for example has a very high R-value).Mud brick walls have a fairly low R-value of 0.4, meaning that heat will transfer through the brick over time. Brick veneer has an R-value of 0.46 and double brick 0.56 meaning they will absorb slightly less heat than a single skinned mud brick wall.

What is Thermal Mass?
Thermal mass is how much energy or heat a material holds. Mud brick has a high thermal mass meaning that when the brick heats up, it holds its heat and releases it slowly. In a well designed solar passive mud brick home, winter sun heats the mud bricks during the day. This heat is held in the brick and released during the night keeping your home warm. Conversely, sun is kept off the mud brick walls during summer so as they stay cool during the day and night.

• Good solar passive design of the home which lets the sun in during winter and keeps it out in summer
• Good insulation of the roof and ceiling
• Planting deciduous trees to the east and west will prevent these walls heating up in summer
• Wide eaves and a verandah along the Northern side especially will block summer sun but let in winter sun.
• Install curtains and pelmets to reduce heat movement through the windows.