Fei Ngeow, eTool LCD Engineer, recently attended the 2014 EBAA Conference: ‘Earth Building – Towards Zero Carbon’, in NSW. The two-day conference was held the the Bamarang Bush retreat in buildings constructed with mud brick and included workshops and guest speakers on varying topics related to earth buildings.
Life Cycle Performance Comparison
External Wall Comparison
Life cycle analysis shows that a 250mm mud brick wall has a 95% improvement in embodied CO2 over a 110mm rendered brick veneer wall.
- Mud brick wall – 250mm puddled mud brick wall made onsite, finished with 10mm clay/bitumen render.
- Brick veneer wall – 110 brick, insulation, plasterboard paint internal finish, render external finish.
Embodied Energy Comparison
Embodied & Operational Comparison
- reverse cycle heat pump (CoP = 3.65, EER = 3.4)
- 85% efficient gas HWS
- CFL lighting
- gas cooking
The house comparisons have been modeled in a cold climate zone (Tomerong) and therefore have a minimal cooling requirement and high heating requirement. When low carbon alternative heating solutions such as wood pellet heaters are incorporated, the embodied emissions make up a larger proportion of the total.
Although the mud brick still requires more heating, because the heating source is very low in emissions in both cases the total operational energy decreases meaning, the embodied emissions proportionally increase. The relative savings from the mud brick walls then become more significant. If houses can be designed optimally, to minimise cooling requirements, low carbon outcomes are easier to achieve through the use of renewable heat sources.
The grid emissions in the above two scenarios are assumed constant throughout the life cycle of the building. In reality the grid emissions will decarbonise if Australia is to meet its commitments to Kyoto (80% reduction in CO2 by 2050). Again the embodied emissions become more significant because the operational makes up a smaller proportion of the overall emissions.