University of Melbourne
“Material selection for optimised embodied energy/carbon”

Posted on: August 20th, 2013 by Dr. Robert Crawford

Meeting held on Tuesday 6th August – GHD offices Melbourne

A range of construction assemblies were selected based on optimised thermal performance and a selection of standard and low impact materials.
Eleven different floor assembly variations and 52 different wall assembly variations were considered.
The total life cycle embodied energy of these assemblies was calculated using a comprehensive hybrid embodied energy assessment approach.
This included the energy embodied in the materials/assemblies for the initial construction of the project as well as the energy embodied in replacement materials over an estimated building life of 100 years. Average material replacement rates were used.
Assembly embodied energy figures were graphed and compared.
Major points that arose from the discussion of the embodied energy assessment results included:
• Materials with a high recycled content are preferred as they tend to have a lower embodied energy compared to virgin material alternatives
• Longevity and durability of materials needs to be considered as materials with a low embodied energy but that require frequent replacement can be a poor choice, resulting in a higher life cycle embodied energy than more durable materials
• Solid timber products are preferred over manufactured/processed timber products
• The embodied energy of some insulation products can be significant
• The embodied energy of glass can be considerable and the need for double and triple glazing systems must be balanced with the level of thermal performance they can provide
• Double-glazed spandrel panels should be avoided considering their high embodied energy
• The importance of minimising the embodied energy associated with the building’s initial construction was highlighted. Energy expended in the future (for replacement materials and building operation) is likely to be less carbon intensive than the energy presently being used in the manufacture of materials.
It is important that by minimising embodied energy that the thermal/operational performance of the building is not adversely affected. The next stage involves assessing the life cycle energy/carbon implications of a smaller range of optimised assemblies, based on the knowledge gained from this initial analysis.

Dr. Robert Crawford
Senior Lecturer in Construction and Environmental Assessment

Click on the images below to open the full documents.

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