Monday, January 7, 2008

more on embodied energy

Back after a while... we've been working on some big things, so stay tuned! For now, a plug:

We really like the site Your Home Technical Manual, sponsored by the Australian government.

We're asked to build "long life, durable and adaptable buildings." Historic homes win on all three! They've obviously had a long life, they're durable, and as anyone who lives in an old home will tell you, are easily adaptable!

Below are excerpts from the site. Visit and click around, there is a lot of great info.


Embodied energy is the energy consumed by all of the processes associated with the production of a building, from the acquisition of natural resources to product delivery. This includes the mining and manufacturing of materials and equipment, the transport of the materials and the administrative functions. Embodied energy is a significant component of the lifecycle impact of a home. Every building is a complex combination of many processed materials, each of which contributes to the building's total embodied energy. Renovation and maintenance also add to the embodied energy over a building's life.

It was thought until recently that the embodied energy content of a building was small compared to the energy used in operating the building over its life. Most effort was therefore put into reducing operating energy by improving the energy efficiency of the building envelope. Research has shown that this is not always the case. Embodied energy can be the equivalent of many years of operational energy.

The materials we use to build our homes have many "unseen" adverse environmental impacts.
The importance of embodied energy and other environmental impacts does not become apparent until we examine the materials from a life cycle approach, usually known as Life Cycle Assessment (LCA). LCA examines the total environmental impact of a material or product through every step of its life - from obtaining raw materials (for example, through mining or logging) all the way through manufacture, transport to a store, using it in the home and disposal or recycling. LCA can consider a range of environmental impacts such as resource depletion, energy and water use, greenhouse emissions, waste generation and so on.

Choices of materials and construction methods can significantly change the amount of energy embodied in the structure of a building. True low energy building design will consider this important aspect and take a broader life cycle approach to energy assessment. Merely looking at the energy used to operate the building is not really acceptable. Operational energy consumption is dependent on the occupants. Embodied energy is not occupant dependent - the energy is built into the materials. Embodied energy content is incurred once (apart from maintenance and renovation) whereas operational energy accumulates over time and can be influenced throughout the life of the building.

Research by CSIRO has found that the average household contains about 1,000 GJ of energy embodied in the materials used in its construction. This is equivalent to about 15 years of operational energy use. For a house that lasts 100 years this is over 10 percent of the energy used in its life.

As the energy efficiency of houses and appliances increases, embodied energy will become increasingly important. Reuse of building materials commonly saves about 95% of embodied energy that would otherwise be wasted.

Try to follow these guidelines:
Design for long life and adaptability, using durable low maintenance materials.
Ensure materials can be easily separated.
Avoid building a bigger house than you need. This will save materials.
Modify or refurbish instead of demolishing or adding.
Ensure materials from demolition of existing buildings, and construction wastes are re-used or recycled.
Use locally sourced materials (including materials salvaged on site) to reduce transport.
Select low embodied energy materials (which may include materials with a high recycled content) preferably based on supplier-specific data.
Avoid wasteful material use.
Specify standard sizes, don't use energy-intensive materials as fillers.
Ensure off-cuts are recycled and avoid redundant structure, etc. Some very energy intensive finishes, such as paints, often have high wastage levels.
Select materials that can be re-used or recycled easily at the end of their lives using existing recycling systems.
Give preference to materials manufactured using renewable energy sources.
Use efficient building envelope design and fittings to minimise materials (eg. an energy efficient building envelope can downsize or eliminate the need for heaters and coolers, water-efficient taps allow downsizing of water pipes, etc).
Ask suppliers for information on their products and share this information.

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