Materials and embodied energy

In addition to the energy used during the occupied life of a building there is also a significant energy factor in terms of the materials used in its construction. It falls into five divisions:

• the extraction from the earth of raw materials;

• the processing of the raw material into finished products;

• the transportation to the supplier and then to the site;

• the construction process;

• the demolition and recycling of materials.

Assuming an average life for an office building in the UK of 15-20 years, about 7 per cent of total energy consumption is embodied in materials. However, if buildings were to be made more adaptable, and thereby more accommodating to numerous changes of work pattern, their lifetime would be extended, thus reducing the overall percentage attributable to embodied energy. In the UK, for example, the present replacement rate of housing means that life expectancy of a home is around 2000 years, making the embodied energy an insignificant element. On the other hand, as buildings become more energy efficient, so the reverse is true and ultimately the embodied energy may become the prime factor.

The problem with embodied energy is that it is difficult to quantify with any confidence. For example, with the first two stages, extraction and processing, the energy used in the processes may be withheld for commercial reasons. The matter will only be resolved when disclosure becomes a legal requirement.

The situation is further complicated when some of that energy is from renewable sources, as in the case of aluminium processed in Canada from hydroelectric power, or bricks in Nottinghamshire fired by landfill methane.

There are strong environmental reasons to use timber in construction, since it is a renewable resource with the added benefit of fixing CO2 during growth. However, in the UK most softwood is imported, adding a significant transport component. Energy inputs into metals such as copper and aluminium can vary according to whether the source is from ore or recycled material.

At this stage in the development of disclosure about embodied energy, the most direct impact can be made on 'carbon miles', sourcing materials as near as possible to the construction site.

A case study will illustrate a whole building approach to recycled materials.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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