Embodied carbon 2 Built-to-last legacy?
practices evolve, with higher levels of material recovery, this in itself will not be sufficient. Buildings need to be capable of being upgraded
and adapted to new purposes, with building services designed so that at the end of their economic or technological life, they can be removed and dismantled to allow high levels of component and material recovery. This is all the more important when you consider
the embodied energy content of a building built in the last 30 to 40 years. It was thought until recently that the embodied
energy content was peripheral in comparison to the energy used in operating the building during its life.
To get the most from our embodied energy ‘investment’, we need to make our buildings last longer
This differential has typically been calculated at 10% embodied carbon to 90% operational carbon. However, as building lifespans have come down, so too has the operational energy footprint. In contrast to what we are seeing with the
building envelope, the embodied energy in plant and equipment has increased as building services become more complex. The net effect is that the embodied energy as a percentage of the whole has gone up and may now be the equivalent of many years of operational energy use. In the case of complex low-energy buildings, the
embodied energy component is not far off the lifetime operational energy demand. So, to get the most from our embodied energy ‘investment’, we need to make our buildings last longer.
We are still designing buildings that will not be
fit for purpose in 40 years’ time – with demolition
rather than refurbishment likely to be the only affordable option
Life assessment For critical building components we are beginning to adopt full probabilistic approaches to lifetime assessment. This method gives a calculated probability of failure and enables plant and engineering systems to be retained beyond their normal considered life expectancy; and, in doing so, provides a more sustainable solution to life-cycle plant replacement. This lifetime model is based on a statistical
assessment of sub-systems and components. While this does not necessarily give a specific failure date
www.cibsejournal.com July 2010 CIBSE Journal 35 >
Chris Bacon/PA Archive/Press Association Images
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