Written by Jason Cooper, architecture consultant Hodgkinson Design.
As the world’s population and its voracious demands on energy and resources continues to grow - and as we are told we now have only around thirty years left to turn things round before runaway global warming leads to our all too plausible end - there are many signs today warning us that our future as a species is increasingly at risk: record global mean temperatures, rising sea levels and the accelerating loss of both sea ice and glaciers are only a few; but when so many are directly attributable to the increase in atmospheric carbon, it is this that has become the leading indicator of the health of our planet. As to the proportion of carbon emissions that the built environment is responsible for, according to the UN's Environment Programme this accounts for fully 36% of global energy use 1; and, by other studies, to almost 50% of energy-related carbon dioxide emissions annually 2.
The energy demands of buildings - and which are broadly related to their atmospheric carbon contribution - can be divided into two key components: the amount of energy they take to operate (to heat and cool, and to run all their remaining services) and the energy they consume to build. To assess the sustainability of any new building proposal, both of these must, ideally, be fully calculated so they can be optimised during the design stage.
As to the first, any building design's operational energy requirements are relatively straightforward to determine; and - whether they are to be new buildings or refurbishments - can be very substantially reduced by good design and specification. Perhaps the most obvious example of this is the increasing importance we all see of high thermal insulation standards; but any number of new technologies - from the latest generation of heat pumps and solar panels to low-energy lighting systems - can, at albeit increased cost, create buildings that are rated ‘Near Zero Energy’ projects. A good example of these are many of the increasing number of Passivhaus 3 buildings that are now being built across the world.
But while most may be familiar enough with such operational energy demands, all too few consider the massive proportion of energy the original construction of any building work makes relative to its total energy consumption over the course of its lifetime, and which is also directly proportional to its carbon emissions: this is called ‘embodied carbon’. To take one particularly egregious example of how such a critical issue can be ignored, the key environmental aim of the HS2 rail project was to reduce overall carbon consumption by replacing carbon-inefficient journeys by road with more carbon-efficient journeys by rail; and yet, over the course of its projected 120-year lifespan, it has since been calculated that - before it can even start making any contribution at all to reducing operational carbon emissions once fully operational - HS2 may never pay-off the carbon cost of its making 4. As to quantifying the embodied energy for specific buildings at their design stage, this remains so tedious, complex, and resource-consuming that such calculations remain rare; but current estimates of its proportion over the lifetime of buildings put this at up to 46% for a low energy building built to today’s highest standards 5: at almost half the total lifecycle energy consumption for such buildings, it is clear that embodied energy simply cannot be as ignored as it generally is.
So what can be done ?
Even when such embodied-carbon calculations are ignored, there remain many straightforward strategies that can be pursued to minimise embodied carbon in buildings. To take just a few examples, every time we consider replacing old buildings with the massive carbon cost of their demolition and rebuilding from scratch, we should instead be asking whether these should not instead be refurbished to achieve the same energy-efficiency standard of their replacements. As to the materials we use, when we do build we should also be specifying as many buildings as we can to be made from materials like timber, bamboo and other natural-fibre materials that all absorb carbon as they grow while replacing their carbon-contributing alternatives: all these are obviously renewable, and - being relatively lightweight and easy to prefabricate - can greatly reduce the carbon cost required to transport their equivalent components in, say, steel or concrete. To take one last example, to minimise the significant carbon cost of transporting materials from potentially remote sources, we should also be constructing as many buildings as we can from either locally-sourced materials; or, ideally, locally-recycled ones.
But when the vast majority of buildings today are driven by design decisions to achieve minimal cost, to expect individuals and developers to drive the carbon-reduction revolution we need is simply unrealistic. If we really want to address this issue, we need radically revised planning legislation that - instead of all too often prohibiting measures to promote energy efficiency - actively encourages them with subsidies; and, above all, we need the global adoption of not only renewable energy solutions as quickly as possible, but mandatory building energy codes that enforce the most stringent limits on both operational energy requirements and the embodied carbon cost of all our buildings. Finally, we need the strictest limitations on the way in which buildings are used: what, after all, is the point of designing low-energy, highly-insulated buildings when we routinely see the abuses we do when they are in use ? The often glacial temperatures we experience when we walk into air-conditioned high street stores through wide-open doors in mid-summer, or through warm-air curtains into heated interiors in winter ? The insanity of warming even outside spaces with external heaters ?
When atmospheric carbon dioxide is accumulating in the atmosphere faster that ever 6, to master the global crisis we all face it seems that three things, at least, are clear: the road to sustainability will be an increasingly hard one; the opportunities of finding it are now fast diminishing; and the sooner our governments and their electorates have the foresight and courage to implement the inevitably tough decisions we must all of us accept to allow for a habitable planet for our successors, the greater the chance they will have of inheriting one.
NOTES:
1. https://www.weforum.org/agenda/2021/11/green-building-global-warming-climate- change/#:~:text=Reducing carbon output from buildings and construction is,37% of global energy-related CO2 emissions in 2020.
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