‘Whole Life Costings’, ‘Carbon Footprint’, ‘CO₂ Equivalents’ and ‘Carbon Productivity Ratios’ are hazy concepts to many who, although vaguely aware that they are used to establish the sustainability credentials of building development, are unsure of their worth and meaning. A new publication by the British Council for Offices (BCO) helps to provide a useful introduction to the subject of Whole Life Costing. The BCO was established in 1990 and brings together shakers (developers), makers (design teams) and takers (tenants) of office buildings to ‘collectively create more effective office space’. In pursuit of this aim they asked Angus McIntosh and Gareth Roberts to provide a simple but robust methodology for measuring the whole life carbon footprint of an office.
The authors start by breaking the life cycle of an office building down into five stages. Most models, such as that developed by the European Committee for Standardization, are four stage models, but the authors have proposed Commuting as a distinct stage. This is sensible – modes of travel, and their consequential environmental impact, are heavily influenced by where a building is, what transport infrastructure is available, and the culture of an organization and its employees.
The five stages (and the (very) rough proportion of life time emissions they produce) are:
- Production (15-20%) – Covers the extraction and transportation of raw material; the re-claiming of existing material for re-cycling and the processing of the raw and re-cycled material into products.
- Construction (1-5%) – The transportation to site and the assembly of the products to make a building.
- In-Use (50-75%) – The longest stage, and the most prolific in terms of emissions, it includes: heating, lighting, cooling, water and small power demands; and the maintenance, repair and replacement of the various components of the building.
- Commuting (20-40%) – How the occupiers get to work, from the ‘good’; walking, cycling, through the OK; buses, trains, tubes, to the not so good; small cars, medium cars, big cars.
- End of life (1-5%) – The deconstruction, transport, waste processing and disposal of the building.
So, just how big is an office carbon footprint? The excepted unit of measurement is the weight of the carbon dioxide equivalent (CO₂e). Different greenhouse gasses, such as methane and nitrous oxide, have different global warming potential and these are expressed as the functionally equivalent concentration of carbon dioxide (CO₂). Over a lifetime of 60 years an office building will produce somewhere between 5.5 to 8.5 tonnes of CO₂e per m² of area or, and this is a new way of expressing it, 80-100 tones of CO₂e per occupant. This ‘output per occupant’ rate is used as justification for intensifying the occupancy of a building using Carbon Productivity Ratios – which factor in location, rent, air conditioning etc.
The nub of the problem though is identifying a simple formula in an ever-evolving, ever more complex world system. Take photovoltaic panels versus ground source heat pumps. A photovoltaic panel replaces grid electricity; a ground source heat pump uses it. These simple facts help inform specification choice. If however, the grid becomes anywhere near as superefficient as its target for de-carbonisation by 2070 suggests, the relative efficiency of the two options changes significantly. Reducing the carbon required by the grid to produce a KWh of electricity from 600 to less than 60g CO₂e, will mean that technologies which use the new super efficient electricity, like ground source heat pumps, will become much more efficient and much cleaner.
The report is a useful addition to the debate and provides a further contribution from those driven more by economics than ecology. In the long term, I suspect the solution to the problem of predicting and controlling building emissions might not be the assembly, publication and implementation of ever more complex formulae, because even the experts can’t agree. Mike Berners-Lee author of ‘How Bad Are Bananas?’ claims bananas are a low carbon food, in ‘Why aren’t We Saving The Planet?’ Geoff Beattie insists that bananas are a product high in embodied carbon!
We should consider different, more flexible approaches. In ‘Adapt’, Tim Harford makes a compelling argument for embracing trial-and-error over ‘designed’ solutions to the inter-related issues of biodiversity, ecology, energy generation and efficiency. He thinks we should embrace experiment, risk, and the potential for failure in pursuit of progress, rather than command-and-control style regulation; maybe he’s right?