Embodied carbon recognised at last | Brussels Blog

Embodied carbon recognised at last

posted by on 5th Jul 2015
5th,Jul

Embodied carbon means…

We must rethink Sir Peter Hall’s eco-town vision

The carbon dioxide emissions due to construction are called “embodied carbon”. It has only recently has it been acknowledged that building homes, offices, factories, shops and roads is very carbon intensive.

In November 2008, I attended a talk by Sir Peter Hall. The slides he showed are on ECO-TOWNS: Will they be Eco-? Can they become Towns? After a short introduction about climate change and the need for more housing, he described eco-towns in England and a few in Europe. He gave a positive impression of all of them and how they were reducing carbon emissions.

Sir Peter Hall – A mistaken vision for eco-towns

Most of the English examples were proposed eco-towns that had not been built at the time – and they probably never will be. However, the first one he showed had been built. It was the Beddington Zero Energy Development (BedZED) for which he noted:
BEDZED: UK’s largest eco-village• Opened March 2002

• BioRegional/ Peabody Trust/Bill Dunster Associates
• 100 homes, community facilities and workspace for 100 people
• Heating requirements: ca 10% typical home
• 60% recycling aim
• Target fossil fuel car miles: 50% national average
• Hackbridge Station 5 mins
• Car Club
• Local facilities: football pitch, club house….

 Carbon emissions from construction

What Sir Peter didn’t know was that BEDZED created large carbon dioxide emissions due to its construction. These emissions are called “embodied carbon”. I can confirm he didn’t know because when I told him and didn’t believe me until a subsequent email exchange. The correspondence is described in the Appendices.
Sir Peter’s reply acknowledged two points:

–The embodied carbon in BEDZED is 67.5 tonnes of CO2 for a three bedroomed flat.
— Government aims to cut the carbon emissions per person to 2 tonnes CO2e per year by 2050.

I estimate that the embodied carbon in the infrastructure required for a new resident in a “city of BEDZEDs” is of the order of 100 tonnes CO2e: Building homes, offices, factories, shops and roads is carbon intensive.

The Beddington Zero energy Development – Huge embodied carbon

Carbon budgets and the Climate Change Act 2008

The UK Climate Change Act 2008 makes it the duty of the Secretary of State to ensure that the net UK carbon account for all six Kyoto greenhouse gases for the year 2050 is at least 80% lower than the 1990 baseline, toward avoiding dangerous climate change. There are two issues with this

1. The 1990 baseline is calculated on a production basis, ignoring such things as the carbon embodied in imports. On a consumption basis, the UK’s carbon footprint is about twice the 1990 baseline.

2. The “Kyoto greenhouse gases” in the Kyoto Protocol use out-of-date Global Warming Potentials. This is unlikely to affectconstruction as the main change concerns methane, which increases the impact of agriculture.

Let us assume that the 2008 Act means the UK target for carbon emissions is 2 tonnes CO2e per person per year as Sir Peter confirmed. What proportion should be allocated to construction? The panel for the Green Ration Book divided this 2 tonnes equally between the categories “consumables”, “buildings”, “transport” and “government”. That leaves 0.5 tonnes for buildings.

How much of this0.5 tonne carbon budget should be used for constructing buildings and site works? Let’s guess half. That’s a carbon budget of 0.25 tonnes CO2e a year for construction.

To spend 100 tonnes of CO2 budget building the infrastructure for an extra inhabitant of a town, even an eco-town, is absurd. A rethink is required. (See also Appendix 1, World wide remaining carbon budget.)

In short, in the kind of European city developments that Sir Peter admired the embodied carbon is enormous: Vauban in Freiburg, Vathorst in Amersfoort and Sjöstad in Hammarby cannot seriously be described as sustainable.

Lifestyles of eco-town residents

In Eco-towns aren’t eco (2009) on NoHighBuildings.org, I pointed out that the residents of the proposed eco-towns were unlikely to have small carbon footprints. One “eco-development”, Derwenthorpe in York, although smaller scale, looks very similar to the images Sir Peter showed of Vauban in his talk. Derwenthorpe won the RTPI Yorkshire Planning Excellence Award. Richard Partington of the Architects commented on receiving the award :

The vision for Derwenthorpe has been sustained through a involved process including a great number of very committed people, representing the Joseph Rowntree Housing Trust, the City of York and the various organisations who have helped design and build the first phase, all of whom have championed the notion that Derwenthorpe should be an exemplar for sustainable and equitable development. We are very proud that our contribution (amongst many others) has been recognised by RTPI.

As predicted by Ecotowns aren’t eco and measured by a research project by the Stockholm Environment Institute, the residents of Derwenthorpe have, on average carbon footprints larger than the typical York resident. Last year, I attended a meeting which presented the research and, from the slides I saw, the residents energy footprint was lower (by about 50%?) but their travel footprints swamped this making their carbon footprint larger than the York average.

This is not surprising: the residents of Derwenthorpe, where houses cost up to £300,000, are wealthier than the York average and, according to the research, what they save on energy they spend on travel. Their extra travel is the main reason that their carbon footprints have been estimated to be higher than average.

“Sustainable” Derwenthorpe – Residents with large carbon footprints

Sonoma Mountain Village

Sir Peter’s reply specifically mentions Sonoma Mountain Village, a development in California by the same developers as BEDZED, Bioregional. I had pointed out the footprint of the residents of BEDZED had carbon footprints that were still too high, although less than the average UK citizen. The reply

true, but as soon as BedZED residents go to work, to school, to visit friends, they are back in the three planet world. In an eco-town, as with the large scale OPL communities such as Sonoma Mountain Village, it will be possible to influence around 80% of people’s footprint. At BedZED, we only touch on some 30-40%.

The SOMO One Planet Community 2011 Annual Review for Sonoma Mountain Village, says

It is important to note that the SOMO plan does not achieve true sustainability on a carbon basis, particularly when examined by itself, because it relies on changes to larger societal systems such as the electrical grid, manufacturing, shipping, government, and farming. Nonetheless the carbon reductions at SOMO are as good as any that can be achieved in the US until these wider societal changes are made.

Table 1 Summary of Per Capita CO2 Emissions at SOMO

Tonnes CO2 Reduction from baseline
Baseline 15.10 0%
SOMO 6.94 54%
One Planet 3.84 75%

It is possible that the SOMO plan could get residents to achieve a 54% reduction from “the baseline” but if the residents drive cars or fly in planes this will be hard to achieve. However, this is in-use CO2 emissions and does not count the CO2 emissions from building Sonoma Mountain Village, the devopment’s  embodied carbon.
It is difficult to see that this embodied carbon is small because, as Susan Kraemer writes, it is built with steel

The town is being constructed in the steel prefab factory in the center of town, which will still provide jobs after the town is built. Six SUVs worth of locally recycled steel goes into every 2,000 sq. ft. of the housing being built. Steel framing is more lightweight than wood framing, which reduces the amount of concrete foundation required and further reduces carbon emissions.

Bioregional are to be congratulated for their work. Sonoma Mountain Village may be much better than other deveopments but it’s nowhere near enough. Aditionally, if much of the improvement in the embodied carbon comes from using recycled steel, it is just a one-off: Recycled steel only becomes available at the time of recycling – when buildings are demolished. There’s not enough of it to expand our cities. If one building project uses steel from the limited amount available,  another project must use virgin steel with it’s large carbon footprint.

The importance of embodied carbon is now recognised

The importance of embodied carbon has recently been recognised. The Embodied Carbon Task Force comprises a group of practitioners, academics and developers who have an interest in ensuring that embodied carbon is integrated into normal good practice building design and development. In 2014 it published Proposals for Standardised Measurement Method and Recommendations for Zero Carbon Building Regulations and Allowable Solutions. This says

–Even before a building is occupied, between 30% – 70% of its lifetime carbon emissions have already been accounted for.
–Embodied carbon makes up the largest proportion of the carbon emissions of a building through its lifetime.

Embodied carbon is important. The eco-developments that Sir Peter championed, have high embodied carbon they are not a model for a future sustainable lifestyle.

We must think again.

Appendix 1

Correspondence with Sir Peter Hall

Sir Peter returned a version of my email with annotations (in blue). The full version is Appendix 2 but it starts:

EMBODIED CARBON IN ECOTOWNS
A three bedroomed flat in BedZED has been estimated to have embodied CO2 of 67.5 tonnes. (correct)
A recent document from DCLG suggests the average carbon footprint for a UK citizen is about 11 tonnes CO2e per year. Government aims to cut this by 80% to give a target of about 2 tonnes CO2e per year. If one quarter of this footprint is allocated to a “buildings budget”, we have a target of 0.5 tonnes per year or 1.2 tonnes for an average household. (correct)
The embodied CO2 in the construction of a residential dwelling must be increased to account for shops, offices, public buildings & etc. A crude estimate would be that this doubles any figure calculated for residential development.

Sir Peter wrote

Dear Geoff Beacon
It took a little while to respond to your email because I thought it fair to consult the people down at BEDZED.
The attached represents a kind of collective reply!
I think the bottom line is: we’re nowhere near the standards you, or any of us, would like – but we’re working towards them, and learning.
Best wishes
Peter Hall
Professor Sir Peter Hall
Bartlett Professor of Planning and Regeneration
University College London

Appendix 2:

Letter to Sir Peter Hall, annotated by Sir Peter et al..

Sir Peter’s annotations in blue.

EMBODIED CARBON IN ECOTOWNS

A three bed-roomed flat in BedZED has been estimated to have embodied CO2 of 67.5 tonnes. (correct)

A recent document from DCLG suggests the average carbon footprint for a UK citizen is about 11 tonnes CO2e per year. Government aims to cut this by 80% to give a target of about 2 tonnes CO2e per year. If one quarter of this footprint is allocated to a “buildings budget”, we have a target of 0.5 tonnes per year or 1.2 tonnes for an average household. (correct)

The embodied CO2 in the construction of a residential dwelling must be increased to account for shops, offices, public buildings & etc. A crude estimate would be that this doubles any figure calculated for residential development.

Embodied CO2e is, of course, only part of the building’s budget. Conventionally, CO2e generated by heating and lighting buildings is assumed to be much greater than the embodied CO2e. This conventional thinking may be flawed but it is not credible to set it to zero under current plans.

Given the above, the presentation of BedZED as a zero carbon eco-town is invalid. Can the other ecotowns you presented fare better? BedZED was intended to be zero carbon in terms of building energy in use. Times have moved on since we had this ambition but BedZED has never claimed to be zero carbon in any other respect. Remember BedZED was designed 10 years ago! It is true that we do now need to look for ways to reduce our embodied impacts of construction by 80% at a national level. I do not believe it is possible to get anything like that kind of reduction within a single project in the short term. As we start to decarbonise all our energy sources (grid, transport fuels, industrial heat sources) it may start to become possible in the medium to long term. In the meantime, we need to look for, say, 30-40% reductions on a project by project basis and then look as a nation to make best use of the buildings and infrastructure and materials we already have and so save ourselves the cost (both financial and environmental) of too many new build projects. We need to think very carefully about what we really need to build and we need to be clever and imaginative about avoiding the need to build.

A word on the embodied CO2 of BedZED: This is discussed in much more detail in the BedZED Construction Materials Report. BedZED invested more embodied CO2 in the built fabric of its buildings so as to achieve the outstanding thermal performance and daylighting levels that enable it to cut its in use energy demands radically. Space heating and hot water demands are reduced by 80% and electricity is reduced by 45% compared with Sutton average. More detailed monitoring is available in our published reports.

The big achievement at BedZED on embodied CO2 is that despite this very effective investment in the building fabric, we managed to reduce the embodied CO2 back down again through use of local, reclaimed, recycled and low impact materials. The embodied CO2 of BedZED is the same as for typical new build at the time, as audited by the Building Research Establishment in the BedZED Construction Materials Report.

NON-BUILDING CARBON BUDGETS

Sir Peter, you mention efforts in the design of ecotowns, to encourage residents to use more environmentally friendly modes of transport. I am sure physical design can have some effect on carbon footprints but without additional measures including well-designed financial and legal mechanisms, physical design will have limited effect. But do economists and lawyers exist with the right skills for ecotown design? Not yet, in anything like sufficient numbers; we have to start to train them!

From what I understand the carbon footprints of the residents of BedZED are currently below the national average but still several times the government’s target. – true, but as soon as BedZED residents go to work, to school, to visit friends, they are back in the three planet world. In an eco-town, as with the large scale OPL communities such as Sonoma Mountain Village, it will be possible to influence around 80% of people’s footprint. At BedZED, we only touch on some 30-40%.

ECO-TOWNS CHALLENGE PANEL

It is obvious that the target carbon footprints for residents of ecotowns should be near the government’s new target. After your presentation can I assume that the Eco-Towns Challenge Panel has no such ambition? I would hope that the panel does have exactly that ambition and to be comparing the eco-towns with BedZED is not giving the full picture. I would hope that eco-towns will go a lot further than BedZED has been able to because they have the benefit of scale and can learn from the experience of BedZED and many other pioneering schemes- including best practice in mainland Europe.

Appendix 3

World wide remaining carbon budget.

Another way to look at carbon budgeting to look at the world wide remaining carbon budget.
Carbon Brief reports the remaining carbon budget to give a 66% chance of keeping global warming below 1.5°C as 243 billion tonnes. That means, if humanity emits 243 billion tonnes more of CO2e global temperature will rise to 1.5°C above pre-industrial. Using the same calculations, the remaining carbon budget to keep below 2°C is 843 billion tonnes.
The UK’s share of this remaining carbon budget by population is 7.4 billion tonnes(x). The Embodied Carbon Task Force estimate that, if no change is made, the construction sector alone could be responsible for additional emissions of over 3.1billion tonnes of CO2e by 2050 – equivalent to over 5.5 years of total UK emissions.) That’s 144% of a budget for a 1.5°C target and 27% of the UK’s budget for a 2°C target. UK construction alone could easily bust the lower budget.

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