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The Zero Carbon Homes debacle

by Mel Starrs on March 27, 2011

in Code for Sustainable Homes, Zero Carbon

Last Wednesday, buried in the midst of all the material associated with the Budget, came a watered down (almost) definition of zero carbon. I shall attempt to illustrate a short history of zero carbon and the past five years below, but the lesson remains this (from Robert Kyriakides almost 3 years ago):

Trying to work backwards – have a definition first and try to figure out what it means – may work in politics, philosophy or even economics but in science it leads to some hilarious outcomes.

I was at the UKGBC conference last year when Grant Shapps confirmed that if elected, the Conservatives would define zero carbon within weeks of coming to power (for the record, despite last weeks announcement, it still isn’t defined 6 months in). I inwardly groaned at the time – here was a fantastic opportunity to ditch the nonsensical goal of zero carbon for homes by 2016, but no. Instead, let’s keep redefining zero until it meets what is physically and economically possible. This offends not only my sense of logic, but devalues those homes which truly are zero carbon.

Please can we ditch the phrase ‘zero carbon’ as a target for 2016? England will still have some of the most stringent Building Regulations in the world, with very low carbon compared to the 1995 Building Regulations, when I started my career. If we need to, we can still call 2016 targets ‘net zero’ or more accurately ‘carbon neutral’, but please can we have the phrase ‘zero carbon’ back so we can use it again for exemplar buildings?

Defenders of the 2016 target (can we refer to it as the 2016 target from now on? rather than calling it zero carbon?) say that it has galvanised the industry and that without the future zero carbon target, we would not have progressed as far as we have today. I don’t see evidence of this myself. The vast majority of projects completed to standards higher than required for Building Regulations, were to the minimum standards required by HCA funding – i.e. CSH3*. As of October 2010, this is now the minimum standard (as Building Regulations have moved on). Were those exemplar projects which have received CSH6* (or CSH5*) ‘test’ projects for the builders building them, to make sure they could build to 2016 today, or were they showcases for demonstrating differentiation against the rest of the market? I would argue the latter and would still argue that this is the raison d’etre of a building accreditation scheme – to showcase the exemplars. Legislate for the bottom of the market, pulling up the laggards, and incentivise the top of the market, pushing the standards forwards, just out of reach, to reward those who choose to go the extra mile (choice is an important part of the equation – legislating will always have to drop to the lowest common denominator). I have heard several people at BRE advocate that a mass-market is required for sustainable buildings. I’m in disagreement here. Incentivise the front runners, and the laggards eventually catch up, with legislation sweeping up those who refuse to change. Mass markets don’t tend to change the world…

Rant over, let’s get on with the history lesson. Looking back through my posts, the goal of zero carbon was always inextricably linked to Code for Sustainable Homes level 6*. Code was released in December 2006 and just a few weeks before the final document, Gordon Brown (then chancellor) announced the goal of zero carbon homes by 2016 (within a pre-budget report – I’ve been addicted to Budget announcements ever since).

So what did the original CSH6* level of zero carbon dictate?

Original CSH6* zero carbon definition

(Excuse the cartoon like appearance above – I’ve been messing about with iPad sketching). Also, the renewables are for indicative purposes only – biomass plus PV plus wind is only one possible solution, community level solutions can also be included, yadda, yadda, yadda. But you knew all that…

The definition was:

A zero carbon home is one with ‘zero net emissions of Carbon Dioxide (CO2) from all energy use in the home’. The definition encompasses all energy use in the home (including energy for cooking, TVs, computers and other appliances) rather than just those energy uses that are currently part of building regulations (space heating, hot water, ventilation and some lighting). It means that over a year there are no net carbon emissions resulting from the operation of the dwelling. This could be achieved either through steps taken at the individual dwelling level or through site wide strategies. So it will not be necessary for each dwelling to have its own microgeneration capacity where development level solutions would be more appropriate.

The inclusion of energy for cooking, TVs, computers and other appliances is key here and has formed the basis of CSH6* for the past 5 years. The amount is worked out using SAP (and there are a number of issues with this, especially if you’re trying to do something innovative with, say, hot water, but that’s for another day – let’s stick to the basics for today) and is roughly 150% of the building load.

So far, so good. The next step down from zero carbon and CSH6*, is CSH5*. The key difference here is that although the net emissions are zero, the energy for cooking, TVs, computers and other appliances is EXCLUDED. This means the energy requirement is much less – 100% rather than 150%.

CSH 5*

Note the contents of the house have shrunk! Appliances and cooking are now excluded.

All this was well and good, and various developers signed up to test out CSH6* – and most of the market (almost all of HCA funded housing) had to meet CSH3* from April 2007.

By summer 2008, it became clear that the original definition of zero carbon may have been a step too far. At the time, I suggested three moves for UKGBC. With the benefit of hindsight, I wish I’d been a more vocal fan of option 1, but we (as an industry) opted for option 3:

1. deliver fewer homes that meet the current definition of ‘zero carbon’

2. reduce the requirement for carbon savings from new buildings

3. find a suitable mechanism for allowing off-site solutions where on- and near-site installations are not practicable or are prohibitively expensive.

The position we find ourselves in today is a mish mash of 2 and 3. Anyway, I’ll come to that. The original proposal was that the sums weren’t going to balance and instead of meeting the entire balance on-site, some off-site solutions would have to be invoked. The level for on-site compliance was originally set at 70% (to a 2006 baseline) (I’m sure most of you will know this diagram):

Zero Carbon Hub hierarchy

From ZCH website:

The definition of zero carbon we have today is level 6 of the Code for Sustainable Homes, which has only been achieved in practice by a handful of exemplar schemes. This definition presents considerable difficulties in mainstream roll out, not least because it treats every home as an individual energy ‘island’ which must generate all the power and heat it needs.
In December 2008, Communities and Local Government (CLG) launched its consultation on the definition of zero carbon homes in response to concerns that the existing definition – level 6 of the Code for Sustainable Homes – was an expensive option and one which would be unattainable on many sites.

So our diagram for zero carbon effectively became:

Fabric Effciency, Carbon Compliance plus Allowable Solutions

This was the point at which zero carbon as a definition for 2016, and zero carbon as defined by CSH started to diverge. Note, CSH6* and CSH5* are still as per the diagrams above. Even today.

Much number crunching was then carried out, and as Neil points out in his blog, much of this research was done by volunteers in the industry. By last summer it was clear that the 70% carbon compliance was not going to work out – the figure shrank to:

  • 60% for detached houses
  • 56% for other houses
  • 44% for low rise apartment blocks

Note that for low rise apartments we’re almost at CSH4* here. The diagram above is slightly misleading as I’m still showing the energy as being totally offset by renewables – this is no longer the case. A minimum fabric energy efficiency level is set and then the carbon compliance needs to be:

  • 10 kg CO2(eq) /m2/year for detached houses
  • 11 kg CO2(eq) /m2/year for other houses
  • 14 kg CO2(eq) /m2/year for low rise apartment blocks

So some carbon is emitted (at this point surely we ceased to be zero carbon? No? OK).

So in the diagram above the £££ grow and the carbon compliance proportion shrinks. So far so good. Until last Wednesday.

To ensure that it remains viable to build new houses, the Government will hold housebuilders accountable only for those carbon dioxide emissions that are covered by Building Regulations, and will provide cost-effective means through which they can do this.

What does this mean? Well effectively they’ve cut out energy for cooking, TVs, computers and other appliances, effectively divorcing 2016’s zero carbon target from the CSH6* definition. Now what we’re left with is:

Zero carbon as of March 2011

The money required to offset will be much smaller, and a smaller proportion of renewables will be required (I’m not saying no wind here, just that there will be a smaller proportion). It remains to be seen what will happen to the Zero Carbon Hub’s definitions and sums behind the carbon compliance figures and the fabric energy efficiency numbers. This work was all done on the basis of the original definition and the maths changes with the goalposts changing.

Part L 2013 consultation will be out in the Autumn. By the looks of things CSH and the 2016 target are now effectively divorced. This is either the best thing to happen to the Code (CSH 6* remains an exemplar to strive for) or will be the death of it. Please don’t misunderstand me, the idea of having an accreditation scheme to measure the sustainability of homes is not what I have a beef about. But the problems with tying CSH to step changes in Building Regulations have shown the weaknesses in the current incarnation. I advocate a son of CSH, grand-son of EcoHomes, which builds on the knowledge we’ve all built up over the past decade.