‘Zero-carbon’: the sad story of the rapid retreat from a difficult commitment to improving Britain’s new homes
In late 2006 the British government announced that new homes in 2016 would have to be ‘zero-carbon’. The net emissions from heating the house, providing hot water, running the lights and powering the home appliances had to be no more than zero. Over the last four years this commitment has been progressively weakened.
In late February 2o11, the committee charged with advising the government set a new target that set a new target about one third as demanding as the 2007 promise. Battered by builders wanting to continue constructing standard houses and by worries about the expense of achieving the best standards for insulation and airtightness, the government has given up. Four story blocks of flats build in 2016 will have emissions standards barely different from well-insulated apartments built today.
The Code for Sustainable Homes came out in December2006 at the height of enthusiasm for radical changes in the way we consumed energy. British houses are built poorly with inadequate standards of insulation, high levels of air loss and low quality window and doors. The Code was meant to jerk the industry into radical improvements in construction performance. While the use of renewable energy was seen as important, better construction standards and, for example, the use of off-site fabrication of major components was at least as important.
The drive persisted for some time. A consultation document came out in July 2007 affirming the commitment to ‘zero-carbon’. And zero carbon meant what it said. All emissions, including those from running homes appliances were meant to be covered. The definition was unambiguous.
By December 2008 worries had set in. Would it be possible to install enough renewable energy in the form of wind turbines, solar panels, biomass boilers and community heating systems? Were the proposed insulation standards too tight? A consultation document was put out, entitled ‘Definition of zero-carbon homes and non-residential buildings’. It quietly dropped the idea that the zero-carbon standard should include the electricity for powering appliances and set a new target of reducing the emissions from heating the house and running the lights by 70% below planned 2010 standards. ‘Zero-carbon’ would be achieved by offset schemes that allowed the housing developer to pay money for renewable energy schemes elsewhere. (Details of how this might work are still to be published).
This line held for a time. The government stood by the revised definition of zero carbon and the reconfirmed it in July 2009.
But the Coalition government of 2010 took two months to retreat again. Housing minister Grant Shapps said that the 70% target ‘needs to be re-examined’. (Nevertheless, at the same time, Mr Shapps repeated the Coalition’s promise that it would be the ‘greenest government ever’). Six months later the government’s advisory body Zero Carbon Hub reported back to him, offering a revised view that 44% reductions were right for apartment blocks, 56% for semi-detached houses and terraces and 60% for detached homes.
In tabular form, here is what happened. The numbers refer to the kilogrammes of carbon dioxide (or other greenhouse gases) per square metre of new building and are taken from the latest report of the Zero Carbon Hub. But the units are not important; what matters is the loss of commitment to genuinely low carbon building.
| Reduction from emissions of typical 2006 house of 45 kilogrammes per square metre | Date | Government document | Policy |
| 45 | December 2006 | ‘Code for Sustainable homes’ | ‘Zero carbon emissions from all energy use over the year’. |
| 45 | July 2007 | ‘Building a Green Future consultation document’ | ‘Zero carbon emissions from all energy use over the year’ |
| 19 | December 2008 | ‘Definition of zero-carbon homes and non-domestic buildings’ | 70% reduction in building emissions from heating and lighting but ambitions to cancel out other electricity use dropped |
| 19 | July 2009 | ‘Defining an energy efficiency standard’ | Continued with 70% commitment |
| July 2010 | Ministerial statement | 70% commitment ‘needs to be re-examined’ | |
| 14 | February 2011 | ‘Carbon Compliance: setting an appropriate standard for zero carbon new homes’ | Commitment reduced to between 44 and 60% reduction depending on house type |
In summary, the commitment to reduce household emissions for new home developments from 45 kg/m2 to zero has been reduced to a commitment to cut emissions from 45 kg/m2 to about 31 kg/m2. This is well above what is being achieved today by careful builders constructing genuinely low carbon homes.
What has driven this change? Four things seem to be important.
- Although we can drive insulation and airtightness standards up far beyond the Zero Carbon Hub recommendations, no-one seems very keen to do so. The proposed energy use standards for 2016 are over twice the maximum limits used for Passivhaus buildings, usually taken as the norm for really high quality construction. Increased cost is a factor, though Passivhaus might only add £6-£10,000 to the cost of a semi-detached house.
- Builders are frightened of moving from standard UK construction techniques. On a UK building site gangs of tradesmen construct a house in the open air and using techniques essentially a century old. The resulting property, they say, is what people want to buy. Better techniques, involving pre-fabricated panels largely assembled in a dry factory to much higher standards of air tightness, are shunned. If we want to keep traditional British housing styles, better insulation is almost impossible.
- Assessments of the cost of improving insulation compared to the equivalent price for getting the same carbon benefit from putting up wind turbines show that renewable energy is cheaper than efficiency. Speaking personally, I am not convinced by these calculations – partly because they rely on assumptions about the future price of energy – but the result of Zero Carbon spreadsheet work is to suggest that housebuilders would get carbon reductions more cheaply from giving money to offset schemes rather than spending it on energy efficiency.
- The regulatory load on builders is increasing. They are obliged to devote a proportion of their developments to social housing and to pay for local infrastructure improvements. On brownfield sites needing remediation (that is, exactly where the government wants housebuilding to happen) the costs of construction in some parts of the country are not far from the value of the houses that are built. Add further to costs and homes will not be constructed. Of course this isn’t true in high price areas such as Surrey but it might well reduce the number of new homes across much of England and Wales.
Whatever the reason for the watering down of what we mean by ‘zero-carbon’, you might expect that the dilution has now stopped. Don’t be too optimistic: having agreed the latest specification the House Builders Association, a trade body, withdraw its support for the proposal for houses. I suspect that we will eventually see regulations for 2016 and beyond that are no better than the agreed 2013 standards. This will leave new homes a very long way from having zero emissions.

