When 'zero' doesn't mean zero at all

Professor Tom Woolley,architect at Rachel Bevan Architects, wasn’t disappointed at all when the government recently failed to define zero carbon. In fact, he’s not a big fan of zero carbon at all.

The term ‘zero carbon’ has become almost meaningless. Ever since the Labour Government began to set targets for zero carbon, any decent work to define what it meant seemed to have come to an end. Zero carbon is a great example of Orwellian doublethink as it rarely means zero and it has little to do with carbon. Thus it is not surprising that the new coalition government has dodged this hot potato.

Many interpret zero carbon as meaning a building should use no energy during its life. This sounds like a great aim until you realise that almost everyone who makes such claims hedges around with excuses and conditions. For housing to reach code level four, five and six means introducing expensive pieces of renewable energy kit that take a lot of energy to manufacture. To meet PassivHaus standards means using active systems that are far from passive.

Furthermore, most buildings are constructed using structural materials and insulations that use a great deal of fossil fuel energy to manufacture. Using cement and concrete and synthetic insulations such as foams and mineral wool can be adding to the problem of global warming rather than mitigating it. About 50 tonnes of CO2 are emitted in constructing a typical house.

Thus zero carbon, even if attainable, which is doubtful, usually ignores embodied energy. There are those who argue that embodied energy doesn’t matter as the most important thing is to save energy over the life of the building, but surely it is preferable to reduce the use of fossil fuel in the short term rather than arguing that it will be saved over 60 years.

There is an alternative to the high-embodied energy approach. If you use low-impact materials, it is possible to lock up carbon in your building fabric as well as starting off with low embodied energy. User timber and other bio-based renewable materials like sheep’s wool, hemp, straw, wood fibre and so on is perfectly possible as these materials have fought their way into the mainstream construction supply chains.

Recent studies commissioned by DECC through the National Non-Food Crops centre by Davis Langdon and the University of Cumbria have begun the process of calculating the carbon saving profile of natural materials. DECC have supported the use of renewable materials through a £50 million grants scheme where hundreds of low-impact houses are being constructed throughout the UK.

Sadly, it seems unlikely that this support will continue under the coalition as they have decide to give a further £600,000 to prop up the Zero Carbon Hub, a quango that has done little to get to grips with zero carbon. They have done little to support the use of natural materials and are unlikely to recognise that renewable materials can have many other benefits. The government needs to support the development of the nascent renewable building materials industry as it is sustainable, uses local resources, creates employment as well as better-embodied energy renewable buildings.