A sustainable energy consultant questions the shifting definitions of the eco friendly home

Not for the first time in the whole zero carbon debate I am torn. On the one hand I want to congratulate the UK Green Building Council’s [UKGBC] Zero Carbon Task Group for a brave attempt at taking the agenda forward in a robust and pragmatic way with their recently published report on "The Definition of Zero Carbon". On the other hand, I can’t help feeling that the phrase zero carbon is now close to becoming devalued beyond repair.

Various attempts have been made to save zero carbon after it was first seized on by politicians and the like as a great sound bite and to distance it from the murkier water of offsetting to become carbon neutral. The most recent being the insertion of the word ‘true’ zero carbon, referring to level six rather than level five homes, in the previous iteration of the Code for Sustainable Homes Technical Guidance which has now disappeared in the April 2008 version.

Somewhere along the line there is an inevitable compromise between purism and technical and commercial reality. The UKGBC’s report goes a long way to addressing this reality but does this have to be at the expense of a phrase which should mean exactly what is implied?

You could argue that the rot started as soon as the line was drawn around only the carbon related to energy in-use. This does represent the majority of carbon associated with the building design, but there is at least a further 10% from the carbon associated with the construction process and the embodied carbon of the materials. This is a minimum for today’s construction standards and becomes a greater and greater proportion as the energy-in-use is driven down through energy efficiency improvements. Nor should we lose site of the carbon emissions which can be influenced by considerate transport planning for low carbon modes of transport, the inclusion of measures for waste reduction and water conservation, and facilities for local food provision.

I can’t help feeling that the phrase zero carbon is now close to becoming devalued beyond repair

In recommending the broadening of the definition of zero carbon to include off-site solutions, the report dismisses the concept of a market-based cap and trade credit mechanism as "it could not guarantee delivery of additional, physical zero carbon installations". This is an area where we feel that further debate is needed. If "true" zero carbon is not possible (or there is not a market willingness to deliver and a consumer willingness to demand it) then let's move towards a system whereby additional emissions reductions are delivered through the efficient distribution of resources to those locations where there are more attractive opportunities to reduce emissions. A Community Energy Fund, as recommended by the report, could deliver the same results but comes with its own risks of successful implementation.

The UKGBC report has quite rightly left the government with some tough questions to mull over through the summer’s consultation, not least the issue of whether the right incentives are in place to ensure that the predicted carbon savings are sustained through the life of a project. The government does have an opportunity to grasp the concept of a new Community Energy Fund or market mechanism to recycle low carbon investment into the much greater problem of existing homes. And I would add, at a time when we have to build end consumer interest and confidence in the concept of low carbon homes, are we still using the right words?