Zero carbon: a shifting definition

We’ve proved we can build houses that use zero carbon in operation. Now we’re looking at embodied carbon – a new challenge for manufacturers

In the UK we have been slightly behind the rest of Europe in considering the issue of embodied carbon. Our approach has been very much to focus on the performance of the house, rather than the carbon produced in manufacturing the elements used to build it.

We have voluntary codes, such as the BRE Green Guide To Specification, which consider the environmental impact of individual products, but no generally accepted methods to assess and compare the carbon emissions of different products, or any legislation to impose limits on embodied carbon in buildings.

The problem with this piecemeal approach is that manufacturers have been free to make their own “zero carbon” claims without having to use a universally accepted definition of what the term means.

Environmental Product Declarations (EPDs) are the internationally accepted way to address this issue. EPDs use a Life Cycle Assessment to measure a product’s embodied carbon emissions. Most significantly, this measurement process includes every stage of the product’s life – from manufacture through to its eventual destruction.

Before any product manufacturer can make credible claims for its embodied carbon, it needs to have concluded the thorough measurement and analysis of every stage of this process. Ideally, this measurement then needs to be examined by an independent authority too.

This is the approach taken by H+H in the publication of its Sustainability Report in 2020. In this document, H+H Group evaluates the environmental impact of its aircrete products throughout their lifecycle and sets out a plan for how the Group will reach a target of net zero carbon emissions by 2050.

In the UK this will involve entirely redesigning the energy supply to the three factories to significantly increase the use of renewable energy sources.

In our view this level of commitment will be required by all manufacturers at every stage of the supply chain. Building a true zero carbon home requires a complex analysis of both the embodied carbon of the materials and the contribution they make to the energy efficient performance of the home throughout its lifespan.

We would welcome legislation that sets out a level playing field by which a product’s embodied carbon can be assessed against others using the same method of evaluation.  

Governments across Europe are on this path, with many set to introduce legal limits on embodied carbon for new buildings within the next decade. All of these are based on Lifecycle Assessments and it seems reasonable to assume that the UK Government will be turning its attention to equivalent legislation in the near future.