Eliminating emissions


Eliminating the carbon emissions associated with housing involves understanding the impact of the dwelling over its lifespan. Anastasia Mylona of CIBSE explains how this should be approached

Regular revisions to Building Regulations over the last two decades have focused on improving the energy efficiency of new and existing homes. We understand how to build high-performing homes and we have a realistic pathway to achieving new homes that are zero energy in use.

However, there is a strong argument around the trade-off between the carbon savings achieved by installing ever more energy efficient materials and the carbon emitted during the manufacture of those materials.  To reach a point where a building can be described as “zero carbon” we need to calculate both the carbon emissions associated with homes in use and the carbon emissions produced during the manufacture of the products used to build them – the embodied carbon.

Combining these figures together over the anticipated lifespan of a building gives a total Whole Life Carbon calculation and it is this figure that needs to be factored into planning for a zero carbon future.

This issue was brought into sharp focus earlier this year when the London Assembly Planning and Regeneration Committee published a report calling for Whole Life Carbon assessments to be part of planning applications. The report followed the high-profile debate over the relative sustainability of replacing or repurposing some landmark buildings in the capital.

This was the latest in a series of influential reports effectively supporting the drive to introduce a new section to the Building Regulations. The suggested Part Z would introduce limits to embodied carbon for the first time and, as the name suggests, is designed to move the dial closer to zero carbon buildings.

CIBSE has supported the concept of Part Z since the beginning, while recognising the challenges around introducing such a radical step.

Top of the list of these is the lack of information around embodied carbon in building products. The introduction of Environmental Product Declarations (EPDs) was a great step forward, providing a robust programme to support manufacturers’ calculations. Each EPD will include a Life Cycle Assessment (LCA) detailing the carbon emissions associated with every stage of the life cycle of the product.

This is important because it is estimated that embodied carbon accounts for between 30% and 70% of the whole life carbon emissions from a building. We are gradually seeing individual manufacturers introduce EPDs, although a lack of consistency in the way carbon emissions are measured and evaluated is still a problem.

It is relatively straightforward to calculate the embodied carbon of a product such as brick or a plasterboard panel – where the number of base materials used in manufacture is limited and their origins completely understood. When considering mechanical equipment, however, the picture is much more complicated.

CIBSE focuses primarily on building services: the heating, lighting, ventilation and air conditioning that make buildings habitable and comfortable. Without understanding the embodied carbon of the materials and components that make up these systems it is impossible to calculate the whole life carbon associated with any building project.

Products such as heat pumps, solar PV panels or air conditioning systems are made up of multiple components of varying materials often sourced from a global supply chain. There is little international consistency in how embodied carbon calculations are made and a very variable focus on the need to do such calculations in the first place.

For this reason, CIBSE embarked on developing a calculation method to allow engineers to do this calculation where necessary. The resulting Technical Memorandum 56 (TM56) is not intended to replace EPDs – a manufacturer’s detailed EPD will always provide the most detailed and comprehensive embodied carbon information.

What TM65 does is provide a consistent approach to the calculation and reporting of embodied carbon for building services plants and equipment. The calculations include the greenhouse gas emissions associated with the manufacture of a product, its installation, maintenance, repair, replacement, and end of life. It covers the whole life cycle, excluding operational aspects and potential recovery, reuse or recycling of materials.

As the momentum to understand embodied carbon gathers pace around the globe, more and more manufacturers of all materials will invest in accurate embodied carbon calculations for their products. TM65 is acknowledged by many manufacturers as a first step on the road to a full EPD.

We see and support a future where building regulations set requirements for embodied carbon in the same way that Part L currently sets performance standards for thermal efficiency and Part F for ventilation. Without this step it is logically impossible to claim that any building is truly zero carbon as its environmental impact is not being properly assessed.

In our view it is a glaring omission from the proposed Future Homes Standard. CIBSE has supported Part Z since its inception and we urge the government to come forward with proposals as soon as possible. We hope that sustained pressure from all areas within the building industry will ensure that Part Z will ultimately form part of the Building Regulations and that we will have the knowledge to build genuinely zero carbon housing.

Anastasia Mylona is technical director at CIBSE