Net Zero Carbon – the basics

Alex MacGruer
In today’s rapidly changing world it can be difficult to keep up with the evolving vocabulary related to sustainability. One of the latest phrases to garner popular use in the construction world is ‘Net Zero’.

But what does ‘Net Zero’ mean and how is it achieved? 

At Faithful+Gould ‘Net Zero’ has become a common conversation amongst colleagues, consultants, clients and contractors.

Our simple guide is intended to help explain the terminology and key aspects.

UK Law

In June 2019 the UK became the first major economy in the world to pass a net zero emissions law. The aim is to bring all greenhouse gas emissions to net zero by 2050. This means 100% of all building processes must operate at net zero by 2050.

Locally, many Councils around the UK have adopted more aggressive targets in achieving carbon neutrality by 2030.

Relevant Statistics

Buildings and Construction are responsible for 39% of all carbon emissions in the world. This is broken into 2 key categories:

  • Operational emissions: 28% of the world emissions are linked to buildings in use including heating, cooling and lighting etc
  • Embodied Carbon Emissions: 11% of the world’s emissions are linked to the materials manufacture and construction processes. Every material releases greenhouse gas through the supply chain and this is usually measured from factory inception to final use on site (e.g. steel (by weight) has a much higher embodied carbon footprint than concrete).

The statistics coupled with the legislation changes highlight why Net Zero has become such a talking point in recent months. 

Net Zero Explained

The World Green Building Council (WorldGBC) defines a net zero carbon building as being ‘highly efficient with all remaining energy from on-site and/or off-site renewable sources.  This means the amount of carbon emissions associated with a building’s usage and construction stages (up to practical completion) must equal zero or negative. 

It can be achieved using offsets or the export of on-site renewable energy, e.g. exporting surplus unused energy back to the grid.

The WorldGBC has provided 4 key defining principles of Net Zero:

  • Measure and Disclose Carbon – carbon is the ultimate metric to track, and buildings must achieve annual operation net zero carbon emissions balance based on metric data.
  • Reduce energy demand – prioritise energy efficiency to ensure buildings are performing as efficiently as possible and not wasting energy
  • Generate balance from renewables – supply remaining demand from renewable energy sources, preferably on-site followed by off-site, or from offsets
  • Improve verification and rigour – over time, progress to include embodied carbon and other impact areas such as zero water and zero waste.

How to Achieve Net Zero:

The two key issues for achieving Net Zero Carbon are:

Operational Emissions:

In construction, combining a fabric first approach (such as Passivhaus) to minimise energy usage, bolstered with carbon offsetting, is considered the most economical way to achieve the Net Zero Carbon target. Adopting a rigorous standard like Passivhaus will significantly reduce the future operational energy.

As an aside, what does offsetting mean? Carbon offsetting is the approach that the legislation has generally taken for reducing carbon emissions in construction. When all feasible measures for reducing carbon, impacts have been reasonably exhausted, offsets can be used to cover any residual carbon. In simple terms, when all the physical site works don’t achieve the net zero requirement, to reduce (offset) the difference, a payment can be made. A simple example of this would be offsetting the use of a flight, whereby the emissions of the trip are calculated, and a cost contribution is made to offset that value by the same amount elsewhere in the world (e.g. the financial contribution would be put towards planting trees), therefore making the flight ‘carbon neutral’. The same would be applied to construction and operation energy. 

Embodied Carbon Emissions:

The fabric first approach does not necessarily take into account the construction embodied carbon, which remains an aspirational target within the construction industry at present. To fully understand the impacts of one material or system compared to another, a whole-building life-cycle assessment would need to be undertaken. This process looks at multiple impacts of building materials over their entire life cycle (from factory to landfill/recycling).

Summary

Recent findings published by the WorldGBC confirmed that the number of organisations committed to net-zero buildings has doubled over the last year. This represents a clear step-change in the thinking of major organisations. 

At Faithful+Gould we have seen a new desire by our clients to reach the 2030/2050 carbon neutral target. A number of our new innovative commissions are seeking Passivhaus accreditation taking the fabric first approach.

There is no question that this trend will continue. As clients, developers, public organisations, councils and governments acquire a clearer understanding of the concept of Net Zero Carbon, the move towards Carbon Neutrality will gather pace.

Our following articles will look at related subjects in more details including: 

  • Passivhaus as a means of achieveing zero carbon 
  • Passivhaus - Project level considerations
  • Passivhaus - Cost Consideration 

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