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What architects need to understand about whole life carbon and where they need to know more

Neal Morris

Learn more about Whole Life Carbon Assessments, current industry-leading standards and regulated energy calculation for Part L compliance

Carbon emissions estimations you have the opportunity to do at design stage become less accurate as you work through the life cycle stages
Carbon emissions estimations you have the opportunity to do at design stage become less accurate as you work through the life cycle stages Credit: iStockphoto

Many small practices will likely see Whole Life Carbon Assessments (WLCA) as the preserve of leading commercial developers who have committed to the greening of their portfolios, high-profile, publicly-funded showcase projects and major schemes in London that are large enough to be referred to the Mayor.

But designers are being forced to look beyond operational energy for carbon savings so they are going to need to know how to make Whole Life Carbon Assessments via UK industry-standard RICS methodology. All of the recent industry definitions and targeting frameworks for low-carbon buildings already assume WLCA (using the RICS methodology).

All architects will be familiar with regulated energy calculations for Part L compliance, and increasingly they are starting to consider embodied carbon associated with products, materials and the construction process, often by using one of the embodied carbon calculator tools that have become available.

But combining these together still covers only a fraction of the considerations of a WLCA, argues Louisa Bowles, Sustainability Lead at Hawkins\Brown.

What are the whole life carbon lifecycle stages?

While it is supported by other environmental standards, the RICS Professional Standard ‘Whole Life Carbon Assessment for the Built Environment’, instantly became the standard methodology after publication four years ago.

This industry-standard module is derived from EN 15978, and breaks down the life cycle stages of a building. They begin with A1-A3, that are Product Stages, while stages A4-A5 cover the Construction Process. Moving through the life cycle, B1-B7 denote Use and, finally, C1-C4 End of Life.

While not included in the WLCA figures, the RICS Professional Standard also requires the reporting of module D, which covers beyond life cycle considerations such as re-use, recovery and recycling. Bowles says that as a rule of thumb, the carbon emissions estimations architects have the opportunity to do at design stage become less accurate as you work through the life cycle stages. However, the proposed 2023 updates to the RICS Professional Standard aim to combat some of these concerns.

The initial stages of a project (A1-A3) encompass embodied carbon associated with the extraction and manufacturing of products or materials. They tend to offer most certainty.

Data comes in the form of generic or specific: generic data is often related to material rather than products but is generally averaged from numerous sources of specific data. Specific data, meanwhile, can be gained from Environmental Product Declarations (EPDs) produced by manufacturers.

There are different tools for different levels of access to generic and specific databases. For example, the Hawkins\Brown open-source tool H\B:ERT uses the ICE generic material database as a default, but can accept EPD information, while others allow a search of EPDs to find the nearest match for your assessment.

The A4-A5 stages cover transport and construction, and installation calls for input from the project’s contractor on transport, site emissions and wastage. However, at the early design stages estimates are based on assumptions and defaults.

Operational energy use is B6, but Bowles says this calls for accurate energy use analysis that goes beyond Part L compliance calculations, which only cover regulated energy use. Predicting carbon emissions from operational energy use (and B7 water use) relies on a number of assumptions, not least the government’s conversion factors that make assumptions about speed of grid decarbonisation.

The established Whole Life Carbon lifecycle schema
The established Whole Life Carbon lifecycle schema Credit: Simon Sturgis/WLCN

What are the further assumptions in both Use and End Of Life modules?

In practice, Bowles says that there are further assumptions made for some of the other ‘Use’ modules, such as maintenance (carbon measurement will often be minimal or subsumed into operational energy uses) and repair (again, usually reported in B4 replacement). Refrigerant leakage is increasingly reported under B1 and can be a large emission but requires knowledge about the MEP systems to include. B4 (Replacement) tends to be the largest emission and currently relies on a like-for-like assumption. RICS default replacement is available, but sometimes analysts choose to review how the assessment service life versus warranty periods compare.

By the time designers get to the End Of Life modules, while tools make assumptions on these emissions based on the quantum of material within the building, End Of Life scenarios are being increasingly interrogated based on the Circular Economy. To justify decisions about how likely a material is to be re-used, designers may find themselves turning to a mix of academic and discussion papers. The default values suggested are often “cautious”, advises Bowles. This is because designers now don’t really have influence over decisions in decades’ time.

It is easy to overstate assumed recycling benefits, such as re-use of steel, which may or may not have to be reprocessed, and crushed concrete, which could be used as aggregate but may simply end up in a hole as sub-base material.

What goes beyond Part L compliance calculations?

While most of the life cycle stages in WLCA relate to the measurement of embodied carbon, a full WLCA covers operational emission as well – from energy to water.

For a design stage WLCA, predicted operational energy use is converted to carbon and reported in B6, but Bowles says this calls for accurate energy use analysis that goes beyond Part L compliance calculations, which only cover regulated energy use. Converting predicted usage from operational energy use (and B7 water use) relies on certain factors: the main source is from the government conversion factors but they include assumptions about the speed of grid decarbonisation.

There are methodologies for evaluating operational energy use at the design stage such as CIBSE TM54 and the Passive House Planning Package (PHPP), but Bowles says designers who want to produce WLCAs may find smaller clients reluctant to pay for such analysis when they discover that operational emissions cannot simply be derived from Part L.

What’s next for WLCA?

The RICS Professional Standard is about to get a major update with a second edition currently out for consultation (architects can download the draft second edition in full).

Bowles says the 2023 proposals include more consistent guidance on measuring demolitions, refurbishments, masterplans and infrastructure projects.

The absorption of CIBSE’s TM65 into the new edition, which translates the energy used in building services into carbon emissions, is seen as a major step forward. But Bowles says TM65 illustrates that trying to undertake WLCA to the fullest extent possible is still at the leading end of the industry: ‘It is early stages. Not many MEP engineers are using it yet and the number of architects taking TM65 measurements on board is very small.’

Given that a low carbon building can be loosely defined as one that optimises the use of carbon resources both to build it and use it over its lifetime, WLCA can be expected to go increasingly mainstream over time, especially as new and improved data sources continue to arrive. Bowles predicts that architects relying on commercially available carbon calculator tools, rather than manual calculation or internal tools, will be adhering to the RICS method anyway as they become more aligned and potentially verified.

Bowles points out that the industry cannot, in any case, move towards zero carbon buildings without taking up WLCA. In order to meet carbon limits you have to do at least one measurement during design and delivery, and you will only achieve the best result if you iterate analysis with design. Based on the current UKGBC Framework definition, you can achieve net zero carbon in operation by minimising, using one-site renewables or purchasing guaranteed renewable energy, but if you are targeting net zero in construction or whole life you have to use a WLCA in order to calculate the cost of any required offset or carbon removal for the embodied emissions. The industry is still waiting for the Net Zero Building Standard to be defined, but it will be aligned with the RICS WLCA methodology.

Thanks to Louisa Bowles, Sustainability Lead, Hawkins\Brown.

RIBA Core curriculum topic: Sustainable architecture.

As part of the flexible RIBA CPD programme, professional features count as microlearning. See further information on the updated RIBA CPD core curriculum and on fulfilling your CPD requirements as an RIBA Chartered Member.


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