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Getting a grip on embodied carbon

Sustainable Design By Dr Thais Sartori, Sustainability Consultant – 14 August 2023

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Head and sholders shot of Thais wearing glasses and a mustard shirt against greenery

Dr Thais Sartori

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This article was originally published at Sourceable an 10th August 2023.

There is an increasing amount of discussion in the property and construction sectors about embodied carbon and the need to reduce its impact in the delivery of new buildings. But as the Green Building Council of Australia (GBCA) and NABERS have noted, it is not as straightforward to measure as emissions from energy use.

Data gaps are one of the major stumbling blocks.

Data for operational emissions is becoming more readily available as comprehensive monitoring and metering systems become more commonplace and as a result, transparency improves. This is also the case at the infrastructure operator level, with, data on the proportion of grid energy generated from renewables on any given day – and therefore the emissions from gas and coal-fired mains power consumption. – produced by the Australian Energy Market Operator and released publicly.

Measuring the amount of on-site energy generated from rooftop solar panels on a building is also visible where smart metering in combination with an energy management platform has been used, and the amount of on-site gas or diesel used is as simple as looking at the invoices. Refrigerants are a little more complicated as emissions from leaks may not be accurately quantified, but there are tools available to provide estimations.

Embodied carbon is different to operational carbon as it is about the physical parts of the building. That means looking at the emissions from construction including raw materials extraction and processing, product installation and commissioning, through to in-use materials consumption for maintenance and repair and then the end-of-life for plant, equipment and building fabric.

There are variations in the visibility of the lifecycle emissions from materials and equipment. While large impact materials such as concrete and steel are becoming better understood in relation to embodied carbon, the industry still lacks substantial data on building services plant and equipment, and also smaller materials such as fixtures and fittings. While many of these elements are relatively small compared to a steel beam, as a class they comprise a sizeable proportion of a building’s lifecycle material-related impacts and embodied carbon. Refrigerants are also complicated as emissions from leaks may not be accurately quantified, but there are tools available to provide estimations. They are also a major emissions source at end of life.

A major challenge to obtaining data about all materials is manufacturers and suppliers may not have that data themselves, or they may have some (or even all) of the data and choose not to disclose it.

Some design and construction projects will specify the need for an Environmental Product Declaration (EPD), but this is not a whole of lifecycle impact assessment, and it does not necessarily benchmark embodied carbon in a way that helps specifiers decide whether an item is going to be lower impact than an alternative product. Basically, the quality of an EPD depends on the scope and the rigour applied by the creator of the EPD.

Lifecycle thinking is essential.

In designing and specifying, it is important to consider the whole lifecycle of the building, as it’s not about focusing on either operational carbon or upfront (embodied) carbon, as the two often intersect.

For example, to have a building that performs well in terms of energy-efficiency, protecting it from external conditions such as heat or cold is the primary tactic. However, many insulation materials are high in embodied carbon due to their composition and the manufacturing process being energy-intensive and emissions-intensive. In this case, there is a trade-off between the additional embodied carbon due to insulation and the energy consumption needed to operate the air conditioning. Another example involves material specifications. Designers may specify materials with low upfront carbon emissions. However, what if this material has a shorter life span? Only a lifecycle approach can effectively determine the most environmentally friendly design strategy.

In a whole life carbon assessment, the calculations need to consider what’s the net benefit in terms of reduced energy vs increased upfront carbon. Looking at the options and the outcomes in the context of the whole building may even reveal some ways of reducing both operational and upfront carbon that would not be visible just looking at the design for insulation or material selection.

Using carbon as a lens for looking at the whole supply chain for thermal protection options may be beneficial, but keep in mind that many lifecycle impact assessments for products may only have included factors that were convenient or easy for the manufacturer or assessor.

Can software help?

The current available software for upfront carbon calculations attempts to meet the needs of designers and specifiers for user-friendly, concise and reliable information and data. But in doing so, it does not always include all the information needed to do a complete whole of life carbon assessment for a project. Product and material types might not be included, or the data might not have been provided with the level of transparency and rigour that gives precise results.

One area where this is becoming obvious is in products that incorporate rare earths. These items might include energy storage batteries, renewable energy generators such as solar PV systems, audio visual equipment, ceramics, specialist glazing, digital technologies including smart building systems and IT equipment. The environmental footprint of the rare earth materials sector is still somewhat opaque.

Ways to get on top of upfront carbon.

In the absence of comprehensive data, there are still ways a design and delivery team can reduce whole life cycle emissions. The key is having effective collaboration between the design and delivery team, so good decisions are made when specifying.

For example, building services equipment comprises a significant share of upfront carbon. Every widget and bit of wiring has a footprint, so designing for the most efficient solution for both energy and in terms of actual equipment required for the building services will reduce embodied carbon. It’s a fine balance to size services equipment to be able to handle a buildings load and account for the future loads due to climate change without oversizing the system unnecessarily.

And even if that reduction only amounts to a few percent shaved from the whole-life carbon footprint of the entire building, that is still a win given the average embodied carbon footprint of a standard commercial office building has been estimated by GRESB to be around 1300kg CO2e per square metre.

Using digital design approaches such as Building Information Modelling (BIM) is helpful, as it gives visibility of decisions such as placement of conduits, plenums and other features. This enables the team to optimise design for the most efficient use of materials (which may also save on construction costs) and ensures clashes are detected early and rectified, saving the carbon associated with rework if clashes are detected only once a project has commenced.

Use of digital modelling and parametric design tools to optimise structure, footings, slab and pilings to the least amount of material necessary to meet operational, safety and structural integrity requirements is also a way to find carbon and materials savings too.

While some of this may seem the domain of only green-certified projects, we are seeing an increasing shift in the government, property and finance sectors towards low-carbon assets. This trajectory is only going to accelerate as the grid decarbonises and the footprint of physical processes like construction becomes more visible within national emissions accounts.