Module D – what is it and why is it important

How additional standards for lifecycle assessments will deliver truly sustainable construction:

Improved standards and guidance for constructors calculating embodied carbon are helping to deliver truly sustainable construction projects.

Lifecycle assessments (LCAs) are commonplace ahead of the use of a wide range of resources and materials and are an essential part of delivering sustainable construction. These now take into consideration an additional, supplementary element, known as Module D, to review the potential to refurb, reuse or recycle construction materials at a building’s end-of-life.

LCAs assess and measure the sustainability credentials of building projects from extraction and manufacture of raw materials to use and maintenance of a building and, later, materials’ end-of-life. By understanding where energy is required and environmental harm is caused during the construction process, the industry can reduce negative impact and work towards global net zero carbon emissions targets.

Previously LCAs took a ‘cradle to gate’ view, considering the environmental impact of sourcing and manufacturing materials only. They then broadened to ‘cradle to cradle’, reviewing the whole-life of a building, including operational impact. And now they have widened further, under European standards.

Completing a whole LCA delivers a comprehensive embodied carbon calculation for a project, by reviewing:


  • Module A – the sourcing of materials or products and delivery of the construction process; from extracting and manufacturing raw materials (A1-3) to transporting and constructing or erecting products or materials (A4-5).
  • Module B – the operational use of a building; from operational energy usage to maintenance and repair, to replacement or refurbishment of materials (B1-5).
  • Module C – the end-of-life process of a building; covering the expected or advisable deconstruction process, including transport, disposal and processing of waste (C1-4).


Now, mandated under European Standard BS EN 15804, LCAs also add in a fourth element:


  • Module D – reviewing the ongoing benefits of materials beyond a building’s primary use; covering the recovery, reuse or recycling potential of components and materials.


For structural steel, Module D analysis includes the potential to recover and reuse members or components, reconfigure building layouts, or recycle steel into new products.

By calculating the additional benefits of reusing or recycling materials, Module D not only improves the embodied carbon calculations of an existing project but also reduces the requirements for Module A primary production for future projects.

However, it’s important to be realistic that Module D can only report on ‘potential’ benefit – not actual, or definite, benefits, as is the case with Module A, for example – based on likely events or requirements in the future. Nevertheless, considering these potentials and reporting on them is mandated for the majority of construction projects, alongside mandated reporting for materials production (Modules A1-3) and end-of-life processes (Modules C1-4).

Guidance within the BS EN 15804 standard provides formulas from which constructors can assess and calculate the embodied carbon for Module D. It also offers recommendations on how to then report the findings, however it stops short of outlining how findings can influence decision-making in the design and construction process itself.

For steelwork contractors, applying these standards is essential to demonstrate steel’s sustainability credentials, mitigating any concerns about the high energy input required for steel production and benchmarking its benefits against alternative materials. Since steel is able to be infinitely recycled without losing its properties, the ability to measure its ongoing benefits in Module D further demonstrates its value and versatility as a construction material.

Including Module D in LCAs is regarded as the final piece of the puzzle for the construction sector to deliver on global net zero targets and create a futureproof circular economy. Without it, analysis cannot be truly comprehensive and any embodied carbon calculations or conclusions risk being reductionist.

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