A building's carbon account starts with concrete and steel. Why operational energy performance is no longer enough

Over the past twenty years, the construction industry has learned to count kilowatt-hours. Energy performance certificates, efficient building technologies, and rooftop photovoltaics have brought operational energy use into the spotlight. Yet it is precisely this success that now shifts the focus elsewhere. The less energy a building consumes in operation, the more decisive the carbon footprint of what it was built from - and how - becomes.

A substantial share of a building's whole-life carbon footprint (roughly 45 to 50 percent) today consists of so-called embodied emissions: the emissions associated with manufacturing construction materials, transporting them, the construction process itself, maintenance, and end-of-life. In highly efficient buildings, their share can outweigh emissions from operation. And there is one further, fundamental difference. Operational emissions accumulate gradually over decades, whereas embodied carbon emissions are released before the first tenant even moves in.

It is therefore at the design stage that the scope opens up for decisions with a decisive impact on the final footprint - and, equally, for missteps, where a well-intentioned "green" measure delivers a range of benefits but, at the same time, incurs unexpected costs in the form of additional material.

A green roof is a case in point. Its benefits for water retention, microclimate and biodiversity are beyond dispute. In some solutions, however, the vegetation layers and saturated substrate increase the structural load. That can mean thicker floor slabs, more reinforcement or more robust load-bearing elements. And every cubic meter of concrete and every tonne of steel carries a carbon footprint of its own. The point is not to call green roofs into question, but to assess their benefits in the context of the building as a whole.

Timber calls for the same approach. Compared with conventional reinforced concrete structures, timber buildings can perform very favorably in terms of embodied carbon. The carbon stored in timber must, however, be assessed across the entire life cycle, including what happens to the material once the building reaches the end of its service life. The resulting benefit is therefore determined not only by the material itself but also by how it is used, the structure's service life, and the scenario for its subsequent reuse or disposal.

The tool that translates such dilemmas into numbers is whole-building life cycle assessment (LCA) in accordance with EN 15978, which draws, among other things, on Environmental Product Declarations (EPDs). Its greatest value lies not in the certificate at the end, but at the start of the project, when options can be compared before changes become expensive. At that stage it is often still possible to change the build-up of a structure, the type of material or the supplier with a considerably smaller impact on the budget than in later project phases.

This is precisely the kind of decision-making that Grinity supports for investors and design teams. Using LCA, the carbon footprint of structural and material options can be compared as early as the design stage and linked to other project parameters, such as energy performance or life cycle costs.

A typical question might be the level of thermal insulation. More insulation can reduce operational emissions, but it also increases the volume of material built into the structure. Where the optimum lies cannot be determined by a single rule applied to every project. The answer emerges only from a calculation for the specific building over its entire life cycle.

European regulation is already confirming this direction. From 2028, whole-life carbon is to be calculated and disclosed as a mandatory requirement for new buildings above 1,000 square meters, and from 2030 for all new construction. Those who learn to read the carbon account sooner will gain a head start. Because that account does not open on completion - it opens with the first tonne of cement and steel.