Optimizing floor systems using precast elements – CO₂ equivalents according to the DAfStb GHG guideline in the overall project context

Floor systems have a major influence on the environmental footprint of structures owing to their high material content, which results in considerable global warming potential (GWP). The new DAfStb guideline on “Greenhouse Gas Reduced Structures Made of Concrete, Reinforced Concrete, or Prestressed Concrete” (GHG guideline) makes it possible, for the first time, to systematically analyze and group entire structures as well as individual floor components into greenhouse gas reduction classes.

As part of its sustainability knowledge series, the Fachvereinigung Deutscher Betonfertigteilbau (FDB; German Precast Concrete Association) thoroughly investigated the global warming potential of various floor systems for a model building:

Whereas conventional cast-in-place concrete floors designed as two-span systems have a GWP of about 100 kg CO_2eq/m²_GFA within the overall structure, prestressed precast TT slabs designed as a single-span system without center beams, for instance, can reduce this value to about 80 kg CO_2eq/m²_GFA. Dispensing with support beams and one row of columns drives down emissions not only at the floor level, but also for adjoining structural components. This is how the structure’s total emissions are lowered by approximately 20% while increasing flexibility of use.

To complement the FDB study, Bremer SE conducted an analysis of built structures composed of steel-reinforced and prestressed precast elements. Even under current conditions, standard designs that use precast concrete elements in multi-story buildings, halls, and complex mixed structures achieve significant savings compared to the THG guideline’s reference value thanks to optimizing their structural and cross-sectional layout. While an isolated analysis of individual floors provides some degree of insight, it is evident that analyzing the overall system is even more meaningful.

In conclusion, it is not only the choice of the floor cross-section, but also of the floor system as such in conjunction with the detailing and number of support and foundation components that provides a key lever for optimizing the structure’s GHG profile. Taking a holistic approach early in the project can unlock considerable saving potential and help achieve ambitious climate targets in concrete construction.