Setting Targets: WBLCA Benchmarks

Baselines provide a whole building embodied carbon for a building type for a given year, and benchmarks project targets for future years based on carbon emission budgets and the projected rate of building growth.

A benchmark curve shows the rate at which the embodied carbon in our buildings needs to decrease.  This section presents two benchmark curves based on a theoretical baseline of 500 kgCO2e/m2, and the one thing that these benchmark curves show is that we need to start thinking about making consistent year-over-year reductions in order to be inline with the temperature goal chosen – this same percentage reduction can be used regardless of the building type and baseline kgCO2e/m2.

The approach used to develop the following two curves is based on the SCORS [external source] method published by The Structural Engineer, IStructE, UK, 2020.  This approach starts with the current total carbon emission budget at a given year, the target maximum temperature, and a 50% chance of meeting the target temperature.  It is worth noting that around 2020 scientists were using a 67% chance of meeting these same targets – those odds are gone.  The Global Carbon Budget 2023 [external source] is used as the total carbon emission budget as of January 1, 2024, and two target temperatures (1.5C, and 1.7C) and their budgets are presented.

This case would be the closest to that recommended by Architecture 2030.  The rate of reduction per year is challenging at 19%, and it will take some material breakthroughs in concrete, steel, and glass to make it with a design as usual approach.  Other options are to change the design paradigm, build less, and reuse existing buildings.

It is interesting to note that the 8% reduction rate shown for this case is the same annual reduction rate for total carbon emissions quoted in 2020 to meet a target 1.5C (at a 67% chance); the world met that 8% reduction in 2020 due to Covid but has not been able to maintain that rate of reduction since 2020.