When speaking about MEICON, a question is often raised about future changes in use of a building: “If we design to 100% utilisation, this will limit future changes in use, and so I prefer to be a bit inefficient” (or words to that effect).
My response is: design for what you really need now, use as little material as you can doing it, and make some sensible decisions so you don’t actively prohibit future retrofit and/or deconstruction/reuse.
Designing for what we need now requires some careful thought. You should be aware of the uncertainty around much of design (loading, partial factors, etc) and the need for measurement of real performance to help inform better design. Can you convince your clients to add structural sensing, and help the sector to improve its design assumptions to further reduce carbon emissions?
If in the design of an office you work within existing design codes and use 2.5kPa floor loading, you’ve already got lots of flexibility (average loading in offices might be around 0.3kPa!). If you are in London, designing to 4kPa or more, you must challenge your design team to justify such criteria. “That is what we have always done” is not a sufficiently robust justification for a design decision that will unnecessarily consume carbon, and leave a structure working at a tiny fraction of its capacity for the vast majority of the time.
I do not think that we should try and predict what will happen in the future, and to design for these predictions. This is a fool’s errand, and you will use material now when it is carbon intensive to produce for no reason other than trying to second guess a future change in use that may or may not happen.
In 60 years’ time we might use office and residential spaces very differently to how we use them today - and we probably should, as one way to cut down on carbon is to just not build as much, and use what we have more effectively. Your offices are empty most of the time, what could they be used for between 5pm and 9am?
The over-design we suspect is happening (based on the MEICON survey) has a material value greater than the entire UK structural engineering fee pot. We could reduce embodied carbon and pay for the design time required to do it. This is a no-brainer. Structural engineers now need to demonstrate to their clients that they can add value by reducing embodied carbon and get paid to think cleverly on all projects.