Post-occupancy amnesia

This week, I’ve been thinking about lead and lag indicators. About how a designer’s job is essentially to predict the future. And about what factors we choose to use when making those predictions.

Where we have precedent, we can use past successes guide what we think is possible in the future. But when we’re working in new territory — unprecedented scenarios, or changing environments — we need new lead indicators to inform the models we build for tomorrow.

Take structural performance. We know a lot about how buildings stand up. That field is well established. But when it comes to energy performance, the field is less so.

It’s only in the last few decades that engineers (and other humans) have paid serious attention to how much energy a building uses to stay warm or cool. More recently still, we’ve started worrying about embodied energy — the energy used in making the materials and building the thing in the first place.

Of course, we now have increasingly sophisticated modelling tools to predict how new buildings will perform. But they are just that: predictions. What I find fascinating is how little attention we seem to pay to what actually happens after the building is built.

I call this phenomenon Post-Occupancy Amnesia.

One of the key ideas in regenerative design is that design is continuous. We don’t just design and disappear. We don’t just predict and leave. We stick around — to learn, to update our models, to deepen our understanding of the systems we’re working with and how our decisions change what they do.

The good news is that every building that currently exists is an experiment already running. Every one of them is producing data on how it actually performs. If we can gather that data, learn from it, and feed it back into our design processes, we’ll stand a much better chance of making smarter predictions for the future.

Maybe it’s time to trade in post-occupancy amnesia for the post-occupancy evaluations we should be doing as a matter of course to improve our models.

Designers tell the future (part 2)

Yesterday, we looked at how the Gothic cathedral architects of northern France used precedent to guide what could be built next.

But what happens when there’s no precedent?

When Antoni Gaudí was designing the Sagrada Família in Barcelona, there was no precedent for the complex geometries he wanted to build. So, he created a model: using hanging chains and sandbags to mimic the geometry and loading of the cathedral’s roof.

This physical model acted as a lead indicator, giving Gaudí insight into whether his structure would stand up. When there’s no precedent, you can’t ask “does that look right?”—because you’ve never seen it before.

The reliability of this kind of lead indicator depends on the accuracy and appropriateness of the model. Selecting or creating the right model improves with training and experience.

Engineers build models all the time. In fact, every engineering calculation is a model of the future. A structural stability calculation gives us a lead indicator about whether a structure is going to stand up. Engineers work very hard to make sure these models are as accurate as possible.

But they are still just models. The truth comes after the fact: did the building actually stand up? That’s the lag indicator. And in those rare cases where something goes wrong, this new knowledge gets fed back into better models for the future.

Thankfully, very few buildings in the UK fall down due to bad modelling. That’s because this feedback loop—between model, reality, and revised model—is quite advanced.

But what about the other areas of engineering where we don’t close the loop?

That’s a question for tomorrow.

Lead and lag indicators in design

This week I’ve been thinking a lot about lead and lag indicators in design.

Whether you floss is a good lead indicator of the health of your teeth. How many fillings you have is a lag indicator.

How many enquiries I have in my business is a lead indicator for revenue. What I end up invoicing is a lag indicator.

Lead indicators are predictors. You can influence them, but they aren’t guarantees. Lag indicators tell us what happened. You can’t change them, but you can learn from them.

We need both in design.

I have many fillings — that’s my lag indicator telling me I didn’t look after my teeth well enough in the past. I now floss — that’s my lead indicator suggesting I’ll still be smiling about my teeth in the future.