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Is there a metric out there that can encapsulate an entire building? I'm searching for it right now. There are several, and they each have their own weaknesses and strengths.
Building Efficiency
I wrote several months ago about building efficiency. It's the standard rule of thumb in the development world. How much of this building can charge rents vs how much of it is dead weight (to the pro-forma anyways). It is...not an awesome metric because it does not take into account much of the rest of the building.
Skin-to-Gross Ratio
This metric takes into account what building efficiency doesn't: the building skin. Less skin, same area built, cheaper building. Right? Well if you follow this theory, the eventuality is to create circular building floor plates--which are hard to construct. This doesn't include any kind of metric to understand more about the building than its "compactness".
Floor Area Ratio
Good ole FAR. This one is how city planners rein in the developers. Limit the FAR! But this can be used as a metric as well. If a building has a low FAR compared to the building next to it, then there might be an opportunity to increase its intensity. It is an awful metric, however. On its own, FAR cannot take into account height or lot coverage. Sites governed by FAR are incentivized to create buildings that are as efficient as possible. What if you limited the net area rather than the gross?
Lot Coverage
This might be the best regulation to force buildings to become taller. If a city limits the lot coverage to 50%, then 50% of all future developments will need to be twice as tall (in theory) to have the same intensity. This is untrue, however. Taller buildings are more expensive. Taller buildings have more elevator shafts, more stairs, more cost.
If you tried to use lot coverage as a metric, a developer might try to make sure the allowable lot coverage is maxed out! It is a dubious metric in a vacuum, because everyone will max out their lot coverage. Horizontal construction is almost always easier than vertical construction.
Height vs Lot Coverage vs FAR
This is the best way to look at your buildings. Look at these three things: How tall is it? How much of the land does it actually utilize? How intense is it compared to its context?
The Ultimate Building Metric
When it comes to generative design, we need to understand the performance of a design without actually needing to look at it. Why? We will be searching through millions of possibilities. The five metrics discussed here will be a start, but with true building optimization, we will be using different metrics in the future.
How about Good View Ratio or Ease of Construction Score- these things are not far off.
