I mean the causation could very well be reverse (more building require more employees etc.)

It could also be from a third factor (population growth demands more work and more infrastructure which leads to more carbon emissions).

I’m not denying the correlation as it exists today (bigger employers probably emit more carbon into the atmosphere; or at least intuitively; I haven’t looked at the data), but that correlation is by no means neither necessary (you could theoretically employ a lot of people without having any carbon emissions) nor sufficient (you can be a very large polluter with only robots doing all the work; like a big automatic aluminum smelter).