I'm not sure if the amount of extra engineering and costs involved to support low rise rooftop farming is better than the opportunity cost of slapping on a bunc

I'm not sure if the amount of extra engineering and costs involved to support low rise rooftop farming is better than the opportunity cost of slapping on a bunch of solar panels. This might be a viable model for Paris due to severe zoning height restrictions, but when I think urban farms that solves big problems, I think of high density vertical farms.