You are ignoring the fact a farm space isn't 100% plants. You need spaces for workers to move and so forth. Lets say you have 3 stories, of which the "center"

You are ignoring the fact a farm space isn't 100% plants. You need spaces for workers to move and so forth. Lets say you have 3 stories, of which the "center" of the bottom 2 is used for workers. You still get additional space compared to a single story for the same land cost. If the cost of construction is less than the cost of land, it works perfectly [as is the case in singapore]. About a third of a farm is just space for the workers to move around and harvest things We are talking literally single light bulb is all the supplemental light you need which isn't what your blog post you linked to is willing to admit. http://www.skygreens.com/ http://www.skygreens.com/ You can see how they layer things in the image, the limits really aren't there in the way you imply in high-land-cost areas.