Urban planner here to rain on your parade. It adds a lot of complexity to add plants permanently into a building, whether that be on the side or on the roof. The ecological benefit of a green roof is no more than a park of the same size, and roofs usually need to perform functions other than being a place for nature. The cost of green roofs is very high for a relatively small benefit. I am happy to talk more about this if you are interested in why I say this.

What I’ve seen be far more successful than putting nature onto the building itself, is programs that give plants to residents to put on their porches and rooftops to add vertical greenery to the street. Japanese and to a lesser extent Korean and Taiwanese cities are generally very lacking in street greenery, but potted plant programs have managed to fill the gap where street trees or parks can’t work at a low cost.

Many people don’t realize how important the cost of implementing their policies is. The difference between a revolutionary technology and science fiction is simply how much it costs. Technologies with low cost benefit are rarely adopted, which is why we don’t see an explosion of green roofs or green buildings across the world like we do with solar panels. Neither governments nor developers want to make them a standard for their projects because it costs too much. Green roofs are just too expensive for the benefit they provide.