Scientists in the Netherlands have assessed how the so-called blue-green roofs can help reduce the operating temperature of rooftop PV panels and have found they provide a significant cooling effect. The irrigation system used for the research project relies on an additional water supply sourced from grey water from showers that is transformed into irrigation water.
I found a green roof web site a while back, but they were using alpine vegetation that did not need a lot of water. Even so, it added a lot of weight, so I would think a wet setup would need a special roof design.
Yeah this sounds like structural issues 10 years down the road
Only if you don’t plan for it. It got really popular here in the 90s and those buildings are still going strong