Ask away mate, bottom line is as much as I am a big fan or urban greening in general for so many ecological reasons. I think in practice they are a nightmare on so many levels, Having a lot of experience i this field as a systems designer I do not thing the are practical. and one hole in that waterproof membrane either vertically as in green walls or horizontally as in green roofs Green roofs being the lesser evil of the two.
In reality we all know as normal building age buildings age things go wrong and damp is a big problem
I do not believe the hype any more. Look up french green wall designer Patrick Blanc I believe he is the leader in this field


