In my humble opinion, one of the biggest pieces of green bling at ECOBUILD was the huge green wall full of hundreds of plants making the weirdest bedfellows (e.g. spider plant next to maidenhair fern). This was the main feature of the Cityscape area. (I can't even keep spider plants alive in my house ..)

As an ecologist I am a fan of good quality biodiverse living roofs in the appropriate places , but I have yet to see evidence of the green streetcred of green walls. They require power, watering, lots of plants, etc. - at least the ones commercially available. If people want an external green wall my simple solution would be to build a supporting structure adjacent to a supporting wall, but leaving a gap of say 30mm, then plant native ivy (which could be contract grown from native seed, by a bona fide supplier of British wild plants, in the ground at the bottom to climb up the supporting structure. This solution will require no watering and should be self-sustaining, providing the plants are established in good soil and there isn't a drought shortly after planting.

However this is a cheapskate idea and not likely to make a company any money. Ivy is great for nesting birds, provides autumn nectar for bees and other insects, and also provides vital shelter in the winter for wrens and other small birds. It is also the foodplant of the holly blue butterfly as well as other native insects. Note my stress on using genuine native stock (which can be easily grown from cuttings - so you could do this and save even more money). Most of the stuff that landscape architects plant is very far removed from our native version.

Suegreenbuilding - I agree with you - ivy' rooted in the ground is a much better idea but not likely to make anyone a shed-load of money. Nor does is have the "instant green bling" factor. Was the Ecobuild wall designed for indoors or out?

They do look nice though! On similar lines I've seen vertical walls of trickling water with orchid and fern gardens in Bangkok and I was quite impressed by Jeff Koons puppy when I first saw is at Bilbao Guggenheim.

If we pick the plants that make the biggest contribution to air quality (do they all?) there are environmental benefits and it's good for the eyes and soul to rest on something green from time to time I think.