[Leanan]

I wonder if you can plant vegetables up there?

http://www.msnbc.msn.com/id/6002705/site/newsweek/

[davidyson]

I've got two little green roofs on my house and a little shed in the garden, respectively.

They are supposed to be dry roofs, so no irrigation there.

You can grow all sorts of thick-leaved stuff up there. I also tried strawberries, but they did not get a lot of fruit and had phases of completely drying out (as you might expect on a dry roof).

If properly insulated agains humidity entering the concrete of the roof, you might also irrigate the roof and yield more veggies and fruit.
But make sure the roof will carry the soil, all the humidity it can soak up plus 1 m of snow (if you happen to live in an area where it snows).

Davidyson

[muhandis]

Greenroofs probably do not offer much in the way of energy savings (although there may be benefits in hot climates with respect to air conditioning loads -- a local study by BC Institute of Technology is underway to determine what their energy savings potential are). However, greenroofs are excellent at rainwater management and have great potential at providing some urban agriculture value.

There is a significant industry for greenroofs with most of the expertise in greenroof optimization in Germany. In Vancouver, Canada there are over 600 greenroofs according to an inventory done in 2002 by their regional government. But like the rest of North America, these greenroofs are not optimized for energy, rainwater or agriculture. Instead, they are there to look pretty. Now in Vancouver's case, about half of the greenroofs are on apartment towers/buildings - what an excellent opportunity for community gardens!

The Germans the lead the way - Dachbegruenung. Their main professional contact is www.fll.de - some documents are available in English. Else, contact Green Roofs for Healthy Cities at www.greenroofs.ca or http://peck.ca/grhcc/ Since these work in Canada, they'll work almost anywhere.

Ideally I would like to see greenroofs fulfil an urban agriculture role. For more information on urban agriculture and the role of greenroofs, contact City Farmer at www.cityfarmer.org I suspect that the time will come when greenroofs become a necessity.