Concept: putting a vine, eg passion fruit, choko, etc over the garden shed to cool it in summer and make use of the vertical space for food production, plus it looks more appealing. Could even grow different vines at same time to add greater visual and food interest. Plus, Great book, apparently ;-). All you need to know about how to build your own little green roof on a shed or outbuilding.
Riefa boards are a new type of green roof substrate. They are a hi-tech fibre board made from organically grown and sustainable natural resources, including rye flour and tree bark. There are some other ingredients in there too, but forgive me if, for reasons of commercial confidence, I don’t expand on them here. But rest assured they are innovative and do what the designer intends. http://www.riefagreenroof.co.uk