Having searched numerous sites on the green roof issue I have failed miserably in my attempts to find any information / CAD drawings or indeed anything relating to venting pitched green roofs.
It would appear (though I might be mistaken) that every picture of a pitched green roof I see on the net has no provision for roof ventilation ? Maybe there are provisions for eaves to eaves ventilation but ridge ventilation does not appear to have been addressed in any of the steeper pitched roofs.
As a building contractor I am well aware of the problems of unvented roofs and have dealt with horrendous problems caused by such practices. The situation worsens in high vaulted/ cathedral ceilings with no loft space and the where requirement to vent each individual rafter space is essential. Maybe I'm wrong but surely ridge ventilation has to be a requirement in such pitched roofs?
I know how I would go about providing ridge ventilation and tying in a roofing membrane but what I am really interested in finding out is why there is absolutely nothing on these sites about ventilation. Are these roofs being built without adequate provision and has it actually mattered in the end ?
As a matter of interest , I recently spoke to the technical department of one major UK supplier of green roofing materials regarding ventilation and they didn't know / had never been asked and had no drawings or info. Am I missing something here or is this a subject that has just never been addressed ?
Any comments or experiences welcome
Books 
Comments
Firstly you would rarely see a green roof with a steep pitch. The growing medium would tend to slide off and also water run off becomes a problem and the roof is too dry.
Where the building has a loft then that would be ventilated at the eaves.
Where there is a cathedral ceiling then you would need to allow a continuous 50mm air gap from eaves to eaves.
I have not heard of anyone that uses ridge vents as you would have problems with the detailing and also preventing the vents becoming blocked over time.
You could detail ridge vents - lot of faffing about! - I'll send you a pdf or dxf of what I would consider if you send your email.
Timber - Yes, you would think a warm roof might be the answer but having just spoken to Kingspan and Rockwool neither have information on the structure and neither could definitively answer the question- You could consider a warm pitched roof covered by a totally waterproof membrane the same as a flat roof with a "large bump" in it / Flat roofs used for green roofs remain unvented and seem to work presumably with a very good vapour barrier underneath.Water vapour would still need to be removed elsewhere in the building.
Not saying that's not the way to do it but not yet convinced - besides which the addition of a substantial layer of insulation on top of the rafters creates yet another awkward detail in fixing on pitched roofs and one which I would prefer to avoid.
Thanks - Keep the ideas going !
J
Also consider those flat roofs added on terrace extensions where they all abut each other and the only vents are at the front of the roof - are those roofs truly ventilated indeed are they actually ventilated at all?