Green roof - does anyone have one? I have a question...

[fallenoverflowerpot]

(I've posted this in property/DIY as well, but I think it's a different crowd here!)

Anyway, I need to know whether or not the runoff rainwater from a green roof can be collected in a water butt. Is it too silty? It'll be mixed with water from a 'standard' roof as well, if that makes any difference...

It depends what you are using it for. If it's just for toilet water etc then so long as it's labelled 'naturally cloudy' it will be safe for general use. Obviously silty water is not good drinking water
To be fair you will have a lot less runoff from a green roof as the soil tends to absorb a great deal of it anyway so it might not be worth it.

the water coming off ours is perfectly clear because we have membranes round it to stop the soil washing away
if the water is coming off silty you have a serious problem with the layout of the roof

we collect ALL the water from all of our roof - 750 gallons of tank storage and then targeted pipes to soak into the soil all over the garden