Green Building - DIY Green Roof - info wanted

If anyone has info on doing a Green Roof yourself, I'm looking. I have a porch with a structured-insulated-panel roof that I'd like to convert to a green roof. I'd like to hear firsthand experience about doing a green roof and/or pointers to info on materials, calculating loads, etc.

A DIY green roof can be a pretty complicated undertaking. First, you need to know if the structure can handle the load and that will depend on lots of variables. Typically, a green roof has several layers: starting with a waterproof membrane, a membrane protection layer, a root barrier, a moisture retention mat, a drainage board, soil and plants. An extensive green roof will have a soil depth of about 3". It's also recommended that the roof has a slope of at least 7 degrees so that water will not pool on it.
Plants can be installed on interlocking mats or in modules, each one having benefits and drawbacks. Plant material is another big choice since they will have to be extremely tough to survive the harsh conditions of a green roof. Usually, sedums are recommended but the final choice will depend on where you are located.
There are some very good books out there that might give you more specific information. Just keep in mind that mistakes on a green roof can be disasterous. No one wants the roof to fall in on someone's head!