tweva, Thank you very much for the link pdf just saved it and will be reading it on my ipad.
On your question about,
(If you can support the roof enough, you could install a rain barrel or two and collect the water from your roof into the rain barrels)
I am thinking of a support on a corner of the house higher then the roof to add one or two rain barrels. I will make a steel frame to hold them up so there will not be a problem with the roof. This has two uses, one is for the plants on the roof and the other is for the bathroom upstairs. I just remodeled the bathroom and the feed for the water is on the roof and I left a piper ready for the feed from the future rain barrel so when they cut the water I and the family can take a shower.
I am now remodeling the bathroom downstairs and will plan for the same two rain barrel system for showing.