We have a small building which is going to be roofed, and I am in the middle of choosing a roofing material. I would like to keep the option of collecting roof runoff open, and keep the roof as fireproof as possible. Those are the primary concerns for this choice of roof.
I have heard/read the negatives about using water which came off asphalt shingle roofs, so those are probably not an option. That would seem to leave only a few choices:
Ceramic tile roofs are out, due to their weight and structural concerns.
Galvanized metal roofing seems like the best choice perhaps, for easy of use, fireproof-ness, and runoff quality (as far as I have heard).
Another potential option is painted metal roofing (usually available in wider sheets than the plain galvanized, and longer lasting. Only problem is no manufacture seems to have any data about runoff water quality from their painted roof materials.
I was wondering what people thought about these options; If there are any others which I’ve missed; and if anyone had any hard data on painted metal roofing leaching whatever into the water runoff.