grapes on greenhouse?

Hi folks,

This is my first post on Permies! I'll be completing my PDC this month (Oct. 2012). We're doing our practicum and I have a strange question:

There is an old greenhouse (built in 1929) that is in pretty good shape, but about 1/4 of the glass is broken (kids with rocks). Until we get funds to repair the greenhouse, could we/can we/should we grow grapes ON the greenhouse? The frame is extruded aluminum and there are no sags or missing metal. IF grapes would grow on the frame, would the vines damage it in any way? I don't know how much weight these frames can support. The greenhouse if 72' x 22' x ?? (about 14'? high), with an attached "office" with clay tile roof, attic and basement. We don't have access to electricity or city water. We are considering rainwater collection, but with all the missing glass.... ? We can probably add gutters and downspouts.