Convert three season porch?

Has anyone in cooler climes tried converting a three-season porch to a makeshift greenhouse?

We have a decently-sized porch that gets very little use in winter. It is surrounded by jalousie windows that face east and north. Very little light actually comes in, so that would have to be supplemented. I know keeping the porch warmer would also keep our house warmer.

I'm curious about materials and such. We don't have storm windows for the jalousies, just screens. It seems like it would be tough to keep those windows from losing heat with the usual tricks like clear plastic.

I do it every year - works beautifully as a greenhouse! I have a 20'x20' Florida room, which is screened. I cover it with 6 mil. plastic every fall - keeps Plumeria and Adenium over the winter just fine. If I can answer any questions, dmail me.