We built a greenhouse here several years ago by following instructions from a book about greenhouses and how to build one. It is attached to the south side of our house. The east wall is made from treated 2x4s, plywood and covered on the outside with siding. The whole south wall is made from treated 2x4s and glass panels from sliding glass doors. The west wall has one glass panel and the rest is like the east wall plus a mostly glass walk in door. We used pvc corragated clear panels for the roof. Its what we could afford at the time. The problem we have been having is the wind keeps ripping the roof panel off. Next spring our very talented son is going to rebuild the roof and any other parts that need to be redone. My question is, what other materials could we use for the roof? Hubby wants to just use corragated metal roofing panels. No light would get in from above. Would there still be enough light to be as effective? What other materials can I use for the roof that would be strong enough? I also need to install some vents in the roof. Are there any that open automatically when the tempature reaches a certain degree? Plus closes when the tempature drops to a certain degree?