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?
Your greenhouse sounds quite a bit like ours. The main difference is that Mike did put heavy welded wire stock panels on the roof first and the corrugated panels on top of them. The stock panel are stiff enough to help keep the fiberglass from sagging. We built the greenhouse 3 years ago and we do get some pretty heavy deep snow and so far there is no sag to them. There are automatic vents and are easy to find online. We don't have any of them so we open all the window and the door and hang a box fan near the ceiling. Not as handy as the automatic vents but lots cheaper. But we are retired so we're at home most of the time anyway.
If you nailed the corrugated roofing in the same orientation as the roof rafters the material will be in a constant state of flex. What you need to do is nail 2 x 2 strapping perpendicular to the rafters. If you are in an area that gets a good amount of high winds, you would be wise to set the strapping across the rafters at 12 inch intervals. Screw your roofing material to the strapping no less than six inches apart, and your roof will hold fast for a long time. As far as venting goes a louvered self closing vent on one end, followed up with small thermostatically controlled gable vent fan on the other end should do the trick for such a small space.
If you are going by poly carbonate panels, the panel ends are to be capped in order to avoid moisture. Firstly consider the variety of glazing materials available, only then one is supposed to do designing and the building of green house. Poly carbonate ones are reasonably light weight and can be done by one person which doesn't shatter like the glass does. It shrinks and expands with the temperature variations. Glazing materials include glass, fiberglass and plastic (acrylic, poly carbonate or polyethylene sheeting) .Poly carbonate has to be installed with the label facing out.The foam trips and caps on the joints between the panels are a good idea because they can be stretched , thus aligning the panels and strips. Use a circular saw to cut poly carbonate panels. I found few roofing designs at roof line east inc. While installing if you need guidance try approaching for expert advise. Now regarding the corrugated , depending on the location, put the screw just above the valley so the water is not running directly over them. Check this image on the installation guide for corrugated roofing. Also use sealants made from high butyl quality rubber which remain permanently and flexible. Do not over apply and apply only a 1/4 bead on top of panel rib.
Transparent corrugated plastic-like roofing panels are for sale over here. Perhaps they are over there as well. They are light weight and yet durable. There are so many choices, perhaps it is difficult to see the forest for the trees? Good luck on this one Bosque.
