oldhousefreak, I mentioned in a thread last year that I was going to try a clear coating made by Top Secret; they told me in emails it would work on polycarbonate, and would provide some level of UV protection, although they were not able to specify how much protection. I did order the product, but I'm embarrassed to admit I have yet to apply it; an illness and a house renovation really messed up my plans. At this point, my roof and south panels are so yellowed I know it will no longer be a decent test for the product, so I really muffed my chance to learn much.

I did quite a bit of internet research looking for such a product, and found very little. The folks at Top Secret admitted they had no knowledge of anyone using their products on greenhouses, so it's a guess at best as to how truly effective it would be. For what it's worth, the link to the product I have (still sitting in the can) is here:
TS-100 1 part epoxy coating

Sorry to not be of more help, maybe someone else has made more progress than I have.
Sheri

thx sheri. the link says "UV stability", but you're right, nothing about any rating. It sounds like the epoxy coating won't deteriorate by UV.

I think window film will probably be the way to go. I was thinking maybe an opaque paint as a possibility also.

I have 80 sheets so even if I do nothing, I have plenty to replace the ones that wear out. I only paid $1. per sheet. I'm more concerned with the plants burning and UV protection for them.

You might shoot the manufacturer of your window film a quick email to ask about applying it to Lexan before you purchase it. I asked one major company about applying it to polycarbonate, and they said their product absolutely would not adhere correctly...that it would bubble up. Plus, the window film I found locally was more expensive than I'd expected (cheapo me.)

Even if my panels had the UV protection as advertised, I know I'd still need shadecloth to prevent my plants from sunburning (our sun is wicked here.) The nice thing about shadecloth instead of a coating is it's easily changed...I can do single layers, double layers, or none at all, on different parts of the greenhouse, as the seasons change.

Good luck with your greenhouse (I love finding bargain materials...) :-)

thx for the tips! I'm in roasting hell OK, so I know the heat problems. I'm wondering how I'll even be able to set foot outside for a summer garden here lol.

I'll definitely research the film. Alot of ppl use lexan for different things now, so there should be some good materials tips out there.

oh yeah I love a good bargain too. I surf craigslist daily ;-)

After reading about yours and others HFGH's, no way. I'd rather scrape up materials and custom build it to site, than pay for a throw away. I'm sick of buying crap that has to be improvised to work.