Longevity of Clear Roofing for Kilns

Clear roofing panels vary widely in composition, quality, and durability. December 8, 2012

I have the clear corrugated roofing from Lowes and after only 6 months it's cracking and even has holes in it. Is there a better material for a solar kiln?

Forum Responses
(Sawing and Drying Forum)
From contributor S:
I sure hope so - I had the same problem, figured it was just a problem of UV degrade on plastic, so bought some stuff at HD thinking it would last until it didn't. I guess I have gotten used to the idea that stuff doesn't last too long and what the heck, neither does my money and neither will I.

From the original questioner:
I'd seen that fiberglass can be used for the roof. It's not completely clear (more an opaque white). Is that okay?

From Professor Gene Wengert, forum technical advisor:
I used corrugated fiberglass that was called clear, but it was not really clear enough to see clearly through. It lasted 25 years. Perhaps the material giving problems is too thin and cheap. Try the corrugated fiberglass panels from eplastics.com or similar sources. When I built the first kiln, we did not have thin material available in stores, so we did not use it.

From Professor Gene Wengert, forum technical advisor:
Are corrugated PVC and corrugated fiberglass roofing panels the same thing? I noted that Lowes and Home Depot have corrugated PVC. Perhaps that is the reason for failure, if they are indeed different. The pieces at Lowes that I saw were indeed quite thin.

From the original questioner:
This was totally clear and I believe it was corrugated (wavy like metal shop building siding) PVC. It was thin. It was durable and flexible when new. I just took it down yesterday and it's as brittle and inflexible as can be. I'd bet I could easily shatter it by tossing a golf ball at the material.

From contributor K:
Not sure if the panels you are looking at are the same ones we have at our local Home Repot, but these are called "poly carbonate" and are supposedly the same material jet canopies are made from. Mine lasted a year or so on my solar kilns before we had a fire and burned them (long story). It stayed clear and I have installed them on the 4th floor of my house as skylights, so I sure hope they don't crack. My house is over 5 years old now, but they are hard to inspect. They are warrantied for life, for what that's worth. 8' were less than $20, as I remember.

From Professor Gene Wengert, forum technical advisor:
Perhaps the UV absorber or stabilizer was omitted. As they are intended for outside use and have failed, return them to Lowes for a refund.

From contributor R:
I've used the poly carbonate panels from Lowes with no problems.

From contributor Y:
Specifically look for the SunTuf panels at HD. They are UV resistant. I've had them on my kiln for about four years now and they're crack free except for some cracks on the edge panels where I drilled holes for the mounting screws and the wind has rattled the panels.

From contributor C:
PVC in plumbing is not rated for exposure to the sun for all mentioned reasons. Contributor K's poly carbonate with the lifetime warrantee is the best going. I have installed it on customer's lanais before. They tend to be good with the warrantee service as well. Most problems with leakage were due to improper installation and not material failure.

On the cheap, I use double ply UV resistant film. Cost me about $25 every 8 months on a 300bft solar kiln. Regular heavy film only lasted 10 weeks in the hot zone.