WARNING REGARDING PLASTIC MATERIAL FAILURE
My greenhouse was built in 2012 and I thought the plastic vapour barrier I used to cover it would be good for at least 5 or 6 years as the material I used at our previous residence had been in use for at least 5 or 6 years and it was still in good condition when we moved. It appears to be still in use there now!
HOWEVER - when I was in the greenhouse the other day I looked up and noticed the plastic on the roof is breaking down, has holes in it! I have checked and it is "normal" vapour barrier with UV inhibitors in it so - maybe there has been a change in regulations as to what or how much inhibitor is now in it.
In any case, I am sure it will last over the summer and if not, then it can just let some rain into the greenhouse - no problem!
My next step was to check and see if there were different qualities of vapour barrier. I could NOT find any information to show there may be different plastics/inhibitors etc.
SO - what to do? I thought about using corrugated clear fiberglass panels. Seemed like the smart thing to do. But there is always a "catch" - something to watch for.
The panels come in two weights/thicknesses.
The lightweight would cost about $150 plus cross strips for the corrugations to fit into and support it. From what I see on some blogs this material is too light and cracks very easily - to the point of being hard to handle without breaking it.
The heavy weight would cost about $350 plus cross strips.
The alternative is to replace what is there with the same poor stuff. The cost of a 59 foot roll by 102 inches wide is about $40 plus tax.
This means I could re-cover the roof three times with one roll. I think the walls will hold up a little longer than the roof as they don't get the sun beating on the as badly as the roof does.
So - it looks like I buy the $40 roll - works out to about $15 per covering which is much more bearable than the expensive fiberglass panels.
Next I am going to have to do some research into the vapour barrier that is available to see if there is something out there somewhere that will last longer than 2 years. It USED to last longer!!!
Could it be that the manufacturers like it to break down sooner so they can sell more? NO NO NO! The wouldn't do that would they?