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I have a small PVC hoop house that I built last winter and plan on using again this winter. I found out first hand, then read about it later on, that the plastic used for greenhouses will react with PVC and turn white. Since I've already invested in the PVC, and it's a much cheaper alternative to metal pipe, I'm trying to come up with a way to isolate the plastic from touching the PVC.

The options I've come up with so far are to use some type of tape (felt, electrical, clear duct tape etc.) and apply it to the outside of the hoops where they come in contact with the plastic. My purlins are attached on the inside of the hoops so I don't need to worry about them. The felt shouldn't react since I've seen this sold on greenhouse supply websites for just this reason, but what about the tape? Are there any other low-cost options I'm missing?

The design is changing a bit the second time around, but this is what it looks like from the inside. As you can see very little PVC actually comes into contact with the plastic covering. The plastic I used was from Green-Tek which I think is really Dura-Film Super 4 from AT Films and it's what I plan on using again this year.

image 1

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As far as I know, regular PVC pipes are not UV-stabilized. This will likely shorten their lifespan. –  bstpierre Sep 9 '12 at 11:53
    
My first thought too. At high latitudes it might be economic, but I wouldn't even think about PVC frames in sunnier climates. –  winwaed Sep 9 '12 at 18:27
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FYI, They make UV tolerant pipes (typically the gray ones marked for outdoor use). –  DA. Sep 9 '12 at 21:28

1 Answer 1

The UV stability of PVC aside I chose to use a roll of clear weather sealing tape from Frost King. This is used to seal windows which means it's not going to react with the greenhouse plastic I'm using. I've applied it to the top of all the hoops and will see how it fairs over the winter compared to last year without it. This is the roll I picked up

enter image description here

Update on 8/29/14: It's now been almost two years since deciding to use this product. My PVC structure has remained setup in the garden the entire time with this tape on it. I've had no issues with it coming undone, cracking, or turning my plastic white (aside from the general wear marks from wind which are much less than that of the chemical reaction). The structure has been up for a total of three years and the stability of the PVC looks to be no different than the day it was setup.

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