Here are soureces for clear vinyl and FClean
https://www.bing.com/search?q=greenhouse+film+fclean&pc=MOZI&form=MOZSBR
FClean has been in service over some greenhouses in Japan and other places, for more than 25 years without showing any signs f degradation.
it is also what is covering the biodomes at THe Eden Project in Wales.
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amleonard is a supplier who sells remnants for cheap. and you have a fairly small
footprint to cover
http://www.amleo.com/poly-remnant-sale/a/35_11/
they update their remnants page often.
if you choose amleonard , i'd go with the Tufflite with condensation control, etc
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I have also over the years just used the vinyl by the
yard at teh
local fabric store, which can also be found
online.
i'd go with something thicker . with vinyl, the gauge is : the larger the gauge the thicker the vinyl.
where as, with steel the gauging measurements are used differently.
overlapping it, starting at the bottom to protect from water coming in.
it does not have to be 'real thick' for this purpose. there is marine vinyl used for windows for boats and yurts that might be too thick.
In comparison, there is vinyl which is used for covering dining chair seats and more. anybody remember vinyl covered sofas and car upholstery
in the 60's?
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THis will also help to keep this side of your home much warmer too.
and wall protected from weather! etc
GOod fortune on your adventures