Hi all I finished building my greenhouse/polytunnel. It is a wooden construction. I would like to lay something under the polythene cover (top of the frame) so that wood/nails/metal plate won`t rip the cover. I have seen this cheap cover. I wonder if it will be safe to use with the polythene? I heard that some materials don`t go well with the polythene and cause chemical reactions and damage it. I couldn`t add a link but it can be found on screwfix`s website. (acoustic-polyolefin-foam-underlay) And here is a photo of my greenhouse, i took it some time ago.