I believe it is an open cell foam. I don't know what was used to give it the popcorn ceiling look. Both my 17' and one of my 13' has this puffy type of liner. Ensolite is more like a skin. The 17' I am working on was partially stripped when I bought it and was due to leaking. The leaks
were never dealt with. Removed the rear and side windows
and will put new butyl tape, but having a difficult time finding replacement seals and glazing bead.
If your foam is not mouldy you could try reattaching and then painting
. It will be easier than stripping and replacing. If you have to remove it and replace...I used 3M 90 spray adhesive to attach reflectix type insulation the lower walls (from mid window to floor along back wall) and then yoga mat on top of that and it seems to hold very well. I don't know if this would be a good option for the ceiling. Contact cement might hold best there but need good ventilation and a respirator to protect from the fumes. Do not use the 3m 77. After sitting in the cold shop (5 degrees max) for 5 months of winter, it has held and look pretty good.