I know there's some glue that more or less cold welds pieces of foamed pvc together, but I don't want to buy that glue (wouldn't see that much use and thus is too expensive).
Super glue didn't work too well (not even gorilla glue, and that stuff is quite effective).
Wood glue doesn't work too well and only if the pieces of foamed pvc will later be covered in various layers of wall or wood filler or the construction doesn't need to support much weight.
So far two part epoxy glue has been the most effective. Any other ideas or tricks?