This 1- 2 mm polystyrene foam was once thought to be useful; my dad put some up in a particularly cold bedroom in about 1960 - the trade name "Kotina" springs to mind but I mght have that wrong. I'm not convinced it made the slightest improvement, and I now realise that the cold dampness was almost certainly caused by the flat roof leaking... I recently found some of the same product on the lower half of the walls in my hall, covered with brown gloss paint - it was a blighter to get off without damaging the lime plaster, but it's all gone nowtycarregydwr said:... the interior lime walls covered in 6 (yes, SIX) layers of wallpaper, as well as one layer of very thin polystyrene foam...