What did people do without this forum! I googled Träullit and it seems to have its advantages, to say the least. Thanks for the answer, I will try not to tear down too much plaster when removing the paint. To be on the safe side, I will knock away the plaster at the bottom near the floor in some places to see if the Träullit looks okay since it is mounted on a previously moisture-exposed wall and has had plastic paint on the inside.