Changed two light fittings for a lady last week. late 50's early 60's house.
First one in a downstairs cloak at front of property. Removed the ceiling rose to find a 1" thick layer of polystyrene between the plaster board and the joists.
Second one was in a room at the rear, same thing, 1" thick polystyrene under the plasterboard.
Never seen this before, what was the purpose? Anyone know?