Before we insulated the place it used to need so much more active heating. Cold walls, damp, it was not great. It’s an old block house with no cavity so we decided to externally insulate it; basically wrap the house in a warm blanket. The difference in cost between thicknesses was marginal once you’d decided to do it so we went for the thickest available. Totally worth it, it’s absolutely transformed both cost and QoL (damp is totally gone). The walls now act as a thermal battery