Insulating walls#
Wall insulation can be outside, inside, or in a cavity within the wall. If you can insulate externally, that’s usually the most effective solution.
If you have existing wall insulation, unfortunately, it might be patchy - some installers haven’t done a very good job with it. It’s possible to check using a thermal imaging camera, keeping our caveats in mind.
Are they cavity walls? Are they already insulated?
In post-1920s buildings, cavity walls are the norm. They have a uniform brick pattern without seeing bricks “end on” - but solid walls can have this brick pattern, too. The usual test is to measure the thickness of the wall by checking through a window. If it’s 300mm or more excluding any render, it’s probably a cavity wall; thinner than that and it might look like a cavity wall but it’s probably solid.
Some buildings have insulation from when they were constructed. If there’s been insulation blown or sprayed in as an after-thought, you’ll probably be able to see small regular holes in the masonry.
It’s hard to say whether it’s worth insulating stone walls, since to preserve the appearance of the building, it’s done on the inside. The thinking about stone is changing as the industry starts to realise that it keeps the heat in better than previously thought, and smooths out extreme highs and lows within the building - although the different kinds of stone and construction, some with rubble in the middle, vary in how well. It certainly seems to be less important than getting the pointing, roof insulation, and draughtproofing right. It may matter how much the wall is exposed to the weather, as the wind can strip heat from the wall. It could also matter how difficult it is to insulate. The supplier could build out a timber frame that holds insulation in place. This will make the room a bit smaller, but in the larger and less decorative community spaces, this might not matter. Sometimes insulation applied to the existing masonry, plaster, or wall linings. It’s also possible to drill lots of holes in the existing plaster, blow in cellulose pellets, and than patch the holes and redecorate.
A quick fix - radiator foil
If your building doesn’t have insulated walls, you can consider at least reflecting the heat from radiators away from cold external walls and into the room. There are products you can mount behind these radiators with foil on one side and insulation on the other.