The addition of insulation is rarely feasible due to the presence of original decorative finishes, such as plaster-work on ceilings and walls. Traditional lath and plaster finishes retain more heat than plaster-on-the-hard-only and may not need the addition of insulation. However, it may be possible to blow loose insulation into the space behind lath and plaster.
Internal insulation (‘dry-lining’) means adding a layer of insulation on the inside of the wall.
If insulation is added, careful construction detailing is required not to trap condensation within the wall. Ask a professional adviser if you might need to add a vapour control layer.
Solid wall insulation could cost you £8,000 upwards and discount schemes are far harder to obtain than for cavity wall insulation.
Houses built from around 1920 onwards often have cavity walls, which are simpler to insulate than solid stone or brick walls: insulation is simply blown into the existing cavity. You can save £110 a year by installing cavity wall insulation, recovering the installation cost in the first two years.
If you are able to insulate your walls, you can prevent moisture becoming trapped, by applying a breathable membrane and moisture permeable insulation such as sheep’s wool, hemp and sisal, which should be as thick as possible for maximum energy efficiency.