Solid wall insulation may be suitable for a variety of property types such as brick, stone, steel-framed and concrete construction.
Internal solid wall insulation works by adding a thermal layer of material to the existing wall. Solid walls can be insulated internally (from the inside) and externally (from the outside). Both are significant undertakings in terms of cost and disruption but both options can make your home warmer and greatly reduce your heating bills at the same time.
Internal solid wall insulation, rather than external, is particularly appropriate where you need to maintain the external appearance of the building (e.g. in a heritage context).