Insulated Lime Plaster

 

Insulated lime plaster is a great way to insulate a solid brick or stone wall while maintaining vapour permeability. This is achieved by applying a lime plaster to the interior face of the external walls of a property. The lime plaster has a base coat that includes a high proportion of an insulation material such as granulated cork, perlite, hemp shiv or one of these combined with aerogel. This base coat can be built up in several coats upto a thickness of 40-80mm then the traditional float coat and finish coat is applied. There are various ready mixed products on the market to make the base coat or it can be made on site like any other plaster or mortar. The U values achievable with a 50mm base coat are in the range of 0.74-1.0 which is a 60-70% improvement over a solid wall. Building regulations now allow for older buildings to be insulated to a lower specification with materials that are suited to the needs of solid wall buildings this means wood fibre or insulted lime rather than PIR boards. While a 50mm PIR board would achieve a better U value of 0.55 it would also lead to the damp issues due to the lack of breathability. Wood fiber is a viable solution too and has a slightly better U vlue than insulated lime plaster, however it can be problematic if there are any air pockets where moisture can condense and hanging pictures and other fixings require care. It is perhaps more suited to ceilingsin attic rooms.