In comparison with cavity wall insulation, solid wall insulation is relatively unknown. As many houses in Hook Norton don’t have cavity walls, solid wall insulation is quite important to us.
Ideally we’d insulate the outside surface of the walls, this keeps the “mass” of the building inside the insulation, preserving the advantages of high thermal mass, slow to cool down, and slow to warm up, but insulating the exterior changes the appearance and would be unlikely to find favour with local planning officers!
Insulation placed on the inside of the walls will inevitably reduce the size of the room, and will often require extensive re-modelling of window recesses etc.
So, not a weekend DIY job, but something that could be considered as part of a major renovation project. There are several different technologies, ranging from aerogel – an incredible insulator, albeit at an incredible price, but offering the best performance for a given thickness. Pavadentro is a wood fibre based system offering high thermal mass, and good breathability and condensation control. More conventional materials such as fibreglass, wool, and phenolic foam boards can be used behind plasterboard in a dry lining type system.
Hemcrete is an unusual hemp and lime based material that has found favour for the renovation of historic buildings as it combines high thermal mass, breathability and being a completely natural material it is ultimately recyclable and compostable. The main disadvantage is the need for about 150-200mm thickness to achieve an acceptable u-value.