Yes. Hempcrete, either in wet-cast or precast block form, can be used to insulate existing stone or brick walls internally – internal solid wall insulation (ISWI) – or externally (ESWI). It needs to be used with other vapour-permeable materials – for example lime or clay plaster, lime render and lime mortar. Generally it should not be used internally where the walls are below external ground level. We usually recommend using between 100 mm (min.) and 200 mm (max.) hempcrete internally, depending on the amount of space you can afford to lose from the internal dimensions. Used externally the hempcrete can be thicker than 200 mm if this can be accommodated.