A comparative study of the hygrothermal performance of solid limestone walls and their effect on internal insulation strategies: Portland Limestone versus Irish Blue Limestone Construction

Portland Limestone, imported from the south of England and valued for its creamy white colour, was a prestigious building stone used in Ireland in the eighteenth and nineteenth century. Irish Blue limestone is quarried in the Midlands of Ireland (Co. Laois) and is one of many limestones used widely in vernacular and formal stone buildings in Ireland. Both stones are classified as limestone and are often grouped together as the same material. However, the stones exhibit significantly different physical properties, with Portland Limestone displaying a porosity and capillary absorption 36 and 265 times greater than the Irish Blue limestone respectively, and the Irish Blue limestone exhibiting a thermal conductivity nearly double that of Portland limestone. Internal insulation increases the risk of moisture accumulation in a wall. This research measures the hygrothermal properties of the two stones in laboratory testing and then undertakes hygrothermal numerical modelling to assess the moisture response of the two walls before and following the application of internal insulation. Different internal insulation strategies such as the type of insulation material and insulation thickness are discussed for the two stones. The research underscores the importance of using accurately defined data on the properties of materials when using hygrothermal software. It is part of the FabTrads-TradFabs series of projects measuring the hygrothermal properties of traditional Irish Building materials.