Traditional Solid Masonry Construction in Ireland: Hygrothermal Properties of its Constituent Materials and their Impacts on Thermal Behaviour and Moisture Risk Assessments

In the global effort to reduce greenhouse gas emissions, retrofitting existing buildings to improve energy performance and reduce operational carbon emissions has become a central strategy. In Europe, and particularly in Ireland, much of the building stock predates Building Regulations and modern concepts of thermal performance and occupant comfort. Traditionally constructed buildings are now classed among the ‘worst-performing buildings’, increasing policy and regulatory pressure to upgrade them. However, the risks of inappropriate thermal upgrades of traditional buildings have been highlighted, leading to moisture-related deterioration and reduced indoor air quality. Such damage will endanger the physical integrity and heritage value of these buildings and may result in greater long-term carbon expenditure through premature replacement. Despite advances in building science, significant gaps remain in our understanding of heat and moisture transfer mechanisms in traditional solid masonry walls, particularly in the context of a maritime climate like Ireland. Addressing these gaps requires detailed knowledge of the hygrothermal properties of constituent materials – referring to the coupled heat and moisture transport processes within such porous media –, supported by both experimental data and simulation studies. This thesis, using Ireland as a case study, investigates how the detailed knowledge of hygrothermal properties and behaviour of traditional building materials and solid masonry walls can improve the assessment of existing buildings and inform retrofit strategies. It presents original research including hygrothermal laboratory testing of traditional Irish bricks, stones, mortars, plasters, and renders, and in-situ U-value measurements of a wide range of existing wall assemblies. Further investigations examine moisture-dependent thermal conductivity and impact of water repellents on hygric behaviour. A long-term monitoring case study enables the validation of numerical simulations in a maritime climate context. The study produces, for the first time, comprehensive hygrothermal characterisations for 47 traditional Irish materials. Results reveal significant regional differences for Irish materials, with Irish historic bricks exhibiting a wide range of porosities up to 45 % and building stones as low as 0.5 %, with associated distinct hygrothermal properties. Thermal conductivity was shown to increase by up to 260 % at saturation. Findings indicate that reliance on default values for thermal assessments is problematic and that short U-value test durations may yield misleading results. Simulations confirm the sensitivity of modelling to material properties, and highlight the inadequacy of one-dimensional models for low-porosity stones. The thesis contributes critical insights into the hygrothermal behaviour of traditional masonry in Ireland, contributing to the necessary and urgent discourse on sustainable retrofit, and impacting conservation practice, simulation accuracy, and retrofit policy.