Hygrothermal performance analysis of bio-based insulation materials for retrofitted brick walls in Jordan

Abstract

This thesis investigates the coupled heat and moisture transport (hygrothermal performance) of retrofit insulation systems for external walls made of hollow-bricks representative of Jordan’s housing stock in three Jordanian microclimate zones. Two bio-based options (sheep wool and hemp–lime) and two conventional options (EPS/XPS and mineral wool) are compared. The materials were selected to span contrasting hygrothermal behaviours relevant to retrofits (vapour openness, moisture storage/buffering, and capillary transport), allowing for a mechanism-based comparison of condensation and mould risk under Jordanian boundary conditions. Methodologically, a mixed-methods design is adopted. Transient heat and moisture simulations using the WUFI suite (WUFI 2D for representative sections and WUFI Pro for annual 1D parametric analysis) quantify moisture accumulation, RH fields, and mould indices across assemblies and climates; DesignBuilder is used in a supporting role to provide building-level heat-ing/cooling indicators and a consistency check on thermal behaviour. Parametric sweeps con-sider insulation type, practicable thickness ranges, and the vapour openness of interior finishes, with emphasis on lime plasters compatible with bio-based systems. Performance indicators in-clude the U-value, moderation of relative humidity indoors and short-term buffering, surface-temperature safety margins, interstitial moisture accumulation, mould growth indices, and indicative seasonal energy implications. A complementary focus group and semi-structured interviews with local stakeholders explore the most consequential implementation determinants—perceived moisture/mould risk, cost and payback expectations, supply-chain availability, workmanship and detail capability, and policy/incentive acceptability. Results indicate that vapour-open, moisture-buffering assemblies –particularly hemp-lime and sheep-wool systems paired with lime finishes – reduce indoor relative-humidity excursions, improve winter surface-temperature safety margins, and lower mould growth indices compared with polymeric foams at comparable thermal transmittance. Although foams achieve low U-values at minimal thickness, their lower openness to vapour increases sensitivity to detailing and workmanship. Bio-based options deliver comparable thermal performance at practicable thicknesses with greater moisture robustness under Jordanian boundary conditions. Originality lies in combining Jordan-specific future climate files with coupled heat and moisture modelling of prevalent hollow-brick retrofits and stakeholder evidence, producing microclimate-sensitive, moisture-aware retrofit guidance rather than U-value-only compliance comparisons. The thesis contributes (i) a Jordan-specific hygrothermal comparison of bio-based and conventional insulators for prevalent hollow-brick typologies; (ii) an explicit treatment of vapour openness and buffering with seasonal interstitial-risk assessment; (iii) microclimate-sensitive guidance on material choice, thickness, and vapour open interior plasters, including detailed considerations; and (iv) a market- and policy-orientated assessment of barriers and enablers grounded in stakeholder evidence. The findings support moisture-aware retrofit pathways that improve comfort and reduce risk, and inform incentives and codes that recognise coupled heat–moisture performance and vapour-open finishes.