Hygrothermal assessment of four insulation systems for interior retrofitting of solid masonry walls through calibrated numerical simulations

The present research project investigates the hygrothermal performance of four insulation systems for internal retrofitting solid masonry walls with embedded wooden wall plate and beam end. The study was carried out through numerical simulations calibrated with 2–4 years of measurements and material data from a large field experimental in the cool, temperate climate of Lyngby, Denmark. The experiment comprised two 40-foot insulated reefer containers reconfigured with 24 1 × 2 m holes, accommodating the solid masonry walls. The calibrated simulation models were used to investigate several untested design variations which included alternative brick and mortar types, masonry and insulation thickness, indoor moisture load and future climate conditions. The findings indicate that a reduction of the indoor moisture load would improve the hygrothermal performance in the interface between wall and insulation, and in the embedded wooden elements. Increased masonry thickness was seen to make the hygrothermal conditions worse due to increased drying time for the built-in moisture, while in the case of low initial moisture content, increased masonry thisckness improved the hygrothermal performance in the interface and embedded wooden elements. Increased insulation thickness also made the hygrothermal conditions worse. Regarding the brick and mortar types, the results showsed increased relative humidity in the critical locations in the case of high cement mortar compared to low cement mortar. The brick type was however found not to impact the relative humidity levels considerably. Robustness against future climate conditions was seen only for two of the four insulation systems, when combined with exterior hydrophobisation.