Hygrothermal Assessment of Solid Masonry Walls Internally Insulated with Bio-based Insulation Materials

This research project investigated the hygrothermal performance of two bio-based insulation systems for interior retrofitting solid masonry walls; loose-fill cellulose insulation and hemp fibre insulation mats. The study was carried out through HAM simulations calibrated with 1 year and 2 months of measurements and material data from a field experiment in Denmark’s Nordic, maritime climate.

The experimental setup comprised a 40-foot (12.2 m) insulated reefer container with controlled indoor climate, reconfigured with several holes (1x2 m each) accommodating the solid masonry walls. Some of the masonry walls had exterior hydrophobisation. The calibrated simulation models were used to investigate the long-term robustness of the bio-based insulation systems to the future climate conditions caused by different emission scenarios between year 2020 and 2050, for several locations around Europe.

The focus of the study was on the conditions in the interface between the masonry and the internal insulation, and the mould risk was evaluated using the VTT mould growth model. The findings showed high relative humidity levels in the masonry/insulation interface with a high risk of mould growth, already exposed to the current climate data.

The results indicate that the future climate conditions would exacerbate the hygrothermal conditions in the insulated masonry walls. Exterior hydrophobisation positively affected the hygrothermal balance in the insulated masonry walls, lowering the risk of mould growth under future climate conditions.

However, the results indicate that in some cases, the insulation systems would still experience critical relative humidity levels despite the combination with hydrophobisation.