Assessment of the impact of interior insulation on exterior walls in three Swedish buildings – based on validated models

This project evaluates the impact of interior insulation on external walls in three Swedish heritage buildings. Field measurements and hygrothermal simulations were conducted to assess available solutions. Measurements of temperature and relative humidity were taken both indoors and outdoors, as well as on the exterior and interior surfaces of the walls. The accuracy of simulation standards for indoor air temperature and relative humidity was evaluated, and the findings indicate that current simulation standards can serve as reliable alternatives when on-site measurements are not feasible. Validated models were used to analyze the impact of 13 different interior insulation solutions, including vapor-tight and open options, some of which were capillary active. The results highlight that the risk of moisture damage depends on the design of the existing external wall and indicate the importance of hydrophobic treatment in mitigating risks. Thinner amounts of interior insulation can significantly reduce transmission losses without compromising moisture performance. Overall, all the assessed external walls can be safely insulated from the interior, although hydrophobic treatment is recommended for optimal results. This research provides practical insights for decision-making in simulation approaches and optimizing insulation strategies to enhance the performance and durability of external walls in building projects.