Thermal retrofits of existing buildings offer a great potential to reduce Europe’s energy use and CO2 emissions. The impact of these retrofitting strategies on the risk for degradation in building envelopes is assessed through hygrothermal simulations. Due to the lack of long term climate data, hygrothermal simulations are performed for a certain location, and the results are generalised over a large region. However, this generalisation may not be valid, since the hygrothermal performance of building envelopes is highly influenced by local climate conditions. Therefore, we assessed the geographical variability on degradation risks in building envelopes. This paper presents the results of 34560 hygrothermal simulations of solid masonry walls, with and without interior insulation, and including a range of other parameter variations, for 20 synoptic weather stations across Belgium. Generally, the risk for degradation is higher at locations with a higher elevation above sea level. For Belgium, the elevation correlates well with the mean temperature (invers correlation), and the annual precipitation and wind-driven rain load. For a known wall orientation, the impact of interior insulation on the risk for freeze-thaw damage is most determined by the elevation above sea level. Also the mould index in uninsulated walls correlates best with the elevation. On the contrary, the brick type is more important than the location when considering wood decay of embedded beam heads in retrofitted walls. To conclude, the risk for degradation cannot be generalised, especially over areas with complex variations in orographic and climatological conditions.