Surface coatings cannot wholly prevent water penetration and potential damage due to fungal growth. The goal of the study was comparison of the impact of cracks in outer surface coatings on moisture content (MC) in window frames made of thermally modified (TM) and native Norway spruce, comparing results of validated hygrothermal simulations in Delphin for Ljubljana with simulation results for Helsinki. The study also investigates the impact of the inner coating damage and compares the results of different orientations of the installed window. TM spruce has about 4% lower MC compared to native spruce in Ljubljana, whereas the calculated difference between both in Helsinki was approximately 3%. A 3 mm wide crack in native spruce coatings for the north orientation in Ljubljana poses significant moisture risks, while in Helsinki, the upper border was calculated to be already at 1 mm, regardless of orientation. Here, a 9 mm wide crack in the coatings of TM spruce remains within acceptable moisture content thresholds. For Ljubljana, analysis of the influence of the size of inner cracks shows that the maximum moisture content in the window profile is generally lower when cracks are present or even if the surface is uncoated. A comparison of different orientations of outside cracks on Norway spruce window frame in Ljubljana shows that for similar moisture dynamics, the crack may be about 2 mm wider on the south side than on the north side. In contrast, for TM spruce, orientation was proven to be not as important.