All side hinged inward opening windows and in my area there are lots will give you problems. Some may be on a catch and only open a few inches and this is ok as the water drips on to the inner frame work and down small drain holes in the upvc sill. If they are not fixed on to the catch, the window will fully open as you press the glass with the brush and water will flood the room, floor, wallpaper ect ect. If no one is in to close these type windows and you still clean them wfp, expect complaints.