It is possible that the blinds are a factor for the buildup of condensation of the window. The reason that heaters are located directly in front of windows is because the windows are the parts of the house that are going to let in the most cold air and allow heat to escape. If your blinds are positioned too close to the window, the heat rising from the heater is going to pass the window and rise to the ceiling. Ideally, blinds should be positioned 7.5 to 15 cm (3 to 6 in.) in front of the window. They will still block sunshine, but rising heat will be able to get behind the blinds and heat the window, thus eliminating the condensation. Some blinds come equipped with brackets that extend them out from the window. If your blinds did not come with brackets, extension brackets can be bought at specialty home decorating stores.