This past winter I have had several customers call to complain about plaster and paint bubbling overtop of their windows. They all believe it is from a roof or gutter leak. I have checked each one from the outside and find no problems and there is no evidence of moisture infiltration upon examination of the underside of the roof decking at the eaves. Every one of these homes have newer aluminum or vinyl clad windows installed in the last 7 years which replaced wood framed windows. The walls are not insulated. I have suggested that they contact the window installer to see if that is the problem and a couple had already done that. The window installer says the windows are not the source of the moisture.

I am thinking that since the walls are not insulated, that the condensation that forms in the space above the window, although minor, is not able to wick out and evaporate as it did with the old wood frames. Plaster or paint damage would happen over time.

Has anyone experienced the same thing? Could you determine the cause? Would it be beneficial to suggest having insulation blown-in above, beside and under the windows?