Dust marks following studs on wall -- Ghosting

Ralph from Red Deer Alberta sees the shadows of every 2x4 and every nail on the inside of the house not long after painting. I don't think he really wanted to hear that we call this "ghosting".\012\012Actually it is caused by thermal bridging; cold following the studs through the insulation and making the drywall cooler right over the stud than over the insulated part of the wall. With 2x4 walls in cold country, and many cathedral ceilings, this is very common. If the temperature outdoors is very low, and the humidity in the house fairly high, one part of the wall will attract a small quantity of moisture, while the other part of the wall will remain dry. This little bit of moisture is not noticeable, but it does attract dust. The dust will accumulate over the studs and nail heads faster than on the rest of the wall, and you get the "ghost" of the structure of your wall showing up on the inside surface. \012\012It is most easily solved by adding a bit of Styrofoam over the studs, inside or outside the house (like when you are re-siding). Just 1/2 inch of Styrofoam is enough to stop the ghosts, because it evens out the temperature of the wall surface.