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Roof-Mystery Suspects To the Editor I'm writing in reference to your May 1987 article "Mystery of the Ghost Lines." From my roofing experience, I have found that with airtight roofs such as these, air escapes from any point possible. The new design that worked well for the author of the article allowed the hot air rising from within the house to escape in a controlled way. What I believe happened (in the problem roof) is that heat escaped between all vertical and horizontal joints. But shingles will not move or show as much movement vertically as they will horizontally. Try putting two nails six inches apart in a shingle, move the shingle, then nail the last two nails, The shingle