No Roof Leaks Here To the Editor: Congratulations on "Not a Roofing Problem" in the May 1987 issue of NEB. I was patting myself on the back for taking a year to figure out that the ceiling damage near the eaves of a house was not caused by ice dams, but by condensate dropping down the inside of the roof. Polyethylene, and bathroom venting go in this summer. Gregg Shadduck, Minneapolis, Minn. Ice-Dam Advice To the Editor: Alex Wilson's article, "Ice Dams," (NEB 5/87) discusses the major factors that influence the formation of ice dams, one of which is ventilation. "Keeping the underside of the roof surface well ventilated," the article says, "is the most important factor you can control." (Emphasis added). Excellent advice. What