Discusses the problem of wet attics and how roofers, following the correct procedure for ventilation, and installing ventilation in a previously unventilated attic were making the problem worse. In a cold climate, ventilating a previously unventilated attic has the effect of making the attic colder. If nothing is done to stop warm, moist air from entering the attic space from the living space, condensation on the now cooler surfaces is a certainty. Mould, mildew and eventually leakage into the living space will follow. Insulating the attic floor makes the attic colder in the same way, and if contractors don't seal as well as insulate, warm moist air will penetrate the space. Describes where and how to seal attic leaks.