If water is leaking from above, it is usually caught by the vapor barrier in the attic. Condensation on the ceiling is usually a sign of a very cold spot that collects moisture from house air. Turbines, installed too close to loose fill insulation, can lift the insulation out of the attic and blow it away. Turbines do draw air out of the attic, but how much they draw is completely uncontrollable. If there is no wind on a hot summer day, when some attic ventilation might be welcome, they are no better than a passive vent. When the wind blows hard, the turbines kick in, sometimes drawing warm, moist air from the house into the cold attic. They are often noisy and have a tendency of freezing and drawing snow into the attic. Check the ceiling, making sure that the condensation spots are well covered with insulation, and replace your turbine with a passive vent. These stand high above the roof, preventing snow from entering the attic, and come with round bases to replace turbines without having to modify the roof flashing.