When humid air comes into contact with cold metal, condensation, and often freezing, occurs. Make sure the attic and crawl space are cross-ventilated. The crawl space should be covered with a vapor barrier. This will prevent water vapor from rising from the soil into your house. Make sure your clothes dryer and all gas appliances are vented to the outside.
Water vapor is one of the products of gas combustion.
If you have a basement, take the necessary steps to prevent leakage of soil moisture into the basement. These steps will vary with soil and drainage conditions on your lot.