1.   During cold nights, air condenses on the grass to form dew.

2.   The cooler air condenses into moisture, which can eat away at the innards of an older chimney and eventually block the vent with the crumbled remains.

3.   This added insulation will keep the ceiling warmer, and the moist air may not condense.

4.   When the air masses hit the mountains of the East, the air condenses and rain forms.