The air up here is cold and dry. The ceiling hung propane furnace exhausts outside, but gets it's combustion air from inside. Since it is consuming inside air during the combustion process, it draws the dry cold air in from outside. Since warm air has the ability to hold more moisture, it pulls the moisture from everything in the room. That air gets used for combustion and is replaced by the dry air from outside. As the cycle progresses throughout the winter, it just keeps getting dryer. That's the way I see it anyways......and my hygrometer reads 10% RH.
