I live in a rural area and I'm always concerned about power outages during the winter months. I've seen products you toss on a fire that are supposed to help clean the chimney. Some produce a green-colored flame. There doesn't seem to be much air coming out of my warm-air registers.
Condensation occurs when air cools below the dew point temperature.
Dew point is the temperature at which air is saturated, unable to hold any more moisture. This extra layer provides a dead air space, which slows heat loss and raises the glass temperature. Meyer suggested applying a heat-shrinkable film to the window because it seals tightly and looks better than plastic. Heat-shrinkable film comes in sizes large enough to cover a sliding glass patio door. Keep in mind that the inside film must be sealed tight to prevent moisture from coming in contact with the outside pane.