Approximately 2 years ago, an attic pipe leak was fixed by Rescue Rooter. Every winter since then---when running a vaporizer for humidity while running my central gas heater at night for warmth---water would condense on the plaster bedroom ceiling in the same area where the pipe leak had been the season before. Having lived in the house for > 15 years and never before having this problem (the plaster ceiling ruined, water dripping onto the floor and furniture), I consulted with two handymen, a plumber, a restoration company, and an attic insulation company. NO ONE could figure out why water can condensed on this portion of the ceiling ruining the plaster only the past ~ 2 years and not the decade and a half or more ever before. BUT!!!! This time, Miguel V came out from Rescue Rooter and the person answering the phone to set up the appointment listened attentively, cared, and spent patient time going over the history of this mystery that NO ONE could figure out. Every winter for > 15 years vaporizers and heaters were run; only now water condensed and dripped from one part of the ceiling. And every time anyone went into the attic to investigate, the area of the ceiling the water dripped from changed a few to several inches. Finally, I taped plastic on the ceiling to protect it from further damage. Miguel V suggested that the ceiling might be slightly slanted, causing the water to "pool" in that area of the ceiling--maybe others locating beams in the attic to walk on changed very slightly the slant of the ceiling, hence causing a slight shift in where the water drips from. THAT MADE SENSE! And he suggested an oil-based water-resistant paint once the ceiling is repaired. He agreed with my neighbor that an added heater vent could be installed on the wall near that region of the ceiling to keep a warm flow of air so as to prevent water condensation on an otherwise cold ceiling. Mystery FINALLY solved after a few hundred dollars, hours of time, umpteen phone calls! Thank you, Miguel!