I just got a new furnace and a/c. A/C ran fine all summer, but we just had to run the furnace for an extended period over Thanksgiving for the first time since we purchased it. The ceilings and wall are drenched. Ive tried several things, but am getting it in every room of the house. I've already checked the roof for leaks and confirmed everything (furnace, dryer, etc) are venting outside properly. I checked the humidity in the rooms for a day and it ran consistenty between 88% and 91%. It's ruining the walls and ceilings and developing mildew every few hours. I clean and dry it at least twice a day. Any ideas what can be causing this? I don't have a humidifier. This is quickly becoming an urgent issue.