I have an issue with a patio door at a second home that my wife owns in western Ohio. The house is around a lake area but not on the lake. We leave the heat on during the winter with the thermostat set at 60*. When you look at the pictures you will see the mold on the door and it has gotten so bad that it is turning into black mold. The door is mounted facing west with only the overhang for any protection. This is the first year we have had this problem with the mold on the inside of the door. The outside is vinyl clad. My thought is because of the location of the heat vent in this space and the whole house is the problem because they were located in the ceiling. The house was already remodeled when she purchased the place in 2007. I think if I move the heating ducts to the floor level in this room it will solve the problem and if I do the same in the other rooms the floor area will be warmer in the winter. Any other suggestions would be great and should I replace this door now because of them mold or not. Thank You. I just attempted to upload a picture but it failed so I will try to upload them from a different PC to see if that helps.