To answer your one question: It appears that only in the winter time this happens. Could my house be too tight? To my knowledge I don't think so since it was built in 1969. I do have new vinyle siding, house wrap and windows that are about 3 years old. As I am writing you now, the humidity level in my house reads around 60 percent and in my boys room it reads around 69 percent. I did notice this past winter that the 2 corners of the cinder blocks in my crawlspace was sweating. This is under my family room, the rest of the crawlspace seems to be ok. It almost seems that the humidity is traveling thoughout my crawlspace. I also noticed that there is no blue foam that goes on top of the cinder blocks that the sill plate sits on. I started spray foaming these areas. The only area that seems to be wet, no water standing is under my family room and there is no plumbing involved in this area. Also, about 4 years ago I had to replace about 7 floor joist in the family room because they were rotted out. Usually, when the temperture outside is aroun 55 degrees or higher there is no condensation on the windows. I also have 3 gable vent, 6 roof vents and all my soffet that i installed has vents in it. The insulation up in the attic is about 12 inches thick. 6 inches of blown insulation and 6 inches of r-19 no vapor barrier. I am grateful of any ideas that you might have or suggestions too. I am running out of answers. I have talked to alot of different people about this situation, and so far no answers, although you are the first person that mentioned a central ventilation system. I do not know anything about ventilation systems and where they go. If they go in the ceiling please remember that I have ceiling heat throughout my whole house. Please responed. Thank-you.