I live in northern Illinois and I have an 8 year old home with Outlook brand wood frame/sash windows. I have painted & caulked these windows every year or two since new. No sign of insects. Sometimes the problem is in the middle, other times at the ends. On the north side I have had a lot of wood rot on the sill & lower trim of some windows. The problem is most pronounced on a double window that sits on a masonry sill. There seems to be no obvious water infiltration point and the masonry sill appears to provide adequate runoff. The caulking is good. But every year the paint starts lifting and I find a new section of wet/rotting wood. I have been removing the wet/damage sections and filling with plastic wood filler (bondo). Over time I have rebuilt a good portion of the sill/trim. Then I prime, paint & caulk. These windows get very little (if any) sunlight and poor circulation. I have looked for leaks and can find none. Can this problem be due to lack of sun and simply never drying properly? Any ideas/suggestions as to why this keeps happening of how to better prevent it? Anyone seen anything like this?

I've looked through pages and pages of old posts and I can't beleive that no one else has asked this....so I must have missed it, and I apologize in advance for asking a question that I know must have been asked many times before. My house was built in 1994, and has wood double-hung windows. I had all the exterior wood trim replaced where needed, repainted, and covered in vinyl 3 years ago, so all that is in great shape. But in the last couple of years, I have noticed 3 or 4 windows that have fog, or condensation really, insided the panes. I was told this is due to the "seal" that is broken somewhere around the window, and is allowing moisture in. How on earth do I fix this? I did call one window place and they said that I should remove the window (they do "pop" out, so I could conceivably do that) and bring it in and they can repair the seal. But that means I have no window in place?? Is that really what people do?? How do most people handle this? Are there companies that come out and repair them onsite? What should I expect in cost? Thanks...and as I said...sorry if this is repetitive!