How do I find out where the condensation on my windows is coming from? I live in central Illinois in a small one story house (no basement) built in the mid-50's. It was extensively remodeled about 3-4 yrs before I purchased it 2 yrs ago. It has a new roof, new siding, new blown-in insulation in the attic, and new windows. The humidity measures around 45-50%, but I have a significant amount of condensation on the inside of all of my windows. When it gets exceptionally cold, condensation also forms on the ceiling along the outer walls.