I lived in a 250 year old uninsulated timber framed house in coastal Massachusetts for 15 years. Most of the sash windows were 200+ years old, about 30 inches wide and 40 inches tall and they were very drafty. (I loved living there, immersed in history and antique gardens.)
After spending 1 winter there, packing strips of insulation into all the edges of the windows (ineffective), I made window quilts that fit snugly into the framing of the sash windows, with pockets top and bottom for tension curtain rods. I could slide the the top rods down to allow warm sunlight while still keeping the lower sash covered and insulated. I faced the quilts with fabric that complimented my interior decor, leaving the white muslin facing out. I never had a problem with moisture "pooling" or cold air drafting out from the bottom - snug fitting of the quilts into the window frames was important.
These window quilts made a very noticeable difference in the winter, eliminating drafts and insulating the window glass. The cotton quilted fabric I used (in 2003) was marketed specifically for "window quilts" and had a layer of thermal insulating fabric. I do not know if that product is still available.
I still miss living in the old house, although I like being able to close my modern windows snugly.
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