We don't have thermo pane on the upstairs windows--just the old fashioned double hung types with single panes and storm glass. I never changed them out as the winter traceries remind me of my childhood--before modern glass eliminated Jack Frost. Above is an unusual example of Jack's work.
And here is a view from upstairs. As you can see by the tracks, the snowmobilers have been having a field day, with the cold winter's ice supporting nearly anything you would want to take on the lake.