For homeowners in colder parts of New England, ductless mini-splits are no longer just a cooling upgrade for the warmer months. What's happening? In one online discussion on Reddit, several people living through freezing winter temperatures said their systems kept them comfortable. A New England homeowner seeking advice described a 1,450-square-foot house with 2x6 insulated walls and double-pane windows, then captured a concern many shoppers sh…