Air leaks through the moving parts of windows accounts for as much as 14 per cent of the heat loss in a typical Canadian house. Picking the right kind of windows can certainly help:
-- Fixed windows with no moving parts can be completely sealed.
-- Fixed window panes with small moveable sections in the bottom have less perimeter to seal.
-- Windows that swing (in or out) can be sealed easily.
-- Sliding windows are born losers; the cheaper they are the more impossible they are to seal. They are betting better and better with time, but they have to be made loose enough to slide, never completely air tight.
All or part of a window can be sealed tight (with permanent or temporary caulking) if it won't be opened for the winter. (Don't forget the need for emergency exits.) The upper sash of double-hung windows is a prime candidate for this treatment, as is one of the two parts of windows that slide horizontally. You will probably find that most of your windows can be sealed off for the winter. Removable caulking is made especially for this job (it works better than tape, and isn't messy if you remove it on a cool day). Moreover, it is less expensive and less troublesome than fooling around with weather-stripping. Sealing most of your windows could save about 10 per cent of your winter heating bill.
For those windows that must remain operative, use weather-stripping.