It depends on where they are leaking from. Make sure they are properly glazed (sealing the glass into the frame), make sure they are caulked around inside and out. If they are weighted windows, cold air can be getting through where the weights are housed in the frame.
Our 14 year old cord controlled blinds are all giving us trouble with raising and lowering and tilting. Many of the top mechanisms are coming unglued from the top. I ...
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https://www.thisoldhouse.com/how-to/making-windows-weathertight
Clear shrink film kit weather stripping best.
Go to a hardware store and get the plastic that covers windows from the inside they should tell you how plus there will be instructions.
https://www.thisoldhouse.com/how-to/making-windows-weathertight
It depends on where they are leaking from. Make sure they are properly glazed (sealing the glass into the frame), make sure they are caulked around inside and out. If they are weighted windows, cold air can be getting through where the weights are housed in the frame.
Caulking and plastic work great. Both sold at hardware stores and on line.