sealing the gap tightly once the window is closed. Most foam weather stripping has one sticky side so it can be adhered to the fixed portion of the window without sticking to the moving one.

Get the most energy efficiency from your insulation by filling all gaps, avoiding compression, sealing holes in framing and ...

You could use weather stripping and window sealing tape to prevent air from leaking through the windows, but another option is a window insulation kit. With these kits, you seal off the entire ...