Plastic Wrap Method
Take a thick plastic sheet and cut plastic to a little bigger than the window, using a sharp scissor.
Now, use a double-sided tape to secure the plastic to the molding of your windows.
Heat the plastic sheet with a hair dryer in order to thoroughly fix it into the window, closing the possible air leakages.
Add some all-purpose cleaner to a sponge and use it to clean up the molding of your window. Leave it for some time until dries out completely.
In the meantime, use a tin snip to slash pieces of weather-stripping that are according to the size of your window.
Now place the parts of weather-stripping into your window’s sash channels.
Attach the weather-stripping to the molding right around the window’s sash channel, using small or medium wood nails.
Use the tin snip to cut some more pieces of weather-stripping that will in shape the upper and lower sashes of your window.
Fix the sashes’ upper and lower weather-stripping of your window with the help of some nails.
Bubble Wrap Method
Use a glass cleaner to clean up the surface of your window and wipe it dry.
Now use a scissor to cut the pieces of bubble wrap to fit over your window’s glass panes.
Spew a thin layer of mild water on the window panes, using a spray bottle.
Position the bubble wrap pieces onto the window. Leave it for some time until the water dries well and secures the bubble wraps in place.
Caulking window is another simple procedure to seal the air leakages around your windows. Check out How to Caulk Windows Properly.