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5 Ways to Insulate Your Windows for Winter- We're getting cellular shades for our new home, perfect! :)
Bubble Wrap as Insulation for Windows
For insulating behind pretty curtains, i went to Hobby Lobby and bought yards and yard of this stuff call Insul-bright. It's meant to be used when making oven mitts and works great on windows. I just hung it behind our curtains. It's only $2.50 a yard and you can use a 40% off coupon too. Really cheap way to make your curtains insulating ones.
Insulate windows with Draft Snake. Need to do this!