DIY Thermal Curtains

http://www.appropedia.org/How_to_make_awesome_thermal_curtains
This kind

In most homes, windows are the single largest avenues of heat loss. Glass is a very poor insulator, having an R-value of 1 (for single panes). Older windows can lose heat where the seal is degraded around the frame. Typical curtains alone provide little insulation from the cold outside, but using thermal curtains can increase the insulative value of your windows by up to 7 times (R-value of 7), keeping more heat in your home. Compared to other heat saving features, thermal curtains are simultaneously the most economic and efficient.

Not only are they helpful for your wallet and your carbon footprint, but typical thermal curtain design is fairly simple, the materials involved are affordable, and you will also save resources used in heating your home. Thermal curtains achieve the goal of effectively insulating your windows through both efficient and clever design and assembly. Making thermal curtains entails combining an insulative material, a vapor barrier material, and a cover material (this part is optional). The material needs to be attached to a hanging mechanism and sealed against the window frame to avoid air leaks around the curtain.