If your windows feel drafty, an energy-saving window treatment, such as thermal window shades, is a quick decor fix that can seriously reduce your heating costs. Thermal shades are like quilts for your windows. They can block cold drafts from entering and hold heat within rooms. Plus, they are easy to install on most types of windows, and they nicely fold up and out of the way when you want to see out the window.
Thick curtains can work just as well. Wool is an ideal material for curtains, as it's a highly efficient insulating material. But there are many other options besides wool for store-bought curtains at various price points that are good insulators.