Your windows could be costing you money. Most windows cause up to 25 percent of a home's energy loss. To keep your home warmer in the winter and cooler in the summer, you can insulate your windows using cardboard shutters made from old packing boxes you can get for free at department and appliance stores. The only cost that you will incur for this project is for the aluminum foil and tape, so it is an economical solution to a common problem.
Measure the window you would like to cover with the cardboard shutter. You will want to measure the window's glass, not the frame, to get an accurate measurement for this project.
Cut four pieces of cardboard to the same size as your window.
Cover one side of two pieces of cardboard with aluminum foil by taping the foil to the cardboard.
Sandwich the cardboard without foil between the two pieces of cardboard that are covered in foil. Make sure the foil-covered sides are facing outwards. If done correctly, the "bread" of the sandwich will be foil and the "meat" will be cardboard.
Tape the cardboard sandwich together. Use several strips of tape on each side to make the shutter sturdy.
Tape the shutter to your window using one long strip of tape for each side of the shutter. The cardboard will insulate your home from the cold, and the aluminum foil will insulate your home from the heat by reflecting the sun's rays.