This step by step method of Plexiglass interior storm window for sealing old windows during the winter tutorial will show you an inexpensive reusable weatherproofing way to keep out cold air.  They are make and easy to install in the fall season and remove in the spring.  Over time, this do it yourself project will pay for itself in reduced heating bills over the winters in the following years to come.

The great thing about this insulating method is you have a clear view out your windows, they are easy to clean and nobody will even realize they are there.  Plexiglass is another name for Acrylic plastic sheets.  Click here to read Plexiglass Interior Storm Window For Sealing Old Windows During The Winter Tutorial from Build it Solar.

http://www.builditsolar.com/Projects/Conservation/acrylicstormwindow.htm