If you want a more effective bubble insulation product, you can use one of the various foil/bubble/foil products. Here's the most common one:
http://www.reflectixinc.com/basepage.asp?PageIndex=389 In various tests I did, I found the reflectix to be almost three times as effective as the simple bubble wrap. It also totally stops the light, so that's something to consider.
Some people make a roller shade device using reflectix so they can open and close it easily. You install a simple wooden track with a groove on each side of the window, and make one roller (like a big dowel, or recycle a wooden broom handle) to roll the reflectix up, and another "idler pulley" at the top of the window. This allows the fairly bulky roll to hide in a valance at the top of the window.
Finest regards,
troy