Plastic on Windows

Jen and I really need to get some plastic put on the windows in our living room and family room. We have some on our bedroom windows...but have found that with this bitter cold...it's necessary to have it on all the windows. When you sit in our living room you just feel the draft from outside coming in. Our windows are older so that is part of the problem. I just don't want the house to be freezing all the time and don't want to lose a lot of heat. Hopefully plastic will help.