Hi Joe,
We recently took up a initiative to analyze energy benefits of various retrofitting strategies in a 1970's vintage home in ten cities across four different climates in the US. We compared the home against IECC 2009 code. You can find details of our assumptions and analysis procedure here: http://www.carb-swa.com/ (under featured resources). You will find a download link to an excel file with the results on the same page.

Hope this helps!
Pallavi