A massize retrofit of New York's iconic Empire State Building was completed at the end of 2010. Now, with two years of data to look at, the building-efficiency experts at Johnson Controls (JCI 0.34%) have shown us just how significant this sort of project can be. In this video, Fool.com contributor Aimee Duffy talks with fellow contributor Tyler Crowe about the success of the Empire State Building, while giving viewers a few other energy-efficiency investment ideas.