In NY and Brooklyn it is normal to get double glazed windows. It is not normal to get triple glazing. But if you look at the attached file you will see that there is a large savings if you go with triple glazing. The attached doc also gives great explanations of how windows are rated etc. The example are not NY but you get the idea.

I think all green contractors and builders in Brooklyn should install triple glazed windows. It is more expensive up front but it pays for itself way before the end life of the window.