I built a very efficient home with all but one exception. The windows. I thought I had bought a mid-line window, and maybe it is. If it is a mid line window I would hate to see the low end cheap-o's. We built the house 3 years ago. They are double hung (which I'm told are not the most efficient). I am not sure how you go about replacing them though. Does the whole window frame need to be ripped out? And if so, how do "replacement" windows differ from just regular new windows? What brand does anyone recommend? Any questions/comments welcome.