I wonder if installing windows has an effect on the intelligence of installers. I have had bids from several local window installers and when I tell them I want the top of the line model with the best possible insulating glazing, they all have bid for lower lines of their windows. I have had to call three or more times and still they don't get it. I am reasonably intelligent and can read manufacturers sites on the net so I know what I am asking for. Why at these guys all so thick headed?