I have had different estimates, mostly salesmen come out. Some are using foil covered duct lines, some I don't know. Condenser 13 seer, heater 80% efficient, 4ton, right now I have a 3ton. I have received estimates for just above builders grade for 14000 to 16000. They don't even look in the attic. Is this the way it is normally done. It just seems really expensive to me. My system is working, but old, is there a lower price in the fall or winter months or is this about the cost of things. My home is 1700 sq feet.