My house is 25-30 years old (but I have only owned it for a couple years). It has a single zoned system. My house has 2800 of finished space, about half in a walkout basement. I spend lots of time in the basement (family room and big TV, office) and am always cold in the winter. There are rooms in my house that are rarely if ever used (basement bedroom, upstairs living room, upstairs guest bedroom).
My heat/air contitioning system needs to be replaced. Is backfitting a zoned system in an existing home practical? There is an outside chance that I will add a two story addition to my home (800 ft2) to expand the kitchen upstairs and make a new master bedroom in the basement. One option is to have a new system just for the addition, but that doesn't address the inefficiency of heating/cooling unused rooms and the cold family room problem. My house is a ranch with walk out basement. Air handler is in basement. I
My reccomendation would be the Carrier Infinity system (Gas Furnace or Heat Pump system) because of the Variable Speed fan. It is cheaper to run and provides very good comfort. Another plus is the Infinity control. Best residental furnace control I have seen. Do a search for "Infinity" on this site and you will see what I mean. The Infinity will most likley be the most expensive unit you can find (No pricing questions, please). To gain the full benifit of it, get a Manual J load calculation done to size it right. I am also in Northern VA and I am getting a Carrier Infinity system for my house. I would get a 13 SEER A/C or Heat Pump unit because of the few days of 90+ degree, 90% Humidity Days. The Carrier 38TXA or 38YXA is a good choice. The Variable speed fan will boost the SEER to like 15 and the fan will slow down to provide dehumidification control