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