Twenty-nine years ago, when we built our forever home, my central air conditioning systems consisted of two 2-ton condensers with two air-handlers in the attic and ductwork that utilized fiberglass ductboard with short runs of flex ducts terminating at commercial-grade ceiling registers. The condensers and air handlers were used that we salvaged from one of our job sites. I kept them with the notion of using them and figured we would upgrade from 10-SEER to higher efficiency units once they died.