duct through chimney to attic?
We moved into a 1960's house about 2 years ago. We are having some moisture problems under the house and part of the problem is very old ductwork (among other items being tackled). Insulation has fallen off in some places, there are rust spots and even cracks. Even to my untrained eye, I can see it is structured in a strange way with weird combinations of flex duct and regular running in seemingly random directions. The thing that is really throwing people for a loop though is that our trunk line runs to the brick chimney, travels up inside it through what I assume is a separate flue, then enters the attic. From there it reaches all the upstairs rooms. The HVAC is pretty old (>15 yrs) and we were thinking of having it replaced with the ductwork. We are being told that the chimney line isn't safe though and that we need to put a second system in the attic for upstairs. Altogether, this is leading to some very high quotes (20-30 thousand) that blew us away. The house is 3,000 sq ft and they are quoting Trane equipment, both top end and mid-tier. current system is 4 ton lennox, but multiple companies have said that it should have been 5 ton based on their load calc.
Anyone dealt with ductwork built into an exterior (active) chimney? Any thoughts on the HVAC proposals?