My wife and I bought a 1940 tudor style home that is just under 4000sf. We are in the middle of a complete renovation and have come to a point where we need to make some decisions on our hvac. Currently we have a newer carrier heat pump that takes care of the first floor master and the laundry room. The second unit is a 1985 vintage carrier 58ss nat. gas furnace for the remainder of the house and second floor. Since this is a gut job all of the ductwork has been scrapped because it was a cobbled mess.
Now we have to decide what to do with the second floor which consists of a 14x16, 12x16 and 11x14 bedrooms and a 6x10 bath. Call the second floor with landing 700sf. I contacted 2 different hvac contractors locally and got two different approaches.
Contractor 1: Replace 58ss with more efficient unit, dedicate it to first floor only, replace ductwork. Install heat pump with 5kv heater on second floor, box out ceiling to keep ducts in living space. Quote pending.
Contractor 2: Run new ductwork from existing 58ss unit to first floor registers like originally, run trunk up to second floor through wall chase as before with return, install flex duct in ceiling to each second floor room (everything is open). Ball park verbal estimate a few thousand.
I am hoping to get a couple more years out of my old furnace because the budget has taken a major hit with repairs we did not anticipate (inspector missed). So dollar wise, #2 is doable now but #1 told me that it would never be comfortable upstairs even with sizing the main correctly. My opinion is that since the second floor will not be occupied full time, we could zone it and use dampers. We don’t have the $$ right now to put in two new units and ductwork at $+? Are we really going to be that unhappy trying to use our main unit to heat and cool the second floor even if we replace and size the unit correctly? Both approaches make sense when talking to the contractors but one is way more $$ and really isn’t an easy thing to change after we have insulation in and drywall up. Very confused. Any help or advice is much appreciated.