Just beginning the process of building a new 1 1/2 story; we hope pretty much duplicate our present home's floor plan of around 3800 sq ft. The house is in Savannah, GA. We have the master and guest room downstairs with a very open dining, keeping or gathering or whatever you call it, kitchen, breakfast area, etc. Two bedrooms separated by large play area upstairs and a finished bonus area over the garage. The upstairs and downstairs have a dedicated AC and gas furnace. The bonus area over the garage has it's own heat pump.
The new house will be built with efficiency in mind; foamed insulation, sealed attic, good windows, etc. My general layman's thought was a properly sized Greenspeed HP downstairs, and a less efficient two speed HP for the upstairs. Looking to have short, efficient properly sized ducting. I'm undecided if I want or need a gas furnace for the downstairs and feel like I would want one just because gas is cheap and I expect that to continue. Savannah has 1847 HDD and 2365 CDD. I'm comfortable that this particular builder's HVAC sub does the necessary Manual Js and Ds and installs a good system.
Now, to my question. While looking at a possible builder's personal home last night he mentioned zoning the master and guest bedroom on one system, the rest of the downstairs on a second and a third dedicated for the upstairs. The thought being the master and guest are rooms that are low use rooms. In my past I remember some larger homes being zoned this way, however, I have never lived in one. I'm not a fan of zoning through airflow adjustment. I had a Carrier system zoned that way in a home 17-18 years ago and never thought it worked well, but I realize advancements have been made.
What's the opinion here on zoning the downstairs master/guest on one system and the rest of the downstairs on another?