If the construction quality in NC is anything like what I’ve seen in VA:
1)They probably forgot to install insulation in one or more places.
2)They didn’t bother to seal up any of the gaps and cracks in the building.
So what you end up with is a poorly insulated, drafty piece of crap.
No heatpump works well in that situation, and a gas furnace will just run longer and cost more.
In the late ‘90s, we worked with NY State to have heat installed in the family homestead where my parents lived. There was a grant to help elderly low-income residents.
It’s a two-story farmhouse, about 2500 sq. ft., built in 1830. The whole place had been heated by one oil stove in the living room for decades — as long as I can remember.
Before NY would commit funds, an inspection was required. The inspector said it was built better thant many of the new houses they inspect.
I would have paid money to be warm, for real. We were so cold. Once the sun went down, it just couldn’t keep up.