I wonder why ducted systems were part of the requirements, is it because it's just aimed at the USA and then mostly at adoptability for existing systems (which seems to be ducted mostly)? I only have anecdotal experience and no numbers to back that up, but it's the only reason I can come up with that would put such a restriction in place.
I'd say rip the ducts out and just use split systems but I imagine other people have thought about that and figured it's not the best way to go. (or at last not in the US)
Yes, because nearly every house in cold climates is ducted, and we’re trying to get people off oil heating quickly, easily, and cheaply. Popping a new heat exchanger in an existing furnace is stupid simple compared to running coolant lines to new, wall-mounted exchangers all over the house.
I think that's true, if the ducts exist already that's simplest and cheapest. If they don't mini-split type systems are. But I suspect that long term those are going to be a pain in the butt because you have a lot of failure points.
Mini splits seem to be pretty reliable. They’re very common outside of North America. Most of the leading manufacturers seem to be from Japan (Mitsubishi, Fujitsu, Daikin)
I'd say rip the ducts out and just use split systems but I imagine other people have thought about that and figured it's not the best way to go. (or at last not in the US)