> Really?  I would think that happens only if you have pure electric
> heating, which isn't particularly efficient (nor quick to change
> your mind about what temperature you wanted.)  Gas or oil heat
> tends to have a central furnace, and it's moderately difficult
> to get more than even a single thermostat or "zone."
here in the uk (where wet central heating is the norm and aircon very rare
in homes) we use thermostatic radiator valves for that, a little slow
responding but normally adequate.

i can't see any reason why hot air couldn't be controlled in a similar way
though the size of the pipework may make designing the valves tricky.

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