>>> 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 & aircon very rare
>> in homes) we use thermostatic radiator valves for that, a little slow
>> responding but normally adequate.

> That's what I was talking about. This is also the norm in Germany. Usually
> the not too old houses have a two-staged control: one central control takes
> care of the water temperature (which can be lower at night or eg. during
> work days when nobody is at home), and individual radiator valves
> (sometimes with remote sensors) take care of the flow through each
> individual radiator. 

Commercial offices HVAC in US (southwest, where I've worked) uses
a central blower installation with radiators in each air flow zone.
Radiator get thermostatically controlled amount of hot or chilled
water to regulate temperature in that zone.  They look like small
automobile radiators (and sometimes leak too).

I've also never seen such equipment in a residential site.


> The "valves" could be something like rotating shutters. 

I've always heard them called dampers.  They're usually manually
adjusted.  They are flaps in the ducting to adjust the overfall
airflow into each zone or subzone.

These are common in better grade residential installations (though
frequently difficult to access).  Easy adjustment is thorugh the
louvers on the wall/floor/ceiling vents.

						Lee Jones

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