On Feb 26, 2:58*pm, harry wrote:
..The boiler(furnace in your parlance) can
be far more efficient, exceeding 100% in some cases.. *

I call it a boiler, too. But it doesn't actually boil anything, so to
avoid confusion I used the word furnace. Sorry if I confused.


Also water is
far easier to mix and control than air. The hot water pipes can be
much smaller diameter than air ducts & therefor can be better
insulated. *Domestic hot water can be produced from the same boiler,
as and when required. (No need to store it hence reduced losses.)
Things are expremely primitive in the USA compared with Europe.-

Well, I'm talking mostly residential, though the office buildings I
saw all had the same kind of hot water heat. There was no air
conditioning except maybe in a computer server room.

Primitive? That's relative. In Germany I saw no VAV, no DDC, no
control systems to speak of, thermostatic control valves on the
radiator where the heat from the unit masks the room conditions,
thermostatic valves that you have to disassemble monthly because they
scale up and always fail to "no heat" condition. No smoke detectors,
heat detectors, CO alarms.

On the other hand, I saw first class furnace/boiler systems in
residential that were well maintained by law, including semiannual
combustion tests and chimney cleaning. And as I mentioned, well
insulated and well sealed; you can get infiltration down to near zero
if you use plaster over masonry and very very expensive double pane
tiltable-closable windows. I wish I could get those in the US but I
couldn't afford it if I could. Even the doors are built with a lip to
seal against the jamb. I was paying 27 cents a kWhr so you can see
why they work hard to save energy.