I have a hydronic heating system in my home. The pipes knock in the
walls when the boiler starts up. I've had 3 plumbers come verify that
the boiler is working properly (valves not flowing the wrong way,
enough space where the floorboard vent pipes come through). The house
was just built shoddily without enough space between the pipes and
joists. The knocking comes from a dozen places throughout the house,
and you can follow the noise via the route of the water. It literally
wakes the house up at night.

So I can rip apart the ceilings of each room and try and track each one
down. Blah.

The last plumber we had suggested that we try changing the boiler to a
new energy effiecient model that monitors the outside temperature and
would not go from zero to 180 degrees when turned on. Instead, it would
maintain a temperature throughout the system, only raising and lowering
when needed, which would vary about 1-2 degrees. This would reduce the
total expansion in the system, and thus reduce the knocking. I'm in
Vancouver, so the temperature fluctuations are pretty small, anyway.

Logically, this makes sense. Has anyone seen this in practice, or have
other opinions? And does ~12K for such a system sound about right?

mk