Mikko Peltoniemi wrote:
Ok, so first time in my life I'm a homeowner, and also first time I have
baseboard heat. The problem is the noise that the baseboard makes when
the thermostat turns the heat off.

The noise is like a big bang or clunk. And when more than one heaters do
it same time, it can scare you. Not to mention the neighbors. Not all
heaters do it though. And it doesn't happen every time.

This seemed to come up every once in a while, but still I couldn't find
any answers with Google that seemed to apply to this case. I live in a
condo, and I don't have my own boiler, so that limits some things that
I can do or check.

Here's a sound file too, that I recorded, maybe that will help:
http://mikkopel.dyndns.org:1000/misc/clunk.mp3

How do I stop the sounds? Thanks!

I have had two homes in Alaska with hot-water baseboard heat. In both of
them there were an assortment of creaking, groaning, banging noises and
every one of them seemed to be traceable to the way the hot water pipes
were run between the units. What was happening was when the pipes heated
and cooled they were expanding and contracting and rubbing against the
nice pitch-laden framing lumber. This movement was not gradual but
grab-and-release causing occasional noises. I found out that later that
new code required that low-friction plastic inserts be used in the holes
in the studs to eliminate the pipe-on-wood rubbing and that noise was no
longer a problem.

I really doubt that any noises could come directly from the zone valves
opening and closing. There are two commonly-used zone valve types in
home heating: one uses a wax capsule heated by the control voltage which
moves the valve and the other uses a small motor. In both cases the
opening and closing is very slow (on the order of 5 - 10 seconds) and
cannot cause the sort of pipe banging that is sometimes experienced with
the quick solenoid valves in dishwashers and ice makers.

As for what you can do about it, short of actually digging into your
walls, you can simply wait a while. After a few years I hardly noticed
it any more...

--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com