" Forced air heating incorporating humidity control is ideal for older
houses
with valuable timbers. The humidity can be set so it is never too dry and
achieves the optimum. If extensive rennovation is being carried out, the
ductwork can be worked into floors and the likes and long thing grills
hidden behind beams, etc.
I don't think just adding moisture would be enough. Hardwoods air dry pretty
quickly in the tropics where humidity can be close to 100%. The chances are
that, after 10 years, it's done all the shrinking it's going to do. Once
timber has acclimatised to an environment, that's usually the end of the
matter.
You can use a basic tell-tale system to determine whether timber is still on
the move by nailing a piece of thin softwood across a joint so that it will
split with the grain if the underlying hardwood moves. Cheap cladding is
ideal because it at least starts off virtually bone dry.