Think I am going to put some  underfloor radiant in "This old House".  Start with a room or two and work up.  Going to get a wood boiler, put on a sidearm heat exchanger for the hot water, and a loop in a couple or 3 rooms.  I now wish I didn't have sprayfoam on the bathroom floor.  So, I will need a pump controller, pump, thermostat, mixing valve, manifold with flow contollers for more than one circuit.  What else?  This will be a non pressurized system, so, shouldn't need an expansion tank, correct?