I would love to replace all 7 TRV in a 85 yr old double brick no insulation house (water 2 pipe, 1 zone system). The old valves are either seized shut or start leaking if you get them to move. The 2nd floor, south facing room gets to 85F in the sun while the rest of the house maintains thermostat temperature.
Now, looking at these old valves I have no confidence in 50% of the piping holding as you get some brute wrenching force, in fact it looks like i may be able to poke my finger through one pipe.
Has anyone had stories about tearing through floors and ceilings as you end up replacing half the iron pipes in your house. Or is there some magical way to replace these things without this happening???? This may not be worth the energy savings. :-(