The Historic District

I use the modern masters paint too, in a color called weathered bronze

Cast iron radiators themselves are just a heat emitter. Efficient heating is accomplished by running a modulating boiler.

Oversized cast iron radiators married to a high efficiency boiler are a perfect combination. The oversized radiators allow you to run with cooler heating temperatures, so less gas used.

A plausible scenario would be this: An old leaky house with cast iron radiators and a regular boiler. As the house is sealed to prevent air infiltration and/or insulated to increase R value, individual rooms require fewer BTU's - you can adjust a radiator valve in that room to reduce the flow, which reduces the output, but a regular boiler doesn't care you did so - it still burns the same amount of fuel.

A high efficiency boiler does care. It's intelligent, and adjust the water temp to match the BTU demands, burning less fuel. An oversize radiator means you can run cooler temps; cooler temps mean less fuel; less fuel means more efficient heating.

The perfect heating system would also including thermostatic radiator valves to adjust the flow. The reduced flow means higher temps are returned to the boiler. That temp feedback results in the boiler adjusting it's burner down, reducing supply temp.

This is an old thread, but I wanted to add another engineers viewpoint re: the paint and energy conservation debate.

Yes, more paint will hold a little more heat in the radiator. But that heat doesnt evaporate into nothing (conservation of energy for you physics geeks). What will happen is as long as the water temp is at the high limit temp, or the pressure is up for steam your boilers burner will just shut off until the heat bleeds out of the radiator - and it has nowhere to go but into the room. It just takes a little longer.

There *might* be some efficiency loss if your distribution pipes or steam mains in the basement are uninsulated as there will be more time for heat to be lost into unheated space, but the excess is not likely to be huge for a painted vs. bare radiator.

If its costing $250 per radiator to have them stripped, and you have all your pipes insulated and the boiler properly tuned, I would bet real money the payback on having that done is measured in decades, not years or months.

I'm sure the main reason people refinish their radiators is because they have layers of peeling paint and generally look like crap. I know for myself that was the reason and I was amazed at the level of detail etched into the radiators once I had them refinished.

My house is a craftsman, and the radiators are very plain, just a slight curve to each side with a raised rib in the middle of each "column". It also has little feet, but no other ornamentation.