Victorian Heat Efficiency

I am the pastor of a Victorian church in Newcastle-upon-Tyne in England. The central heating boiler, originally fitted in the 1950s, has been condemned, and we are now replacing the system. How does the efficiency of handsome, original cast-iron radiators compare with modern ones made from pressed steel? The church buildings are listed, which means we have to get permission to deviate from the original style. Modern reproduction radiators are very expensive. What do you think?

Although your question seems straightforward, definitive answers are few and far between. Even the venerable American Society of Heating, Refrigeration, and Air-Conditioning Engineers was unable to come up with much information.Most of those I spoke with seemed to think pressed-steel radiators would be somewhat more efficient. But no one was able to offer a means of quantifying that hunch or an industry rule of thumb on the relative efficiencies of the two radiator types. It left me thinking that if there are differences in overall performance then they are probably minor.

What we do know is that cast iron is denser than sheet steel, so it will take somewhat longer for a cast-iron radiator to absorb and transfer heat from circulating hot water. Cast iron also retains heat longer. As a result, cast-iron radiators should show a "flatter heat curve," as one manufacturer put it, meaning fewer fluctuations in heat output.

With a few caveats, stick with what you have.

In a Victorian-era church hall, what could be more fitting than handsome period radiators? Steel radiators are available in lots of styles and shapes, but none of those I've seen look like antiques. Your old radiators may need sandblasting to remove layers of grime and paint, but that's hardly reason enough to replace them and a careful cleaning will probably improve their efficiency.

In fact, the radiators could be too big for the job. If the church has been updated with new insulation since their original installation, the radiators might be throwing too much heat. Many cast-iron radiators can be taken apart so a section or two can be removed.

Focus attention on the boiler.

If comparing steel and cast-iron radiators is a murky subject, boilers themselves are extremely well understood. Modern heating equipment is much more efficient than what was available in the 1950s. Investing in a high-efficiency model will save you a pile of money with lower operating costs.

Your contractor should start with heat-loss calculations that take a variety of factors into account - the amount of insulation in the walls, for example, the size and type of windows and doors, and the volume of rooms heated. This will result in a required heat output, expressed in BTUs per hour and that, in turn, dictates the boiler size.

Up-to-date controls can help, too, by monitoring outdoor conditions and adjusting the temperature of the water in the boiler accordingly - hotter water when it's really cold, not so hot in spring, summer, and other low-demand times of year.

It seems you may have the best of both worlds: A modern boiler in the mechanical room and classy radiators where they can be seen and appreciated. Old World meets New World, and the result is efficient warmth on those chilly English days.