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The history and future of the cast iron radiator (and steam heating)


 It's funny, if you browse through $20 - $30 million apartments in pre-war buildings in New York City these days, you'll see that the good old cast iron radiator has actually become a selling point and a design fixture in those apartments. What's crazy is that this iconic piece of modern design is still the dominant form of heating in most buildings in New York City, despite it being over 170  years old.

In fact, the cast iron radiator was actually invented in 1855 by a guy named Franz Sangali in St. Petersburg. Where, needless to say, it gets very, very cold. His original design looked very different than the ones you see today. The design we see today was really pioneered by the American Radiator Company in the 50s and 60s. In cities like New York, that had a huge boom in construction during that era, you see most of the buildings to this day still using those cast iron radiators.

The question is, is why do we still use steam heat and cast iron radiators? And the answer is, well, it's still pretty efficient.

You create steam centrally by heating water. The steam rises without any need for electric pumps, goes through the building's pipes, and then condenses back into hot water, which goes back into the boiler, and then only needs to be reheated a little amount to make it steam again.

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Cast iron radiators serve two purposes. First, all of those tubes have a lot of surface area. That surface area means that a lot of heat can get out and into the space very effectively. The second purpose is cast iron itself retains heat very effectively. So even though the heating system may go on for 20 minutes and then off for 40, that cast iron will stay hot for almost the entire hour.

It's an incredibly innovative, simple, and effective way to heat buildings, and is the reason that many buildings are still heated that way today.

What's changed is that we've been able to actually make it much more efficient. And the way you do that is you replace archaic timer based controls (the systems that control the heating system) with more modern, smart controls.

Timer based controls are exactly what they sound like. Depending on the temperature outside, the boiler will turn on and make steam for a certain number of minutes every hour.

It was a genius idea in the 1960s, but it's an incredibly inefficient way of running the system today because the system has no idea what the temperature is indoors. And so what ends up happening is we end up overheating apartments because we never want people to be cold.

With modern smart controls, we can put sensors in the individual apartments and a prediction of where the weather is going, not just what the outside temperature is now. And we can precisely turn the heating system on and off just enough to make the apartment the perfect temperature. Not only does this save energy, but it makes the apartments much more comfortable.

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The beauty of historic cities like New York is the fusing of history with modern innovation. And it's that rich combination of the two of those that makes cities places people want to live. Which is probably why people are paying 20 million dollars for modern cast iron radiator apartments.