Tom Eagar's residential high-efficiency boiler chimney

Personal anecdote, late 1970s. Tom declined to pay $2,000–$3,000 to line his chimney stack with superferritic stainless steel to route boiler exhaust up the stack rather than out the side wall; still vents through the side decades later. Used to illustrate the superferritic / chloride-cracking-resistance application and the role of mortgage-scale economics in materials selection at the consumer level.

I had a fireplace and I said, well can't you send it up the stack? They said only if we line the stack with this special stainless steel. I asked what type, or I looked it up and found out — it was one of the superferritics. When you're burning gas or oil, they're worried about the carbon monoxide and there might be some chlorine if you're an oil burner. I'm burning gas, but there shouldn't be chlorine in my gas. But some people are burning oil and there'll be some chlorides in your oil. They don't want cracks in your liner for your chimney. They want a superferritic that can take moist chlorides and not crack.