There was a time when stainless steel was the default material used for venting high-efficiency appliances such as propane furnaces and boilers, Robert Empie writes in Engineered Systems. But today, manufacturers are including new material options in their installation instructions and those materials are appearing more often in project specifications. In addition to the traditional AL29-4C stainless steel, 316L stainless is a low-cost alternative available almost everywhere AL29-4C venting is sold. “316L is also a great option for multi-fuel appliances capable of burning either gas or oil,” Empie writes. In addition to the two types of stainless steel, polypropylene is gaining global acceptance and increased usage.

“Having a temperature rating of 230°F/110°C for flue gases, polypropylene offers a more environmentally friendly option to other plastic materials currently used as venting on appliances and furnaces,” Empie writes. “An additional benefit of polypropylene is that it is lightweight when compared to comparable metal venting options and faster to install when compared to comparable plastic venting options.”

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