Adding On To Forced Hot Air

Heating systems are a mystery to most builders, even those who talk a good game. When the moment of truth comes and they’re face to face with an old forced hot air furnace in a dank, dusty corner of a customer’s basement, the best they can do is find the manufacturer’s stamped label and read the capacity rating. But it takes more than Btu’s to make a forced hot air system work efficiently, especially when adding on to an existing system to heat an addition.

One of your responsibilities as G.C. for an addi- tion or renovation is to figure out if the existing heating system can handle the extra ductwork. The more you understand about the heating plant, the better you can avoid costly surprises and work with your clients and your hvac sub to design a safe and efficient system. In this article I’ll review the issues and tradeoffs involved in adding on to an existing hot air system.

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