What measurement is critical to ensure a safe draft hood installation in a heating system?

The critical measurement for a safe draft hood installation in a heating system is the chimney height. This measurement is essential because it directly affects the draft's effectiveness, which is necessary for the proper venting of combustion gases. A chimney that is adequately tall helps create the necessary upward force, or draft, that draws flue gases out of the heating appliance and safely into the outdoors.

An appropriately sized and positioned chimney ensures that the gases are vented effectively, which is crucial for both safety and efficiency. Insufficient chimney height can lead to backdrafting, where combustion gases flow back into the living space, posing a significant safety risk, including carbon monoxide buildup.

While other factors such as the internal flue diameter, the height of the vent connector, and the total BTU input are important considerations for the overall venting design and performance, they do not have the same direct impact on creating a proper draft as chimney height does.