Final answer:
The vent of a draft hood-equipped water heater that runs through a concealed space must be insulated to maintain safety and the integrity of the venting system.
Step-by-step explanation:
When a draft hood-equipped water heater is vented through a concealed space, the portion of the vent passing through the concealed space shall be insulated.
This is a safety measure to prevent the possibility of a fire by reducing the chance of igniting nearby combustible materials. Proper insulation ensures that the temperatures within the concealed space remain safe and that the integrity of the venting system is maintained.