I want to add a branch circuit to my house. The easiest route appears to be from the breaker box up the (inside of the) wall to the garage ceiling; along a cavity between joists to where the hot water heater flue goes up to the second floor, to the attic, and out the roof; and once the cable is in the attic, across the attic to the destination. There is a chase in the second floor bedroom, about 3x3 foot (which seems rather large to me) to accommodate the water heater chimney. This seems like the perfect route for the cable. My question is, how far do I need to keep the Romex from the chimney? The ductwork is metal and I don't know if it is double-walled or not. The sticker on the elbow above the water heater says it's Simpson Dura-Vent Type B.

 

Simpson Dura-Vent Type B requires a clearance of 1" clearance to combustibles in single and multi-family dwellings. While Romex is not combustible I would still keep it at least 1" away from the vent. More would be better.