In cases such as shown in the photos, I recommend you shoot pics of the listing sticker on the B-vent. Once back at the office, you can reference chapter and verse where that mfr. requires a listed firestop, part#123xyz and so on. BTW, I doubt you have the requisite 6" clearance from that single walled pipe to the wall and ceiling. The single walled is not properly supported either. In the attic, you would need a listed firestop (and fire blocking per IRC 602.8) AND an attic insulation shield to keep the insulation and Romex off the vent or better yet, Vertical Fireblocking, which is needed because I see plywood. The presence of plywood means there is a reasonable expectation the occupants can access that area where they can be expected to come in contact with the vent. This could result in personal injury or damage to the vent. This can be addressed by simply enclosing the vent with 2x4s and plywood while maintaining clearances. You also woul want to double check the appliance listing for suitability of this vent and any special venting considerations.

As with all listed products and appliances, you answer always starts with the listed instructions.
HTH,
Bob

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