Roofer finished the overall roof job, replacing a faux chimney box around what I think is an 8" type B chimney pipe. What is clear is that the penetration is big, and the attic fan pulls air volume through it instead of the opposing vents. Am concerned about CO refluxing as well as pests and then heat loss in the winter. The pipe is only used for a gas water heater.

I believe the faux chimney is properly flashed and sheds water. But I do want to ditch this hardware cloth hack.

What am I supposed to ask for?