using b-vent for 2- 3" pvc pipes for condensing boiler

CPHNed

Good afternoon all,
At a job i will be doing the only reasonable way to obtain exhaust/combustion air is to use the existing cast iron 10" b-vent as a chase. Any recommendations on sealing the b-vent when i remove the vent cap permanently? (or maybe i drill two 3 1/2" holes in vent cap)
I think it would look better to remove vent cap.
I was thinking of stuffing newspaper(to allow spray foam to set up) in the top of b-vent and spray foaming, and finishing it off with Gorilla waterproof patch/seal.
Thoughts?

EBEBRATT-Ed

I would put a B vent cap on the top and hole saw a couple of holes in it. You can seal it with something. The other way would be to have a sheet metal shop make you some flashing you could solder on. A couple of sheet metal sleeves 3 3/4" diameter with 2 Ice cream cone flashings on it.

EdTheHeaterMan

Is there such a thing as Cast Iron B-vent?

realliveplumber

Do you know a roofer? They probably would have a few tricks up their sleeve.

CPHNed

Mistakenly omitted the word "boiler" Ed. I am sure you knew that...
Thx all. I appreciate your time.

hot_rod

Venting a mod con? CentroTherm and others have kits for using an old B vent as the chase. I think they include the top flashing.

https://www.centrotherm.us.com/products/innoflue-polypropylene-vent-systems/flex/b-vent-kits/

CPHNed

Here's what I'm gonna do. Most reasonably priced option.

thx all.