Remove or seal off B-vent chimney??

Damien

I am getting mixed messages from contractors, plumbers, chimney guys, and my town code enforcement, and I'm not sure what's the best option. Please help!

I am replacing my current boiler and water heater with a combi direct vent. The chimney, which is a b-vent from the boiler, through the walls, through the roof, will be decommissioned. We removed one of the walls between the kitchen and dining room and thus we need that b-vent gone, at least on that floor.

Contractor says once the new system is we can just cut the vent (it's like a sheet metal), and seal it on both sides.

Plumber suggests we remove it because it can produce condensation and then we'll have leaky walls.

Town code enforcer, to my surprise, says there's really no code for de-commissioned chimneys, but he does recommend complete removal.

I am lost as to what is best. To be honest I want the cheapest route - this was a huge unexpected expense for our renovations, and getting the new system is costly enough -but I definitely don't want to risk something unsafe.

Does anyone have experience just cutting part of a vent and leaving it in the house? Is total removal the best option? Thank you!

EdTheHeaterMan

Your main problem will be some years from now when the old vent is rusting away. The part that penetrates the roof will allow for condensation to form on cold winter days and the air can freely move around the pipe from the cold sections to the warm sections. By cutting it off below the roof and sealing the roof you will eliminate that possibility. If the roof work is what is too expensive, then I would just place a custom cap made from aluminum flashing and sealed with plastic roof cement is the next best thing. some time in the future, when the roof is replaced, the roofer can just cut it out and roof right over it.