Type D or type O

Hi, I usually do not ask too many questions, this one has me stumped, can not find info on the internet.

House has type D or O vent by Metalbestos. Original heating system was a floor furnace, common for that build date, likely asbestos flue pipes. System has been changed to a crawlspace Goodman gas fired furnace. Type B vent off the furnace in the crawl.

One concern is that there is dried condensation / moisture marks from the joints. I get that the floor furnace was less efficient, and the new furnace 80% eff has cooler gases that cause condensation.

Just not sure if that type should have been installed. No green tag. My guess is no, wrong type. Want to make sure.

Not sure what you are asking, you say the system has been changed to a gas fired furnace with a B vent, so why the question about the old vent?
Gas vent that fits between framing has not been made for a long time (40 years, 60?) so call it out for a chimney inspection by a gas code qualified tech if it going to be used, if it is not going to be used, leave it there, do not disturb, cap off any openings inside.

Hi Erik,
The Metalbestos was a replacement at some point. One existing vent pipe is still used as an exhaust flue, the other is likely combustion air.

The B vent is only a small horizontal section in the crawlspace, attaching to the vertical Metalbestos.

Please excuse any inadequacies in the description.

In that case consider having a gas code qualified person check the sizing and condition of the metalbestos chimney, gas chimneys are sized by BTU input and chimney height, if the chimney size is too big there could be condensation issues as you observed.

Yes, thank you Eric, that was all completed before asking the question.

Maybe I will never see that vent type again.

Most likely, I have never seen it and I was putting in furnaces in the 1970’s :slight_smile: