Thread: How would you write this?

Vent through concete

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What are you wanting to say about it?

Looks like a furnace vent pipe into chimney. The indication is there was once a larger pipe, probably from an older oil furnace. I see this in a lot of older houses.

looking for some verbiage. Sleeve required? Other protection? There is a thin sheet metal around the vent through the concrete. Perhaps it's fine, it just didn't seem right.

Is that venting into a fire place? If yes it needs a clean out.

Best

Ron

It's going into a chimney. Two flues - one for fireplace, one for furnace. Is there an issue with the sheet metal through concrete.

Sheetmetal through concrete is done all the time.... fireplace and furnace combined? I don't think that's allowed.

Edit - Sorry, I had one flue in mind. Are you saying there are two examples of what the picture shows? Or, are they combined?

Thanks Matt. One masonry chimney, two flues

Yup, the fireplace needs it's own flue, not to be shared with anything else.

Fireplaces do not need separate cleanouts because the code considers the open hearth a cleanout in and of itself. They may have optional ash dumps with tight fitting ferrous doors.

Think of your typical chimney like a double barreled shotgun: one barrel for the fireplace and one for the heater. This looks like a typical heater flue breeching with the vent/ chimney connector entering a metal sleeve or thimble. You should have some sort of sleeve or thimble in the breeching so the connector can be easily withdrawn and replaced. However, you must have a cleanout for the heater per code. Also, where this connector enters the flue, it must be flush to the inner wall and sealed with furnace cement for a smooth, sealed transition. This, I NEVER see.

You want to measure your clearances to the ceiling joists off breechings.

The sleeve should be either stainless steel or terra cotta. Galvanized steel rots out.
HTH,

Bob,

Question for you about that photo in the original post (being as I never seen them ):

With that vent buried in concrete, does it pose a problem with causing the vent to cool and collect condensation? Should they be in wall thimbles instead?

Kind of like the reverse of encapsulating the vent in insulation?

Jerry, if you're talking about combustible wall construction then of course you would use a listed wall penetration/ thimble. If we're talking about masonry construction, you will have some cooling regardless of what you do. I think with masonry the issues are liner integrity first, then condensation reduction second. The liner mfrs. recommend you insulate their liners regardless of fuel type. There is some disagreement as to the best insulation system--blanket or cementitious versus dead air. Solid fuel requires very specific insulation but oil and gas do not.

If you want to use B-vent as a 'vent connector', that will tend to minimize cooling of the connector. However, it would need to be run through a masonry sleeve so it can be inspected and replaced as needed. A another approach is to use a single walled connector to the face of the breech so the B-vent is only exposed to the room and none buried in the wall.

If the thimble/ sleeve is large than the OD of the connector, then you stop most of the heat loss and thus insulate it. You still have to seal it at the liner face and wall penetration but that would be a better mousetrap.
Bob

Originally Posted by Bob Harper

If we're talking about masonry construction, you will have some cooling regardless of what you do.

If the thimble/ sleeve is large than the OD of the connector, then you stop most of the heat loss and thus insulate it. You still have to seal it at the liner face and wall penetration but that would be a better mousetrap.
Bob

That's what I was thinking, that the masonry would cool the vent if single wall vent.

Sounds like using the thimble and then sealing it would be the "better mousetrap", is it ever done, or done very often?

Usually when I see photos posted here the vent looks like single wall or B vent embedded in cementitious material at the masonry wall, that's why I was wondering.

Rick,

If you would like a satisfactory response, you will need to provide all relevant information in the initial posting. Do you believe there is a metal liner in the chimney? (Did you see a tube rising from the chimney top?) Is the first 4" of the pipe visible at the bricks aluminum? It looks different than the rest of the material?

Please don't call a vent a duct. A vent carries combustion products. A duct carries air.

Is the chimney exterior to the building?

If the chimney does have an aluminum liner and the vent is for a gas fired appliance, assuming proper sizing, the liner will maintain the temperature of the combustion products (water vapor and carbon dioxide) above their dew point. Condensation is not likely unless the vent is oversized.

The would be a problem here if the chimney has no metal liner and the masonry chimney were in a cold environment. This could lead to corrosion at the connection to the chimney, particularly if the vent connector is galv. steel.

I hope this helps.