Question about venting mid efficient furnace and gas water heater

First time seeing this configuration for a 20190904_093019|651x500 gas furnace and water heater venting through a metal B-vent installed on the exterior of the home. Does the 2 foot 10 foot clearance rule apply? and is there a clearance from grade.

My thought is the stack will cool in the winter time (allowing combustibles to become heavy) and backdraft. Water heater with draft hood (Rheem) ,mid efficiency furnace with induction fan (ruud) could not find any information in manuals

I have only seen this configuration for pellet stoves and boilers

Please post an inside picture.

The inside configuration look fine there’s a water heater and furnace running to a Y pitch looked good.

Another thing that got me was they had a return vent pulling air from this utility room also… that could make another possible backdraft situation.(

Don’t have a very clear picture of the inside

The height is fine, so long as the vent is properly supported and secured. This is a gas appliance vent not a chimney. Don’t try to inspect it as a chimney.

Gas appliance vent less than 12" in diameter can vary in height depending on roof’s slope, however! only if it’s 8 feet or more away from nearest obstruction. I cannot tell exactly how close the vent to the roof is from the pic you posted alone. Otherwise it has to be 2ft above any obstruction within 10 feet. Also, the listed vents come with a tag on them, always snap a pic of those for later research & verification.

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Improper installation of this venting, as indicated above.
The bigger issue may be the combustion air depending on the size of the utility room.
Either way, recommend a mechanical contractor review.

What exactly, do you see improper about the vent installation in this photo?

From where I sit, the vent’s termination appears be closer than 8’ to the roof and not 2’ above nearest 10ft obstruction.

I believe that would pertain to a vent on a roof slope with a wall, or such, closer than 8 feet and needing to be 2’ above that obstruction. At least, that is how I understand it. YMMV

Larry, I could be wrong, but when a vent is on a side of a house and isn’t penetrating the roof, the roof now becomes the vertical obstruction. Think how the wind and pressures act on a side vs above a roof. We’re trying to avoid backdrafting.


OK. I see where you’re coming from. The vertical obstruction is the wall below the roofline. I would contend that the vent extending up past the roof at the eave is equivalent to passing through the roof. Without measuring, the vent appears to extend 2 feet above the roof eave which would accommodate the obstruction clearance requirement and a roof pitch of up to 9:12. IMO that the height of the vent is OK as-is. If it has an issue, it’s with the length of the exposed portion of the vent, however, since we can’t determine the exposed length or the manufacturer from the info available, we can’t determine if that’s a deficiency (G2428.2.9)

Yes, and since it’s not >8’ from the wall, it now has to be 2’ above the roof within 10’ It does not appear to meet this from the pics OP provided.

LOL! We have two non-authoritative graphic sources, one of which supports each of out contentions.

I’ll concede that your interpretation follows the more literal wording of the IRC, but I’m not sure it’s the intent (BTW: the vent in both graphics needs a strut and a shroud due to the length of the exposed section). I can’t argue that your reasoning is flawed.

FYI: Per DuraVent concerning the exposed vent:

  1. Construction. Laterals, offsets, and
    vertical components should be securely
    supported with wall straps, as previously
    described. Components of the vent which
    are in occupied areas should be enclosed to
    prevent accidental contact and damage to the
    vent system. Ensure that insulation, building
    materials, or debris do not extend into the
    required clearance spaces. In cold climates,
    the exterior portions of the vent should be
    enclosed in a chase. Outside portions of the
    vent system with may be painted with high
    temperature paint to help prevent rusting and
    corrosion on the exterior surfaces.

In my area I only see them exposed in commercial applications, never in residential. Like the OP mentioned only for pellet/wood stoves they are exposed. Otherwise, they are in a chase and act more like a flue.

Thanks, guys. I appeciate the education.

That could be, Simon. :grinning:

I worked way more hours yesterday, like many of us, and didn’t get a chance to respond to Chuck.
It looks like others did and referred to the 8’ rule for category III venting…thanks.
Didn’t look at where the OP came from but if in Northern climates, snow will be a factor too.
We inspect installations with B vent both straight up through the shingles and through framed chimney chases.