Exposed B-Vent in closet

[Stan Croenne]

At inspection yesterday I ran accrossed an exposed 4" B-vent in a closet. Hot to the touch. Right next to the horizontal pole where coats hang. Not sure this is safe. What do you think. Enclose in chase? Stan

[Charley L. Bottger]

There is a MFG sticker on class B vent pipe that clearly states one inch clearance to combustibles most contractors in my area don't read or are unable to read the English language or simply don't care. I don't think I have ever written a report that the clearance was not listed as a repair well maybe on a electric appliance

[Chuck Evans]

Most of the B vent manufacturers specify that when the vent passes through an accessible area the vent should be enclosed with proper clearance to prevent damage or accidental contact.

Oddly, I can't find a reference in either the IRC or NFPA 54

I would advise to enclose it.

[Michael R. Boyett]

Originally Posted by cevans

Oddly, I can't find a reference in either the IRC or NFPA 54

Chuck, do you have the Commentary for 2006 IRC G2426.5?

[Chuck Evans]

Originally Posted by mboyett

Chuck, do you have the Commentary for 2006 IRC G2426.5?

Dang Mike. Make me drag out the old printed book, why don't you? Yes I have it. Thanks for the reference.

In a nutshell (this is heavily abridged and paraphrased because it's long and I suck at typing): The commentary says what the code does not. After saying that clearances, etc. may vary by mfr. It says it must have physical protection in accessible areas to prevent damage and contact with combustibles. Don't forget firestopping...

The real requirement will be what the manufacturer states. If you got a photo of the label, you can pull thier install instructions and use as a reference.

In any case, Thanks to Mike , you can confidently state that it should be protected and firestopped. But there is no model code reference to cite, unless you count commentary.

[Michael R. Boyett]

I wouldn't want to have to type all that in manually either, here's a cut & paste:

G2426.5 (502.5) Installation. Vent systems shall be sized,
installed and terminated in accordance with the vent and appliance
manufacturer’s installation instructions and Section G2427.

Commentary: The standards with which vents and appliances comply
require that venting instructions be supplied by the
manufacturer of the appliance and the manufacturer of
the vent system. These instructions are part of the labeling
requirements. Any deviation from them is in violation
of the code.
The instructions for Type B vents and for gas appliances
approved for use with Type B vents may be
specific to a certain appliance or manufacturer’s
B-vent material. The clearance to combustibles for a
vent system is determined by the testing agency and is
stated on the component labels and in the manufacturer’s
instructions. Not all vents have the same required
clearances to combustibles. The clearances
are determined by the vent’s performance during testing
in accordance with the applicable standard. Different
vent materials and designs impact the vent’s ability
to control the amount of heat transmitted to surrounding
combustibles. It is critical that the vent system be
installed in accordance with the clearances listed on
the vent’s label and in the manufacturer’s installation
instructions.
The termination of a natural draft vent must comply
with the requirements of the manufacturer’s installation
instructions and Sections G2427.6.3, G2427.6.6 and
G2427.6.7. A vent used in conjunction with a mechanical
exhauster must meet the termination requirements
established in Sections G2427.3.3 and G2427.8.
Physical protection of the vent system is required to
prevent damage to the vent and to prevent combustibles
from coming into contact with or being placed too
close to the vents. Such protection is typically provided
by enclosing the vent in chases, shafts or cavities in the
building construction. Physical protection is not required
in the room or space where the vent originates
(at the appliance connection) and would not be required
in such locations as attics that are not occupied or used
for storage. For example, assume that a vent is installed
in an existing building and that it extends from the basement,
through a first-floor closet, through the attic and
through the roof. The portion of the vent passing
through the closet must be protected from damage. The
means of physical damage protection should also be
designed to maintain separation between the vent and
any combustible storage. To prevent the passage of fire
and smoke through the annular space around a vent
penetration through a floor or ceiling, the vent must be
fireblocked with a noncombustible material in accordance
with the IBC. Vent manufacturers provide installation
instructions and factory-built components for
fireblocking penetrations.

[Christopher Currins]

Thanks Mike, and Chuck.

Added to my library;


The vent for furnace is installed from the basement through a (closet), through the attic and through the roof. The portion of the vent passing through the (closet) should be protected from damage. The means of physical damage protection should also be designed to maintain separation between the vent and any combustible storage. To prevent the passage of fire and smoke through the annular space around the vent penetration through floor and ceiling, the vent should be fireblocked with a noncombustible material. Vent manufacturers provide installation instructions and factory-built components for fireblocking penetrations. Recommend to repair as needed.

[Charley L. Bottger]

Ok lets take this one step beyond conventional thinking. Why the clearance to combustibles on class B piping if in most cases the piping does not reach temps on the outer wall that would burn your hand??????