Thread: Combustion air

The IRC allows combustion air for fireplaces to come from the attic however it does not allow the combustion air source to be from a sousce higher than the firebox. We commonly see the vents taking the air from the attic or from the exterior out the side of the chimney structure which are above the firebox. The IRC also allows the combustion air to be set up according the the manufacturer's installation instructions. We don't have access to the instructions. Any suggestions on how to report this?

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Originally Posted by Gary Mohel

The IRC allows combustion air for fireplaces to come from the attic however it does not allow the combustion air source to be from a sousce higher than the firebox. We commonly see the vents taking the air from the attic or from the exterior out the side of the chimney structure which are above the firebox.

Gary,

Having a brain freeze here ... where is that at in the IRC?

Section R1006 covers exterior combustion air for fireplaces.

Originally Posted by Gary Mohel

The IRC allows combustion air for fireplaces to come from the attic however it does not allow the combustion air source to be from a sousce higher than the firebox. We commonly see the vents taking the air from the attic or from the exterior out the side of the chimney structure which are above the firebox. The IRC also allows the combustion air to be set up according the the manufacturer's installation instructions. We don't have access to the instructions. Any suggestions on how to report this?

Originally Posted by Gary Mohel

Section R1006 covers exterior combustion air for fireplaces.

From the 2006 IRC.
- R1006.1 Exterior air. Factory-built or masonry fireplaces covered in this chapter shall be equipped with an exterior air supply to assure proper fuel combustion unless the room is mechanically ventilated and controlled so that the indoor pressure is neutral or positive.
- - R1006.1.1 Factory-built fireplaces. Exterior combustion air ducts for factory-built fireplaces shall be a listed component of the fireplace and shall be installed according to the fireplace manufacturer’s instructions.
- - R1006.1.2 Masonry fireplaces. Listed combustion air ducts for masonry fireplaces shall be installed according to the terms of their listing and the manufacturer’s instructions.

- R1006.2 Exterior air intake. The exterior air intake shall be capable of supplying all combustion air from the exterior of the dwelling or from spaces within the dwelling ventilated with outside air such as non-mechanically ventilated crawl or attic spaces. The exterior air intake shall not be located within the garage or basement of the dwelling nor shall the air intake be located at an elevation higher than the firebox. The exterior air intake shall be covered with a corrosion-resistant screen of 1/4-inch (6 mm) mesh.

R1006.1.1 and R1006.1.2 are different from R1006.2 and are referring to different things.

Thus, when installed in accordance with R1006.1.1 or R1006.1.2 and in accordance with their manufacturer's installation instructions, their location, regardless how high they are, is acceptable.

Here is the difference.

*IF* it is a "factory-built fireplace": (underlining and bold is mine)
- R1006.1.1 Factory-built fireplaces. Exterior combustion air ducts for factory-built fireplaces shall be a listed component of the fireplace and shall be installed according to the fireplace manufacturer’s instructions.

*IF* it is a "factory-built fireplace" the exterior air SHALL BE A LISTED COMPONENT OF THE FIREPLACE AND SHALL BE installed as listed.

Okay, here is the next difference:

*IF* it is a "masonry fireplace" *AND* the exterior combustion air duct is listed:
- R1006.1.2 Masonry fireplaces. Listed combustion air ducts for masonry fireplaces shall be installed according to the terms of their listing and the manufacturer’s instructions.

*IF* it is a "masonry fireplace" AND the exterior air IS A LISTED COMPONENT, IT SHALL BE installed as listed.

Okay, that takes care of the "listed components".

What about unlisted components?

Ah, THAT is where R1006.2, .3, .4, and .5 come in.

Thus ...
- If you are looking at a factory-built fireplace, you stop at R1006.1.1.
- If you are looking at a masonry fireplace with a listed combustion air duct, you skip R1006.1.1 and go to R1006.1.2 and stop there.
- If you are looking at a masonry fireplace with an unlisted combustion air duct, you skip R1006.1.1 and R1006.1.2 and go to R1006.2 through R1006.5

How do you determine if a masonry fireplace combustion air duct is listed?

Originally Posted by Gary Mohel

How do you determine if a masonry fireplace combustion air duct is listed?

THAT is the $64,000 question.

You would have to see enough of it exposed to see the listing and labeling information on it, or, hopefully, the listing and labeling would be visible at one of the vents - intake or outlet.