Vent Clearance Again

[inspectorwill]

I am hoping to settle this issue once and for all. B vents require 1" clearance from combustible materials. Old transite typically requires 1 1/2" clearance from combustible materials. Most homes over ten years old have vents in contact with the drywall at the water heater or furnace closet ceiling. Drywall (gypsum) is rated for use as fire separation but considered combustible material per the UMC. Was there a change in the UMC at some point? Please see the photos attached for examples. All feedback is much appreciated.

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[Jim Katen]

I am hoping to settle this issue once and for all. B vents require 1" clearance from combustible materials. Old transite typically requires 1 1/2" clearance from combustible materials. Most homes over ten years old have vents in contact with the drywall at the water heater or furnace closet ceiling. Drywall (gypsum) is rated for use as fire separation but considered combustible material per the UMC. Was there a change in the UMC at some point? Please see the photos attached for examples. All feedback is much appreciated.

I think the change is related more to enforcement than to changes in the codes.

- Jim Katen, Oregon

[Darren]

Attached see New Jersey's take on this subject.

Also note the date of the original release is 1990.

Download Attachment: b_90_3.pdf

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