B-Vent Safety and Combustible Clearances

By
Home Inspector with King of the House Home Inspection, Inc

I was rummaging through my inspection photos and found a couple that I thought make a good point about an often seen problem -- combustibles packed around the B-vent in the attic. Especially in older homes, time and time again, the inspector sees insulation resting in contact with the B-vent. A B-vent is the metal duct that is normally used to vent gas and propane appliances such as furnaces and water heaters. These vents can achieve temperatures of 300 degrees when gas appliances are operating. Therefore, insulation, including fiberglass, should be a couple inches away from a B-vent to eliminate the hazard of a fire. This is easily accomplished if a homeowner gets a piece of sheet metal and bends a collar or a ring of metal to fit around the vent. Tack it in place, remove all insulation between the ring and the vent, and the job is done. In a newer home, a commercially manufactured shield is often put in when the vent is installed. The photo on the right is the concern that an inspector sees frequently at an older home -- it seems to be a problem most of the time in older houses. The vent on the left is neatly done with a collar or shield made for that purpose in place. This is at a newer house. I hope this description and the photos clarify an often misunderstood, but easy to fix, concern.

  

Nice Job!                                       No clearance to vent!

For a chart showing recommended combustible clearances click here. For further information on B-vents and this topic, from Seattle Home Inspector Charles Buell, please click here.

Steven L. Smith

Thanks for stopping by,

Steven L. Smith

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Comments 2 New Comment

Rainer
2,721
Hector Hernandez
Hector Hernandez
Inside Edge Real Estate
Great solution to a commonly overlooked problem.
October 24, 2007 10:23 AM
Rainmaker
1,172,441
Steven L. Smith
Bellingham WA Home Inspector
King of the House Home Inspection, Inc
Thanks Hector. Glad to get the point across. This is really overlooked as you said.
October 24, 2007 10:35 AM
Rainmaker
1,172,441

Steven L. Smith

Bellingham WA Home Inspector
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Additional Information

Steven L. Smith, King of the House Home Inspection, provides information for real estate buyers, sellers and real estate industry professionals. Blog posts emphasize issues commonly found in Bellingham, WA and Whatcom County. Smith is Washington State Licensed Home Inspector #207, a state licensed structural pest inspector, ASHI certified inspector #252760 and one of the most experienced inspectors in the northwest corner of the Pacific Northwest. Steven L. Smith is lead instructor of home inspection at Bellingham Technical College and teaches classes for Washington State University and the Washington State Department of Agriculture. Steve was a two-term member of the state licensing board.