Replies

1. GBA Editor
   Martin Holladay | Oct 06, 2013 07:18am | #1

   Thomas,
   It looks like you forgot to ask a question. In any case, here is a link to an article on the topic you listed: How to Provide Makeup Air for a Wood Stove.

2. 
   heidner | Oct 10, 2013 02:12am | #2

   Martin gets extra stars for answering the question before it is asked.....

3. Expert Member
   Dana Dorsett | Oct 10, 2013 06:13pm | #3

   From the referenced article, Martin wrote in reference to a preference for proximity-air over ducted combustion air.:

   "Some homeowners have used PVC for these ducts — a bad idea. Obviously, metal ducting is safer, but hot coals in the air intake duct are always scary."

   Using PVC for combustion air ducting would constitute a code violation in most states. Combustion air ducts are required to be non-combustible, and have a minimum 1" clearance to combustibles. IRC section R1006 prescribes some aspects of ducting installation, but some local codes are more stringent. (Probably due to the folks Martin refers to who figured PVC would be good enough?) IRC only demands the 1" clearance withing 5' of the duct outlet (the stove end), but my personal take (based on no actuarial or other science :-) ) is that it's prudent to keep those clearances for it's entire length, which usually isn't a very tough constraint.

   Using direct-ducted combustion air significantly mitigates against backdrafting directly into the house. While wood stoves are not nearly as air tight as sealed-combustion gas-fired appliances, they're tight enough to make a difference if the combustion air is ducted to the outdoors. Even if there is some leakage at the gaskets when the house is at a lower pressure than the firebox, the cross section of that leakage is a tiny fraction of the 5-8 square inches of a combustion air intake on a wood stove, with a correspondingly tiny fraction of the combustion products ending up inside the house under adverse wind/drafting conditions.