Backdrafting Fireplaces and Wood Stoves

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Permalink Reply by Kyle Chase on December 2, 2010 at 3:05pm

I think a WCD of -5pa is pretty reasonable, but like Adam I would love to see some data!

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Permalink Reply by Paul Raymer on December 2, 2010 at 3:48pm

The guys at the energy conservatory did some work on this a number of years ago. As I recall, 6 Pascals is enough to backdraft an operational fireplace. BPI does consider fireplaces and woodstoves CAZs.
Couple of things, though. 1. The worst part of a fireplace fire is at the end of the burn, when the chimney is cooling, and combustion is incomplete. Those romantic embers can be deadly. If a fireplace or woodstove backdrafts at the beginning, people usually don't like the smoke and open a window, which may or may not help.
2. I think you have to consider a fireplace or woodstove as a serious participant in sucking the air out of the house for worst case depressurization. I use the blower door to draw 250 to 300 cfm out of the house along with all the other exhaust appliances. No, I don't start a fire and see what happens!

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Permalink Reply by Adam Zielinski on December 2, 2010 at 4:16pm

Wow that is interesting, running the blower door at 250 to 300 cfm to simulate what the real worst case would be like with a fire in the fireplace or wood stove.

BPI may consider fireplaces and wood stoves to be CAZs, but they don't have any depressurization limits or action levels to implement for them. So as far as BPI goes, you could have a house with a worst case depressurization of -10 pascals and a fireplace or wood stove, and it would pass with flying colors with no requirements or recommendations to fix anything.

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