Combustion air from attic

[bbrinke (Brad Brinke, CMI)]

@cbottger

You are not scientist but as a CMI you should know that the difference in temp of the air is what makes the air move from attic to enclosed closet thus the pipe one foot from the ceiling and one foot from the floor. Get in the attic above these two pipes with the furnace closet door closed take a piece of paper and place it over the two pipes and come back and tell me if there is air movement:shock:

Sorry that question was probably not on your CMI test. OHHHH dumb A** me there is no CMI test

Passive combustion air does not do what its told. The opening is dependent on pressure difference for flow to occur. Air flow goes both ways.

I realize how air flows in a building. I have done probably 1500 blower door tests. I am saying that perhaps, just perhaps, things are not always the way they seem to be. You are correct, there is no CMI test. I am a CMI based on 17 years of home inspection experience. I appreciate you trying to make me look stupid, or perhaps inexperienced. Maybe one day I can wear a red hat and be cranky.

[cbottger (Charley L. Bottger)]

@bbrinke

Passive combustion air does not do what its told. The opening is dependent on pressure difference for flow to occur. Air flow goes both ways.

I realize how air flows in a building. I have done probably 1500 blower door tests. I am saying that perhaps, just perhaps, things are not always the way they seem to be. You are correct, there is no CMI test. I am a CMI based on 17 years of home inspection experience. I appreciate you trying to make me look stupid, or perhaps inexperienced. Maybe one day I can wear a red hat and be cranky.

Well Brad you came charging in on your white horse like a two pipe C air system was stupid and I became defensive of something that has been used here for as long as I can remember + after Nickie proclaimed what Russell Hensel little Org was a consumer fraud I decided to take a whack again at CMI with all the new 3 year CMI’s now in place I assumed (my Bad) you were one also I apologize for jumping your case so hard I don’t normally do that unless your name is Larson or bushy

[bbrinke (Brad Brinke, CMI)]

Thanks buddy. No worries

[jfunderburk (Joe Funderburk, CMI)]

@bbrinke

So what tells the air it has to be used for combustion purposes? Is there smart air in the attic that knows this? What happens when the attic is under negative pressure and pulls air out of that room? This may be allowed by code or AHJ but the design is stupid. I am no scientist but I dont think smart or stupid air has been invented yet.

Air is a fluid and will move from one area to another based on pressure differences. As air is taken from the room by combustion, a vacuum is created and the air is replaced by attic air. The physical connection essentially makes the room part OF the attic. The limitation is on the size of the opening. Two straws would not provide enough air. A completely open ceiling would be more than enough. Someone has figured out that 2 tubes will work fine. There is sufficient air in an attic to support combustion, most would agree.

We are all waiting for your suggestion to the homeowner/builder/code writers about how it should be done.

[jfunderburk (Joe Funderburk, CMI)]

Everyone should know that the tubes have to be rigid metal. I sometimes see HVAC flex ducts used. That’s a code violation as the ducts can be compressed in hidden areas.

[bbrinke (Brad Brinke, CMI)]

@jfunderburk

Air is a fluid and will move from one area to another based on pressure differences. As air is taken from the room by combustion, a vacuum is created and the air is replaced by attic air. The physical connection essentially makes the room part OF the attic. The limitation is on the size of the opening. Two straws would not provide enough air. A completely open ceiling would be more than enough. Someone has figured out that 2 tubes will work fine. There is sufficient air in an attic to support combustion, most would agree.

We are all waiting for your suggestion to the homeowner/builder/code writers about how it should be done.

Who is “we”? Is it the royal we?

I am simply suggesting that perhaps air does not always flow in the direction you hope it will. I have seen this setup fail. It’s not often, but it does happen. Combustion testing is part of my energy evaluation so I take it seriously. Are you telling your client that code says its fine and there should be no issues?