Reverse Draft Issue — Smoke in House

[Cyb33r]

My wife was building a fire last week and was having a hard time getting it started. She started with small kindling and a decent amount of newspapers. It was about 20 degrees F, snowing and 20 mph wind. I walked in during her efforts to get a fire started and smoke was pouring out of the flue collar, door gasket and the air intake on the bottom of the stove even after the damper was closed. The room has 25 ft ceilings and the room was full of smoke. I had a vented propane hot water heater in a closet close by and the pilot light was blown out too. I did not have my furnace on or any exhaust fans on while lighting.

We have had a few smoke issues in the past three years but nothing like this. Mostly back puffing every once in awhile or a little difficulty starting.

Any thoughts? Is this a negative pressure issue? The wood stove is in the center of the room so an OAK would not work. I saw some people have luck with a Condar ASV.

Thanks for your help!


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[webby3650]

Get a small pile of kindling and paper ready, loosely roll up newspaper, light it and stick it right in the flue, or as close as you can get to it, Not sure what stove you have..
My basement setup is about the same as yours. I’ve started using a small propane torch to get things warmed up. Could try that too.

 

[Cyb33r]

Will do. I have a pacific energy t-6. So you think it might be a cold flue issue vs a pressure issue?


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[jetsam]

At 20°F with 25+ feet of flue? Hrmm. Is your house in a valley? I wouldn't normally expect reverse draft from a warm space to a cold one on a 25' flie.

 

[Cyb33r]

Flue is 30 ft. Not in a valley. I am at 5000 ft elevation. Nothing was clogged. I did find it interesting that the water heater 20 ft away in a closet also had the pilot blown out from a separate vent pipe.


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[Hot Stuff]

Have you checked the flue for blockage/buildup?

 

[shoot-straight]

I vote for some sort of blockage.

 

[Cyb33r]

I took everything apart and no blockage all the way up to the chimney cap.


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[Cyb33r]

That is why I was leaning forwards a downdraft or negative pressure issue. Obviously I have no idea and am asking for help. I read as much as I could online before bugging you guys. I was expecting to find a clog in the chimney. I am using the wood stove right now with no issues. Took multiple days to clean the soot off the floor and ceiling. Trying to troubleshoot this so it doesn’t happen again. My wife is now scared to use the wood stove.


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[ryanwc]

Here's my not particularly well-informed thought.

The wind seems like the variable that changed, especially given the blown pilot light. It's hard to see how a blown pilot light elsewhere could be consistent with blockage. Blockage should lead to a consistent small difference in pressure, that couldn't possibly starve a little pilot light of oxygen. The pilot had to be blown out by a severe if momentary pressure issue, for instance, a sudden, hard backdraft caused by a gust.

You've still got an issue, since even under windy conditions, this shouldn't happened, and you mention milder smoke issues at other times.

But considering the wind as the factor that made draft issues more extreme that day may give you constraints within which operation is less likely to be worrisome while you try to troubleshoot.

You mention back-puffing every once in a while. Is that at random times, or always at firestart? If it's always at firestart, that's consistent with a cold flue. Otherwise, it seems likely you're always kind of borderline in terms of pressure, and a certain wind velocity or direction across the chimney top can push you past the edge.

 

[Cyb33r]

Mostly at start up or when the fire is smoldering on low. We added triple pane windows into our house two years ago and it definitely got worse. So maybe the combination of the wind and pressure?


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[ryanwc]

Installing new windows and seeing a change is certainly a big clue. It's probably not the triple pane, but maybe the fact that the new installation didn't have the air gaps of the old windows. Air was coming in at the windows before. Now it has to come in somewhere else, and on occasion that somewhere else is the chimney.

Where is the stove? You can still make things work with a tight house, but the trick is to be tighter higher. If you're house is tightest below the stove, then the chimney is the best source of cool air to feed the leaks in the attic. If your house is tightest in the attic, then your chimney will be the outlet for leaks in the basement. The latter situation is much better. You may want to consider closing air gaps anywhere above the level of the chimney, and see what this does for you.

 

[Cyb33r]

 

[Cyb33r]

I was thinking of putting passive air duct below one of the windows near the stove. Everything is sealed well because it is all fairly new. One of the old trapezoid windows leaked like crazy which I am sure helped feed the stove. It had a 1 inch gap on one sides of the window.


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[Das Jugghead]

How high is the top of the chimney in relation to the peak or ridge of the roof?

 

[Cyb33r]

2.5 to 3 feet taller.


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[Cyb33r]

 

[Das Jugghead]

View attachment 237411


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Just throwing out a guess here but I would think it should be insulated pipe above the roof - appears to be uninsulated single wall galvanized? Also the screen at the top has rather small holes in it which may make it difficult to draft well.

 

[Cyb33r]

It is double wall insulated galvanized pipe on the roof. I can change the cap out if that will help.


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[Das Jugghead]

It is double wall insulated galvanized pipe on the roof. I can change the cap out if that will help.


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I would see what the other members with more experience say before springing for a new cap.

I also wonder if a dedicated fresh air feed would make any difference.

Interested to see how this ends up.

 

[Cyb33r]

I appreciate all the help.


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[ryanwc]

I think you just included the second shot to show off the view from your windows.

And I'm duly impressed! Very nice.

 

[Cyb33r]

Haha. I was trying to show the height of the ceiling. We were -20 F last week in Idaho so as long as you can put up with that.


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[jayoldschool]

Since following advice on this site, I have not had any reverse drafting. Here's what I've changed when starting a cold stove:
- if I open door, and feel cold air, then:
- preheat with propane torch (not long, maybe 30 seconds to a minute) while lighting firestarter
- newspaper rolled/knotted, lighted, up in the flue/top of firebox
- use smaller kindling with my firestarter to get things going hot, fast
- shut door as soon as I light the kindling (I used to think that the door needed to be open to get the fire started)
- use a magnetic thermometer on the pipe (checked with IR thermostat)

All these have made a huge difference in my fire starting. Stove comes up to temp fast, I let the kindling burn down to coals, then load it up for a long burn. I load much, much more wood than I used to, and am getting loads that still have glowing coals after 12 hours.

 

[Cyb33r]

I agree with everything you said about process. I want to try and solve the issue as well. Either a chimney cap or passive vent or both?


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