Fireplace chimney blocked by cold air?

[rtroxel]

A few years ago, I had a wood-burning stove installed within my fireplace, and since then, it has worked very well - until now.

The problem is: After I have lit the tinder, and the fire starts, the smoke begins belching out of the fireplace. I talked with the installer about this and was told that there must be some very cold air in the chimney which is blocking the smoke. This answer sort of made sense, since the temperature recently has gone down to the 'teens just after sunset.

My solution has been to insert a lot of rolled newspaper over the tinder, to make the stove, and thus the chimney, very hot, and this allows the smoke to exit the chimney. However, after the flames have died down somewhat, they quickly are extinguished, I'm assuming, by more cold air building up in the chimney.

Has anyone else here had this experience?

Thanks, as always,

Roy Troxel
Taos, NM

 

[MRG]

Yes I have. The only answer I found was to burn more, hotter faster bigger. I used a propane torch to light the kindling I started adding more kindling and burning the torch longer to heat the cold draft.

 

[Mark1]

Although, the "cold air block" might be true, I'm not a big fan of this theory. For example, why did it work well for several years without any cold air blockage? Also, where does the cold air come from once you have the fireplace burning?

It sounds more like you lost your draft somehow. I have an EPA fireplace which draws air into the fireplace from outside of the house on an exterior wall, so if I was to block my air intake I might expect to see some affect on my draft. Also, what about a bird's nest or squirrel's nest within the chimney blocking the flow? For starters, I would recommend investigating any changes to the air into the fireplace, or flow out of the fireplace through the chimney, since it worked fine for several years.

 

[pb4uski]

Sounds like a downdraft. When we had that we would roll up a piece or two of newspaper, light one end and put the burning end as far up the chimney/stovepipe as we could... the hot air would produce an updraft and then we could like the fire. and try to get a good fire going as quickly as possible.

A 1/2 cup or so of mineral sprits sprinkled over kindling does wonders but does smell a bit... mineral spirits is not explosive.... don't use gasoline.

https://www.drsweep.com/services/chimney/downdraft-problems/

 

[pb4uski]

Although, the "cold air block" might be true, I'm not a big fan of this theory. ...

IME, the severity of downdrafts can vary a lot based on temperature, humidity, barometric pressure, etc.

 

[GrayHare]

See if wind direction correlates. For example, if your chimney is on the north side of your house, depending on the design of your roof, a wind from the north can create pressure on that side of the roof, pressure that pushes down the flue. In that case your better flue ventilation will come with a south wind.

 

[Gremlin]

We had this problem and purchased a draft inducer fan kit for about 80 bucks on eBay. After installation, we would run it for the first 10 minutes or so when starting a fire. Works like a charm. No more smoke-filled starts.

 

[marko]

Try opening a door or window for the first 10 minutes? Get some flow going?

 

[ejman]

The flue has been inspected and cleaned periodically (at least every year) with brushes to make sure no creosote deposits have built up right?

 

[OldShooter]

The flue has been inspected and cleaned periodically (at least every year) with brushes to make sure no creosote deposits have built up right?

Also check the cap. At our lake place, the cap had a sort of screen arrangement to keep critters out and over the years creosote accumulated until the day the draft stopped.

 

[zedd]

Try opening a door or window for the first 10 minutes? Get some flow going?

+1


Since the remodel our house became more airtight and necessitated the need to crack a door open to get the fire drawing properly

 

[mountainsoft]

A few years ago, I had a wood-burning stove installed within my fireplace, and since then, it has worked very well - until now. The problem is: After I have lit the tinder, and the fire starts, the smoke begins belching out of the fireplace.

I would clean the chimney making sure it's not clogged with soot, bird nests, etc. When I clean ours I lift the firebricks on top out of the way so soot falls down inside our wood stove. Then I clean out the wood stove when I'm done.

I would also make sure the air intake to the wood stove is free and clear. When I installed our wood stove our codes required a fresh air intake from outside the building envelope. In our case, that is a hole in the floor with a duct drawing fresh air from the crawlspace.

Finally, check to see if you have any exhaust fans running in the house. Homes are built a lot tighter than they used to be and turning on a range vent or bathroom fan can pull air from inside the house. If the wood stove door is open it will pull air down the chimney, which will pull smoke into the room. Once you get a fire going the draft should overcome this, but I've seen it happen a lot when starting a fire, or if the fire is just smoldering.

 

[ckelly78z]

Make sure your chimney, and cap are clean with no hidden bird nests. The only time I have ever had this happen is when birds built a nest a few feet down from my chimney cap (25' off the ground). Use your chimney brush and rods to clean the chimney, and visually inspect the cap for blockages.

 

[TromboneAl]

Here's the solution I use: a heat gun.

Before I light the fire, I point the heat gun up the chimney and run it for about thirty seconds.

Heat guns are also fantastic for reviving a fire if it starts to die or after adding more wood.

Here's the general idea, but you only need a $20 heat gun, not the Looftlighter that lights the "vood." Förlåt, Richard.

My other trick is putting cheap vegetable oil in a Dixie cup, adding a paper towel, and lighting it. Never fails, you don't need kindling, and it burns cleanly.

 

[OldShooter]

Most of these ideas are workarounds. @Mark1 is correct: Something has changed. Find what has changed and fix it. A workaround is rarely the best solution to a problem.

In this case, too, there may be risk of carbon monoxide poisoning. That risk is not to be trifled with.

 

[TromboneAl]

Did the installer inspect (or suggest inspecting) the chimney?

>Something has changed.
It could just be the colder weather or having the heat on in the house. But I agree, an inspection/cleaning is in order if it hasn't been done.

 

[Sunset]

...

Finally, check to see if you have any exhaust fans running in the house. Homes are built a lot tighter than they used to be and turning on a range vent or bathroom fan can pull air from inside the house. ....

Also be aware if the furnace is running, especially if it does not have an outside air intake (like our old one) as that will create lower air pressure in the house.

 

[CRLLS]

A furnace and hot water heater, when running, will draw fresh air from outside. Traditionally, if not high efficiency devices, there was a fresh air makeup tube running from outside (attic, chimney or?) to a few inches off the floor in the utility room. Perhaps the change in fireplace lighting could be related to a blocked fresh air tube. This could create a downdraft in the fireplace chimney to provide that fresh air.

 

[pb4uski]

Most of these ideas are workarounds. @Mark1 is correct: Something has changed. ...

Yes, something has changed... it could be as simple as wind direction, barometric pressure, humidity, who knows?

 

[NgineER]

We have it happen once in a while in our stove, and it is probably a combination of external factors and internal factors such as exhaust fans etc. Cold air is dense and wants to go down the chimney, especially if you have another warm air leak or exhaust elsewhere in your house. Much like PB does, we usually solve it by lighting a piece of news paper and stuff it up the chimney and then light the fire. Never fails even if there is a substantial cold air flow.

 

[RobbieB]

I always start the draft in my insert with the torch before lighting the fuel. When you open the door you can feel the cold air coming out. So load in fuel then set the torch in the crack in the door pointed up at the chimney and let it run for a minute. The absence of cold air exiting is the proof. Then I torch the fuel and all goes well.

But once lit, the stove never back drafts ever. As long as it's warm the draft is up the chimney. Yes, get a sweep out there for a look see.

 

[ransil]

Are you sure there is not a dead coon in blocking air flow, i get birds in mine, someday i will put in a screen

 

[rtroxel]

Thanks, everyone! The cold-air-downdraft theory sounds like the most obvious one to me. (Now I just need to find my propane torch.)

Happy holidays,

Roy in New Mexico

 

[rtroxel]

Are you sure there is not a dead coon in blocking air flow, i get birds in mine, someday i will put in a screen

I don't think there is any blockage, because on warmer days, the chimney works perfectly.

Roy in New Mexico

 

[ER2B]

I solved my back draft problems on my wood stove by burning only seasoned wood - 2 year old at least. The uglier the wood the better. Less than 10 on my wood dryness indicator gauge.