Smoke coming inside when I try to feed fire

[Promark808]

Seeking advice on an issue I've not encountered since installation in 2000.

I live in a geodesic dome with two 34' free standing chimneys that are located in a fireproof chase directly in the center of my home. My wood burners are inserts built into fireplace facades that appear as if they are indeed inserted into a fireplace. I have a Buckstove in the basement and a Squire wood stove on the main floor. These have helped to heat my home for the last ten years with no trouble. Each stove is piped into it's respective chimney with 8" pipe into an 8" clay lined chimney that gets cleaned a minimum of once a year; but, usually they are cleaned twice.
The problem I'm experiencing now has me really confused. It seems that the only way I can use the stoves now is to build a fire and not feed it any until it burns itself completely out, otherwise smoke gets into the house and finds it's way into the master bedroom suite on the top floor. The buck stove in the basement seems to be the worst of the two. I have cleaned everything including the stoves themselves. I have even tried to surrender to local " professionals";but, it has become painfully clear to me that if these "professionals" didn't sell me the stove(s), they won't even consider having a look.
I would appreciate any advice or suggestions that I can get at this point as I am sure the stoves are in great working condition and I do not feel either needs to be replaced.

 

[branchburner]

Are there any other variables that might have changed, like type/dryness of firewood, new renovation/addition/neighboring structure, etc.?
EDIT: Renovation would include anything that might be competing for air, like kitchen/bathroon fan or dryer, or anything that has tightened up the house and reduced leakiness.

 

[LLigetfa]

It sounds like there is a serious pressure deficit situation in the home. You need to do an air infiltration evaluation to determine where you are losing air causing this deficit. Lining the flues with insulated SS liners may increase the draft enough to overpower the deficit but I think you will need to provide more make-up air to the home and control air loss better.

 

[begreen]

Do the two flue caps terminate at the same height or is there a significant difference in them (>6")?

Also, is there an upstairs window being kept slightly open?

 

[LLigetfa]

I assumed that the smoke was entering at the stove that was being fed at the time but if that is not the case, BeGreen poses a very could question. In a multi-flue home with stoves at different levels, one flue can out-draw another and in the case where one flue is connected to a stove that is not in use, that flue can reverse, sucking smoke down from the other flue. If that is in fact the case, I missed that in the OP.

 

[Promark808]

Pyro - There have been no renovations done since 2005 when the basement was finally finished and turned into a family room. I'm also getting my firewood from the same source that I have always gotten it from. The moisture content varies as well as the types of wood as it always has. For the most part, I burn hardwoods such as white oak, ash, locust, as well as cherry, and maple.

LL- I'm not sure of the best way to perform an air infiltration evaluation nor what would be the best way to provide make-up air. You were also correct to assume that the smoke was entering the home at the stove that was being fed at the time.

BeGreen- The two chimneys are the exact same height. Removed the caps a couple of years back due to constant clogging up and reluctance to go on the roof to clean them repeatedly in the winter time. Too dangerous to get on roof if there is a remote possibility of snow or black ice. The only place to tie off for safety are the chimneys themselves. Also, there are no windows being kept slightly open on any level of the home. Should there be? I have opened the third level windows after the fact to facilitate getting the smoke out of the house.

To all- Thank you very much for the replies. Please keep them coming. There has to be a simple solution to this problem, I just can't seem to see it.

 

[begreen]

The two flues should not terminate at the same height. Smoke from one can siphon into the other, usually the lower stove or fireplace. There should be at least a 6" offset in height. http://www.extendacap.com/main.html . I'd take care of this and would put caps on them, if necessary without a screen. FWIW, a screen normally doesn't clog unless unseasoned wood is being burnt or a lot of paper or cardboard.

Did something in the remodel get added that may have exacerbated the situation? Did anything get moved to the basement with the remodel that can create negative pressure. This would be items like a bathroom fan, dryer, exhaust fan, or gas hw heater?

 

[Promark808]

BeGreen- If I were to extend one of the flues, would you recommend it to be the one for the basement stove or the main floor?

The only thing added in the renovation that could possibly create negative pressure would be the bathroom exhaust fan. This is not a very large fan and is not ran for extended period of times. All of the other items you listed: dryer, gas water heater, were there all along. Also, the renovation took place in 2005; the smoke issue just came up this year.

It is quite possible that some of the fuel I use is not properly seasoned,and we have never burned large quantities of paper or cardboard. These are seldom burned; in fact, we do not even use it to start fires. We generally use the fire starters or little pieces of fake logs that are manufactured from sawdust and wax.

 

[Shari]

Sounds like it is the wood. Take a split, re-split it and take a moisture reading from the inside of the just split piece - a good read should be less than 20%. Also, raise one of your chimney's a bit as previously suggested and add a carbon monoxide detector or two if you don't already have them.

 

[branchburner]

Was this a problem with a gradual onset, or a sudden one, and how long has it ben going on? It is strange that both stoves are affected, with separate flues. Is it possible there is an air leak common to both, such as a cleanout door that used to be sealed but no longer is? Or some other leak below the thimbles that could be compromising the draft?

 

[Promark808]

Perhaps I should clarify my problem a little better as I do not wish to confuse or offend anyone in the forum. I know you guys want to help and I want to get to the heart of the problem and correct it.

I do have the problem in both stoves. The basement stove is worse than the stove on the main floor. There was a little of this going on last year towards the end of the heating season. I attributed it to perhaps the chimneys needing another good cleaning. I thought I would be in the clear after a thorough cleaning. This year however, it seems to be an ongoing battle. I don't know the best way to answer the question as to weather it was a sudden or gradual onset. I would like to say it was gradual as this was happening a little last season, hence, the thinking a good cleaning would solve the issue. It seems to me though, it has been going on this entire season; again, with the basement stove being the biggest culprit.

I have been concentrating my efforts on solving the issue with the basement stove as we tend to use it the most. All of the piping has been removed, cleaned thoroughly to the best of my ability, and reinstalled. All of the pipe joints have been taped with an aluminum foil type tape to help ensure a tight seal. There is also a redundant seal on the pipe where it is connected to the chimney. All access doors have been sealed up. I am at the point where I am questioning my piping installation. I am thinking there are too many 90's involved that I know will reduce draft and wonder if I might be better off with a single piece of pipe that is flexible at certain points, or perhaps completely flexible, rather than slip together joints of pipe with slip on 90's.

Any thoughts on this? Can one connect a wood stove to a chimney using flexible pipe from the transition piece to the chimney?

To be clear, I concede that part of my problem could indeed be the moisture content in the wood. However; part of my wood stash has been piled up for at least a year, and this is what I am trying to burn now as it may be the most well seasoned

 

[LLigetfa]

When staggering the height of flues, the longer flue should be below the shortest one, so the upstairs flue would be the one to extend. If it was a case of flue reversal sucking smoke down from the other flue, that normally only happens when one of the stoves isn't being used and without the additional heat to maintain the draft, the pressure deficit causes the reversal.

Within a multi-storey home, you will have varying pressures. At the highest part of the building envelope the hot air will push against the envelope just as it does in a hot air balloon. If the envelope is not air tight for whatever reason, the hot air will leak out. These leaks often go unnoticed because no draft is felt but there may be tell-tale signs like melting snow, ice dams, etc. A thermal imaging camera would show the areas as warm spots when viewed from outside. Some of the points of air egress can be observed using a smoke pencil.

At the lowest point in the building, there will be a pressure deficit meaning the air pressure outside will be greater than the pressure inside. It is this same pressure that makes a hot air balloon rise. When people maintain and/or renovate their homes, they put a lot of effort into sealing any leaks where cold air tries to enter the home, thereby starving the home of make-up air and increasing the pressure deficit. Not that a hot air balloon stays inflated and aloft despite it having a huge hole at the base of it. This is because the hot air is not allowed to leak out at the top.

Somewhere between the basement floor and the upstairs ceiling, there will be a neutral pressure plane (NPP). That is the point where inside and outside pressures are the same. If you open a window a crack and air flows outward, you are above the NPP. If air rushes in, you are below the NPP. You want this NPP to be as close to the lowest stove door opening as is practical.

The dynamics of pressure in the home versus outside will vary depending on factors. When a flue has more draw due to more heat servicing it, it will try to suck more air out of the home. When bathroom and/or kitchen exhaust fans run, they will suck air out of the home. So too with some appliances like furnaces, water heaters, wood stoves, clothes dryers, etc. This air needs to be made up for, hence the term make-up air. If the sources of make-up air have been sealed up too tight, the pressure in the home is said to be in a pressure deficit and may start to pull smoke from the stove.

Some appliances may have direct vents and not draw indoor air while others certainly will. Some, like certain models of wood stoves have outside air kits (OAK) as an option. I should point out that having an OAK on a stove does not mean you woill not have smoke issues. An OAK can in fact, worsten the smoke problem as the OAK tries to be the make-up air source for the entire home, pushing the smoke into the room. The entire home needs to be treated as a whole to mitigate a pressure deficit issue. Start by controlling all sources of air egress. Seal around window casings, replace powervent water heaters with direct vent, install OAKs on the woodstoves, and most importantly, provide make-up air to the home.

 

[Bugboy]

Could it be neighboring trees getting taller?

 

[LLigetfa]

One would think that 34 feet of chimney would provide excellent draft but sometimes more is not always better.

Marginal wood will certainly affect the draft as draft is a product of flue temperature and dry wood burns hotter than marginal wood. Installing an insulated SS liner in a clay tile flue can help increase draft even with the smaller flue diameter. The smaller diameter means the flue gasses move faster and so have less time in the flue to cool and the insulation also reduces cooling. Cooling causes a loss of loft which can be observed outside by smoke/vapours that don't rise up beyond or roll down the outside of the chimney.

Elbows in the smoke pipe will affect draft and replacing one 90 with two 45 degree elbows can help. Replacing single-wall smoke pipe with double-wall works like the insulated liner, keeping more heat in the flue to service the draft.

If pressure deficit is not the major factor, perhaps sending more heat up the flue is the first thing to try. Burn dry wood, try double-wall smoke pipe and reduce the number of 90 degree bends.

 

[golfandwoodnut]

Have you actually looked at the chimney caps? I can tell you I had the identical problem this year and did not have it last year. Smoke came in the room when I opened the door. I did a bottom up cleaning and not much came out. I got up to the cap and the screen was plugged. I just tapped it and the stuff fell out and the stove has been great ever sense. Also on a tall chimney it will be cooler at the top which can lead to clogging, I think this is why they say to not go above 35 feet. That is my bet. I am getting a different cap installed this year with a larger screen and easier to clean. Also my installer screwed up and did not properly insulate/seal the cap when also leads to this problem.

 

[Promark808]

Golf & wood nut- I Removed the caps about three years back. Kept clogging up and very difficult & not very safe to get up to and clean in winter. Chose to remove them rather than risk killing myself trying to keep them clean.

 

[jotulguy]

Golf & wood nut- I Removed the caps about three years back. Kept clogging up and very difficult & not very safe to get up to and clean in winter. Chose to remove them rather than risk killing myself trying to keep them clean.

If they are both clogging up maybe we havent explored the wood issue enough on this one? Its either that or the stove is not hot enough. They should not under normal use clog shut. That is where i would focus my attention on this one.

 

[LLigetfa]

If they are both clogging up maybe we havent explored the wood issue enough on this one? Its either that or the stove is not hot enough. They should not under normal use clog shut. That is where i would focus my attention on this one.

They are 34 feet tall with 8 inch clay tile liner. You would have to run some hot fires to keep the flue hot enough the full length. Even the humidity in the air drawn from the house through the stove would likely condense before reaching the top of the flue. The moisture could condense on the mesh screen, building up like a snowflake does, attaching carbon soot as it does. A little bit of paper to start fires would just hasten the buildup.

I'm not saying it cannot be the wood because it very well could be, only that cap screen clogging can happen in such a situation even with ideal wood.

 

[golfandwoodnut]

Promark, if I were you I would definetly have the chimney cleaned and inspected if you have not already done so. It could be the top is squeezing shut just like the screen was. 10 years of burning with a tall chimney, I would think that this is the problem.

 

[Renovation]

I have cleaned everything including the stoves themselves.

So this is a dumb question, but are you sure your chimneys are clear all the way to the top? I say this because you don't like getting up there, and I wonder if you've verified that the top is clear?

 

[Promark808]

Usind a flashlight and a mirror, I have verified to the best of my ability that neither chimney is clogged. There is some minor build-up at the bottom that I have cleaned up to the best of my ability however.

It is my intention to have a professional perform a thorough cleaning and inspecting if and when I can find one that is willing to have a look. This has proven to be a monumental undertaking as well, thus, I am trying to figure it out on my own while I continue to find someone willing to physically help me out.

Once again, the wood could very well be a part of the problem; but, I am trying to burn up what I believe to be the most seasoned parts of my stash right now.

Thanks again for all of your replies, I need all of the advice I can get on this one!

 

[Renovation]

Promark, if I were you I would definetly have the chimney cleaned and inspected if you have not already done so. It could be the top is squeezing shut just like the screen was. 10 years of burning with a tall chimney, I would think that this is the problem.

+1 Holy Synchronicity, Batman!

You're welcome, Promark, I appreciate your attitude.

I was thinking the same thing--if your screens used to clog, maybe the coolest place now is clogging--your chimneytops. It's just a guess, but it would be nice if it were that simple.

Keep your chin up, the great folks here will help you figure it out.

 

[savageactor7]

Sounds like a restriction to me as well. Today use a mirror from the bottom and angle it up toward the sky...you'll be amazed how much better that is compared to a flashlight. Now if the chimney isn't 'perfectly' round, oval or rectangular or whatever it's supposed to be there's the restriction.

If there isn't a restriction hummm there may be a tree upwind, close to the house that trumps your chimney height. Then again if your in the mountains or knolls that can create fickle winds known to defeat a good chimney draft.

 

[woodchip]

Whenever I fire my stove, I open the door slightly first to get some air mixing into the coals, brightens them up and gets an additional draught up the flue. Clean flues, clear flues, and good dry wood are vital, but also is the actual firing method, and the amount of ventilation in the home. Something that is not often mentioned is the fitting of extracter fans in kitchens. Over here, if you have a stove fitted, they check to see if you have extractor fans etc. but once the stove is in, you seems to be free to install anything anywhere to suck air out of your home, thus creating a huge vacuum.

Just a few thoughts to go along with everybody else's ideas......