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Coal Stoves - Wood Stoves - Heating with Coal



Coal Stove - Heating with coal      


The indoor temperature in the winter months (usually over 80) is not an error; nor the result of a temperature sensor having gone "berserk".   We heat entirely in the winter via a Harman Coal Stove located in the Sunroom, capable of outputting 92,000 BTU when running at max...   This is more than enough to heat the entire structure  - even with outside temperatures approaching -20 deg f.

The building faces directly south with ample amounts of glass to captures the sun reflecting off the waters of the cove in the mid afternoon winter sun.   With large amounts of glass on our southern exposure, it's an ideal setup for passive solar. Even during the coldest winter days with the coal stove "throttled back" as much as possible, sunroom temperatures can easily soar to over 95 degrees f. with the sun "pounding in" off the water.....    Even at sub-zero temperatures, a sunny day will  necessitate opening a window or two, lest we get "roasted out".... 

Even here in frigid Maine, with passive solar - coal heat  - a well insulated structure with few infiltration/exfiltration losses, we average only 2.3 tons of coal consumption, or about $700 in annual heating costs based on current 2007 coal prices. (and that's  with keeping the interior at a toasty  80 + degrees !).  Today, just a single 250 gallon tank of oil that lasts but perhaps 6 weeks here in Maine in the dead of winter, runs that.  Surprisingly, the home is far warmer in the winter than it is in the summer with the air conditioners running !

A lot to be said for passive solar...  but in the Northern Hemisphere, one needs a house with an unobstructed southern exposure.  Unfortunately, most structures were (and still are) built & designed with no consideration as to the sighting benefits of passive solar heating. What amplifies the solar loading here even more so, is the sun also reflecting off the waters of the cove, which comes close to almost doubling the solar loading for about 2 hours each sunny winter day.

Anyways, I digress...   back to coal stoves...



Harman Mark III Coal Stove

We use a Harman Mark III to heat the entire house & have fallen in love with it !

Note: Picture is from Harman's Brochure for the Mark III    http://www.harmanstoves.com/Default.asp
(Don't ever expect your viewing window or firebricks to ever remain this clean - that only happens in a marketing department's dreams !)


Coal also makes for a nice toasty convective as well as even radiant heat.  (Sensing a good thing, our Company cats all "swarm" around it come winter - even with inside temps approaching 80 !)...   "Missing" kittens are often found in "kitten mounds" beside it and some who really want to stay toasty, directly underneath it, soaking up the radiant energy.

There is a lot of mental resistance to burning coal still held..  Burning coal as a source of heat conjures up in most people's minds the clouds of black soot belching from the chimneys of 19th century London...  That is the mental image most people have of burning coal...   But that is high sulfur coal and not Anthracite which is used today, that burns amazingly clean..  Much cleaner than wood.  Once up to normal temperature, there will be no visible smoke whatsoever...   None - Natta - Zilch !

There are some major benefits to burning Anthracite Coal....

Plenty of  Even - Dry - Steady - Radiant  Heat.   If you contract the flu or a bad cold, both you and that stove will quickly become the best of close "Pals".  Snuggle up close to "ole Bessie" (you'll probably give her a name, since the bond will become so strong) and the strong radiant heat will permeate your bones & bake the infection right out of you !   In my personal opinion, antibiotics can't compete with the curative powers of a radiant coal or wood stove !   Also consider that any bacteria or viruses passing over the hot surfaces, will not survive the high temperature  shock. So not only does the stove serve as a source of heat, but it is also somewhat effective at eliminating harmful bacteria and viruses....

Burns clean (for coal anyways)   -  When burning Anthracite, no trace of black smoke will emanate from your chimney once up to operating temperature.

Compared to wood, coal stoves are very efficient.  Stack temperatures average well below those of wood stoves that usually run at 60% efficiency (typically here: only 250 to 275 deg f stack temperatures even when putting out full 92,000 BTU's) per hour. In other words, much more of the heat goes to heating the building interior, rather than going up the chimney !)

Though recommended to be shaken down twice daily, unlike wood stoves that must be constantly stoked and banked for the night, most air tight coal stoves will easily run 24 to 30 hours without being re-fueled. (Translation: You will awake to a warm toasty house with the stove still outputting full BTU's!)

No Creosote buildup.   Unlike wood based fuel products, there is no creosote build up, and thus little risk of a chimney fire. (Far fewer chimney cleaning tasks - though you're still going to want to check it).

Since there's no creosote buildup, roofing shingles will not become stained.

Coal stoves by default, will also happily and successfully burn wood, which makes them very versatile in a pinch !    (Note: a wood stove designed to burn only wood, will not be able to burn coal.)

Unlike a pellet stove, non self-stoker models are not dependent on electric power.  You may not have the electric blower when the AC goes out, but it will still most likely "roast you out !)

Coal is still reasonably cheap - half to one third the cost of heating with oil & about 36% less than the direct cost of heating with wood.

Coal heat is not for everyone however.... 

before rushing right out to buy one, first consider some of the downsides which many folks would never tolerate.

Ashes must be shaken down twice daily & emptied (depending on the size of the ash pan)  once per day.  It's not optional....   Your stove may be different, but that's the "norm"...   (A pain in the "butt" and you'll need insulated welders gloves or equivalent to transfer the hot ashes outside to dump in a galvanized steel barrel.)

Be willing to accept in a few months, everything in your home being covered in a splendid "patina" of fine light grey coal ash....  No matter how careful you are about containing ash dust, there's no avoiding it.  Course, if you love to dust, then you'll think you've died and gone to heaven !    For those not so blessed with that affliction, a good standalone Hepa Filter helps a lot, plus as a major side benefit, also circulates the warm air. Before getting your hopes up too high and regarding the filter as "problem solved", it does not completely eliminate the ash dust.  (We use a Whirlpool AP510 available at Sear & Roebuck)...  If your house  must always pass the "White Glove Test" (or perhaps more accurately the Grey Glove Test for that matter)  then don't even consider burning coal (or even wood for that matter)....  Just grin and bear your outrageously high priced oil, gas or electric bills !   No matter what the ads proclaim (or fail to mention), the reality is that a coal stove is for those who value it's even, low cost radiant heat  far above any minor dust/ash concerns.

Put another way: If a toasty 80 degree house in the dead of winter is your primary focus, then by all means get a coal stove. If a clean dust (ash) free house is a mandatory requirement & you love the convenience of a "set it & forget it" idiot proof thermostat, then stay with  gas, oil or electric.  Personally after outside in sub-freezing weather, I want to come in to a toasty house !.... and don't want to have to put up with having to wear heavy clothing inside just to survive another Maine winter !  (at least without having to go broke)...

Coal stoves take a long time to get up to temperature and a long time to cool.  Unlike a pellet stove, they cannot be "throttled back" nearly as much or instantly "switched on and off".  If you just want a fire only for the early evenings, then coal is not for you....  It takes far too long to get one started and build up a good bed of coals.

You'll need a safe place to dump the ash or bag the cold ashes after they've cooled for several days, for local trash pickup. (another chore added to your list)

Similar to the requirements of a wood stove, you will need a well designed chimney with a good draft.

In high wind conditions, expect an occasional back-draft.  (Where the winds swirl outside in such a way as to blow back DOWN the chimney & out the stove).    Even with a good chimney, it's a rare but "memorable" event the first time you experience it !  - - - A simple chimney cap will negate much of this effect.

Coal stoves by their very nature are HEAVY (figure about 600 lbs when loaded with coal)...   Then add another 1,000 lbs or so for a good brick/slate base plus backing on which to site it.   Your floor structure must be able to easily support the total load.

Coal stoves must NEVER be left running completely unattended for long periods of time.   You must religiously remember to constantly check the position of the air regulator when getting it started....  If there is no one living at home to attend and monitor it when operational, then a coal stove is not for you..  Once up to temp and stable then it's ok to focus on other things, as once burning normally, there is no further adjustments...

Our Garage coal stove and the one aboard the boat have thermostatically controlled air regulators (The Harman that heats the house, does not)   Getting coal started requires quite a bit of oxygen, so even on those, one MUST remember to re-set the thermostat once it's up to temperature & burning normally

Unlike a wood stove, getting a coal stove started is a pain....  (there's no other way to put it !)    Figure on 3 to 5 hours to get it fully up to outputting full BTU's with a good bed of coals. Then figure another 6 to 8 hours just to shut it down (though you'll probably never want to do that til spring - -  (at least by choice))....

Operating a coal stove is much like driving a car, in the sense it requires common sense to safely operate.....  Running it "Cherry Red" or even hotter, will result in a warped grate/damaged stove at best, or a devastating house or chimney fire at worst.    You must know it's quirks (that's a topic not mentioned in any of the ads !).... There are no built in alarms, auto-shutdown or micro processor controlled runaway safety features of any kind.   YOU alone are its' primary  and ONLY safety feature !    To put it rather bluntly:   they are NOT "idiot proof"...   

With that said: Our ancestors as well as successful coal/wood burners today, had/have no trouble...   Generations of families where knowledge of how to safely operate them was passed down from generation to generation - all without incident...    All my Grandmother's kids  swapped weekly chores of taking care of the central heat coal stove (and they were 10 years of age at the time when first assigned the chore). It's not "Rocket Science" & all it takes is some very basic common sense.   However; It is NOT merely setting a wall thermostat & forgetting about it either...   Don't even consider a coal stove unless you intend to understand their individual quirks , and in a sense "bond" with it.   The air regulator on a coal stove is like the accelerator on your car ( I keep on using the "car analogy")   If used correctly, it will safely get you to where you want to be (like: toasty warm !).  Ignore its' "throttle" setting, and it can result in being made homeless or worse !       If operated within its' parameters, it will provide you an inexpensive source of cozy, convective and "therapeutic"  radiant heat unsurpassed by any other heating methodology.

For those that live near the ocean, the analogy is this:  Similar to the ocean, we love it's ambience...  But like the ocean, neither is it wise to turn your back to it for too long... 

With that said, once up to temperature, no further adjustment is usually required !

You will have to get to know your stove.  I have 3 of them (1 on the boat - a Gi-normous Hitzer that heats the garage, and the large Harman heats the entire house).  All of them behave slightly differently....

Once every 6 weeks or so when burning 24/7, you'll have to shut it down and let it cool to remove the unburned "chinks" of coal that sometimes builds up to the point of blocking the airflow and sometimes even losing the fire. (another task)   What are "chinks" I hear you asking ?   Well "chinks" are those bits that are not pure coal and thus do not completely burn.  As they build up, they remain above the grate and block the airflow to the point that the burning of the coal bed is not efficient, or sometimes even possible...  When that happens, the only solution is to shut the stove down, clean it out, and start again...

Unlike a wood or pellet stove, a coal stove cannot be "throttled back" nearly as much. Coal likes to burn over a narrow temperature range.  Though you can vary its' output a bit, it's most efficient when burning hot.  (When properly burning, nearly all the coal will be reduced to a very fine ash, with few unburned chinks.) Thus on warmer days (temps above 30 deg f.) you'll probably have to "crack" some windows to keep from being roasted out.  Attempting to throttle it back too much, will most likely result in losing the fire...

And if all this hasn't dissuaded you, beware that Anthracite Coal or even high sulfur coal  is not readily available in some parts of the country !

Anyways, if  "Ole Bessie" should "give up the ghost" here tomorrow beyond any hope of repair,  then before the end of the day, I'd have a new one on order.

The Hitzer 82 is designed to burn either Coal or wood. I've had it since 1992 and performs as new, also pumping out 92,000 BTU's. What's unique & a very desirable feature, is the thermostatically controlled primary airflow regulator.



Tips on Purchasing a Coal Stove


Having grown up with them, I figure that makes me somewhat of another self proclaimed expert ...  (read: ok... maybe not an expert.  more of a "take it for what its' worth in the "school of hard knocks" dept).

Here is what I personally look for  - (or don't look for):

Stove must be of an airtight design. Not also will it burn efficiently, but this alone is a major safety feature. Should you ever over-temp the stove, or a chimney fire ensue, closing down the air regulator will cut off ALL the air supply......   Short of hosing it with water which will crack cast iron or warp steel plate, it's the safest way to immediately "turn it completely off" & let it slowly cool naturally without damaging the stove.

Burning coal does not result in a creosote buildup as does burning wood. However, a coal stove will happily burn wood and some people will switch between the two fuels.  If you burn wood in it, you  WILL have creosote in the chimney that accumulates with each wood burning.  Merely switching back to coal does not make it magically go away.... It must be physically removed...  Should a chimney fire ever get started, (the result of the creosote igniting)  this is one time where you will wish you spent the  $ on an air tight design. In a properly designed system, closing the air regulator, also cuts off the air supply that is feeding the chimney fire in a properly designed chimney system.

Have an internal baffle system so the hot exhaust  gasses follow a long serpentine type path to the chimney. This  effectively increases the surface area and extracts the most heat before it exhausts up the chimney.  In some designs, it results in a secondary burn further reducing emissions and extracting  even greater BTU's.  The greater the efficiency also results in reduced stack temperatures.

A blower and air system also designed to blow cooler floor air through internal channels , so as to again, extract the max amount of heat into the living space.

Be at least 1/4" steel plate or cast iron construction for stoves intended for 24/7 continuous operation.  Note: Steel plate construction stoves (though not as "quaint", are much easier to repair using a standard AC Arc Welder. (Cast Iron is MUCH more difficult to weld - requiring MIG welding equipment and far more welding skills & experience !)    With that said;  a cast iron stove if not over-temp'd, will most likely outlive you and possibly several generations of your descendents !

Internal firebrick design.  This keeps the hot coals from burning through the metal over a period of years (or over a span of a few minutes in the case of carelessness or committing an act of sheer stupidity).

Shakedown grates (almost all coal stoves are equipped with these). Warped grates are an indication that the ash pan was not emptied. The grates that support the red hot coals depend on the natural draft of cool room air passing through them to keep them cool and thus from warping. An overflowing ash pan blocks off this much needed cooling airflow, and warped grates will be the result.

View window is nice, but also not necessary.....    (just one more thing to keep clean).  Even if you manage to keep the viewing window clean, coal to look at, doesn't burn "pretty" like wood or even pellet stoves.  No romantic flickering flames or crackling sounds !  (How boring) ....   Just a steady, silent, dull red glow.  By not having a "view Window",  you're not missing out on any real excitement ...    Truth is:    there isn't any !  -  Might be visually/audibly "dull" if not downright boring, but the suckers will pump out an even steady stream of raw BTU's, that few wood/pellet stoves of comparative size can come close to matching for far less cost !

Purchase a stove that  has the capacity to easily heat the desired space.  The fact that this takes position #8 is not to mean it's of little importance.   The reality is, that too small a stove, and you'll be too tempted to over-temp it to stay warm ...   The lure of keeping warm when the outside winds are howling and the outside thermometer reads  a number that could have been recorded in Antarctica, and you will be too tempted to over-temp the stove.  Far too many times common sense has taken a back seat to shivering and trying to stay warm.  Get one with enough BTU output to do the job....

Too large, & you'll be continuously roasted out (or praying for sub-zero outside temperatures)...  Neither will the stove burn efficiently if operated too cool.  The fuel will not be completely burned resulting in too many unburned "chinks" and higher emissions....    There are a lot of variables, but a good rule of thumb is to figure on a stove rated at 70,000 BTU to heat a 2500 square foot living space if the building envelope is tight and well insulated, & 90,000 BTU for even typical new construction that has not been surveyed & optimized. (See Below...)

If the size falls on the cusp and you can't decide, then always opt for the next larger BTU output, unless there are other extenuating circumstances such as physical size constraints, flue position etc.  Ironic as it first may seem, a larger stove that is operating at it's normal "Q" point, will consume LESS fuel than a smaller one operating much hotter, yet  providing less BTU's  to the living space.  (for those that doubt the validity of this statement, ponder the immutable  2nd law of thermodynamics for a bit)


Wood Burning Stoves - Advantages

Ever since a kid, we burned mostly coal with some years spent burning wood. However, the first 2 years after moving here were spent heating entirely with wood - the result of land clearing and winter blow-down.  (Free heat as it were !)    Though today I burn strictly coal,  I'm not against heating with wood....  it does have some several distinct advantages over coal.... 

Namely, nothing beats the smell of burning wood that permeates the entire house with a highly desirable pleasant aroma that has never been able to be artificially duplicated.  It's almost akin to the wonderful aroma of freshly baking bread. If it could, I'm certain it would corner an important segment of the air freshener market ! ( at least for some of us) 

Wood burns with a bright flickering glow, complete with stereophonic hi-fi crackling sounds. It's both a magical light and audio show that is mesmerizing, hypnotic and triggers some deep primal instinct in all of us, suggesting a strong sense of  warmth and security.  Which one of us hasn't  gazed into a crackling campfire not having experienced it ?   Whatever it is, it's deeply ingrained and genetically programmed into our psyche. I really miss that aspect...

Closely tied to that, is that gazing into a crackling fire is amazingly relaxing...  Stress is generally recognized as being a killer....  Perhaps no better stress reliever (read: "medicine")  than gazing at a crackling fire on a cold winter's eve curled up with a cat or two in your lap....

Wood ash is more environmentally friendly. In fact; it makes for a great fertilizer when spread over your lawn,  garden or flower beds  !

Wood Burning Stoves - Disadvantages

Burning wood does have some major disadvantages as compared to coal however... (not many - but unfortunately, significant)

Even the best wood stove will not burn cleanly & evenly for 24 hours straight.  Most must be "banked" for the night, & even then, one will probably awake to a chilly house.

To effect a longer burn, some decide to close down the regulator to the point where there is a slower burn so they don't wake up to a cold house.  Although effective, doing so is not wise: As the temperature in the combustion chamber drops,  the amount of un-burnt creosote generated, skyrockets.  That's  a recipe for a potential chimney fire.

Wood should be seasoned. Green wood burns dirty, produces far less heat & adds dramatically to the dangerous creosote woes.

All wood burning results in a creosote buildup in the chimney.  Creosote is simply the 4 letter word of wood stoves...  If not removed & cleaned religiously each year, the risk of a chimney fire and possible loss of the entire house (not to mention your life) is far greater.  One chimney fire is enough to ruin your entire day (and perhaps everything else the house contained)...  I rated this #3, since the simple act of cleaning the chimney, solves the problem. It's not a big deal - just a simple task to be added to your winter prep list or chimney sweep service to call.

Wood should not be stored inside - especially old wood that may harbor termites and carpenter ants.    Ergo: the concept and invention of the woodshed...

Unlike coal, wood must be cut & split..... though at first a novelty to some; trust me:     The novelty will soon wear thin !

Pellet Stove Advantages

Though this page is not intended to discuss pellet stoves, their advantages/disadvantages does warrant some brief comment.

Generally burn reasonably clean - cleaner than either a wood or even a coal stove...  Far less ash in the house since there is not the constant need to shake down and empty the ash pan at least every day.

Can be "turned on and off" usually in a matter of seconds. (Great for folks with someone not always at home all day)

Automatic feed, thermostatic controls and auto ignition on the more advanced models - set it and forget it !

Can be throttled back to meet the heating needs

About as close as one can come to being idiot proof !

No splitting/stacking of cord wood.

Almost "too good to be true" ....  What's not to love ?

Pellet Stove Disadvantages

The real "Biggie':    No electricity = No heat  
that's  a major disadvantage here in Maine where a good ice storm can take out power over a wide spread area for a week or more.

Because the pellets are accurately metered into the burn pot and the pellets are consistent, the flame is very even. No "wild dancing" of the flame or much of the way in changing colors...

Pellets are consistent in moisture content...  That means no neat crackling sounds

Though manufacturer's have gone to great lengths to reduce the noise, blower and auger motors are not silent, thus detracting from the experience in my opinion...

Expensive auger motors that despite most marketing claims, last only on average 3 years before failure  (Figure about $300 for a new motor - installation will run you a bit extra  )

Even the largest room pellet stove available, is no BTU match for a large coal  stove that sells for about one half to one third the cost.

Far more expensive to purchase and to operate than a coal or wood stove.  Outrageously over priced in my opinion...

Although they generate far less creosote than a wood stove, the chimney will still need a cleaning and an annual inspection.

Pellet shortages are likely, as the demand for pellets begins to outstrip the supply. The law of supply and demand, dictates that pellets will cost more per BTU than will coal.

The biggest downside:  Pellet stoves are Technically far more complex. Motor driven augers, blowers, temp sensors, flame detectors, micro-processors to control every facet of operation depending on what data the sensors are feeding it...   Like anything else complex, there is simply too much to break and go wrong...    There are many cast iron coal stoves still in operation even after 100 years or more..  I dare anyone with a pellet stove to find a source of high tech circuit boards and microprocessors to maintain them in only another 25 years...    In short: they are far too complex and have relatively short lives.  Simply too many things to go wrong, which means that it's a mathematical certainty that they will !

Coal Burning Links and Forums

The following links make for interesting reading. However, beware that like any other forums, some of the opinions are posted by those with little or even no experience or understanding about why coal stoves behave the way they do, purpose of dampers, use of barometric dampers etc etc etc...  In contrast, there is much valuable info from those that have years or literally generations of  practical "hand me down" experience in the operation/maintenance/installation of wood or coal stoves.   As with any open forum, you will be forced to sift thru it to separate out the truth based on the physics involved, from personal opinions, rumors and just plain good old fashioned BS from those proclaiming to be "experts" without themselves ever having owned or even experienced a coal stove in operation !  There are more of those than you might ever first suspect !

There are many examples of inaccuracies on some of these forums and even some dangerous ones should you opt to adopt them and understand that all recommendations will be safe for your situation.  Here's one ....

Barometric Dampers

Guess first order of business is to explain their purpose. 

Nearly every oil burning furnace has a barometric damper usually mounted just above the stack exhaust port.  It's purpose is to isolate the burner in the furnace from changes in pressure at the chimney exit.  (HUH ? you're probably muttering..)  

The rapidly expanding warm air in the combustion chamber, creates a higher pressure, and thus the air pressure at the bottom of the chimney is greater than that which is cooler at the top or exhaust of the chimney.  That part of the effect is similar in concept to a mini jet engine or even the internal combustion engine where a small amount of air is taken in, then heated and a greater volume under pressure is expelled. The concept and rules of physics don't change just because the combustion chamber is now called an oil burner, coal or wood stove.. 

The other dynamic in the chimney effect is that the expanding warm air is less dense than the colder air above. The warm air will naturally want to rise just because it is more buoyant than the denser and heavier cold air above. It wants to rise like a cork in water !  The two dynamics working in concert, create the natural "chimney effect" as it's so aptly named,  which also creates the draft or suction to expel the combustion byproducts....

There are many times when the draft can become too great, as the natural draft is dependent on a number of various factors such as :

Wind direction & velocity that can sometimes create a venturi effect as it blows over the top of the chimney. A simple chimney cap which you should have anyways just to keep out rain and animals, creates enough turbulence to negate much of the venturi effect.

Infiltration where the wind blows in thru voids  on the windward side, and pressurizes the building envelope. The higher pressure will result in air trying to achieve equilibrium by escaping thru the air regulator.  The pressure differential increases the draft the stove sees.... This is often the major source... not having a barometric damper is not the problem.... Instead the house leaks like a sieve !    (Read further on how to locate them).

Topography also can play a role in hilly or mountainous country where downdrafts can play havoc by attempting to "ram" air back down the chimney. The effect is called a backdraft.  Again, a chimney cap can help here again as well.

Temperature Differential...  how hot is the fire and outside air temperature thus temp differential. The greater the differential, the greater the chimney effect.

There are others, but the first two often account for the Lion's share, where wildly fluctuating drafts are experienced. When that happens, the chimney suction can be greater than the furnace’s needs. (In most cases, the first two or even 3,  can be easily remedied or the effects greatly reduced)

The crux of the matter is this:

Oil burners only operate efficiently over a relatively narrow range of chimney draft.   Why so "finicky" ?  The fuel sprayed into the combustion chamber is accurately metered and the pump and nozzle deliver a consistent, accurate supply of fuel. In fact, the nozzle size will be specified in gallons/hour. An abnormally high draft serves to draw in more air than normal into the combustion chamber thus leaning the mixture beyond it's point of peak efficiency as well as disturb the flame pattern, much as a room draft causes a candle to flicker.  Too little draft and the mixture would then be too rich. (No different than a fuel injected engine)-  To compensate for an over-draft, the counter weighted flap of the barometric damper rotates open and lets cool room air into the chimney. This mixture of much colder ambient room air added into the chimney, cools the air column in the chimney which serves to reduce the draft. The sheer volume of air added also serves to equalize the differential, but the main dynamic in play is that the influx of colder room air cooling the air column in the chimney, which serves to reduce the chimney effect.

The purpose of the barometric damper is not to directly regulate the burn, but to stabilize the draft under various operating conditions.  In an oil fired heating system where the fuel is sprayed in, a steady even draft is necessary for a clean efficient burn. Any wavering or "flickering" of the flame, results in inefficiency...

Use of a Barometric Damper insures a steady draft, and thus a steady stable flame in the oil fired burner combustion chamber...

Why a Barometric Damper should NEVER be used for a wood burning stove or cases where a coal stove is used to burn both.

First thing I should point out is that it is not that Barometric Dampers cannot be used on wood burning stoves, in fact, they will allow a more stable draft if set up properly.   The problem with them and real danger when used in this application comes should a chimney fire get started...

All the benefits of a barometric damper as they apply to oil fired furnaces, don't translate well to wood stoves or coal stoves even occasionally used to burn wood (other than that used only to start the coal stove). There are some notable differences...

First of all, Barometric Dampers are simply not required for air tight wood or coal burning stoves, which happily operate over a wide range of conditions (unlike an oil fired furnace that accurately meters the fuel and requires a stable draft to maintain a stable consistent flame). Unlike an oil fired furnace, the fuel supplied to a coal or wood stove is anything but accurately metered in that sense. It is metered instead by the air supply.  The more air, the hotter the fire and more volatile gasses are emitted from the coal or wood and vice-versa. The fire and thus heat generated, itself becomes the fuel metering system.  Once a wood or coal stove is up to temperature, changes in the chimney draft make very little difference in the rate of burn. It's the size of the opening (air source regulator) that primarily determines the amount of oxygen supplied for combustion.  Yes, having a barometric damper would make for a more stable draft, but you simply don't need a barometric damper on a coal or wood stove. There is more than enough thermal mass in the stove itself and the mass of it's own fuel supply to smooth out any transients in the draft even if it did make much of a difference...  WHY ??? - - -  Consider an oil furnace reaches a full burn in about 3 seconds and goes out nearly instantly when it shuts down.  Not so a coal or wood stove that often takes over an well over an hour or two to build up a hot bed of coals and many more hours just to completely extinguish.    Short term transients in the draft make little difference......   Not that you can't use a barometric damper on a wood or coal burning setup, it's just doing so is unnecessary & potentially extremely dangerous.  Here's why.....

Though coal when burning does not generate creosote, there are some that use their coal stoves to burn wood when it is available, which does create creosote. If all you do is burn coal in a coal stove, then all  is well, and you can choose to ignore the dangers of Creosote build up in chimneys, since burning coal generates no creosote. 

Should you have burned wood even in a coal stove, Creosote once ignited is a wonderfully rich source of fuel. When it builds up to the point where there is enough to sustain a good burn, all it needs is a source of ignition and an adequate oxygen supply.  Your wood/coal stove will supply the heat and flame necessary for ignition (especially with a wood fire or getting a coal stove started or when careless and left to burn cherry red).  Normally the rising air column is made up of exhaust gasses that are somewhat deficient in oxygen, thus making it more difficult for any creosote build up to ignite.

In the case of an air tight stove, should a chimney fire get started, the chimney's only air supply is from the exhaust gasses of the stove itself, which isn't much, and what there is of it, is not all that rich in oxygen.  A chimney fire then is then a much less spectacular event. It might seem ironic, but in many cases, you may not even be aware that you had one !

Use of a barometric damper in the event of a chimney fire however, makes for a completely different scenario which will prove far more memorable.....  It's normal operation now introduces a nice oxygen rich mixture directly into the chimney from below, where all that's needed is an ignition source. Not too tough to figure out what that might be (after all, they are stoves !)  Once the creosote ignites,  the genie is now out of the lamp so to speak.  The chimney itself has now suddenly become the combustion chamber....  a chimney and combustion chamber all rolled into one with a rich oxygen source being supplied from the barometric damper...  An engineer would be hard pressed to design anything more efficient for converting fuel into heat with the materials at hand in the shortest possible time span....  The chimney stack temperature now climbs dramatically, and the barometric damper in a futile attempt to cool the air column and thus reduce the draft, now opens fully. That introduces all the oxygen rich air into the chimney needed to feed a raging chimney fire. Within minutes, chimney temperatures can soar to well over 1800 degrees (and no chimney liner is designed to tolerate such temperatures).   You now have a runaway condition....  The hotter it burns, the greater the draft, and the greater the draft, the hotter the fire etc etc etc ....  and the barometric damper is all too happy to supply all the oxygen it can muster !    

With the barometric damper  fully open and a chimney fire now raging, you will hear a load roar of air being drawn in thru the barometric damper.  Pretty dramatic I'm told...  There will be no mistaking that chimney fire...

Until the creosote is finally burned or the oxygen source cut off, now it's just a matter of time before the house is lost. This happens either due to the now hot chimney igniting the surrounding structure or the hot embers of burning creosote being blown out onto the roof which then itself ignites. A chimney fire if nothing else, is often spectacular !

Yes, one could close the barometric damper as well as religiously having the chimney kept clean, is the argument . But the reality is that not everyone has their chimney swept every season, and many of those burning coal are lulled into a false sense of security, forgetting about the times they opted to toss in some pine logs for a romantic evening experience watching the flickering flames or simply switched to wood if it was suddenly more affordable or available !  Most chimney fires where the house was lost, started at night when everyone was asleep or no one was at home.   Point is: Anytime you operate a wood/coal stove effectively unattended with a barometric damper as part of the system and the chimney has any creosote, you could be playing Russian Roulette.

Amazingly, even some manufacturer's of  wood stoves even recommend installing them....

Again... No problem if you burn coal and only coal, as then there will not be a creosote buildup....  But should a chimney fire ensue, you will curse the day you ever installed one..

Standard Manual Air Damper

A standard damper is a completely different device. This was invented in 1801 by Count Rumford and it served several purposes....

regulating the draft
serve as an emergency shutdown.
preserve room heat by closing off the chimney when the stove was not in operation
to regulate the fire in the case of non airtight stoves or the open Ben Franklin design type stoves

Instead of regulating the chimney draft by introducing cool room air into the chimney, it instead is mounted in the stove exhaust pipe and serves to cut off the draft the stove sees by literally blocking the exhaust pipe.  Thus a manual damper is a completely different "beast"... This was the first type of damper invented and widely adopted.  It was designed specifically for coal & wood burning stoves. Might be 200 year old technology, but no one yet has come up with anything better !  The installation of a manual damper is highly recommend for non-airtight stoves. For air tight designs, the use of a manual air damper is rarely required except in the case of the most severe excessive draft  problems.

When understood and used properly, a manual damper affords in the case of non-airtight stoves, a necessary level of both draft and rate of burn control. Shut it down too much, and you risk a smoke filled room or in case of coal, CO2 poisoning.

Having an air tight stove does not give you license to be careless.  Chimney's still must be inspected, the stove never over temp'd etc etc etc....  We love our stove's warm radiant heat  and will snuggle up to it on those cold winter nights or in cases of bouts of the flu.  It may be your best pal, but neither is it wise to turn your back on it for too long. 

Pay attention !

* * * * * * *

With that said, there is a lot on the web concerning heating with wood, coal, pellets, cherry pits, soy and even corn in the Midwest   (guess they don't call it the "corn belt" for nothing).  There are also many books written on the subject,

There is a lot of good information on the web... You'll just have to do your homework after listening to some of the conflicting suggestions.  The following is one of the better sites.



Bottom Line:

I suppose everyone has an opinion, so consider perhaps this but another added to the heap.  But no matter one's opinion,  rationalization, agenda or personal viewpoints, the laws of physics and thermodynamics are rather rigid, stubborn, pig headed and unyielding, no matter how much each of us might believe or wish they weren't so....


BTU Equivalency of Common Heating Fuels

When purchasing any fuel, keep in mind that you are really buying BTU's * whether you pipe it, pour it, shovel or stack it.   It's all just BTU's, but in different forms... The following are the heating equivalencies for the common heating fuels.  Note: when comparing costs, beware that  electric heat is 100% efficient, where a coal stove for example averages 75% and a wood stove averages 60%. Thus the total cost to take in to consideration, are what numbers of BTU's can be extracted and used.

Anthracite Coal:  1 Ton                                                     25,000,000 BTU's / ton

Natural Gas: 1,000 cu ft (1 mcf) yields                                 1,030,000 BTU's/ mcf

LP Liquid Propane Gas   per gallon                                        91,600 BTU/gallon

Electricity:  1 Kilowatt Hr yields 3413 BTU's                              3,413 BTU's/kwh

Oil:  138,690 BTU/Gallon                                                        138,690 BTU's/gallon

Wood Pellets: 17,000,000 BTU/ton                                     17,000,000 BTU's/ton

Hard Wood - White Oak - Seasoned                                  24,700,000 BTU's/Cord**                      

* BTU - British Thermal Unit...  the amount of heat energy required to raise the temperature of one pound of water by one degree F   ( 1 gallon of water weighs 8.34 lbs)

** 1 Cord of wood = 128 cubic feet, or a pile 8 ft long by 4 ft high, by 4 ft deep.

1 Ton of Anthracite Coal has the energy equivalent to: 180 gallons of home heating oil, 1.47 tons of wood pellets,  24,271 cu ft of Natural Gas, 272.9 Gallons of Liquid Propane, 7325 KWH of electricity or about 1 cord of seasoned white oak in terms of the total BTU's the various materials contain. 

Fuel Cost Comparison - Coal - Pellets - Oil - Natural Gas - LP Liquid Propane - Electricity - Hard Wood



* Here's a useful link to compare the costs to heat with different fuels. 

http://pelletheat.org/pellets/compare-fuel-costs    (Pellet Fuels Institute - 1901 N Moore St - Suite 600 - Arlington, VA  22209   703-522-6778)

The default prices are not always kept current, so you will have to research your own local area prices. The computation does take into account the efficiency of the type of stove or appliance you would be using.  (Not all appliances with the exception of electric based ones that are always 100%, have the same efficiency).

The image to the left is based upon fuel prices in effect in the Midcoast Region of Maine last updated 10-5-2010. We only occasionally update this, so you will have to research the prices in your area and Plug them in as appropriate.

The cost for different fuels can vary widely in different areas of the country especially  as in the case of coal & wood pellets, where transportation costs when factored in to the price can dramatically affect the residential price.  Efficiencies of  various stoves and appliances can also vary.   The heat content of various hardwoods can also vary widely depending on the species & moisture content.

Market prices for home heating fuels can vary even over a matter of a day - especially in the case of Oil, Natural & LP Gas as traded on the International markets....

There are a LOT of variables that affect the total number of BTU's you must purchase. But for Midcoast Maine in the typical 2500 sq ft living space of average insulation and tightness of the thermal envelope with minimal solar loading, figure on  80 million to 100 million BTU's  to stay comfortable over the long frigid Maine winter.  This place based on prior history, requires  only 57.5 million BTU's in a typical Maine winter, and that's keeping it at 80 deg f, but with passive solar & a tight building envelope. To get a good handle on your upcoming costs at current prices for the typical structure, refer to the section on Heating Degree Days near the top of this page under the weather graphs.

* Note in the case of natural gas that 1 Therm is the equivalent of 100 cu ft.  Thus 10 Therms = 1,000 cu ft .    The prices used here are what the end consumer pays. (The prices were last updated Oct 5, 2010)


The following was a humorous comparison of the Economic Justification for Wood Burning  vs. oil.

There is probably more truth in it than one might first suspect however....

Humorous or not:  Anyone who contemplates burning wood as a heat source, will undoubtedly experience at least half.


Description     (values rounded to nearest full dollar) Credits Costs
Top of the line Wood Stove with approved chimney -  fully equipped and professionally installed   $2777.00
Pay plumber to remove hot water baseboard system w/boiler (no longer needed)   238.00
Sell hot water baseboards w/boiler 125.00  
Pursue reputable wood dealer     (unfortunately, none available to be found)   76.00
Buy Inexpensive (Cheap) Chainsaw   210.00
Axe, hatchet, wedges, maul, cant hook   119.00
Old truck - scrapped   (rusted bed fell off under first heavy load and also snapped a spring)   595.00
New four-wheel-drive truck - including taxes & dealer prep   21283.00
Insurance & excise tax on new Pickup truck   893.00
Wheels chains (all 4 wheels)   133.00
Replace cheap chainsaw  that seized with commercial quality one   753.00
Replace truck rear window   (twice)   388.00
Work gloves (swiped from Shop)   Free
Sell old chainsaw for parts on eBay 14.00  
eBay service charges   5.00
Pay to have old Pickup towed away & scrapped      (unable to even give it away)   175.00
Fine by State and local Warden for cutting wrong trees   1000.00
Purchase 10 acre woodlot   14250.00
Lawyer's fees, closing costs, Transfer tax on woodlot   722.00
Wood splitting machine (30 ton heavy duty)   1699.00
Trailer for wood splitting machine   583.00
Miller Beer - 14 cases      126.00
Ginger Brandy - 6 fifths     (for medicinal purposes only)   44.00
Fine for littering   250.00
Towing charge (creek bed to hardtop road)   150.00
Gas, oil, chain sharpening, and Band Aids   97.00
Doctor's fee for splinter removal from eye   310.00
Safety glasses    (also swiped from Shop)   Free
Medical costs for broken toe: Emergency room,  X-Rays , cast  etc     (log fell off splitter onto toe)   1274.00
Crutches   145.00
Safety Shoes     (with OSHA approved steel toe)   79.00
Repair burned hole in living room carpet   -  (unsuccessful)   77.00
New Living room Carpet   699.00
re-paint living room walls and ceiling   145.00
Taxes on woodlot   723.00
Wood lot boundary dispute settlement legal fees   1500.00
Roof repair after chimney fire   1234.00
Fine for assaulting fireman & policeman  (2 counts)   3000.00
Extension  Ladder   90.00
Chimney Brush   55.00
Medical costs for broken leg   (fell off roof)  Crutches were re-used however, at no additional cost   4857.00
Chimney cleaning service   90.00
Coffee table replacement   (chopped up and burned while too cold & drunk to locate firewood pile)   277.00
Divorce Settlement   157556.00
Annual Fuel Savings  (last year's oil bill no longer applicable) 2753.00  


2892.00 217677.00

Net Profit / Loss after First Year Wood burning Operation:                            - $ 214,785.00

Last Modified:  Nov 12, 2011

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