Sierra Club looking for response to reader's question

[John Ackerly]

A writer for the Sierra Club, Bob Schildgen, aka Mr. Green, forwarded me a question from one of his readers about wood stoves. He is looking for response of "experts." I told him I could post his question to this list and we can collate best responses - minus everyone's names. Then, he will give credit to hearth.com in the Sierra Club magazine and/or their website, wherever they use the response. So, please offer some insight and this can be good way to get hearth.com out there to a bigger readership too.

"We have a small to medium size woodstove that resembles a Mama Fisher, Baby Fisher, etc.: an old Sweet Home with a front load, recirculating passive damper system for a 1200' house. We have a chimney thermometer just above the stove and by watching and inspecting, we have never had to clean the metalbestos 6" diameter pipe chimney for ten years.

"Some say a wood stove heats the house faster if you always leave the stove's front door open (with a firescreen to catch sparks). Some say the stove door must be closed after the chimney reaches operating temperature (about 250 degrees) for the stove to circulate air inside the firebox and burn efficiently. Some say just close the door after you got it started, and MYOB.


"I use the middle way, reasoning that if stoves worked so well with doors open, then they would put screens on the stove doors instead of glass or steel. Either way, we use paper or cardboard to get to 250 degrees, and we never need a chimney sweep. I also reason that if stove doors are open, the heating efficiency is like a fireplace, maybe 20%. If the doors are shut, I presume a reasonable simple woodstove would be about 60% for a fisher type, a recirculating passive type, 80%."

Thanks!

 

[begreen]

This is not a simple question. There are so many variables in stove and flue design, the wood being burned, stove maintenance and operation, that a simplistic answer might serve to confuse more than educate. I would say that the unspoken difference for this user is that they are burning well seasoned wood and keeping the flue hot enough to avoid creosote accumulation. However, I wouldn't recommend that anyone skip cleaning a chimney for 10 years unless it is closely inspected annually. Along with dry wood, the biggest single improvement the reader can make is upgrading to a properly installed, modern EPA stove. Burning with the stove door(s) closed is the correct way to burn for best efficiency.

Craig has a good article to quote from. Look down the page to the section Ten Steps to maximum wood burning efficiency.
https://www.hearth.com/econtent/index.php/articles/choosing_and_using_wstove

 

[jeff_t]

So what's the question?

 

[DanCorcoran]

So what's the question?

Yep, not a single question mark in the "question".

 

[nate379]

The Sierra Club would allow a wood stove? I figured they all lived in dirt huts becoming one with nature.

 

[eclecticcottage]

I'm not really sure what the question is, but I agree with begreen.

I am reasonably sure an EPA stove, and probably those that are considered Pre-EPA, are made to be burned with the door closed. We've burned ours with the door open a few times, and we've observed to to be smokier, and not as effective at burning all of the wood. I can see why someone would think that it would heat better with the door open. When you open the stove with a good coal bed, you'll get a blast of heat, which would lead you to just conclude that heat is being wasted. However, I find our stove NEEDS the heat to effectively use the tubes and reburn the offgassing, thereby reclaiming more "waste" to be used as heat.

It would be interesting to see a controlled study of these to see what the real differences are. Like two exactly duplicate "rooms" with the same stove, pipe, etc burned with the same size, species and moisure content splits burned for the same time. A measurement of room temps and particulate released from the flue.

 

[dorkweed]

The Sierra Club would allow a wood stove? I figured they all lived in dirt huts becoming one with nature.

x2 there!

 

[jharkin]

Maybe I'm dumb...but what the heck is a "recirculating passive stove" ??


I believe the question is what's more efficient, door open or door closed.

 

[begreen]

"recirculating passive damper system" - I'm hoping this is not a magic heat, but it sounds like one.

 

[KaptJaq]

I know each situation is different but in general I need to keep my door ajar until the wood is completely involved. At that point the stove is hot enough to create a strong draft that can pull air through the small openings of the secondary air tubes. I seal the door and slowly reduce the primary to maintain the secondaries. At this point the stove is pulling the least amount of heated air up the flue and burning fuel most efficiently. The secondary burn tubes are burning the fuel that is normally lost up the flue as smoke.Due to this increased efficiency less wood is needed to generate the same amount of heat in the house.

With the door open the smoke exits the flue too quickly to be burned by the secondary combustion. Due to the reduced air flow up the flue with the door closed there is less cold replacement air required to infiltrate the house. Rooms not near the stove do not get as cold. With the door open the stove room gets hot fast but the rest of the house cools down.

If sealed stoves were not more efficient why would so much money be invested in them? An open stove is about the same as an open fireplace, pretty to look at but not an efficient or clean burning heating device. There are so many variables not brought up in the original post that there will not be one answer. The above is what I have experienced using an EPA secondary burn stove. More efficient than an open fireplace, pre-EPA stove (I have both), or any stove with the door open.

KaptJaq

 

[jharkin]

Magic heat has an electric fan... + no way they would have gone 10 years without a clean out on one.. Unless chimney fires where doing the cleaning

 

[Slow1]

Yup, I'd like to know the question as well. So many things brought up in that note that could be commented on.

Door open/closed - (I agree, closed)

Chimney cleaning for 10 years? - If it is inspected and has remained clean that long, bravo! Doesn't say much for anyone else really though.

Pre-EPA stove vs current (not brought up in the note but...) - Clearly an EPA stove can be more efficient and cleaner to run.. Sounds like they are running very clean (at least their flue is) but that doesn't say anything to efficiency - how much wood do they burn each year? What climate are they in and how well insulated is home? If one is looking to be "green" as I presume the sierra club folks are then minimizing wasted wood burn likely should be near the top of the list.

Burning enough cardboard/paper to bring temps up to 250 - I don't know how much that would take for any given stove, but it seems like quite an unnecessary step to me if it is more than normal kindling a fire amount. I imagine if they learned how to build a proper top-down fire it could do just as well with less paper etc.

 

[jharkin]

If he is keeping the chimney that clean with an old fisher I'm guessing they are burning HOT and fast...lot of heat up the flue.

I wonder if his passive recirculating damper is a reference to the early secondary combustion systems like the horizontal burn mode of pre-epa Vermont castings. Either way I think his assumptions of 60% efficiency for that fisher are off by a bit.

 

[Wood Duck]

I would answer that, in general, a stove will be more efficient and produce less pollution such as smoke and particulates is the door is closed. With the door open the stove is more or less a fireplace. Excess air will pass through the stove, carrying heat up the flue and reducing temperatures in the firebox, which in turn reduces the ability fo the stove to burn wood gases and particulates. At the other end of the spectrum you have the door closed and the air supply turned very low; an excessively low air aupply will result in smouldering, smoky burns whichgreatly increases air pollution and also leads to creosote buildup in the chimney. The ideal air supply is achieved with the door closed and the air supply adjusted to achieve a lively fire.

Modern wood stoves are far more efficient and produce far less pollution than older stoves, while also producing more heat from a given amount of wood. Many people report using 1/3 to 1/2 less wood after switching to a modern stove, reducing the discharge of CO2 as well as pollutants such as particulates and volatile gases.

 

[mellow]

If I didn't know any better I would swear you pasted that from someone over at AS.

 

[firefighterjake]

Random thoughts . . .

Door open or closed for best efficiency? I would figure that unless someone is attempting to "turn" their woodstove into a "fire place" than the doors should be shut . . . in both a pre-EPA stove and a modern EPA stove.

If the chimney is good and clean after 10 years of use I would guess that the folks either have had a chimney fire (or regularly have them), they're running pretty darn hot in the flue, the wood is exceptionally well seasoned and/or they're stretching the truth about just how clean the chimney is . . . that said . . . I would never recommend someone go 10 years in between sweeping the chimney . . . hopefully these folks at least inspected the chimney at some point.

Final thought . . . I would hope a group like the Sierra Club might encourage or educate its members about the benefits of heating with a modern EPA stove vs. the older stoves . . . while I may not have purchased my stove for the environmental benefits (for me it was the ability to get long burns and use less wood), knowing your woodstove is not putting as much pollution and particulates into the air is for me a very nice side benefit.

 

[Sprinter]

Sounds like the question is whether keeping the door open heats the house faster ("...always leave the stove's front door open...") . That would be a different question than operating efficiency.

I'm not sure how to even answer that one. Does anyone operate that way? I can't imagine.

 

[BrotherBart]

I'll take wood stoves for $1,000 Alex.

 

[Huntindog1]

Well they are using the old type stove not a new EPA type stove.

With the door open your burning at a higher rate but wasting more of the heat. Yes sure it will heat the house faster burning at the higher rate but your also increasing the air flow thru the stove and flush alot of heat up the flue. Which means your wood isnt going to last as long. You can also look at the angle that yes your wasting heat up the flue but burning hotter your burning more efficiently. Efficiently as getting more of the BTU's outo f the wood from burning at a higher rate. As if the wood is burnng at a lower rate causeing more smoke that smoke is wasted energy. The newer EPA higher efficiency stoves are basically smoke burners get a high efficient burn and getting more heat out of the wood with out having to flush it alot of it up the chimney. The key to the EPA stove is your door is shut and input air is almost completely closed but your still burning highly efficient and getting alot of heat out of the stove. That old type stove if your burning with the door shut and the air turn way down , your producing alot of wasted smoke polluting the air and not getting very good heat at the very low setting for the long over night burns people want.

 

[northwinds]

I love standardized tests. This one is clearly of the true/false variety.

1. Some say a wood stove heats the house faster if you always leave the stove's front door open (with a firescreen to catch sparks).
True. Some people do say that, but they're wrong.

2. Some say the stove door must be closed after the chimney reaches operating temperature (about 250 degrees) for the stove to circulate air inside the firebox and burn efficiently.
True. Some people do say that, and it's hard to burn efficiently or to keep warm air in the firebox without closing the door.

3. Some say just close the door after you got it started.
True. Some people do say that, and they're right.

 

[PapaDave]

It would be interesting to see a controlled study of these to see what the real differences are. Like two exactly duplicate "rooms"

Might be easier to just change the stoves in the same house/room.

 

[Sprinter]

I'll take wood stoves for $1,000 Alex.

Answer: Leaving the door open.

Question: What is the worst way to operate a wood stove?

 

[jharkin]

Well they are using the old type stove not a new EPA type stove.

With the door open your burning at a higher rate but wasting more of the heat. Yes sure it will heat the house faster burning at the higher rate but your also increasing the air flow thru the stove and flush alot of heat up the flue. Which means your wood isnt going to last as long. You can also look at the angle that yes your wasting heat up the flue but burning hotter your burning more efficiently. Efficiently as getting more of the BTU's outo f the wood from burning at a higher rate. As if the wood is burnng at a lower rate causeing more smoke that smoke is wasted energy. The newer EPA higher efficiency stoves are basically smoke burners get a high efficient burn and getting more heat out of the wood with out having to flush it alot of it up the chimney. The key to the EPA stove is your door is shut and input air is almost completely closed but your still burning highly efficient and getting alot of heat out of the stove. That old type stove if your burning with the door shut and the air turn way down , your producing alot of wasted smoke polluting the air and not getting very good heat at the very low setting for the long over night burns people want.

Even in a pre-epa I'd be very skeptical that the stove heated faster or burned more efficiently with the door open. It would be operating like an open fireplace, probably sucking hot air out of the house faster than its adding heat.

 

[gregbesia]

My answer to them would be "no comment ". I am sure that anything that its said on this site sierra gang can twist in their favor

 

[eclecticcottage]

Might be easier to just change the stoves in the same house/room.

Actually, no, that would mess up the "control". There's no way to guarantee the exact same temps, humidity, barometric pressure, etc from day to day. If both stoves were burned at the same time in the same room set up, on the same day, then the exterior variables like temps, wind speed, etc would be equal, or as nearly so as possible .