Damper Use - Who to Believe?

[GreenMountainBoy]

I've read many articles advocating backing off the airflow to your woodstove to achieve a longer burn and to regulate temperature. Makes perfect sense, and this has worked for a lot of folks for a long time now.

But recently I've come across several articles which advocate leaving the damper wide open all the time and regulating things by the amount, size, and type of woods you burn. Advantages? Less creosote buildup and particulate matter... cleaner air, better for environment, etc. I even saw this approach recommended in a Jotul brochure.

So I figured I'd ask the folks here with way more experience than I have. Is one approach better than the other? Or are they not better, not worse, just different?

Thanks.

 

[bholler]

I've read many articles advocating backing off the airflow to your woodstove to achieve a longer burn and to regulate temperature. Makes perfect sense, and this has worked for a lot of folks for a long time now.

But recently I've come across several articles which advocate leaving the damper wide open all the time and regulating things by the amount, size, and type of woods you burn. Advantages? Less creosote buildup and particulate matter... cleaner air, better for environment, etc. I even saw this approach recommended in a Jotul brochure.

So I figured I'd ask the folks here with way more experience than I have. Is one approach better than the other? Or are they not better, not worse, just different?

Thanks.

Well that depends upon the stove and what you are calling the damper. If you are talking about the air control no you should never run with that wide open for all that long.

 

[Todd]

I'm pretty sure in most EPA tests modern stoves are most efficient and have the cleanest burn in the low to medium air settings. A higher air setting flushes those unburnt gases and smoke up the chimney before they have the chance to be reburned in the stove. Now if you were to burn 1 or 2 sticks at a time maybe a higher setting would be better? The EPA test is done with basically a full load and a 15' straight up chimney. I would think manufactures would design their stoves to be most efficient around this test.

 

[Highbeam]

Option 1, every time. If your stove doesn’t offer sufficient control then look for a better stove.

 

[MainePatsFan]

I don't think I have ever read to leave the air control open full time. Sure not providing enough air when a fire is getting established you will end up with a choked barely going fire that will not burn hot enough and keep the chimney in the creosote zone.

The only way I could burn in my stove with the air open all the time is if I just burn one split or two smaller splits at one time. Otherwise the temp would soar into the overfire zone.

 

[ABMax24]

With regards to emissions too much air is just as bad as too little. Too much air cools down the firebox and limits or even stops the secondary burn. Much in the same way too little allows unburnt wood gases and soot to escape the stove and exit the chimney.

Edit: The above assumes you are running a few splits at a time, if I tried to run my stove wide open with a full load it would go nuclear in 10 minutes, many others would have the same issue.

 

[RobbieB]

I run pretty much wide open the whole time. But I like the "flame show" and I burn for the look and not to heat the house. I fire it up for the evening along with the TV and feed it more wood as needed.

 

[bholler]

I run pretty much wide open the whole time. But I like the "flame show" and I burn for the look and not to heat the house. I fire it up for the evening along with the TV and feed it more wood as needed.

Most stoves really cannot handle that very well

 

[begreen]

I run pretty much wide open the whole time. But I like the "flame show" and I burn for the look and not to heat the house. I fire it up for the evening along with the TV and feed it more wood as needed.

Indeed that is just sending the heat up the flue. Modern secondary stoves need a vacuum to pull air through the secondary tubes. Decreasing the primary air increases suction on the secondary tubes, thus increasing secondary combustion. This, by the way, provides quite a nice light show of its own.

 

[begreen]

Most stoves really cannot handle that very well

Not just the stove that ages with the excess heat, but also the flue system which is not designed to take a continuous high temp of over 1100º that is possible with a steady high burn.

 

[RobbieB]

I run the stove top thermo between 4-500 and also adjust the blower speed. If the fire seems to get "too big" I throttle the air back to half. So I do throttle the air, but most times not needed. And I go through maybe 4 splits or 2 sawdust logs (plus the newspaper and kindling) on an evening burn and the temperature in the room always goes higher than 80 even with the recirculation fan on.

But hey, this is the central valley of CA and it never even gets to freezing here.

 

[MainePatsFan]

But hey, this is the central valley of CA and it never even gets to freezing here.

I don't even live in the coldest part of New England but I've had cold snaps where 3 days will go by where the temperatures don't get above 7 degrees and the nights will hit -15. On those nights even with me keeping the stove going to max without overfiring, I struggle to maintain 68 in the house.

 

[bholler]

Not just the stove that ages with the excess heat, but also the flue system which is not designed to take a continuous high temp of over 1100º that is possible with a steady high burn.

Very true

 

[firefighterjake]

I've read many articles advocating backing off the airflow to your woodstove to achieve a longer burn and to regulate temperature. Makes perfect sense, and this has worked for a lot of folks for a long time now.

But recently I've come across several articles which advocate leaving the damper wide open all the time and regulating things by the amount, size, and type of woods you burn. Advantages? Less creosote buildup and particulate matter... cleaner air, better for environment, etc. I even saw this approach recommended in a Jotul brochure.

So I figured I'd ask the folks here with way more experience than I have. Is one approach better than the other? Or are they not better, not worse, just different?

Thanks.

Well my first inclination was to say it is always a good idea to simply follow the manufacturer's suggestions in the owner's manual . . . but a quick look at one Jotul woodstove seemed to contain some inaccuracies (i.e. they recommend not burning wood seasoned for more than two years as they claim it will burn too quickly, state that checked marks on the end of splits means the wood is seasoned and that the air control should be open if more heat output is desired -- all things which have a degree of truth to them, but aren't quite right either.)

So that all said . . .

Damper closed or open . . . a lot depends on the woodstove.

By this I mean to say, with a modern EPA woodstove such as my secondary burning Oslo I get longer, cleaner and hotter burns by bringing the stove up to temp and then closing down the stove's air control as this will result in the stove's secondary burn occuring. On a pre-EPA woodstove closing down the stove's damper would result in a longer burn, but most likely at the expense of partially suffocating the fire resulting in a dirtier burn.

I am also assuming by "damper" you mean the stove's air control and not an actual stove pipe damper.

Now I will also add that it is also true that the amount, size and type of wood one loads in the firebox also will have a huge impact on burn time, efficiency, clean burns, etc., with EPA stoves it really is in conjunction with the air control -- in my case specifically -- closing down the air control -- that results in the best results for me and for the environment -- i.e. lots of heat, clean burn.

I would never leave the air control open for the entire length of the burn due to potentially over-firing a stove or chimney.