Firewood moisture content debate for EPA FURNACE

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

brenndatomu

Minister of Fire
Aug 21, 2013
7,219
NE Ohio
The owner of Lampaa stoves has been using his vapor fire for almost 50 years exactly! I'll say it again, longer than most have been alive and longer than even more have been burning or working! The longest he has seasoned his firewood is two years.

Must know something, no? He firebox is the older smaller version (16" length pieces as opposed to 20-21") and the most per year he has burned is 5 cord during a unusually cold year. Otherwise, it's average of 4 cord. And not creosote buildup.

Very easy people to speak with. We should all be that way.
What's even more impressive is he says he has never, not once, cleaned his chimney...regular inspection only...nothing to clean.
A clip from their website:
1643677673856.png

And as far as using 4 cords on average per year to heat...that's pretty good considering they are ~15 miles from Canada and considered one of the colder spots in the USA...set a few records IIRC.
 
Last edited:

yooperdave

Minister of Fire
Oct 26, 2010
1,220
Michigan's U.P.
What's even more impressive is he says he has never, not once, cleaned his chimney...regular inspection only...nothing to clean.
A clip from their website:
View attachment 291262
And as far as using 4 cords on average per year to heat...that's pretty good considering they are ~15 miles from Canada and considered one of the colder spots in the USA...set a few records IIRC.



You know, its looking better all the time!
 
  • Like
Reactions: woodey

lampmfg

Burning Hunk
May 16, 2011
200
Tower, MN
lamppakuuma.com
I said I would share the reference materials we often refer to here at Lamppa Manufacturing (Kuuma). Perhaps the most informative book is "The Woodburners Encyclopedia" by Jay Shelton. This is an older book, originally published in 1976 with 8 additional printings. It is a wealth of wood burning information, but better than that, it puts it into "numbers.". Daryl Lamppa and his father Herb (a math instructor) repeatedly said that burning wood efficiently is all about the numbers. We strongly recommend you download or purchase a copy of this book if you are into wood burning.

An additional question that was asked on the forum was, "why does Kuuma suggest a wood moisture content between 18 and 28%? The reason is that this is the range that the EPA's NSPS Phase 2 emission mandate says your furnace must be able to operate and emit below the emission levels spelled out in the standard. If your furnace can not operate with wood in this moisture range – your furnace can not be certified to phase 2.

Personally, I prefer wood that is between 20% - 24%. We don't have great hardwood here in northern Minnesota like much of the U.S., so we normally burn birch. In previous years when our firewood was around 20%-22% moisture, we would consistently see between 12 – 14 hour burn times in a Vapor-Fire 100 with birch. This year we let our wood get way too dry. With this really dry wood, we are only getting around 7 hours of burn time with the exact same Vapor-Fire 100 furnace – again with birch. The dryer the wood (and hence, the lighter the wood), the less available Btu content in the wood. Primarily the wood has lost significant amounts of the combustible carbon compounds either through evaporation or through some deterioration of combustibility of these compounds over time.

We still find that "green or living wood" that is cut, split, and cured outdoors for 9 – 12 months is generally at a pretty good moisture to provide good heat. Of course, this will vary by species of wood and the climate conditions of your location.

Dale

We are open to continued dialogue about this moving forward but would appreciate it being respectful. Both Dale and my Dad (Daryl Lamppa) don't use the internet for this kind of stuff, so it involves printing out and me scribing responses. It will always take us a while to respond. There will also be a lull between our response and comments added after. Dale was doing this off last week, and I know there have been other comments since then. It's also much easier to discuss stuff over the phone so feel free to call. I can tell that winter is in full swing throughout the rest of the country because it has been a crazy week for furnace questions, installations, and orders.

Thanks,

Garrett

IMG_5458.jpg
 

Micdrew

Member
Jan 15, 2021
53
Maryland
I said I would share the reference materials we often refer to here at Lamppa Manufacturing (Kuuma). Perhaps the most informative book is "The Woodburners Encyclopedia" by Jay Shelton. This is an older book, originally published in 1976 with 8 additional printings. It is a wealth of wood burning information, but better than that, it puts it into "numbers.". Daryl Lamppa and his father Herb (a math instructor) repeatedly said that burning wood efficiently is all about the numbers. We strongly recommend you download or purchase a copy of this book if you are into wood burning.

An additional question that was asked on the forum was, "why does Kuuma suggest a wood moisture content between 18 and 28%? The reason is that this is the range that the EPA's NSPS Phase 2 emission mandate says your furnace must be able to operate and emit below the emission levels spelled out in the standard. If your furnace can not operate with wood in this moisture range – your furnace can not be certified to phase 2.

Personally, I prefer wood that is between 20% - 24%. We don't have great hardwood here in northern Minnesota like much of the U.S., so we normally burn birch. In previous years when our firewood was around 20%-22% moisture, we would consistently see between 12 – 14 hour burn times in a Vapor-Fire 100 with birch. This year we let our wood get way too dry. With this really dry wood, we are only getting around 7 hours of burn time with the exact same Vapor-Fire 100 furnace – again with birch. The dryer the wood (and hence, the lighter the wood), the less available Btu content in the wood. Primarily the wood has lost significant amounts of the combustible carbon compounds either through evaporation or through some deterioration of combustibility of these compounds over time.

We still find that "green or living wood" that is cut, split, and cured outdoors for 9 – 12 months is generally at a pretty good moisture to provide good heat. Of course, this will vary by species of wood and the climate conditions of your location.

Dale

We are open to continued dialogue about this moving forward but would appreciate it being respectful. Both Dale and my Dad (Daryl Lamppa) don't use the internet for this kind of stuff, so it involves printing out and me scribing responses. It will always take us a while to respond. There will also be a lull between our response and comments added after. Dale was doing this off last week, and I know there have been other comments since then. It's also much easier to discuss stuff over the phone so feel free to call. I can tell that winter is in full swing throughout the rest of the country because it has been a crazy week for furnace questions, installations, and orders.

Thanks,

Garrett

View attachment 291484
Thanks for responding Garrett, when I originally posted this I didn’t think it was going to cause such an uproar I was just wanting to start a conversation on the subject, it was not my intention to drag the Lampa name through the mud as I am a proud owner of the VF100 and couldn’t be happier with it.
 

usernametaken

Burning Hunk
Nov 25, 2017
168
Western, MA
What I don't understand is other Kuuma owners not having the same experience with wetter wood having more BTU output than dryer wood. I don't own a Kuuma product but my PSG product absolutely doesn't work that way either. A person or company can quote all the literature in the world but if it doesn't match real world experience.... hmmm.....
 
  • Like
Reactions: bholler

lampmfg

Burning Hunk
May 16, 2011
200
Tower, MN
lamppakuuma.com
What I don't understand is other Kuuma owners not having the same experience with wetter wood having more BTU output than dryer wood. I don't own a Kuuma product but my PSG product absolutely doesn't work that way either. A person or company can quote all the literature in the world but if it doesn't match real world experience.... hmmm.....
I'm not even sure how do reply to this? There are a ton of variables when it comes to burning wood. That's why our testing results speak for themselves especially when we were held to a more stringent standard.

The above comment just said he couldn't be happier with his furnace. There are plenty of threads and feedback on this forum about real word experience from very knowledgeable and experienced users.
 

stoveliker

Minister of Fire
Nov 17, 2019
4,525
Long Island NY
@lampmfg

Have there been studies that you know of that have used e.g. mass spectrometry to analyze the gases that (you claim) are getting out of the wood during drying? And have those been analyzed in terms of the BTUs they would have provided (if they still would be in the wood when burning time comes around)?

You stated that drier wood has less BTUs.
I wonder how much that actually is, and how that compares to the large quantity of BTUs needed to boil off the water in wetter wood. That is a balance you claim is more beneficial for wetter wood, and I assume you have seen the studies that determined that.
 
  • Like
Reactions: bholler

lampmfg

Burning Hunk
May 16, 2011
200
Tower, MN
lamppakuuma.com
@lampmfg

Have there been studies that you know of that have used e.g. mass spectrometry to analyze the gases that (you claim) are getting out of the wood during drying? And have those been analyzed in terms of the BTUs they would have provided (if they still would be in the wood when burning time comes around)?

You stated that drier wood has less BTUs.
I wonder how much that actually is, and how that compares to the large quantity of BTUs needed to boil off the water in wetter wood. That is a balance you claim is more beneficial for wetter wood, and I assume you have seen the studies that determined that.
I'm not aware of any studies. We have designed and operated the VF100 for 40+ years on a shoestring budget, with test results showing it's the cleanest and most efficient. There are also plenty of users on here who have one and share their own experiences. We definitely don't have access to dedicated testing facility onsite like our large corporate competitors. If you're ever in the area, stop by and see what we used to test and develop. I would also love to show you the quality used to make one right in Tower, MN.

D5310262-26EF-4BA4-8A20-FAE104AF833D.jpeg
 

stoveliker

Minister of Fire
Nov 17, 2019
4,525
Long Island NY
I'm not aware of any studies. We have designed and operated the VF100 for 40+ years on a shoestring budget, with test results showing it's the cleanest and most efficient. There are also plenty of users on here who have one and share their own experiences. We definitely don't have access to dedicated testing facility onsite like our large corporate competitors. If you're ever in the area, stop by and see what we used to test and develop. I would also love to show you the quality used to make one right in Tower, MN.

View attachment 291544

I have no doubt about the quality. From what I read many companies will be jealous of your customers as they are so much praising your products.

I have no doubt about the experiences of folks here. I am only wanting to understand how a bit of gas escaping wood (if not otherwise consumed by e.g. fungi) would be a bigger loss than the BTUs needed to boil off e.g. 10 pct in weight of water (from 15 to 25 pct).

I do understand and respect that the experiment (the experience) beats any theory. I.e. if your data and that of your customers show this, it's a fact.
It's just in my genes to want to know "how, why".

I'd be glad to stop by - but other than the airport in Minneapolis I have not much opportunity to visit MN. Thank you for the invitation though!
 
  • Like
Reactions: bholler and lampmfg

usernametaken

Burning Hunk
Nov 25, 2017
168
Western, MA
I'm not even sure how do reply to this? There are a ton of variables when it comes to burning wood. That's why our testing results speak for themselves especially when we were held to a more stringent standard.

The above comment just said he couldn't be happier with his furnace. There are plenty of threads and feedback on this forum about real word experience from very knowledgeable and experienced users.
You're awfully defensive. People can ponder your counterintuitive statements in videos or say they have different personal experiences and none of that needs to be construed as an attack on you or your company. So my advice would be to calm down, grow a bit thicker skin and engage in a dialog instead of mounting a defense... No one is saying you don't make a great product. Heck, if you had one big enough to handle my needs, I might well have gone that route after reading so many wonderful reviews. (Although the lack of a glass door would have probably been a pretty big factor in my decision.) In my view I don't think anyone here was disparaging your products in any way. What folks were commenting on was a poorly done video that contradicts the real world experiences of many.
 
  • Like
Reactions: bholler

yooperdave

Minister of Fire
Oct 26, 2010
1,220
Michigan's U.P.
OK. Here is a stove manufacturers recommendation for moisture content. Interesting, no?

Have we all been brainwashed into "the drier the better" firewood approach because of the stove we have been burning that we are wearing blinders and not able to see that there are processes out there that are effective also?

Check out the "wood moisture content" info on pages 1 and 2. No pictures but it's a short read! ;)

 

brenndatomu

Minister of Fire
Aug 21, 2013
7,219
NE Ohio
OK. Here is a stove manufacturers recommendation for moisture content. Interesting, no?

Have we all been brainwashed into "the drier the better" firewood approach because of the stove we have been burning that we are wearing blinders and not able to see that there are processes out there that are effective also?

Check out the "wood moisture content" info on pages 1 and 2. No pictures but it's a short read! ;)

If you like that, read from the bottom of page 25 onto page 26! !!!
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,682
central pa
OK. Here is a stove manufacturers recommendation for moisture content. Interesting, no?

Have we all been brainwashed into "the drier the better" firewood approach because of the stove we have been burning that we are wearing blinders and not able to see that there are processes out there that are effective also?

Check out the "wood moisture content" info on pages 1 and 2. No pictures but it's a short read! ;)

Ok so a bit wetter wood works better in a gasifier because they can't handle the rapid off gassing from drier wood.

That doesn't mean wood is loosing BTU content with the moisture. Or that drier wood isn't better in every other type of wood burning appliance.

Again the issues I and others had was mainly with the delivery of the info
 
  • Like
Reactions: usernametaken

sloeffle

Minister of Fire
Mar 1, 2012
986
Central Ohio

brenndatomu

Minister of Fire
Aug 21, 2013
7,219
NE Ohio
  • Like
Reactions: yooperdave

brenndatomu

Minister of Fire
Aug 21, 2013
7,219
NE Ohio

stoveliker

Minister of Fire
Nov 17, 2019
4,525
Long Island NY
The point still is that more moist wood wastes more energy by having to evaporate the water.

And thus that secondary air (as they mention would be useful for drier wood) is a better system to burn - because it can burn drier wood, meaning that it can burn fuel where less BTUs are wasted in pumping the water out of the chimney.

So, we've not been biased by the stove we are burning, we have just seen a better system out there that is able to run on better fuel, leading to more efficiency (less wood cutting and less pollution).

I mean, seriously, "we can't control the better fuel so let's make it worse (water spray) because it then works better in our system that is not as efficient"??
 

yooperdave

Minister of Fire
Oct 26, 2010
1,220
Michigan's U.P.
The point still is that more moist wood wastes more energy by having to evaporate the water.

And thus that secondary air (as they mention would be useful for drier wood) is a better system to burn - because it can burn drier wood, meaning that it can burn fuel where less BTUs are wasted in pumping the water out of the chimney.

So, we've not been biased by the stove we are burning, we have just seen a better system out there that is able to run on better fuel, leading to more efficiency (less wood cutting and less pollution).

I mean, seriously, "we can't control the better fuel so let's make it worse (water spray) because it then works better in our system that is not as efficient"??


Well then, I wonder just why the manufacturers won't use the dry wood? Wouldn't this increase their efficiency ratings?

Yeah....
 

yooperdave

Minister of Fire
Oct 26, 2010
1,220
Michigan's U.P.
Ok so a bit wetter wood works better in a gasifier because they can't handle the rapid off gassing from drier wood.

That doesn't mean wood is loosing BTU content with the moisture. Or that drier wood isn't better in every other type of wood burning appliance.

Again the issues I and others had was mainly with the delivery of the info


Not entirely true.

There are a number of members here who are completely satisfied with burning the drier wood in their appliances that call for a "non-traditional MC".
 

sloeffle

Minister of Fire
Mar 1, 2012
986
Central Ohio
Yeah, but only within the programmed limits...that's why they talk about tuning specs on page 33
Correct, for that specific boilder.

I wonder if there are boilers / furnaces, etc out there that don't need any manual intervention. From the Kuuma video the OP linked it sounds like the Kuuma can deal w/ various levels of moisture without any human intervention needed.
 

stoveliker

Minister of Fire
Nov 17, 2019
4,525
Long Island NY
Well then, I wonder just why the manufacturers won't use the dry wood? Wouldn't this increase their efficiency ratings?

Yeah....
because many have not updated their system to be able to handle drier wood.

See, from the pdf you posted:
1646151361463.png
\

This begs the question of why one would make a water spray system to be able to burn better fuel rather than add such a secondary air system to be able to burn that better fuel without wasting BTUs in pumping out the water.

This vendor apparently does have a secondary air option. I.e. the technology exists (not surprisingly). Hence I'm slackjawed by the "add a water spray or use crappy fuel" advice.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,219
NE Ohio
This vendor apparently does have a secondary air option. I.e. the technology exists (not surprisingly). Hence I'm slackjawed by the "add a water spray or use crappy fuel" advice.
Did you notice that the spray system was for burning sawdust? Might be other issues beyond "its just too dry"...
 
  • Like
Reactions: LogCabinFever

stoveliker

Minister of Fire
Nov 17, 2019
4,525
Long Island NY
Did you notice that the spray system was for burning sawdust? Might be other issues beyond "its just too dry"...
that is not how I read it. It was *also* for sawdust.

1646151995597.png


Very dry wood -> back puffing (b/c gasification too fast) -> Sawdust less of a problem than ... logs (!).
Secondary air option. But "In rare cases it may be necessary to add moisture to the fuel".

To me that does not indicate the spray is only for sawdust. Very dry logs are a bigger problem. Secondary air helps. But in (rare) cases water spray may be needed.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,219
NE Ohio
that is not how I read it. It was *also* for sawdust.

View attachment 292901

Very dry wood -> back puffing (b/c gasification too fast) -> Sawdust less of a problem than ... logs (!).
Secondary air option. But "In rare cases it may be necessary to add moisture to the fuel".

To me that does not indicate the spray is only for sawdust. Very dry logs are a bigger problem. Secondary air helps. But in (rare) cases water spray may be needed.
The first line...

"A water spray kit is available for all commercial
Wood Gun systems and is normally
recommended if you are burning kiln dried
sawdust or shavings"
 
  • Like
Reactions: stoveliker