[Greenbuilding] firewood moisture content - a question for Norbert perhaps

Norbert Senf mheat at mha-net.org
Sat Dec 17 09:43:06 PST 2011

Interesting discussion, I haven't had a chance to 
check the list as regularly these days.
Something really interesting that I only learned 
recently is that tar (creosote) is only formed by 
smoldering combustion, which is without flames. 
On the other hand, soot is only formed by flaming combustion.
You can have both types of combustion happening 
at the same time, in different parts of the firebox.

Dry wood burns faster (hotter) and small wood 
burns faster (hotter). If you restrict the air 
supply, wood will burn slower (cooler), and can 
go from flaming to smoldering. Wood with 25% 
moisture can burn clean, if it burns fast enough. 
You can burn cleanly with even an old-tech stove 
by burning with the air supply wide open. The 
problem is with matching the heat output of the 
stove to the requirement of the house.

A good way to tell is if your chimney stays 
clean, like Corwyn's. Burning wet wood, he might 
still be able to keep it clean if he is able to 
burn the wood hot enough by using smaller pieces, 
burning with the air wide open, etc.

Nothing beats dry wood (20%), it just makes the 
job so much easier. You pretty much need to have 
a woodshed, and get your wood in there a year ahead of time.

Probably the best resource on the web on how to 
burn a stove is John Gulland's woodheat.org website:

Best ...... Norbert

At 10:10 PM 12/12/2011 -0500, Corwyn wrote:
>On 12/12/2011 9:38 PM, Sacie Lambertson wrote:
>>RT said:
>>     I would be more concerned about potential creosote
>>     formation/accumulation from burning wood at 25% MC than I would be
>>     about the reduction in heat output.
>>Me too.  Reuben once mentioned he lights his fires several times a day
>>only; from this I infer he lets it go out, then later, as the house
>>cools, fires up the stove again.  Is this correct, Reuben?  If so, how
>>do you prevent creosote buildup in your chimney?  Or maybe you simply
>>clean it several times a year?
>The wood I am burning this year is particularly 
>wet, so perhaps I will have something to say on 
>the matter come spring.  That said, my chimney 
>has never needed cleaning; I clean the stove 
>pipe, and the basement clean out, but the flue 
>has always been clean. I burn almost as hot as 
>possible, though at most one fire per day.  I 
>contend that creosote buildup comes from burning 
>too cool while in the initial stages of wood 
>burning (i.e. before the wood is reduced to 
>coals).  I can imagine Reuben being able to burn 
>multiple small fires without creosote buildup if they are hot enough.
>Thank You Kindly,
>Topher Belknap
>Green Fret Consulting
>Kermit didn't know the half of it...
>topher at greenfret.com
>(207) 882-7652
>Greenbuilding mailing list
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Norbert Senf---------- mheat(at)heatkit.com
Masonry Stove Builders
25 Brouse Rd.
RR 5, Shawville------- www.heatkit.com
Québec J0X 2Y0-------- fax:-----819.647.6082
---------------------- voice:---819.647.5092

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