"Hot" Firewood?

I enjoy reading books, forums, blogs... about firewood and the concept of "hot" firewood versus "medium" has always caught my attention. Since most hardwoods have nearly the same heat per dry pound while softwoods have a slightly higher heat per pound (+5% by lab tests), why is any wood any "hotter" than another?

I will admit basswood, a low density firewood, does struggle to heat my house but does medium density (elm, cherry, walnut, hackberry...) also deserve some demerit compared to so called "hot" firewood (apple, oak, hickory, sugar maple, white ash, ironwood...)? Many medium density sticks actually dry faster than some "hot" woods, especially red oak. Actually, many blogs mistakenly label cherry as "hot" when the density charts indicate cherry is a medium.

Keep in mind I am a numbers person... A firewood which is 25% heavier (oak, hickory...) than a medium density wood can be compensated for by increasing the diameter of the medium density firewood stick by only 12%. The volume and so the weight of each stick is calculated by the radius squared and so a stick volume increases 25% for a 12% increase in diameter or radius.

Besides, I am getting bored with oak, hickory, sugar maple... (heresy!!)

And so... I found the county cut 15+ medium sized hackberry (2/3) and slippery elm (1/3) overhanging a road and stacked them neatly (stems cut off tops and stems set on top of the tops) on the county right-of-way. I called the land owner and got permission to cut the stems for firewood (no one else wanted them). Folks did stop to thank me for cleaning up the mess (not my intention, I only want heat). I collected 2 1/2 full cords of medium density green firewood with a short carry, road edge.

Meanwhile, I will get some real time feedback because the dry firewood row schedule for this winter contains more than a cord of slippery elm and hackberry. Is the "hot" firewood a myth? Time will tell.

One word of caution: I heat with a furnace with a full size grate and rarely fill the firebox since that would overheat the house. If firebox size matters, then places with mostly low to medium density wood should simply order a stove with a larger firebox.

 

IME aspen (low BTU) is a hot firewood. Lots of heat output for a short duration, perfect for burning down coals. Black locust and Osage Orange are also hot, but take a while to get going and then output heat for a long time. I’d consider cherry middle of the road. Being kind of a low flame wood I never had to open windows burning it before. It does have good coaling properties though. Good to know about basswood (no experience with it here); there are days where I’d like to burn some “cooler” woods.

 

It’s hard to find high quality free standing woodstove over 4 cubic foot firebox! I looked

have a lot of cubic feet high ceilings..
IME most firewood has same BTU per pound dry; heavier wood coals more so in my 3.2 cu ft firebox heavy hitters at night and poplar lighter wood’s during day when awake to burn down coals..
At below negative 20 burn it hot and fast!!

 

All hardwoods will put off relatively close to the same amount of BTUs per pound. With the heavy hitters you are able to pack more available BTU’s (pounds) in the stove than with the lower density woods. Agree with the post above…when it is really cold, I run some lower density stuff to get more heat and less coals.

 

There are 3 or 4...this is the big dog here, 4.7 CF
J. A. ROBY - Wood stoves - ULTIMATE 2015 TOR

 

Higher density wood means less trips to the stove.

 

I always wondered about this because I burn in an open fireplace. Last winter I was burning mostly ash and maple but would occasionally add in pine. One day I loaded several small splits of pine and the temperature in our living room went up several degrees in just a few minutes. It was really a hot fire but didn't last that long. Luckily I didn't burn the house down .

 

I've burned enough poplar over the years, and here's my unscientific take. Some wood simply gives up the goods easier, maybe due to the wood grain structure??? Who knows.

 

I agree. I also feel this also applies to wood drying to explain why red oak takes so long to dry (hard fibers). Lower density wood may have insulating qualities which slow the solid wood heating in the interior and so slow vaporizing of the wood. Only a vapor burns, not a solid. Splitting smaller would heat the wood interior faster and so folks can have a different results depending on split size and/or moisture level.

I have decided on my definition of "hot": a wood burning fast enough to keep my furnace blower locked on, inlet draft full open or pinched. The blower is thermostatically controlled by the furnace shell temperature. All the "heavy" woods can keep the blower running full time but what about the mediums?

So far, American Elm (White) and Slippery Elm (Red) are keeping the furnace blower running steady, no cycling, and so could be rated as "hot" (but obviously not "heavy"). Slippery Elm is coaling better than American (White) Elm. Black Walnut is not keeping the furnace blower running without cycling, and so not "hot", but does coal better than the elms. A mix of 2 parts American Elm and 1 part Black Walnut does keep the blower going steady with better coals than American Elm alone.

All these woods are testing at 17% moisture, dry basis, fresh split by the moisture meter.

I agree with advantages everyone has listed for the "heavy" woods (White Ash or heavier). My issue is how the word "hot" is applied unfairly in firewood publications. Though, I have never read the suggestion to include available wood density (light, medium, or heavy) when sizing a new stove installation (firebox).

 

Like mentioned, Black Locust, Osage Orange, Honey Locust (large thorns), any Hickory, Sugar Maple are all great at putting out sustained heat and a nice coal bed afterwards.

 

That's been exactly my experience. The worst cherry I ever burned was a long dead/down tree I cut that was already below 20% MC. It sat in my stacks for a few months before burning. That stuff barely burned, it more or less smoldered. I had to mix pine and ash with it to get anything out of it. Even then, like you said it left heaping piles of coals that were difficult to burn down. Yet after that experience I'm still hoarding cherry (burned some this morning actually, mixed with ash).

 

I burned some cherry crotches during a cold snap last year and I was screwed. Stove full of coals and not much heat.