Heating with Softwood

Readers of this blog often inspire a post by asking a question. I figure that if one person is interested, it probably means that others have wondered the same thing and so I sometimes write an entire post in order to answer a question. This time I had just written this post (but hadn’t published it yet) when Brian happened to ask, “is that Poplar you are cutting up? If so, how does it hold the heat? What is the average burn time for a block?”  This question was in response to the photos in my post, “What the Well-Dressed Woodsman is Wearing this Season.”

I’ve spoken with many people, especially those out living out west, who feel that they couldn’t heat with wood because all they have is softwood in their area. I had never really thought about it too much until this year when I started to pay attention to what wood I heat with.

We have two buildings on our property, both with about 1,200 square feet of usable space.  The guesthouse is 25’ x 25’ x 2 stories, so 1,200 sq. ft. The main house is story and a half, and an “L-shpae,” but still close to 1,200.

Our main house was built in 1888. It was insulated and new windows were installed about 20 years ago and while it’s fairly efficient, it’s not leak proof. Since we live in an area with radon gas, I don’t mind the air turning over fairly frequently.

Our guesthouse was built about 20 years ago. It is frame construction using 2”x 6”s so it is much more efficient. It also has lots of windows on the south side and very few on the north side.

guesthouse

We use about 1/3 as much firewood to heat the guesthouse as we do to heat our main house and I use softwood in the guesthouse woodstove. It’s actually poplar, which is as soft a wood with as little (few) BTUs of heat value as you can get. Poplar contains 18,500 BTU/cord versus 27,000 BTU/cord for oak or 22,000 BTU/cord for maple.

Now I need to qualify a few things. We do not keep the guesthouse as warm as the main house. I have to keep it heated because that’s where our battery room is, and we cannot let our deep-cycle lead acid batteries freeze, and their performance goes down as the temperature drops, so there is an incentive to keep them warm.

My office is in the guesthouse, so I like to heat it to keep my hands from freezing up on the keyboard. But I don’t want it too hot. My strategy during a cold spell in winter is to have a big fire on Monday to heat the building up. On Tuesday I don’t need a fire and if it’s sunny on Wednesday and Thursday it often warms my office and the rest of the building up enough to not need another fire. If we have cloudy week though I may have two or three small fires during the week.

We keep the main house much warmer, and are always heating kettles, dinner, bathwater, etc. on the woodstove, so we naturally use much more wood there. I’ve always used softwood in the swing seasons of fall and spring, and saved my hardwood for winter. We moved here shortly after there had been a gypsy moth infestation, which had killed many oaks. The oak leaves came out in the spring, the moth larvae ate them. When the trees tried to re-leaf, it used up so much energy that many of the oak trees didn’t survive. So during our first decade here I was just trying to keep up with cutting 150 acres of dead oaks. I have cut most of them, many which had fallen over after their roots had rotted, so now I’m more conscious of what I cut.

I have been trying to cut back some areas near the house that I think will eventually be a wheat field in the future. It is surrounded by poplar, so I’ve been cutting those and burning that wood in the guesthouse. And it’s fine. Yes I need a bit more of it than if I was burning hardwood, and yes, technically I have to fill up the woodstove more often because it burns through the fuel more quickly, but it still has lots of heat in it. And I’ve got to tell you, I love cutting live wood like poplar. When all that I was cutting was hardwood from dead oaks they were making my chainsaw blade pretty dull pretty quickly. Cutting live poplar is like cutting “butter.” Around here poplars grow like weeds, so I can cut an area then a few years later the smaller trees are back ready to be harvested.

poplar-pile

with two more rows, for a total of six, it's more than enough to heat the guesthouse

All this to say that if you are concerned about only having access to softwood in your area, well, you shouldn’t be. Build a really efficient home. That’s the key. The less heat that escapes, the less wood you’ll need to burn to heat it. From a sustainability standpoint I’m sure you can grow more than enough fast growing poplar on 10 to 20 acres to heat a home. And if you were managing your woodlot, and made sure to plant some hardwoods, like maple, in the mix, by the time you’d thinned all the softwoods a couple of times the hardwoods would be ready.

It’s just another reason that I love heating with wood. No drilling rigs for oil or natural gas. No trucks bringing out propane. No fracking. No pipelines. Just you and some tree seedlings. And once the woods get going, there’s no stopping them. The trees here just keep coming and coming in waves. I can’t cut them fast enough. They’re renewable, and sustainable, and the trees “fix carbon” from the atmosphere in their woody mass that is released when they’re burned, just like if they fell down and rotted. They are releasing the same amount of carbon they absorbed; hence heating with wood is carbon-neutral.

When I’m 85 and living comfortably on my Canada Pension Plan (social security) I’ll have all winter to cut firewood. I’ll have to pace myself, but it’s something I look forward to. Just like I look forward to every weekend when I know I get to put on my chainsaw pants and heat the house!

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9 Responses to “Heating with Softwood”

  • SteveR:

    Cam, your BTU figures are off by a factor of 1000x. That should be 18.5 Million BTUs/cord for Poplar and so on.
    As someone pointed out, the energy in wood is the same by weight, no matter the species. So even amongst the same species there will be variations (slow growing vs fast growing oak, different kinds of oak, etc).

    Also, an interesting fact is that wood contains about 1/2 as much energy as fossil fuels. Considering that wood is renewable, that’s actually not too bad. Waiting around a million years to produce oil seems to have diminishing returns. So actually, wood is a much better fuel – but we probably could not grow as much in one year as the amount of oil we are burning – but that will end soon anyway!

    Good luck getting CPP when you are 85! I’m not counting on it being there.

  • Melanie Ann MacKenzie:

    Hello Cam,
    Very interesting reading. The small farm we purchased is mostly pine, spruce and cedar with a few dead elms here and there. We do have a bit of open space and I guess we will start to plant poplar right away since we will need to purchase most of our wood for a few years. I have been told that you can burn pine, etc. if it is really well seasoned but I worry about all the gunk in the stovepipe.
    Cheers, Melanie
    p.s. I have read your book, Little House off the Grid and very much enjoyed it. As we are currently packing house, getting ready to move, I have already packed it and I cannot remember how many PV panels you have. We are doing our calculations for what we will need and I would appreciate a quick reply from you to let me know what you have. Thanks very much.

  • Brian:

    Thanks for the answer on the poplar…and you just helped make my decision. I will be cutting some poplar this spring to have ready for next fall and early winter. Mainly we use maple, white birch and beach for wood but will now add poplar to the mix.

  • Oh, oh, oh. I can make a contribution! This one’s for you, Joe.

    I just found a blog yesterday about wood burning stoves. Looks like it could be very useful. Here is the link:
    http://woodcookstovecooking.blogspot.ca/

  • Neil:

    I also use “lighter/softer” woods for late fall and early spring and save my beech and maple for the cold depths of winter. I also have a a good selection of dead and near dead (reminds me of Monty Python “I’m not dead yet”) elm around. Sadly, in a few years I may be saying likewise for ash due to the impending EAB.

    The plantation areas of my woodlot are red/white pine and larch (European sibling of tamarack). I have read that larch is a reasonable firewood in terms of BTUs (perhaps the best of the softwoods) but I have some concern about pine… even well seasoned, does all the resin cause dangerous coating of the stovepipe?

    To respond to Joe Belmont’s comment: Cam and Michelle may be too polite to hawk their own book but I can tell Joe that the answers to his questions (and much more) can be found in “Little House Off the Grid” by Mather & Mather.

  • Jeff Marchand:

    I saw the poplar in the woodpile in your picture and thought, “That’s a sign of good woodlot management. Good for Cam!”

    All woods have approximately the same BTU per pound. I believe its not what you cut that’s important, but what you leave in the bush to grow and produce seed for the next generation. Cut poplar to make openings in the canopy for maple keys to blow into and you will have more maple seedlings.

    My bush is maple/ash/poplar mix. I like to take at least half the volume of firewood as poplar. Although at the moment with the emerald ash borer heading my way I am cutting mostly soon to be dead ash and dead elms. I can keep the house warm just by burning trees killed by disease and pest. How sad!

    I burn the poplar in the fall and spring when the house does not need an over night burn and save the real hardwoods for December to February.

  • Cam Mather:

    Hi Ron
    I use The Renewable Energy Handbook as my reference because I know how thorough Bill Kemp is about this stuff. His definition of a ‘full cord’ is 4’deep x 4′ high x 8′ long. A ‘face cord’ is one row or face of a full cord, so 16″ deep x 4′ high x 8′ long. Maybe that’s where the confusion comes from.

  • Cam,

    18,000 to 27,000 BTU in a cord ?
    I would have expected a heck of a lot more. What do you call a cord.
    When I was a kid we sold a lot of firewood (that I split) and it I remember a cord was a stack of 16 Feet By 2 feet of wood about 16 inches long.

    That was a fair amount of wood. 22,000 BTU’s is not that much , one BTU will raise a pound of water by one degree.
    Water is about 10 lb’s to the gallon (Canadian / imperial gallon) so that means 10 btu’s are required to heat 1 gallon of water 1 deg / F
    To boil 1 gallon of water starting at 52 deg would be a delta T of 160 deg. requiring 1600 BTU’s. That means that your Cord of softwood would only boil just over 10 gallons.
    Doesn’t seem right to me.

  • Joe Belmont:

    Dear Cam,

    What about reviewing types of wood burning stoves.

    What’s better: cast iron or steel?

    Catalyst or Non-catalyst?

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Cam Mather and his wife Michelle live independently off the electricity grid using the sun and wind to power their home and their CSA. Cam is working towards the goal of making his home “zero-carbon” and with his extensive garden he aims to grow as much of his own food as possible. He is available to speak at conferences and other events and has motivated many people to integrate renewable energy into their lives, reduce their footprint on the planet and get started on the path to personal food, fuel and financial independence.
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