So how much is in a cord of wood?

As anyone who heats with firewood knows wood is generally measured in cords, but you also would know a cord is a pretty fuzzy measurement. Technically a full cord is a stack 4 feet high by 4 feet deep by 8 feet long. The problem is every time you stack that pile of logs it will sit a bit differently altering the gaps between pieces and thus changing the overall volume of the pile. Then there is the other issue that how much potential heat energy in that pile also depends on what type of wood it is, how dry it is, and so on.

(Please note some of the links in this blog post are affiliate links. What this means is that should you click through them and make a qualifying purchase I will receive a commission which I’d certainly appreciate since it helps support this blog project. However, this shouldn’t increase your cost any, and certainly don’t ever feel like I’m pressuring you to buy things through the links I offer or anywhere else. I’m all about being frugal first!)

For years I had been heating my home with a small wood stove using between 2 and 3 cords of wood each winter. This is wood that was split and stacked to look similar to this first photo.

Last year when I began using my newly made rocket mass heater (RMH) I went out and split the wood I was going to use up a bit further using my ax and maul. This is because the RMH has a much smaller burn chamber and generally does better with smaller pieces of wood.

In the old days with the wood stove on an average winter day I would fill my wood hod with logs as full as I could, then grab an extra one to carry inside in one hand while the other hand hauled the hod full of logs. I would burn all of this, and then do it one more time. So that would be two loads of logs, plus a couple extra logs each day.

Once I started using the RMH my use for the average winter day dropped down to just one hod full of wood split a bit smaller, with no extra logs grabbed. Thus I estimated that I was using 50% to 55% less firewood.

Over the summer I’ve been working to refine my system. I’d heard the RMH works best with smaller pieces of wood. This exposes more surface area at once, allowing it to burn hotter. A regular wood stove might not be able to take the extra heat, but the RMH is designed to burn super hot and then transfer much of that heat into a storage mass to be slowly released over many hours. From what I read, the greater the temperature difference between the hot exhaust and the cooler mass the more heat gets transferred, and thus not sent out the chimney as waste. So I want to burn as hot as I can to store as much as I can.

So the first thing I did this summer was build a kindling splitter so I could much more safely and easily split the logs up into smaller pieces that I was able to do with an ax.

Then I began splitting up my pile of firewood into smaller pieces. It became a nice daily exercise regime. Each day after hammering on some vessels in the studio I would then go and split up a wheelbarrow load or two of firewood.

The other thing that makes the firewood burn hotter is to make sure it is good and dry. Storing it in a wood shed is a much better way to go than in a pile outside, under a tarp. The tarp method is actually about the worst way to do it. So I converted part of my old metalsmithing studio into my new wood shed and began filling it up.

As I was filling the woodshed it seemed to me that the pile in the shed was growing at a faster rate than the pile I was pulling logs from was shrinking. At the time I just noted that, but didn’t think much of it.

The cold weather started early this year, with snow on Halloween even! So I’ve been burning wood for a while now to heat the house. This new, more finely split firewood does indeed seem to burn hotter which is nice. However, as the temperature dropped down low to what I expect to have during the bulk of the deep winter days I noticed that burning the one full hod of wood didn’t seem to be keeping the house quite as warm as it was last year. I was puzzled, and a bit concerned. Did my RMH suddenly become less efficient? Was all my work splitting the firewood into smaller pieces a bad idea? Did this really result in me storing less heat in the mass from a burn rather than more?

Then I began to think about how splitting the regular sized logs into much smaller pieces and stacking it in the woodshed seemed to “fluff” up the wood, making the newly stacked pile seem bigger than the pile I was splitting. A new question came to mind. With more finely split firewood do I actually have less wood when I fill a hod?

So I thought of a small experiment to test this which I just ran this morning. I went out and filled the hod with as much firewood split as I used to use it when I had the wood stove. Again, that is what you see in this picture.

Then I got out my kindling splitter and split these logs up into my new size making the pile you see in this next photo.

Finally I took all this more finely split wood and went to stuff it back into the hod it used to all fit into. As I suspected the wood did indeed “fluff” up. I filled the hod, but still had enough left over wood to fill it a third or more again!!

So from this I conclude that this winter as I’ve been burning just one hod full of firewood I’ve actually been burning less wood than I was last winter when I had only split the normal logs a little smaller. When I feel the need to burn a bit extra beyond a full hod I’m not really burning any more wood than last year. The RMH didn’t get more inefficient. I’m burning the same weight of wood, it’s just the smaller pieces end up filling more volume.

So I prepared 1.75 to 2 cords of finely split firewood for use this winter, hoping that I would only use half of what I’d stored away. It turns out these “cords” of wood are not as much as the cord I burned last year, so I can expect to burn more. I might even burn most of what I prepared. We shall see. It makes me feel better to realize this though.

This also makes me rethink just how efficient my rocket mass heater is compared to my old wood stove. I had thought it was 50 to 55 percent more efficient, but I now realize the hods of wood I burned last winter, even though they weren’t split as small as I have it this year, were still “fluffed” up a bit from what I was using with the prior wood stove. So I’m going to guess I was using about 60% less wood by weight. What will this winter be as I tweak the system more in search of greater efficiency?

If you want to know more about my rocket mass heater you can check out this post on the making of it, and what they are in general, or this post about my efforts to clean out the accumulated fly ash this fall in preparation for the new heating season.

Studio Snippet

In the studio right now I’m trying to get a batch of work finished up so I can send it off to some of my galleries before the holiday shopping season really gets going. I fear, as normal it seems, that I’m running behind. (Why am I typing this now instead of chasing metal I wonder…)

Anyway, I’ve finish the raising and planishing of a dozen or so pieces that will become part of the Luminosity series, and I have a couple more elaborately chased pieces ready for final finishing. Now I am focusing on finishing the chasing work on this piece and one other for this batch of work. For the next few days it should be all about chasing!

I also thought I’d note I’m using a new additional light at my chasing station. This is a flexible goose neck LED lamp. It lets me focus a bright light right into the zone I’m working at from an angle where my fingers aren’t creating shadows. I’m still deciding if I fully like it. I love the extra light, the awkward part it that the lamp feels like it’s in my way when I get it positioned where the light is coming in from the proper angle for no bad shadows. I can position it to where it’s not actually in the way, as in I’m not hitting it with my hammer back swings, or knocking into it with my face. However, it is right there in that zone and thus feels like it’s in the way. I’m getting used to it though.

I’m happy to have a site where I can again allow comments. (I had to shut them off on my main website because the spam was simply uncontrollable!) So please I encourage you to share thoughts of your own. My general rule about comments though is just to play nice. Differing views are fine, but I’m not interested in engaging in or moderating verbal fights. If I feel things get out of hand, by whatever criteria I decide, I’ll just start blocking or deleting things.