Lahey: Green Wood

Mar 7, 2014

We are at that point in the winter where our best-laid plans of last fall have become untidy. Orderly rows of seasoned wood, have become jumbled chaos, strewn with weather-beaten tarps and tumbling, unruly, onto the snow. In contrast, the orderly, square stacks of green wood stand tall, and because of poor planning on my part, tantalizingly close to our mudroom door.

Those stacks only hold the promise of heat however, because once inside, the joke’s on us. That green wood barely smolders, mocking our impatience and haste, as water bubbles and steams out the cut ends.

This week, it was my ten-year-old son Finn’s job to keep the wood racks full, and as the temperature struggled to reach zero, he finally fell victim to the green wood’s siren song.

I could tell the moment I slid into the driveway. The perfect piles we’d stacked last month looked as if they’d been targets of a mortar attack, and bright, sweet-smelling green wood was stacked tall in the mudroom rack. Finn’s snowsuit lay abandoned in a heap outside the living room door, boots standing tall, still jammed into icy pant legs.

When I shouted my hello, Finn ran to the top of the stairs, announcing with glee that he’d fulfilled his household duties, and please, please, could he play a game of Minecraft? Fine, I said, but first, I had to show him something.

Sensing a problem, he crept into the mudroom with trepidation. I handed him a log from his newly stacked cache.

“Hold that,” I said. “feel how heavy it is?”

He nodded, impatient, eager to escape back into the warm house.

“Now feel this log. About the same size, right? Feel how much lighter it is,” I said as I handed him the seasoned wood.

His face registered the difference, the reality of his situation not yet sinking in.

“Green wood is heavier because it’s still full of water,” I said, “and all that water also means the green wood won’t burn.” Then I paused for effect and looked at the rack.

His eyes moved from the log, to the rack, then back to the log, then returned to my face, and realization dawned.

The next hour of our negotiation revealed the depth and breadth of his creativity and skill in the art of emotional manipulation, but in the end, he relented, if only to end my tutorial on the science of wood heat.

Green wood is about forty to sixty percent water, so when it burns, much of its heat energy is spent evaporating the water. For every percentage point of water lost to seasoning, the log gains about one percent of heating energy.

Finn’s immediate concern was more practical. A green log can weigh 1-2 pounds more than a seasoned log of the same size, a difference that’s particularly noticeable the second time you carry it, one log at a time, to be stacked neat and square for next year’s fires.