Ben Falk on Wood Heat & Homestead Security

From the Vermont Commons article.

Ben Falk writes: Amid the excitement surrounding technological advances that may be useful in our transition beyond fossil fuels, there is surprisingly little discussion about the daily living techniques required to make this transition a reality.  This proficiency-building of the individual, home, and community – increasingly referred to as “The Great Re-skilling” – is the focus of this Homestead Security column.

Food, clothing, shelter… and in Vermont: heat.  There’s no escaping this part of life in the Northern Forest, and as the age of cheap and available liquid fuels draws to a close we face both new and old methods for keeping warm.  For a short generation we’ve become accustomed to the ease of cheap liquid fuels flowing from tank to boiler controlled only by the flick of a dial.  Now we find ourselves already making the transition back to the solid fuel lifestyle and its requirements:

•    Skills – both new and old
•    Labor and time
•    Keen awareness (it’s much easier to freeze the pipes, burn the house down, or combust your fuel poorly with a wood stove than an automated furnace).

Self-reliant heating involves the laborious and skill-intensive process of fell-in-the-forest, haul, buck, split, stack, haul again, tend.  Whoever famously said that “wood warms you twice” obviously had their wood split and delivered.  This article briefly outlines one oft-neglected step in the complex art and science of generating your own heat from this currently forested landscape.

Why wood?

In rural New England wood is the only sustainable and seasonally reliable source of heat that most of us can afford.  Super-insulated passive solar homes are great, and if you live in one you’re exceptionally fortunate, but you’ll most likely still need some wood. And then there are the rest of us, who live in 99.9 percent of the other homes and can’t afford a $40,000-$150,000 complete thermal retrofit.

“But wait,” you say, “there’s solar hot water.”

Solar hot water is also great, but let’s face it, it’s still mostly for rich people here (until Vermont’s incentives catch up with other states) and for the minority of Vermont homes with good solar access. Even after you spend the $8,000-$40,000 on solar panels, plumbing, and weatherization, you’ll still need a solid cord or two to get through the overcast deep freeze of November-through-January.

“But wait,” you say again. “No need to worry. They will be making cellulosic ethanol and biodiesel… and hydrogen!”

This article is for those of us not holding our breaths waiting for Them to provide us reliable and affordable heat.  So, Technotopia aside, warmth=wood.

STEP 1: Secure a firewood source, either your own woodlot or a close friend and neighbor with a large one.

STEP 2: Process your firewood – fell, haul, buck, split, stack.

This last step is where most of us tend to go wrong.  Traveling around the state I see more people slowly rotting their wood than quickly drying it.  A stack of wood against the north side of a house with a tarp over it is an ideal way to grow mushrooms but it won’t yield wood fit for your stove, although many people burn such wood year after smoky year.  The following is an overview of why it’s hard to dry wood well and what it actually requires, putting you one step closer to local self-reliance.

Wood wants to be wet

Really, really wet.  In fact it’s the only typical raw material that holds more water than good soil (usually 120 percent to 200 percent of its dry weight).  The cells in a tree’s wood have such a stubborn grasp on water (it’s their life currency) that they only release it fast enough to avoid rotting under specific conditions.  And it’s in these conditions that you want your fuelwood.

To make things even more difficult, these conditions are hard to come by in Vermont: Throw a hundred pieces of wood from a plane flying over New England and 99 of them (or probably all 100) will begin rotting within a handful of months.  This is why finding a large supply of dead wood to burn in the forest is often impossible – the fungi get to it first. Burning green wood (more than about 20 percent moisture content depending on species) is a bad idea because it promotes creosote build-up in the chimney, is hard to keep ignited (while at the same time keeping air flow through the stove to a minimum), reduces heat output by 20 percent to 70 percent (causing one to need about one-and-a-half to three times as much wood for the same amount of heat), emits much more air pollution, and is heavier to process.  The only tree in our Northern Forest that is burnable in close to its green state is American ash, due to its exceptionally low standing moisture content.

Drying time frame

Under average conditions it takes about one year or more to dry 16-inch cordwood thoroughly.  Under good conditions cordwood will dry within five to seven warm-season months. Under the best of conditions (very sunny, lots of air flow, tall thin stacks, and stacked with lots of air space between the billets) one could dry wood adequately for efficient burning in three to four warm-season months if the billets (pieces of cordwood) are in very short lengths (14 inches or less) and split on most or all sides.  Even small billets that are unsplit take a very long time to dry as the bark holds moisture in the wood very effectively.

Remember that wood only really dries in Vermont between April and November when temperatures are above 40°F and humidity levels are relatively low.  A well-sited and -built wood stack does most of its work during July through September with high heat and low humidity.  If, like most people, you find yourself needing to rapidly dry a small amount of wood, piling it near the stove for a week or two before burning it can remove as much moisture (especially in small billets) as months of drying – as well as humidifying your house.  Having the wood near the stove for even just a few days before burning can polish off the remaining excess moisture of marginally dry wood and is an oft-used strategy.

The soundest approach to properly heating with wood is to put it up well in the autumn or winter a year or more before it will be burned.  This requires a surprising amount of space dedicated to wood drying: about 128 square feet for four cords, typical (minimum) of most home needs; that’s one stack 4 feet high by 4feet wide by 32 feet long per year, two of them at the beginning of winter.  In addition to food gardens, the life-after-oil front yard will be dedicated to wood storage – about two car parking spaces worth of wood; more if you’re home isn’t very well insulated and/or your stove burns inefficiently.

Drying methods

Skillfully drying firewood (or building lumber) requires managing all the moisture factors – precipitation, temperature, and air movement – through the proper location and construction of a wood stack.

Optimal wood drying and storage sites are:

○    Easily accessible to sled, cart, truck, or tractor
○    Off the ground
○    In a warm sunny area (against a south-facing wall can be ideal)
○    In an area with good air flow
○    Near the point of use

Proper construction of your fuelwood stack (you’re crafting a stack not making a pile here) involves the same things as any building: a stable foundation, stable shape (not too tall for the width), solid connections (the way the wood stacks against itself) and a sound roof.  A solid foundation can usually be made by propping up pallets or 2x4s to form a wide, level surface with plenty of support points.

Ensure air access underneath the stack. Remember that the bottom layers are most likely going to get wet in snowy weather as it drifts against the pile and by lower air flow volumes and wetter air near the ground.  Ideally, you burn the top three-quarters of the pile and then restack the remaining one-quarter on top of another stack for the following year. Stable connections between the layers of cordwood are made by ensuring that the wood is of a uniform length – usually 16 inches or 18 inches – that they are layered up neatly and flatly, and that any retaining of the walls (see figure 1) are rock solid.

A sound roof is best made out of anything impervious, large, flat and rigid, like scrap plywood or, best of all, scrap metal roofing. Ensure that the roofing is pitched and drains water away from any area that would backsplash onto the wood.  Drying wood under a tarp seems like a fine idea until you try it.  When you do, you realize how hard it is to keep the wind from removing or mis-aligning it and snow from forming depressions in it so that water slowly percolates into the pile.  If you must use a tarp, heavy canvas or rubber tarps are infinitely more workable than light poly tarps.

Figure 1: A Well Made Stack of Solid Fuel

Wood Stacked Right.Wood Stacked Right.

Once you have a good supply of well-dried fuelwood on hand you’re ready to heat with it – and that’s where the fun and challenge continues.  From air-tight stoves to old school cook stoves to masonry ovens to wood boilers, the options are many.  Similar to the drying process, wood burning is usually conducted poorly, with excessive consumption, inefficient combustion, and excess pollution typical – issues that are increasingly coming to the fore as Vermont turns again to wood as our primary heat source.

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