Outdoor Wood Heater -- Keeping your home warm for almost nothing
Using an outdoor wood heater has been a great decision for me.
For six years I have heated my home in Alaska almost exclusively with an outdoor wood heater (wood boiler.) Although it has been a lot of work, and I have had more than a few questions about the environmental impact of heating with wood, I feel that it has ultimately been a good financial decision for my family, and also an environmentally responsible decision.
Here is my experience and my take on the environmental impact of heating with wood (in a responsible manner).
The Outdoor Wood Heater Choice
From the moment I saw an outdoor wood heater advertised in a magazine, I was hooked. Having experienced the mess and inevitable smoke inside my house associated with using a wood stove, and the unfortunate experience of having a runaway chimney fire, the idea of getting all combustion out of my home was very attractive.
Living in Alaska, my heating bills (oil-fired at the time) were truly astronomical. Waste wood from local road building projects and housing developments was plentiful, as were the dead standing Spruce Bark Beetle killed trees on my property.
I was looking at largely free heating fuel to replace the dirty, inefficient, and expensive oil fuel that I had been relying on.
An outdoor wood heater looked like a perfect answer to my biggest heating problems.
My Outdoor Wood Heater (Wood Boiler)
I purchased an old-stock Central Boiler outdoor wood furnace from a friend who was just getting rolling as a new dealer with the company. I opted for a fairly large system, a 385 gallon model.
After looking through the extensive installation guide from Central Boiler, I felt comfortable doing the install myself.
Since I had a forced-air furnace in my home, the installation of a water to air heat exchanger was my only option. It was also about the simplest systems to retrofit an outdoor wood heater into.
I got really creative and built my own sidearm tube and shell heat exchanger to heat my domestic water, which complicated the installation a bit.
The actual install was pretty easy. I placed the outdoor wood heater on a cement pad I formed and poured myself. The boiler is very heavy and I had to borrow a neighbor's front-end loader to both unload the unit on delivery and to move it into position once I had the pad ready and underground PEX tubing buried.
I buried the 1” PEX supply and return lines at a depth of about 3 feet, using a commercial insulating tube material that surrounds both pipes. I also added a layer of 2” extruded polystyrene “Blueboard” (R-10) on top of the insulating umbilical. I was careful to back fill with clean sand and gravel. The result is that the snow does not melt on the area above the heated water lines at any time during the winter.
I placed the indoor heat exchanger in the plenum above my updraft furnace. A separate electronic thermostat that controls only the furnace fan provides heat control when we are relying on the wood system. Should the fire go out, I have a second thermostat set at a much lower temperature which would take over and activate the burner on my furnace (now gas-fired, as a gas line was finally available to us a few years ago).
Using our Outdoor Wood Heater
The day-to-day usage of our wood boiler has become part of our regular routine. I place a load of wood into the burner in the morning before work and a second in the evening just before dinner. Other than that, I empty the ashes once our twice a winter and check the water level every week or so.
The aquastat in the boiler maintains water temperature at between 174 and 185 degrees. A small pump circulates this hot water into our home 24/7.
One problem associated with an outdoor wood heater is the smoke that they generate and the effect of that smoke on neighbors.
The Wood Boiler Controversy
Many local governments have severely limited or even banned the use of outdoor wood heaters due to this problem.
I have found that my outdoor wood heater produces a great deal more smoke if I burn poorly seasoned or wet wood. I have also experienced more smoke problems if I try to load too much fuel into the firebox at once. The large fuel loads will demand more air than the furnace can draft, causing incomplete and smokey combustion.
Small, hot fires using well-seasoned wood create much less smoke. And appears to consume less wood as well.
A few years ago I bought a retrofit power draft fan kit from Central Boiler. I've found that this option greatly reduces the total smoke output of the furnace. While all of these units produce more smoke when they first actuate and go into a burn mode, the power draft greatly reduces the duration of this smokey phase. A power draft system really should be standard on all outdoor wood heater models.
A newer series of outdoor wood heaters was released a few years ago (phase II) that meet all EPA requirements for wood heating appliances. Although the cost of these models is higher, their efficiency is significantly improved.
The Environmental Question and Heating With Wood
Several studies have pointed out that the carbon produced by burning wood is freely circulating carbon that is in the current ecosystem, causing no net gain in the overall carbon balance of the atmosphere.
Burning fossil fuels, on the other hand, releases carbon that was naturally sequestered centuries ago, causing carbon to build in our current atmosphere.
Other studies have pointed out that while wood heating creates more particulates, there are fewer other contaminants when compared to fuels such as oil, coal (from coal fired electric plants), or natural gas. Most sources have suggested that of the combustion heating fuel sources, gas or wood are considered the cleanest.
Responsible Wood Burning
I try to burn wood that is kept dry and is seasoned for at least two years. In addition, I burn no wood that was cut specifically for firewood, opting only for wood taken from construction project clearing operations, or from naturally dead wood or storm blow-down trees from my own property or neighbor's property.
Wood pellet stoves are another good environmentally appropriate way to heat with wood. In fact, many outdoor wood boilers manufacturers have introduced models with pellet hoppers designed to use wood pellet fuel.
My Bottom Line on Using A Wood Boiler
First, check your local regulations and limitations. A lot of areas will not allow the use of these heating methods. Many other areas have introduced restrictions on chimney heights, clearances from property lines, and visible smoke allowances.
Outdoor wood boiler units are really not appropriate for most suburban or urban situations.
Be prepared for a significant outlay of cash. If I put in my system today, it would cost in excess of $13,000. Other systems will be less, but they are far from free.
Heating with wood is something of a lifestyle. I spend a lot of my summer cutting, hauling, splitting, and stacking firewood. It also takes planning. I am busy looking for wood this year that I will burn two years from now. It can also be a challenge to get out in a wind storm at 5:00 am to add wood to the stove.
Be realistic in your outdoor wood heater planning. It's been a good decision for us, but the reality is that it probably would not be a good fit for most homeowners.
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