Outdoor Wood Furnace: Heating with Biomass

The last few pages of any magazine are chock full of advertisements that sound too good to be true, and Popular Science is no exception.   For example, I recently covered Edenpure and Sunheat Infrared heaters.  Both of these heaters (they're nearly identical) had advertisements in the back of Popular Science that promised to slash home heating bills.  If you see my posts, you will see that I think both of these heaters are slightly misleading about their optimistic claims.

But I actually have some hope for one of the home heating methods that I recently saw in a Popular Science ad: Central Boiler.

The premise is very simple:

  • Use firewood, a renewable resource as long as it is managed sustainably, to burn in a boiler
  • The boiler heats water that is transferred in underground pipes to the house
  • The water can be used for home water heating and home air heating

A more detailed description of how the Central Boiler works can be found here.  Since the heater heats water first and uses that hot water to heat your home's air, it can also use that hot water in the hot water heater!

Using wood as a heating fuel is a great option if you live in a heavily wooded area and can find a lot of down trees and branches or if you know the wood is being sources sustainably.  Unlike natural gas, heating oil, or electricity, you know that no fossil fuel is being used to heat your home.  This is one of the best options I can think of if you plan to live off-grid and need to heat your home in the winter.

Another nice thing about outdoor wood burning furnaces is that they are eligible for a tax credit for 30% of the purchase price up to $1500.  From the IRS notice for energy purchases that are eligible for the tax credit:

A stove that uses the burning of biomass fuel to heat a dwelling unit or to heat water for use in such a dwelling unit, and that has a thermal efficiency rating of at least 75 percent as measured using a lower heating value.

Central boiler isn't the only option for an outdoor wood furnace.  Heatmor makes stainless steel wood furnaces but their website wasn't as informative.  I found a great forum discussing some of the advantages of each of these biomass heating options at Forestry Forum.

The best configuration of a biomass off-grid heat system would be a wood furnace combined with a solar thermal system.  In the summer you wouldn't need to heat your home, but you still might like hot water for showers and laundry and you could rely on the solar thermal system for this.  In winter, you would still get a little heat from the solar thermal system but would rely more on the wood furnace.  This system would be more complicated and more expensive, but may be good for locations that don't have as much access to sustainable wood.

In any scenario, a wood furnace is another great option to free yourself from the chains of fossil fuels!

Does anyone have wood furnace and if so, what have your experiences been?

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I have been hearing really good things about <a href="" rel="nofollow">outdoor wood furnaces</a> for some time now, but haven't had a chance to own one myself. The article was really helpful, Chris, and I look forward to getting a wood boiler as an early Christmas gift for the family.
Think on this just a bit. If you burn wood indoors in an indoor furnace like I do there are advantages: 1) Outdoor furnaces lose heat despite their insulation. This heat loss warms the outdoors. An indoor wood furnace or boiler also has heat loss, but it is lost inside the house and helps to keep the basement warm. 2) Take a look at the pretty Central Boiler picture above. You've got to pump that heated water through the cold ground. It helps to heat the ground and you burn more wood to stay warm. 3) Are you always home? What happens to the water in the outdoor boiler when you take off for a week in the middle of Winter? Frozen water can burst your piping and your expensive outdoor boiler. This doesn't happen with an indoor burner. 4) Price an outdoor boiler vs an indoor burner. I'll betcha you can get a free year of wood on the price difference. 5) Furnaces and boilers are machines. They require work to keep them running. Do you want to work on an outdoor furnace / boiler or an indoor furnace / boiler? 6) There is a type of efficiency known as combustion efficiency. Many outdoor boilers sit and smolder while waiting for the thermostat to call for additional heat demand. This is inefficient combustion. It creates foul smelling creosote. Indoor burners burn much cleaner. They utilize secondary combustion and burn off the combustion gases. You get more heat from each lb of wood. But you know - I still like outdoor boilers. They are kind of cool. Less practical, but cool.
great post on outdoor wood furnances would it be possible to add any particular brands you would advise purchasing one of these rom ?.
I have a Heatmor outdoor wood burner. We have 25 acres of hardwood so wood is not an issue. We built our home to be heated by wood. We have heat exchangers we purchased through Heatmor that we put into our two main air handlers. We also put Pex tubing in our basement and garage floors and heat both. It also heats the domestic hot water. We ran a 3/4" line and heat exchanger to heat our hot tub. I only burn the wood burner mid October through March. I would like to use thermal solar panels to heat the water in the woodburner to heat the house and domestic water the rest of the year. Any thoughts on this would be appreciated.
Before committing to a wood-fired heating system be sure you check current and anticipated air quality regulations, which can come down hard on some woodburning systems. The pic in the post shows logs next to the furnace. Can you really achieve low particulates and other emissions when burning logs?
Great point. For me, clean air is more important than CO2 emissions. I believe these come installed with all the air regulating equipment, but I may be wrong. I know I saw a lot of info on the vendor's website regarding this.
I'm really hating having a wood stove in the house... so messy ! the dust is unbelievable !!! We live on acreage that is wooded and sustainable. So heating with wood makes great sense for us. But i'd VERY MUCH like to move toward sustainability AND heat with an outdoor woodstove.... Have any of you found a good outdoor stove that heats WITHOUT electricity ?? is this even possible ?? or that incorporates another type of fuel to propel the fans, etc besides electricity.... I really hate being dependent on the pwr company, oil company, gas company, etc.... but i've not seen a unit that incorporates wind or solar.... Have You ??

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