Outdoor Wood Furnace Facts vs Fiction

One of the many reasons why some homeowners refuse to use outdoor wood furnaces and wood burning stoves is that the belief that these are dirty and the use could cause emissions. Take the question of someone that has never tried this method before:

“Outdoor wood furnaces are dirty and produce more emissions than other wood burning devices.”

Outdoor wood burning furnace facts:

When tested by the U.S. Environmental Protection Agency (EPA) in 1995, Central Boiler’s non-qualified outdoor wood furnace was found to have similar emissions as wood stoves: EPA 600/SR-98/017: “Compared to a wide range of residential heating options, these furnaces’ emissions were of the same order as other stick wood burning appliances.”

The US EPA has announced a voluntary emission program on January 29, 2007. This program was specifically for the outdoor wood furnace industry and was the first that was ever developed and made available for this class of wood heating appliance. The EPA OWHH (Outdoor Wood-fired Hydronic Heater) Phase 1 Program included a test method (Test Method 28 OWHH) and an emissions limit of 0.60 lbs. /million Btu of heat input. The Phase 1 Program ended on March 31, 2010.

The EPA HH (Hydronic Heater) Phase 2 was launched on October 23, 2008. This phase included Test Method 28 OWHH and ASTM E2618 and E2515 and an emissions limit that should be met for manufacturers to participate in the program. The US EPA announced Phase 2 of the voluntary emission reduction program for wood and wood pellet furnaces with an emission limit of 0.32 lbs. /million Btu of heat output. Appliances that meet the requirements for Phase 2 are tagged as “Program Qualified.”

You will be able to identify appliances that have passed or qualified the EPA Phase 2 Program Qualified by the EPA Phase 2 Program Hangtag (White). This tag means that the output based emission limit of the appliance is very clean and extremely efficient.

It is expected that there will be very few indoor EPA certified woodstoves that would be able to meet the EPA Phase 2 output based emission limit (0.32 lbs. /million Btu output).

Nature’s Comfort offers the EPA Phase 2 Qualified GT-6000, which you can look at here.

So to answer the question regarding the cleanliness of outdoor wood burning stoves, it would be safe to say that stoves that are recently manufactured may be considered clean and emission-free. Stoves that have been in service for quite some time now should be tested or replaced if dirty emissions are your concern.

Remember the following:

  • Purchase only from qualified manufacturers such as Nature’s Comfort. Be sure to read online reviews and look for professional recommendations regarding the safety of an outdoor wood burning stove brand.  A good site to read about furnace reviews is Furnace Compare.
  • Look for the white EPA Phase 2 Hangtag when buying new stoves. If possible, avoid purchasing second hand stoves or used stoves but invest in quality and efficient outdoor stoves instead.
  • Always follow manufacturer’s instructions on how to use new stoves especially in operating and maintenance. Only when users make the most of their outdoor wood burning stoves will they be able to burn fuel and heat their homes more efficiently.

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