Non-catalytic woodstoves use secondary combustion air in order to burn off wood gases before they can leave the firebox. Because of this, they are not as controllable as a pre-E.P.A.
Non-catalytic woodstoves use secondary combustion air in order to burn off wood gases before they can leave the firebox. Because of this, they are not as controllable as a pre-E.P.A. “airtight” woodstoves. It was possible to “turn down” a pre-E.P.A. woodstove and achieve a long low smoldering fire. This was often perceived as being highly efficient. From an emissions viewpoint nothing could be further from the truth. From a user-friendly viewpoint, I fully understand why this was perceived as being efficient. For example, let’s load a non-catalytic woodstove with six sticks of wood. Over a period of 4 hours let’s say it produces 30,000 btu’s of heat per hour with less than 7.5 grams of particulate emissions per hour. Now let’s load the same six sticks into a pre-E.P.A., “airtight” woodstove. This stove may burn for 8 hours producing 10,000 btu’s per hour with around 80 grams of particulate emissions per hour. 4 X 30,000 = 120,000 btu’s; 8 X 10,000 = 80,000 btu’s. You see a difference here of nearly 40,000 btu’s. The E.P.A. stove has produced more heat from the same amount of fuel. The “airtight’ burned longer (more controlled) than did the E.P.A. certified stove but wasted 40,000 btu’s of energy up the chimney in the form of wood smoke (unburned wood gas). Some of it went into the environment and some of it condensed in the form of creosote in the chimney. I’m making numbers up but under the identical conditions (same chimney, same house, same fuel, different stoves) these numbers are accurate. An E.P.A. certified woodstove should produce about the same amount of heat with a third less wood than an old “airtight” but it does it at a price. It will burn much faster and for a shorter period of time than the old “airtight”.