Author – Todd Woofenden
Since EPA-certified stoves are a recent phenomenon, there are lots of older, pre-EPA stoves in use.
Also called Franklin Fireplaces, these are cast-iron stoves that look more or less like a fireplace (except they stand on their own, on a hearth, and are connected to the chimney with a stovepipe). They have loose-fitting doors, and aren’t at all airtight. They are designed to be operated with the doors open or closed. And while Franklin stoves are often beautiful, and offer the charm of an open wood fire, they rate at the bottom of the list for overall efficiency, even when operated with the doors closed. About the only thing with a lower efficiency is an open fireplace (or a campfire!).
There are countless models of old, non-airtight stoves other than the Franklin. These include barrel stoves (an oil barrel with a load door, legs, and a flue collar retrofitted to it), small camp stoves with un-gasketted doors, turn-of-the-century pot-belly stoves, and a myriad other stoves built without airtight technology. Ironically, although these stoves offer low overall efficiency (since lots of heat is lost up the flue), their leaky design actually causes them to burn fairly cleanly under most circumstances. Since you can’t regulate the air very well, the fire tends to burn hot, consuming most of the combustible materials. But try to heat your house with one, and you will wonder how people managed to keep from freezing to death back then!
Before the EPA regulations came along, everybody thought airtight stoves were just terrific. (For those of you who still do, read on!) Tight, gasketted load doors, carefully fitted seams, and tight air inlet controls give the user great control over the burn rate. Airtight stoves achieve a long burn time by allowing very low rates of airflow into the stove, causing a low, slow, smoky fire.
So what’s wrong with that? In short, airtight stoves offer a long burn, but not a clean burn. The advantage is: you get a long burn, so you don’t have to add wood as often. The disadvantages are: you waste lots of fuel, since all that smoke represents unburned fuel; you pollute the environment (and maybe annoy your neighbors); you get less heat from a piece of wood, since, again, smoke is unburned fuel; and you run a much greater risk of creosote buildup in the chimney and potentially-disastrous chimney fires.
Why is that? The answer is that the “airtight” generation of stoves allows the user great control over the air entering the stove, but doesn’t maximize combustion. Burning wood (or anything else) requires heat, fuel, and oxygen. Air tight stoves create enough heat, and the wood is the fuel. But during low-burns, they starve the fire of oxygen, so combustion is incomplete. Smoke exiting the chimney is a telltale of incomplete and wasteful wood burning.
Modern, EPA-certified stoves offer the best of both worlds: a long burn time and a clean burn. So you get maximum heat and minimum fuel consumption. We will discuss how they accomplish this below.
If you have an older stove, what can you do, short of buying a new stove?
Although older stoves can’t achieve anywhere near the overall efficiency of the new EPA-certified stoves, proper operating techniques can at least reduce pollution and increase fire safety. For advice on better stove operation, see “Tips for Wood stove Users”
~ Todd Woofenden