Keeping a chimney clean means a lot more than just using dry firewood. If you use a wood stove to heat your home more than once a week, you should really get yourself an EPA certified stove.
Most EPA certified stoves emit an average of around three to four grams of particulates per hour, compared to 20-40 grams for the uncertified wood stoves made before 1988.
Also, the EPA tells us that certified stoves are “50% more energy efficient” than uncertified stoves. This means, for example, that instead of burning wood at 50% efficiency, you could be getting 75% efficiency from your wood. Instead of sending smoke up your chimney, the most efficient stoves reburn the smoke before it goes up the pipe, either with secondary burn tubes or a catalytic converter. Smoke, after all, gives off plenty of heat because it has lots of Btus.
There is a catch: the EPA does not require companies to test for efficiency, so consumers have no idea which stoves are more efficient than others. The piece of information most valuable to consumers, which helps them understand how much money they can save, is still missing.
As a general rule, if you really want a high efficiency stove, get a catalytic stove or one of the new catalytic hybrid stoves. The EPA is just beginning to list actual efficiencies on their list of certified wood stoves, instead of just using estimated default efficiencies. Today, the most efficient stove on the EPA list is the Woodstock Soapstone Progress Hybrid with 81% efficiency at higher heating value (HHV). A close second, the Travis Cape Cod Catalytic Hybrid has 80.1% efficiency.
Both these stoves would be around 90% efficient using the European lower heating value (LHV) method. The United States typically uses HHV, except now almost all stove manufacturers use LHV to make their efficiency numbers look better.
If you are trying to assess efficiency, you have to know:
- if the listing is HHV or LHV
- whether it is estimated or actual
- what test method was used
For now, if you really care about efficiency, only trust numbers that are actual efficiencies using the B415 test method. If they report in LHV, look for numbers in the 80s. If it’s HHV, efficiency numbers in the 70s are quite good.
If not you’re not shopping for a wood stove, pellet stoves have an even greater range of efficiency, starting in the 40s and up to the 90s. Ask the manufacturer for actual efficiency numbers using B415. If they don’t have them or won’t share them, consider buying from one of the companies that do provide them.
Guest blogger John Ackerly is President of the Alliance for Green Heat, a consumer organization promoting cleaner, more efficient residential wood heating.