Build a Top-down Fire for Cleaner, More Even Heat
September 26, 2008
In wood stoves and boilers, the largest amount of pollution and the lowest efficiency at any one time usually comes when a fire is started the “traditional way”: paper on the bottom, then kindling, then your logs. When the paper and kindling flame up, the entire load of wood catches fire. The wood starts giving off gasses in the form of smoke that travels very fast through the cold firebox and does not have time to burn. The result is a lot of smoke out of the chimney and less heat for your home. That smoke is not just pollution, it is also valuable fuel. Sometimes, the kindling and wood collapses onto itself, killing the fire entirely (this happens to me every time!).
To avoid the smoke and collapsing fire, try out the “top-down” fire method. First, place your logs in the firebox leaving room in the top of the firebox for kindling, paper and an air space. Then add a few pieces of heavy kindling followed by some fine kindling. Finally, roll up single sheets of newspaper; tie each piece into a knot and place four or five on top of the kindling, finishing with a couple pieces of fine kindling on top of the paper. Knotting the paper keeps the pieces from rolling off of the wood. Light the paper, close the door and the fire will start.
Rather than having the entire load of wood catch fire at one time, the fire starts at the top of the load and burns down, like a candle. The firebox heats up gradually when the fire is small. As the firebox gets hotter, the logs on the bottom start giving off wood-gasses which are burnt as they pass through the flames above. When the logs on the bottom start to burn, much of the creosote-producing gasses are gone and the logs burn more cleanly. This fire building method will reduce the emission from fire starting by as much as 80%!
This type of kindling fire can provide a long period of effective heating without having to open the door to add wood or adjust the fire. Top-down fires work best with stoves and boilers that have the air flow parallel with the logs. It may take some practice to use this with stoves and boilers with air intake coming in against the long side of the logs. Top-down fire starting will not work with true down-draft boilers where the combustion air flows down through the coals sitting on a grate. And it is not good for an open fireplace or campfire where you want a lot of flames all at once.
When trying the top-down fire starting method, remember to be patient; it takes time to get used to the fire not flaring up all at once. Adding a new-fangled starting technique to an old-fashioned heat source might just be the recipe for cleaner air.
To learn more about making smart home energy choices and to watch a video on efficient wood stove operation please visit MaineDEP.com.
This column was submitted by Louis Fontaine, Compliance Manager for the Department of Environmental Protection’s (DEP) Bureau of Air Quality. In Our Back Yard is a weekly
column of the Maine Department of Environmental Protection. E-mail your
environmental questions to infodep@maine.gov
or send them to In Our Back Yard, Maine DEP, 17 State House Station, Augusta,
ME 04333.
