How to make a grate fire really great
If you have a fireplace, why not make it more efficient in providing a heat source for the house? Here are some tips that have worked well for me: * Stack the logs in such a way as to cause the flames (a) to lick only the back and side walls of the fireplace, and (b) burn on the room-facing surfaces of the logs for maximum radiation of heat.
Fig. 1 shows how to build the stack. Place the large logs against the back of the fireplace and the small ones (or twigs) in front of them. Be sure that a draft gap is left between the large and the front logs, especially if the surfaces are not sufficiently uneven to form the gap naturally.
The flames originate in the gap and provide the heat that maintains the burning on the front of the large logs.
The ashes underneath should be sloped forward to expose all the glowing embers to the room. You do not have to prepare the sloping ash bed. It forms inevitably when the logs are stacked and the fire fed, as shown in Fig. 1.
Remember, big or fresh logs should go on the back; small or partially burned logs on the front.
Fig. 2 shows an improvement on the basic idea. The stack of logs is identical. The improvement is achieved by placing a shield close above the logs, the purpose of which is (a) to reflect heat at them so as to maintain burning of the facing surfaces with less attention and at a higher temperature (radiational output is proportional to the fourth power of the surface's absolute temperature); and (b) to force flames closer to the fireback to extract more heat.
The shield should be made of thermally insulating material. I use 9-mm (roughly three-eighths of an inch) asbestos plate, resting on two steel rods that are wired to the andirons.
* Prevent burning on the back side of the main logs. This is best accomplished by keeping the ashes near the fireback so high that the lowest log can be sunk into them and ash shoveled into the crotch between the fireback and the logs. The arrangement is illustrated in Fig. 2.
* Make the logs burn evenly along the whole length and, if possible, have them fill the complete width of the back wall. Doing this will utilize all the available radiating surface. More important, placing the logs touching all three walls helps their ends to burn. This eliminates the usual smoke plume on them and prevents cooling of the fireplace by blocking fresh air rising in the corners.
Avoid high flames and the common mistake, shown for comparison in Fig. 3, of concentrated burning in the middle and on the wrong side of the logs. Spread the wood into the corners.
If the directions are followed, the burning is almost smokeless and only glowing embers are left at the end. In other words, there are no smoldering logs.
The creosote buildup is minimal as well, and the ashes need to be removed less frequently (two or three times a season in weekend usage).
* Remove obstacles to radiation, such as screens and glass doors. About one-fifth of all incoming heat is stopped by them. Whether this is safe for you depends on what kind of wood you burn and on the arrangement of the room.
* Place radiation-reflecting material - for instance, aluminum foil - on the hearth and the adjacent floor. Common flooring absorbs heat and, instead of warming the room, warms the air drawn into the fireplace.
* Keep the damper open to the minimum. Throttling the flue avoids drawing more air out of the room than the fire needs. The expelled air is replaced by the cold air from the outside.
* Your fireplace will probably be hottest when the last log burns low. Take advantage of the accumulated heat. Position the damper on the lowest notch and remove the screen or glass at this time, assuming they were used when the flames were present.
* Feed the fire with smaller logs toward the end to make sure they will be burned out before bedtime. Following the above steps should result in no smoldering coal left at that time.
Close the damper about a half hour after the flames disappear. The heat and gases from the remaining embers will cause no harm. My latex-painted mantle is as white today as it was years ago when I stopped wasting heat for the many hours it took the embers to cool down and go out.
The benefits of even slightly increasing the efficiency of a fireplace are astonishing.
Authorities generally agree that between 85 and 95 percent of the wood-heat content goes up the chimney. If building the fire properly means that only 85 percent rather than 95 percent of the heat is lost, the output of the fireplace has tripled.