Dear James: Whenever we use our great room fireplace, some smoke comes out into the room. I am going to add one to the master bedroom. How can I keep the new fireplace from being smoky? — Ron T.
Dear Ron: You definitely are not alone with the problem of a smoky wood-burning fireplace. More than half of fireplaces cause some smoky conditions inside homes, and it is difficult to ever totally rid the room of the smoky odor.
There are many possible causes of a smoky fireplace. The fact that your existing fireplace belches smoke out into the room whenever you use it indicates a fireplace design error. When fireplaces smoke only occasionally, it may be from an improperly laid fire or unusually windy conditions outdoors. These can blow the smoke back down the chimney and/or create a negative pressure inside your home.
With proper design, your new fireplace in the master bedroom should be relatively smoke-free indoors. The relationship between all the dimensions of a fireplace is critical to its creating a strong draft up the chimney. An aesthetically pleasing fireplace size and style are nice, but don’t let this override sound fireplace design principles.
The size of the opening and the depth of the fireplace are most important to keep smoke from coming out in the room. Most fireplace design books have many sets of acceptable dimensions. As an example, a fireplace with a 28-inch-wide opening should have a height of about 24 inches and a depth of 16 inches.
Also, the sides of the firebox should not go straight back. They should be tapered so the back wall of the fireplace is narrower than the opening. If your remodeler cannot find the correct dimensional relationships, you can order the booklets “Residential Fireplace Design” and “Residential Fireplaces — Details and Construction” from the Brick Institute of America, 11490 Commerce Park Drive, Reston, Virginia 22091.
If your budget is tight, you can scrimp on the quality of the face brick or mantel, but not on the chimney. Each year, many house fires and deaths are caused by fires that start in the chimney. This can be a particular hazard in the bedroom, where you may fall asleep and not realize a chimney fire has started until it is too late.
Creosote builds up in any chimney over time. It is very flammable, and when hot materials are raging in the fireplace, this creosote can start burning the inside of the chimney. A well-built, quality chimney can generally withstand this heat. A poor-quality chimney can allow any nearby combustible materials in the wall to catch on fire.
Install an outdoor combustion air inlet duct to the new fireplace. This makes it burn more efficiently and reduces the heated air sucked out of your house. It also minimizes the possibility of smoke coming out into the room. Many new fireplaces are designed with a combustion air inlet. If you have a fireplace built from scratch, it is not difficult to add an inlet.
To improve the smoky conditions from your existing fireplace, try reducing the opening height by placing a strip of sheet metal across it. If this helps, you can permanently reduce the height with an attractive trim strip. Open a window in the room to see if eliminating a negative indoor air pressure helps.
Send your questions to Here’s How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.
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