Recently we answered a question from Larry, a reader who was having a problem with his fireplace. Seems that whenever he started a fire, he was nearly smoked out his house.
Larry questioned us about a previous column in which we recommended that a couple install a chimney-top damper to lessen the smell of ash in their house when a fire was not burning.
The damper will stop outside air from migrating down the chimney when the fireplace is not in use, but Larry wondered how a damper would help the smoke problem in his house. It won’t.
We suggested Larry’s problem was insufficient combustion air, which is required for a fireplace to draft properly.
As often happens, this response generated reader feedback. When this feedback contains solid alternative suggestions or valuable information, we want to pass it along.
Two readers responded to our column about the smoky fireplace. Homeowner Greg Hartwig supplies a practical tip, and Steve Tillman, a professional chimney sweep, provides some detailed information on the workings of a fireplace.
Hartwig writes: “If the fireplace system is working OK, I would check the quality of the fire first.
“We had the same problem of getting smoked out. I cut the wood into kindling and built the fire in stages and we have never had a smell of smoke since.
“What I discovered is that when the fire is first started, if the logs are too big, they will not light well, therefore, the inadequate draft. When a fire is first lit, the flames must move briskly toward the (flue). If they don’t, smoke will wander into the house.
“This is less important once the fire is hot enough, because the heat will ensure the up-draft will continue. We got smoked out almost all of the time before I started using kindling, now you can hardly tell we have a fire.”
Thanks for the tip, Greg. Your suggestion is a reasonable first step to avoid getting smoked out.
Tillman writes: “You two were right on about the causes of fireplaces smoking. I’ve been a chimney sweep for 24 years and this is the biggest complaint I get.
“Many customers don’t realize that the air and smoke going up a flue has to be replaced by an equal amount coming into the room from another source such as a window or draft vent. Otherwise, a vacuum will take place and the updraft will stop, bringing the smoke back down the flue and into the house.
“With today’s nearly air-tight homes it’s hard for a fireplace to pull air in. Often, replacement air ends up coming down through either the chimney flue or down a furnace or water heater flue bringing dangerous carbon monoxide gases with it.
“When two flues terminate through a single chimney stack at the same height, the flue that is not being used can act as a vacuum and suck down the smoke that is escaping up the flue that is being used, creating a ‘loop,’ or cycle.
“That is why it is a good idea to have each flue pipe terminate at different heights, usually several inches apart.
“Back-draft problems are often caused by wind blowing down a flue pipe. A proper cap often solves this problem.
“As a sweep, I have seen some bad construction that often contributes to draft problems. Your article was very accurate. If all my customers only read it. Thanks for printing it.”
And thank you Steve, for the kind words. To sum up, consider the following if you have a smoky fireplace:
- Make sure you have enough combustion air entering the house to support a fire. This may be a simple as cracking a window. But, consider installing an outside air vent into the firebox.
- Start the fire with kindling, and do not overload the firebox when starting a fire. A Presto log works well with larger pieces of wood to get a fire going.
- If your fireplace does not have a damper, consider installing a chimney-top damper to limit back draft down the chimney when the fireplace is not in use.
Stay warm and be safe.
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