By Bill & Kevin Burnett
Often we receive e-mails from readers about the columns we publish. Sometimes we get thanks and kudos and occasionally we get raspberries. Often we get suggestions on better ways to do a job, and a column occasionally generates a follow-up question or two.
In a recent column we responded to a homeowner who wanted to eliminate the ash smell coming from his damper-less firebox when the fireplace was not in use.
According to the homeowner, the smell was strongest when a ridge of high pressure was in the area. We directed him to a chimney-cap damper that attaches to the top of the chimney and seals the chimney from outside air. This prevents a downdraft through the chimney spreading the smell of ashes in the house.
But one reader wrote us with a similar problem and questions how the damper would prevent the smell of smoke while a fire is burning.
He writes: "I was thrilled to read your response to the question regarding the smell of ashes. I was surprised when I discovered that our 1937 home also did not have a damper. I have looked online and found several chimney cap dampers.
"However, I must have missed how you addressed the smell of smoke and ash in the house when the homeowner had a fire. We also have glass doors on our fireplace. We opened the side vents on the glass doors, but still had smoke in the living room. How will the damper prevent the smell of the smoke?
"I must also point out that our downstairs fireplace in the rumpus room has only a screen and no glass doors. That room was awfully smoky when we tried to have fire in the living room fireplace. Any thoughts on that?"
We believe the root of the problem in both of our readers' fireplaces is a lack of combustion air. A damper retards the flow of air to and from the inside of the house to the outside. If a properly installed damper is open, it has little to do with how a fire burns.
Fire needs air to burn. While it is true that warm air rises, the air must be hot enough to suck in combustion air from a source outside the firebox and create a draft carrying the smoke up the chimney. For the upstairs fireplace, we suggest the glass doors be kept open until the fire gets going. This allows enough combustion air into the firebox for the smoke to go up the chimney.
Opening a window a bit will also help to provide combustion air. If this doesn't work, the readers may have to investigate providing combustion air from outside the house. This entails consulting with an experienced masonry contractor to determine if a combustion air kit could be safely installed in one or both fireboxes.
For a more detailed discussion visit www.askthebuilder.com. There, you'll find an article titled "Second Fireplace Smokes When Not in Use."
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