Expert: James Ball - 11/23/2009

Question
I have a friend with an open double sided fireplace that smokes into their house when used.  We added 2 feet to the chimney today, but it is still smoking a bit with or without the cap, but smoked worse when we put the cap on.  The fireplace has no doors or screens, and the damper is open the whole way and is working properly as far as we know.  The damper is 4-5 feet higher than the top of the firebox itself and I wondered if that could be part of the problem.  The chimney has 12x12 liners and I wondered if it would help to neck the cimney down to say an 8x12 at the top of the chimney?

Answer
Hello Justin, What is happening is you are getting Negative Pressure in your home (house stack effect) that is hot air rising in your home (and getting out through the attic vents, doors, lights) your house is a better chimney than your chimney. Also kitchen/bathroom exhaust fans, clothes dryers, Radon systems and the boiler/furnace all take house air out of the house (mechanical negative pressure) your house needs make up air, perhaps an open window or door? Or stop the air from getting out the attic and other area’s.
Trail and error until you get this fireplace to work for you, maybe close off the room from the rest of the house to use it (close doors)
Or it could be dirty? I would have a local Certified Chimney Sweep (www.csia.org, there you can look up by zip code to find one near you) take a first hand look at what you have.
James