Smoke filling basement through 2nd flue
Hi,
Hoping for some help on a fireplace chimney problem. We have 2 fireplaces in our home that exhaust through 2 separate flues in the brick chimney. When ever we light a fire in the upstairs fireplace, the smoke will fill boil out of the downstairs fireplace flue. I believe the smoke is exiting the flue at the top of the chimney and immediately being sucked back in by the second flue.
Do you know of any solutions short of rebuilding the chimney? Thanks in advance for your help.
Replies
close the bottom damper for one thing..or install a "lid type" top mounted damper on that Downstairs flue.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
You might want to be sure other combustion devices aren't back-drafting too. Do you have a CO detector?
Al Mollitor, Sharon MA
More common than you might expect.
This is what is happening:
For every unit of air that exits your home, the same amount must enter to displace it.
When the fireplace is operating, it pushes air out of the active flue. The 'stack effect', literally in this case... The air to displace this will enter through the path of least resistance, which in your case would appear to be down the inactive flue.
Any other air exiting the house will add to the problem. This includes bath fans, range hoods, other combustion appliances, and air leaks at the top of the structure.
So how to fix:
The simplest solution would be to crack a window near the active fireplace to provide combustion air when operating. The downside is that you may feel a cold draft.
A better solution would be to devise a way of providing combustion air directly to the fireplace. Some are designed with a small air supply vent in the floor of the firebox that can be ducted to the outside. Best if it can be sealed tight when not in use.
Better still would be to combine fresh intake air with chimney caps that seal tight at the TOP of the flues. Even when not sucking smoke, you are losing a tremendous amount of heat through that flue (and even the active one when not operating).
Here are a couple of examples:
View Image
View Image
Mark
There are a couple of thoughts:
Firstly, any fireplace needs combustion air. In an older drafty house this is usually not a problem but if the house has been sealed up, the air that goes up the chimney needs to be replaced creating a low pressure which “sucks” outside air in through other opening (such as the second flue). Try lighting it with a window in the room open – that may identify if air is the issue.
We also had a problem a few years ago since squirrels love to build nest in warm chimneys at this time of year - may be worth checking. In a multi-flue chimney corrosion can let smoke go between flues and if it can’t get out the top it can come down
Good luck!
Andrew
Edited 11/18/2004 11:44 am ET by andrewh
Edited 11/18/2004 11:45 am ET by andrewh