Fixing a Fireplace That Smokes Into the Room

A fireplace draws because hot gas in the flue is lighter than the cold air outside. Anything that slows that column down sends smoke back into the room. In a Twin Cities winter the usual suspects are a flue that starts out ice cold, a house so well sealed that the fireplace is fighting the kitchen fan and the furnace for air, a chimney that is too short for the roof around it, and a cap or damper that is blocked or sized wrong.

We do not guess. The draft check is free: we look at the height and surroundings of the chimney, the size of the flue against the fireplace opening, the damper, the smoke chamber and how the house breathes. Then we write down what is causing it and what fixes it. Our smoky-fireplace work runs $140 to $850, from a top-mount damper cap to a new chimney cap, and a height or flue-size fix is priced at the inspection.

Signs you need this

• Smoke spills out of the top of the opening when the fire starts
• It only smokes on windy days or when a bath or kitchen fan runs
• Opening a window an inch makes the smoke stop
• Soot stains are building up on the brick above the fireplace
• A smoke smell comes down the chimney when no fire is lit

How we do it

1. Watch the symptomWe ask when it happens, then look at the fireplace, damper and smoke chamber.
2. Check the chimney topHeight, nearby rooflines and trees, the cap and the condition of the crown.
3. Measure the flueWe compare the flue size to the fireplace opening; a mismatch is a common cause.
4. Check how the house breathesExhaust fans, a tight envelope and the furnace all compete for air.
5. Write the fixYou get the cause, the fix and the price in writing.

Chimney height and the code rule

The current Minnesota Residential Code, which adopts the IRC chimney chapter, requires a chimney to rise at least 3 feet above where it passes through the roof and at least 2 feet higher than anything within 10 feet. Additions, second-story dormers and tall trees can leave an older chimney short of that over time, and wind then pushes air down the flue. Extending a chimney is priced at the inspection, because every stack is different.

Common causes we find, and what fixes them

• Cold flue at startup: warm it with rolled newspaper held near the damper before lighting
• Negative pressure from a tight house: crack a window or add a fresh-air source
• Downdraft from wind or a taller roofline: a new cap or a draft-reducing cap
• Damper that will not fully open or seal: a top-mount damper cap, $140 to $420
• Flue too small for a wide fireplace opening: glass doors or an insert

Smoke smell with no fire

If the room smells of smoke on humid days, air is flowing down the chimney, often because the house is under negative pressure. A top-sealing damper stops that flow and keeps warm air in. Creosote that needs sweeping makes the smell stronger, so we check for both.