Fixing a Smoky Fireplace That Won't Draw

Smoke goes up when the flue is warmer than the air outside and the house can spare the air to feed the fire. In a Chicago winter the first part is easy. The second part is where houses get into trouble. A bungalow or two-flat that has had new windows, spray foam and a powerful kitchen hood can end up pulling air down the chimney instead of letting smoke go up it.

Height and the roof matter too. A short stack on a low hipped roof, a taller building next door, or a two-flat flue that sits beside a busy boiler flue can all upset the draft. The draft diagnosis is free. Common fixes include a cap with a top-sealing damper, typically $140 – $420, or a new chimney cap, typically $200 – $850. A flue or height correction is priced at the inspection.

Signs you need this

• Smoke rolls out of the top of the fireplace opening
• The fire is hard to start and dies down quickly
• Smoke smell in the house the morning after a fire
• The problem gets worse when the kitchen fan or dryer is running
• A draft of cold air coming out of the fireplace when it isn't in use

How we do it

1. Watch it happenWhere we can, we light a small test fire or use a smoke pencil to see where the smoke goes.
2. Check the flueWe look for blockages, a damper that doesn't fully open, a crumbling smoke chamber or a flue too small for the opening.
3. Check the houseWe look at exhaust fans, the furnace and the dryer, and test whether opening a window changes the draft.
4. Recommend the smallest fixYou get a written explanation and price, starting with the cheapest change likely to work.

The most common causes we find

Most smoky fireplaces have one of a short list of problems.

• A cold flue: an outside chimney on a freezing night needs a few minutes of warm-up before it draws
• Negative pressure: a tight house with exhaust fans running pulls air down the chimney
• A blocked or partly blocked flue: nests, fallen tile or heavy creosote
• A damper that is rusted half shut or a smoke shelf full of debris
• A fireplace opening too large for the flue above it
• A stack too short for the roof around it, or downdraft off a taller neighbor

Why a top-sealing damper often helps

A top-sealing damper sits on the crown and closes the flue at the top, with a cap over it. When the fireplace is cold, it keeps the warm air in the house and stops cold, smelly air from falling down the flue. When it's open, the flue is fully open, which a rusted throat damper often isn't. A cap with a top-sealing damper typically costs $140 – $420.

Try this before we come

Crack a window near the fireplace for the first ten minutes of a fire, turn off the kitchen hood and bathroom fans, and warm the flue by holding a lit roll of newspaper up near the open damper before lighting the fire. If the smoke stops, the problem is pressure or a cold flue, and you have already learned something useful.