What You Need to Know About Chimney Draft Problems

The exhaust system employed with a fireplace and chimney really is an amazing operation.  While humans designed the physical units, Mother Nature has always provided the draft, without which a fireplace would become a disaster.

If a fireplace’s natural draft is interfered with, smoke can pour into your house and residents may be subject to CO poisoning.  If you’re having chimney draft problems, here are some things you’ll want to know.

How drafts are supposed to work

Hot air rises, and air doesn’t flow in a vacuum.  Those two principles are really all you need to understand about the drafting operation of a chimney.  Because all fires produce hot air, you’ve got one of the principles taken care of any time you have a fire going.  It’s the vacuum issue that’s responsible for most chimney draft problems.

What stops or impedes a chimney draft?

Essentially, anything that hampers the rising of hot air and creates a vacuum can lead to a problem in drafting – which can lead to smoke and toxic gasses backing up into the house.

Here are some common draft-preventers:

1. Firebox size-to-chimney size.  A firebox that’s the wrong size for its attached chimney often will generate a sluggish draft.  The rule of thumb is 10 square inches of firebox space for every 1 inch of chimney space.  A wider ratio will make it more difficult for the hot air (and smoke) to rise.

2. The firebox itself – or, specifically, where within it the fire is burning.  The firebox should be aligned with the back wall of the chimney, and the log stack should burn below the chimney, not at the front of the firebox.

3. Non-vertical flue.  If the flue design isn’t straight up-and-down vertical, the fire might not generate sufficient force to send air up it.

4. Clogged chimney cap.  Chimney caps with mesh can become clogged over time, blocking the air flow.

5. Flue obstructions.  Depending on the condition of the chimney cap – or if there isn’t one – various debris can get into the flue and impede the natural draft.  Debris can include sticks, twigs, leaves, animal nests and the animals themselves.

6. Damper issues.  Obviously, the damper must be open for any kind of draft to be created.  But a faulty damper that doesn’t open fully also will cause drafting problems.

7. Air-tight home.  Newer homes tend to be built very air-tight, which prevents the necessary air from entering the firebox.  A cracked window or two often solves this problem.

Issues with chimney drafting can be very serious and shouldn’t be overlooked.  Some of these problems can be rectified by the homeowner; in other cases, a professional needs to be called in.

Chimney Specialists of Highland, Wis., provides full-service chimney inspection, cleaning, maintenance and repair.  We can determine why you’re having a chimney draft problem and solve it quickly.  Your safety and comfort is our #1 mission.  Schedule an appointment, or get your questions answered at (608) 929-4887.