Is your chimney not drafting properly? Does your fireplace backdraft smell like a campfire, but you haven’t used it in months? Is your basement fireplace backdraft filling the room with smoke?

Chimney Downdraft Troubleshooting 

Chimney and fireplace backdrafting problems are common, but more often than not, the issue lies with the home, rather than the chimney itself. If a home cannot give the needed amount of air for combustion, a wood or gas-burning fireplace, we’ll notice some unique symptoms when the fireplace is used.

 

The Home & It’s Chimney Must Work Together

We’ll examine the possible causes if the wood stove a homeowner enjoys, drafts well durning power failures, but begins to smoke every time the heating system turns on. Finally, we’ll discuss the possible causes of trouble in the event our basement fills with smoke when we have a fire in the living room.

The first steps in addressing any chimney issue is understanding the dynamics of a homes influence on chimney performance and fireplace backdraft.

Basement Fireplace/Chimney Draft Problems

Location:
The fireplace on the lowest level of the home

Symptoms:

  • Visible smoke, during startup
  • Odor. Especially after the fire has been going for a few minutes
  • Presence of cool air coming from the fireplace while at rest, even with the damper shut
  • Smoke stains above the fireplace opening (above the lintel, on the facing)
  • Lingering odor days after the fire has gone out

Assuming the fireplace chimney system has been checked for proper construction and it’s determined the home is suspected of not providing sufficient air for combustion, you’ll check to see if the home is using the fireplace as a fresh air source for it’s make-up air.

How to Stop Fireplace Draft - Newspaper Test
Stop Chimney Downdrafts Newspaper Testing

Testing for Basement Fireplace Downdraft:

With the face of the fireplace covered with a hanging newspaper secured with tape across the top, observe the effect of air movement on the paper drape.

  • If the paper is trying to be sucked into the fireplace, this could indicate the fireplace is cooperating with the home, at this moment, and that another external event triggers the draft reversal.
  • Paper swings into room. (This is to be expected with lower fireplace.) Now the fun begins!
  • Try opening a door or window (on the windward side of the home) on this level. Does the paper indicate a lesser degree of air entry? If so, this indicates the home is using this fireplace chimney system as a source of make-up air.

Problem solved? Not so fast.

Most folks would not like the prospect of an open door or window during the time of year they want a fire in the fireplace. However there are ways to minimize the home’s dependence on using the fireplace for make-up air and lessen the need for household make-up air in general.

As seen in our Part 1: Fireplace Backdraft and Chimney Downdraft the home is constantly sending warmer air to higher and higher floors of the home. Likewise, certain other appliances are sending household air out of the home (both with fans and the burning of gas). If the home could do without a bathroom vent fan or a smaller exhaust fan for the kitchen range, then there is more “free air” for the fireplace to consume. Weather stripping/sealing of all air leaks in the upper half of the home will also limit the amount of backdrafting and pressure of our basement fireplace backdraft.

Visit Part 1 to get more information on this diagram. 

If the above suggestions still present the same symptoms, the sure cure is to add a fresh air inlet. A designated fresh air venting system to encourage outside air into the lower levels of the home. If the home receives a sizable portion of it’s fresh air from a fresh air vent, then the fireplace chimney may get its downdraft under control, allowing you to have a less smokey fireplace.

During this test, we can simulate the benefits of a fireplace fresh air vent by simply opening a window or door on the lowest level of the home (being careful to have the rest of the home closed up, as it normally is in the winter). Does this reduce the “blow” of the newspaper into the room?

If not, open a window on the opposite side of the home (still on the lowest level) instead, check the results. An open window could be on the downwind side of the home, hurting our fresh air efforts rather than helping.

So our newspaper test shows an open window and additional fresh air helped reverse our downdraft.

Now to Test for Fireplace Backdraft:

With help from a professional chimney technician, we’ll remove the newspaper and prepare a small fire for the fireplace. We will want our window open as in test #1.

With Kindling and Tinder prepared on the grate, the technician will preheat the flue with a rolled up newspaper on fire. (Extreme care must be taken to avoid injury or smoke inhalation or risking near by combustibles with fire).

Once the flue has been heated for a few moments, and long before the newspaper burns half its length, the technician will light the prepared fire. Carefully checking for draft and flow, they’ll adjust the fire, windows and fireplace doors. With a little luck a draft will be established and plans to get a fireplace fresh air vent can be made with confidence.

If you’re ready to begin to enjoy your homes hearth again, give the chimney sweeps at Full Service Chimney a call at 913-642-6171. We can help stop your fireplace/chimney backdraft problems!

Check out the first post in this two-part series >> Fireplace Backdraft & Downdraft Part 1: Making Chimneys Work

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