Does your wood stove or fireplace seem to create an unusually high amount of smoke in your home.
Normally in a fireplace or wood stove an updraft is created that takes waste gases up and out the chimney. Those gasses are then dispersed into the outside air.
Sometimes a draft may develop that moves in the opposite direction, this fills the house with smoke and poisonous gases – this is called a backdraft.
Causes of Backdrafting
There can be a number of reasons why smoke is backdrafting into your home. The main causes are:
1. Negative pressure (common in newer homes & basement installations)
2. Backdraft (common with outside chimneys, short chimneys or high-wind areas)
3. Blocked chimney
4. Burn technique / wet wood
In order to recommend solutions to reduce smoke coming into your home, it is important to know whether the cause is 1), 2), 3) or 4).
1. Negative Pressure
Negative pressure is essentially the process of heat in your home rising inside and battling the air escaping through your chimney. In other words, heat rises. As the air in your home rises from your basement to your upper floors, your lower floors tries to recoup that air. You may have a negative pressure problem if:
1. Your home is airtight around your lower floors (common in newer homes)
2. Your wood appliance is in the basement or a lower floor
3. Everytime you open the door smoke enters the room even when the stove has been on for a few hours
1. Open a window near the wood-burning appliance before you open the door. This will provide ‘make-up’ air for your basement.
2. Open the door of your wood appliance very slowly when re-loading it with wood.
2. Backdraft / Cold Chimney
Hot air rises and cold air falls. If your chimney has cold air, smoke may come into your home until the air in the chimney is heated. You may have a cold air chimney problem if:
1. You get smoke into your home on light-up
2. Your chimney is not much higher than surrounding roof lines or trees
1. Extend your chimney higher
2. If it is an outside chimney, build an insulated chase around it
3. Keep the fire burning 24 / 7
4. See item 4) Burn Techniques
3. Blocked Chimney
Having a chimney blocked with creosote is not uncommon. Most modern appliances have 6” flues and if your wood or burn technique is not perfect, it could get clogged with creosote (or even an animal). Your flue may be blocked if:
1. All the smoke enters your home (there is no draft)
2. Upon light-up it seems ok, but after the fire heats smoke begins to enter your home (as the flue is restricted)
3. You hear ‘poofing’ sounds as your fire heats up
1. Hire Friendly Fires to clean your chimney and/or purchase the proper equipment for you to thoroughly clean your system.
4. Burn Technique / Wet Wood
Wet wood. Everyone says they burn dry wood because they know the guy who knows the guy…. The reality is that if your wood is not split and stored in a top-covered area where wind and sun can dry it out for a minimum of 12 months (preferably 24), your wood is wet. If you are unsure, look at purchasing a wood moisture meter (available in our store). You will be amazed at how much water is in your wood and how much energy is consumed by your system to simply boil the water in the wood.
Improper Burn Techniques. New efficient wood burning systems must be used and operated in a specific fashion. As a general rule, follow these guidelines:
a) Get your flue gas temperatures up to approximately 700 degrees – hot!
b) Fill the firebox up with wood (again) and wait 5-7 minutes
c) Close the door, shut off most of the air and do not open the door for 6 – 40 hours (depending on the size of your firebox) or until only a few coals are left. Every time you open your door you are cooling your entire system.
If you have any other questions about burning wood, or any other fireplace or stove related question – please leave a comment and we’ll get back to you right away!
We built our house nine years ago with an open fireplace on the main floor, old wood stove in the basement and a tall chimney extending above the second floor, attic, etc. Separate flues in the chimney for the fireplace and wood stove.
This year, for some reason, smoke from the open fireplace is getting into the wood stove and leaking into the basement.
The only change I can think of is that last spring we had our chimney sweeper install chimney caps over the two flues at the top of the chimney. But we had a few late-season fires afterwards, and I don’t recall a problem.
I’ve never replaced the gaskets on the wood stove’s double doors, because they’ve never been a problem.
This may be a simple or complicated issue and not always easy to diagnose over the Internet. Some thoughts that may (or may not) be helpful:
1 – Why is your basement ‘sucking’ air down your chimney? Does your basement now have negative pressure ? Try opening a few windows in the basement to see if that helps.
2 – We have a heat generated backdraft collar that can be installed on wood stoves = these often can help.
3 – Maybe extend your open fireplace flue higher than your wood stove flue.
It could be the caps (unsure what was installed in your home) – but this is typically not the issue.
If you are in our service area, we have great certified full time chimney sweep installers and would be pleased to assist.
I have a froling p4 pellet boiler. On start up i often get a large and violent backdraft. I currently don’t have a fresh air source vented for my unit as the sell said it wasn’t required if my space isnt air tight. The boiler is in my garage which is not air tight. Just wondering if the backdraft could be caused because its not getting enough fresh air and i should look at venting. Thought i would ask before i star cutting holes in my walls
Thank you for your question. Unfortunately, Friendly Fires is not experienced with boiler systems (we don’t install or service them) – so we can’t comment on the issues you are experiencing – other than any relevance on the blog posting above. We would recommend you return to your place of purchase and request some service assistance.
I have a wood stove and i always seem to get smoke inside when adding wood even after the fire has been burning for hours. I was wondering if having my clean out not sealed very good in the basement would cause the air to go through there and by pass the wood stove instead?
Hi Alex, yes it is a good idea to have that clean out fully sealed.
You also want to open air control on the stove fully before opening the door, and then open door slowly. This could help as well.
Thank you for all the details in describing the challenges you are experiencing. Unfortunately, this is simply too complicated for us to comment online like this as there could be many factors at play as you’ve outlined. We would recommend that you continue working with your local professionals in your area in order to bring the issues to closure – and we would be afraid to comment here in case we are missing something as never having been to your home. Sorry for your challenges.
Patio fireplace with backdraft issue during north wind.
I have a wood burning fireplace on the first floor and a gas burning fireplace in the basement. Twin flues. The basement fills with light smoke even if the basement damper is closed. Any thoughts? Do i need to add a chimney cap damper on the gas flue side to prevent backdraft down to the basement?
Hi Zach, if you have a gas fireplace in your basement, then technically, that flue should be sealed / closed off for the gas unit so unsure how smoke is entering your basement. This is potentially a more complicated issue, we would recommend having a local fireplace technician visit and try and work out solutions for you. Thank you for your question.
You suggest opening a window to help with air flow but I live in Canada and that is not an issue. ITs going to be -40F/-40C really soon and i cant just have a window open!
my fireplace worked amazing for the last years but about 3 days ago, half of the smoke started to come back in. It is a large stone fireplace. 3/4 of the smoke rises but you can see a point where a draft is forcing it out the front of the fireplace.
These issues can be difficult to deal with online, but the fact that that your fireplace used to draft fine means something has changed in your environment. Something to check is a potential blockage in your chimney or environmental change in your home that may affect draft pressures (exhaust fan, new windows, etc…) – so it would be great to focus on those things to see what has changed in your home. Good luck!
Hi… i have a small fireplace outside in my shack. Ive used it about 15 to20 times this year and all of a sudden i have smoke coming back into my shack. The chimney is clean so i know its not plugged. I have smoke comming out of the stovepipe joints and out of the fireplace when i slowly open it to stoke it. I open my flu above the fireplace, crack the door and wait 5 oe 10 seconds b4 i load er up with wood. And now all of a sudden the smoke just instantly comes billowing out??? I dont understand how this can be happening all of a sudden
These are very tough to diagnose over the web. Sounds like your system is not drafting. Most probable causes are environmental (tall trees?), negative pressure in the shack (pulling air down chimney for some reason), or improperly installed baffle or air restriction part in your wood stove. A good resource with more information that could be more helpful is: https://woodheat.org/.
We are having the issue of our wood stove making our house smell like ash when the stove is completely cold. So much so, that our carbon monoxide alarms went off this morning and we had to have the FD come out. I’m not sure what we are doing wrong. When the wood stove is on, we have no smoke issues, never see or smell anything. But when it goes out, we have to leave a window cracked in our house to prevent it smelling like ash.
Tough to diagnose over the web, but judging by your description, it may be a case of negative pressure in that room that is ‘sucking air’ down your chimney. We are not home pressure experts, but solutions we’ve been told include a ‘saskatoon loop’, opening a window a little at all times, an outside air feed on the wood stove, other other methods that can solve home de-pressurizing issues (such as a reduction of exhaust fans…). This could be a tougher one for you to solve.
Another option (not the best) – and we can’t say for sure this would work, is an SBI draw collar – as these keep the chimney warm at all time (but requires electricity).
You can find this draw collar here. https://friendlyfires.ca/products/stovepipe-heat-shield-adjustable-straight/
We have a wood stove that, only occasionally, poofs smoke when we damp it down all the way at night. It just sends poofs of smoke out of the dampers, even when the fire has been screaming hot for hours. Can damping down too fast be a problem? I’ve started doing it incrementally but it still happens sometimes. Other times it does great. Outside temps don’t seem to be a factor. Any ideas? Thanks so much in advance.
That is a tough question / interesting issue. We are not sure what the cause could be. I would have a local fireplace expert in your city review the stove and installation of your system to ensure everything is installed appropriately (ie are your baffles installed properly?). In addition, the following independent resource may be helpful as well for this issue.
Good luck. Sorry we could not be more help.
We got a brand new wood stove. I love it, it keeps our trailer warm. But when we open the door of the stove, ash comes out and goes into the air and settles on our table, on top of the stove, etc….do you know why this happens? Thank you.
Hi Helen – if you open a window in your trailer to the outside before opening the wood stove door – does the same thing happen?
I have my Woodstove in the basement and often when I open the door to get a new fire going I can feel the air blowing back at me. I open a window but can’t start the fire without getting the basement filled with smoke. Close the door of the Woodstove and the fire suffocate. Restart the fire, and it goes as it should. Last time this happened, i tried to continue to put newspaper in to get the fire as hot as possible thinking it would fix the issue, but smoke and fire just continued to pour into the house until I closed the door and it suffocated itself. Restarted no problem, just lots of smoke in house now I can never get it right. It’s odd because, half the time there is no down draft and the othertimes I just know there will be an issue. Basement install, 2 story house, so chimney is aboit 30′ tall.
You may want to try a backdraft collar:
Also, may want to try extending your wood chimney or adding a high draft rain cap.