Why do I have smoke in my basement when I use the upstairs fireplace?

Why do I have smoke in my basement when I use the upstairs fireplace?

Q: Jason, We have a 2 sided fireplace on the ground floor of our house and a 3 sided fireplace in the basement. Our house was insulated from electric heat. When we have a fire in one fireplace we get smoke coming back into the house through the other one. Would a chimney pillow stop the smoke from coming back in? Thanks very much for your help. – JJ

A: Dear JJ, Correct me if I am wrong, but it sounds like you have two separate chimneys for your two fireplaces and the two chimney flues go up one main brick chimney structure?

If the answer is Yes, you do have two separate fireplaces. Then the Chimney Balloon will stop the smoke from crossing over and re-entering the house through the other chimney flue. This is called smoke crossover. It is when the one chimney is breathing out air from the home and smoke from the fire mixed together, the other chimney is breathing in outside air to equalize the pressure in the home but is also sucking back in smoke.

Many people assume closing the damper on the unused fireplace will stop this crossover, but that is not the case. Dampers are not tight enough to stop this air draw. That is why a Chimney Balloon is needed in the unused fireplace to stop the air draw inward through the second flue. This forces the house to find another location to draw air in at where there is no smoke.

Can Two Fireplaces use one Chimney Balloon?

Can Two Fireplaces use one Chimney Balloon?

Q: Jason, We have a fireplace upstairs and one directly below it downstairs. Sometimes when we use one fireplace the other one will be smoky. Do we need more than one chimney pillow, or can we even use a chimney pillow in this situation? – LK

A: LK, When you have a fireplace that is one above another the two hearths usually have separate flues and dampers and they run to the roof in the same chimney structure. See the diagram of the two fireplaces sharing a chimney structure.

When you are using one fireplace and chimney your home is drinking in air from other places to allow enough airflow to feed the fire and to draft the smoke and heat upwards out the flue. The home will suck in air from the path of least resistance which is usually the other unused chimney (even if the damper is closed). This draw of air into the house is known as the “stack effect”.

So when the other chimney sucks in air from the roof it also sucks back in some smoke from the other fireplace chimney.

The solution to this problem is to use 2 separate Chimney Balloons, one for each flue. When you have a fire in one of the fireplaces then remove that Chimney Balloon in the used fireplace and leave the other one in place in the unused fireplace. This will force your home to find another less-smoky place to draw from, like doors or windows. – Jason

How can I start a fire in the fireplace without the livingroom getting smokey

How can I start a fire in the fireplace without the livingroom getting smokey

Q: Jason – I have a heck of a time getting my fire started without getting smoke into the house. How can I get the fireplace fire burning without smoking the living room up? – PR

A: PR – So you start a romantic evening with your lovely wife, a bottle of wine, a comfy blanket by the hearth and then you set the smoke alarm off while trying to start the fire and the kids wake up and blow the whole evening. I only know this because I have done it myself.

Houses can be very tight nowadays, and it can be hard to get that initial air movement started to get the fireplace to draw well. Once the fire is blazing the natural lift of heated air helps to keep the smoke going out the chimney instead of into the living area. Starting a fire that is smoke free from the beginning is a bit of an art. Here are a few tips to start it off right.

  • Glass doors are invaluable especially if you have a vent on them that is low to the floor. Open the lower vent, start the fire, then close the glass doors and they will keep 99% of the smoke going where it is suppose to go.
  • If you have no glass doors, then you have to get the fire as hot as possible as quick as possible. My favorite way to do this is to use paper shopping bags. You can fill the bag with cardboard (not glossy print cardboard is preferable) or more bags. I usually fill two bags with dried twigs from the ash tree in the back yard. These twigs are excellent kindling and the tree drops them all year long. Light the bag in three spots on the bottom and you will have a roaring start to a fire in no time. Some people swear by newspaper, but I have read quite a bit on how the ink can create an undesirable sticky property to soot in your chimney.
  • As a last resort you can crack a nearby window or door to allow a better draft for the fire. But who the heck wants to do this in the winter?! It is bad enough that the fireplace is going to suck your expensive home heat out the chimney. Like you really want to open up a window and let the cold winds blow! As I said, this is an absolute last resort.
  • Once the fire is going strong you will get less smoke if you keep it burning hot. When you get down to coals it will not be producing much smoke as long as you have well seasoned wood. – Jason
My fireplace is smokey when i have a roaring fire in the fireplace, how do i stop the smoke from entering the house?

My fireplace is smokey when i have a roaring fire in the fireplace, how do i stop the smoke from entering the house?

Baffled chimney Cap

Q: Jason, whenever we have a really good fire in our fireplace, the whole house gets smokey. The flew is open so I’m not sure why. What should we do to fix this? I called my fireplace shop and they said to open a window a crack, that seems counter-intuitive since it is 5 degrees outside. I kind of like being warm.

A: I always get a kick out of people who say if your fireplace is smokey when you use it just open a window a little. Those people must not live in a cold climate because who wants to open a window when it is cold outside?! Tell them: “I live in Minnesota for crying out loud!”

Honestly, the best thing you can use to keep smoke where it belongs is some glass doors for the fireplace. They will keep the smoke and the sparks in and keep you from loosing quite so much interior heat to the combustion process and the suction of the chimney draft.

Another option is a directional wind may be blowing down at your chimney. Often winds can bounce off nearby trees and push wind currents down at your chimney. In this case, a baffled chimney cap will do the trick. My fathers Avalon wood stove had this problem and a baffled cap fixed the issue. See the image below of the baffled cap.

Remember to close that damper up good and tight when the fireplace is not in use. If you still have outside air entering even with the damper closed. Get a plug like a Chimney Balloon and it will keep the room more comfortable.

I have two fireplaces and when i light the upstairs fireplace the downstairs fireplace lets in smoke.

I have two fireplaces and when i light the upstairs fireplace the downstairs fireplace lets in smoke.

Three Chimneys

Q: Jason – I have two fireplaces in my home, one in the living room and one in the basement. When I light one fireplace the other one gets smoky. My fireplace shop said to crack a window so this wouldn’t happen, but it is -1 degrees F out, who wants to open a window when it is so cold?! Why would that help keep the smoke out? – KM

A: KM – You are experiencing a very common problem among new homes with multiple fireplaces. Let’s look at this in sections

1) Your fireplace sucks air when lit.
When you light one fireplace that fire starts drawing air from the rest of the house like a vacuum for the combustion process. To replace that air the house will start drawing in outside air through the path of least resistance in order to equalize the pressure. This is called the “stack effect”. Your home could draw this air through worn weatherstripping, power outlets on outside walls, cracks, under insulated windows, or many other ways. One of the weakest points in a homes air envelope seal is the metal fireplace damper. In you case your home is pretty tight but your fireplace damper is the path of least resistance for cold air to gain entry. See the image below of 3 chimneys that are too close together, they may draw smoke from each other.

2) Your fireplace damper is weak and is the easiest way for cold outside air to gain entrance.
When the air is drawn down the chimney  to equalize the pressure in your home it also draws down the smoke that is wafting around your roof. This is why your basement gets smoky.

3) Seal your basement damper.
If you seal up the basement damper and flue with a Chimney Balloon it will then be air tight and will not draw in smoke.

4) Your home cannot be a vacuum.
When you burn in your fireplace your home will continue to draw in air from the outside. It just wont be drawing smoky air from your roof. But it will draw from somewhere. That is why burning in your fireplace does not save you on heat, it actually costs you heat in most situations.