Fireplace Downdraft - Smokey Smell

[NewbieHomeowner]

I have an open hearth stone fireplace. Since buying the house, we've had a pretty bad smokey smell when the weather gets bad. There is often negative air pressure in the room and and a bad downdraft which brings the smell with it.

Last year we tried a top sealing damper, which did not help all and we had it removed.

A few months ago we installed airsealed glass doors in front of the hearth. It has helped a lot, but on very humid days, the smell still comes through. I had a blower test done (unrelated to the glass door insulation), and not surprisingly, the doors are not perfectly airtight. Even the slightest crack allows the smell to come through when it is really humid.

So I'm looking for any other idea on how to fix this. As a temporary fix, I'll light a small fire or a few candles to reverse the draft, but I'm looking for a more permanent solution.

 

[double-d]

Sounds like there may be a couple of issues, The first one would be, the chimney may need to be cleaned, you may have creosote build up and the humidity brings that smell right into the house.
I'm surprised the Top Damper didn't help or work, I had the same issue and the damper stopped the smell completely. You also may be getting a negative pressure/draft, down through the chimney.
I would start with a good cleaning....and a Top Damper after that. If you do not have a Stainless liner in place, having one installed would close off the smell.

 

[NewbieHomeowner]

The chimney is cleaned regularly, and there does not appear to be creosote build up. My chimney company installed the Top Damper, but it didn't work. They consulted with their engineers and were told to remove it. The bottom line is that it's a negative pressure issue.

I don't have a stainless liner in place - just the original clay liner. How would a stainless liner help? Pardon my ignorance.

 

[begreen]

Is the fireplace installed in a basement?

 

[NewbieHomeowner]

Is the fireplace installed in a basement?

No, first floor Great Room that has a step down floor and cathedral ceilings.

 

[jetsam]

I would line the chimney and put a stove insert with an OAK in the fireplace. Backdraft issue solved, free heat for the house.

 

[jatoxico]

Any sealing/insulating you do especially in the attic may help. They do have balloon type flue stops that could presumably be inserted nice and low in the system to stop the air flow.

 

[NF22]

First post on this forum and unfortunately, I have the same exact problem as NewbiHomeowner....

The only difference is that I have an ash dump in my basement. Today, I sealed off the ash dump with concrete in the fireplace thinking it might have solved the problem but it hasn't, as I also had a little smoke in my basement when I made a fire by the dump pit..

i have had two top dampers put on. (First one replaced). The chimney is swept regularly and I use CreAway once every 4 fires to help with the cleaning.

This is by far the most frustrating issue I have in the house (been in the house for 2 years now)

I have also been told to install air sealing doors but I know that I need to fix the issue, as the seal is not 100%.

Also, another problem that I have is that my chimney guy just doesn't know what to do either besides wanting to charge me an arm and leg to do a camera inspection and then perhaps redo the entire chimney....

 

[jatoxico]

If you have negative pressure (look up stack effect) it can be tough to solve. Basically hot air rises in the house and escapes. The house makes up for the negative pressure created by pulling in air from the chimney. This is why is sometimes helps to open a window to get a fire going at start up. Of course you can't leave a window open all the time.

From my understanding it's not a problem of chimney construction (although it may be a placement issue) or condition. That's not say either of the chimneys in this thread don't need attention but even in perfect condition the problem would continue. Read up there are some fixable issues especially air loss.

If the problem only occurs when other appliances are operating (dryer/furnace) that create - pressure it may be that.

 

[NF22]

If you have negative pressure (look up stack effect) it can be tough to solve. Basically hot air rises in the house and escapes. The house makes up for the negative pressure created by pulling in air from the chimney. This is why is sometimes helps to open a window to get a fire going at start up. Of course you can't leave a window open all the time.

From my understanding it's not a problem of chimney construction (although it may be a placement issue) or condition. That's not say either of the chimneys in this thread don't need attention but even in perfect condition the problem would continue. Read up there are some fixable issues especially air loss.

If the problem only occurs when other appliances are operating (dryer/furnace) that create - pressure it may be that.

Thank you. I've read about this before and had an HVAC guy at my house who checked it out. (Not sure he knew about stacked effect) but I asked the question regarding the appliances and my roof venting...

I'm now putting that window wind sealer plastic over the face of the fireplace and using painters blue tape around the sides to seal it off and I can still smell it....

 

[jatoxico]

NF22 is this a multi story house?

 

[NF22]

Yes, it's a colonial. The chimney is at the end of the house and on the outside...

Also, when it's hot out in the late spring, summer, early fall and we put the AC on, the smell goes away with the air on and circulating and we do not have a return in the entire home, just AC vents throughout the entire home in the ceilings. Base boards hot water heat in the winter

 

[begreen]

Is the AC ductwork all sealed and taped? If not, leakage there might be creating negative pressure down below. This would be something like an upstairs window left open a little or leakage around an attic stair door.

 

[jatoxico]

Yes, it's a colonial. The chimney is at the end of the house and on the outside...

Also, when it's hot out in the late spring, summer, early fall and we put the AC on, the smell goes away with the air on and circulating and we do not have a return in the entire home, just AC vents throughout the entire home in the ceilings. Base boards hot water heat in the winter

It does sound like hot air rising in winter is creating - pressure. In summer the temp difference is not as much and cool air from AC doesn't rise. Do you have an unsealed attic stair?

 

[NF22]

I have gable vents in the attic at both far ends. The attic is just a simple pull down door on top of ceiling with the stairs that come out. Not sure if it's unsealed but I never feel a draft upstairs.. I get a major draft into my family room (where the fireplace is) when the fire is roaring and it's just sucking air up through the chimney. If I close the doors in the family room, the draft between the doors due to the fire will blow out any match. It's very strong.

 

[jatoxico]

There's your proof that open fireplaces are poor heaters. You stand in that room and feel the radiant heat but you're sending several hundred cubic ft/min of conditioned air up the chimney. That air has to be replaced and will be with outside air.

It may help to seal the attic stair with weather stripping and add an insulation tent above the opening. Any other thing you can seal to stop air from rising into the attic may (may) help.

 

[begreen]

I have gable vents in the attic at both far ends. The attic is just a simple pull down door on top of ceiling with the stairs that come out. Not sure if it's unsealed but I never feel a draft upstairs.. I get a major draft into my family room (where the fireplace is) when the fire is roaring and it's just sucking air up through the chimney. If I close the doors in the family room, the draft between the doors due to the fire will blow out any match. It's very strong.

You wouldn't feel a draft if the attic door was leaky. Warm household air would be migrating toward the cold attic. What do you think is the cause of the family room draft? That might be a clue.

 

[NF22]

Family room draft is only when there is a fire going, so assume it's the hot air going up the chimney. I really want to break down the wall between my family room and living room to make a great room. This way the house is not as compartmentilized and I don't have a tiny doorway into the family room where the fireplace is...

Thanks for all of the responses from everyone and sorry if I hijacked your thread NewbieHomeowner. Hopefully we can both get a cure to this nasty problem..