exterior fireplace downdraft

[sdhearth]

Hi,

I have a wood masonry fireplace (built in the 50s) that is on the exterior wall. The fireplace is on the first floor of a two story (1 1/2 cap cod) house. The fireplace the highest point of the house. The hearth is always cold and when I open the damper there is a downdraft. I've tried building a fire a few times and I always get smoke in the house. Granted I am new to fireplaces so I may not be doing it right.

I had the fireplace cleaned and the sweepers mentioned that the fireplace looked like it was hardly ever used. So I believe the previous owners of the house always had this problem and just didn't use the fireplace. They were the original owners of a 1950s house. So it is kind of hard to believe they lived so many years with such a problem. Anyhow, I moved in and now it is my problem.

I had one chimney company come in and they said it was a downdraft problem, probably wind hitting a building or something and coming down the chimney. There is a house within about 12 feet of the chimney that is a mirror of my house and a few feet higher. They didn't look to see if there were any buildings close by, so I got the feeling they were just guessing. Anyhow, they suggested a vacu stack. They said it stops air from coming into the chimney opening. They said they could do it for $1200. They didn't mention anything about the exterior chimney being a problem.

So my questions are, with an old exterior masonry fireplace, the fireplace is always going to be colder than the inside of the house. And the fireplace is below the halfway point of the house. Does that mean that air will always flow from outside to inside (as explained in (broken link removed to http://www.gulland.ca/fhs/coldhearth.htm)?) Would a vacu stack solve this dynamic at all? Is there a better solution? Or should I just follow the wisdom of the previous owners and never use this fireplace? In that case I would put one of those fireplace baloons to stop the air from coming in.

 

[double-d]

My understand of a Vacu-Stack is when the wind blows across the cap it creates a positive draft in the chimney and does not allow the air to blow into the chimney. There are solutions that can help and most here will probable agree, that the Fireplace should be used with a wood burning Insert or free standing stove, since Fireplaces do not really add heat to a house. If you are looking to close off the flue, a simple close off cap, that slides over your Clay Tile flue, if you have one, works great, or a top damper may be a better option, it allows you to open and close the flue should you wish to have an occasional fire, and has an air tight seal when closed.

 

[Simonkenton]

You may be able to get this fireplace to work right. Once you get some hot air flowing up that chimney it ought to work fine.
You need some really dry pine kindling, split small, like one half inch diameter. You even could go to the building supply place and buy a bundle of cedar shingles, these things really light up quick. Cut a shingle with the circular saw so that it is 10 inches long. Split the cedar so that it is one half inch wide.

Get about 8 pieces of cedar and 8 pieces of pine stacked up with a couple pieces of crumpled up newspaper underneath the wood.
Light that crumpled newspaper.
And then get a sheet of newspaper that is not crumpled up. Light it and set it on top of your kindling fire. This piece of newspaper will light up immediately and will, hopefully, burn with enough energy to send the hot air up the chimney, and not out into the room. Then your kindling pile will be burning and hopefully you will be up and running.

It is easier to light the thing if it is not windy, also more difficult to light the colder it is outside.

Good luck, let us know how it goes.

 

[jatoxico]

I have/had a similar situation due to placement of the fireplace in the house and a cold exterior chimney. When I went to use it I would often find that I was getting cold air rushing down. Sometimes it was just weak draft and I would get smoke spill. Lighting a piece of newspaper stuffed right up into the damper area would get rid of the cold slug of air and establish draft.

Problem was that as the fire died or just on some days, the draft would weaken and smoke would roll out.

the Fireplace should be used with a wood burning Insert or free standing stove, since Fireplaces do not really add heat to a house.

I agree DD that a fireplace insert or stove with an appropriately sized stainless liner would be a huge improvement in many respects and I'd put the $1200 towards that before spending on Vacu-Stack. I put in an insert with a liner and even though I have to establish draft now and then I've never had draft collapse and I get a great deal of usable heat.

 

[sdhearth]

thanks for the great suggestions!

A stove is out of the question. The fireplace would only be used for entertainment, not heat.

I think starting a draft with the cedar first is a great idea and would work. However, that doesn't solve the draft issue when not using the fireplace. So I like the top damper idea. Only concern there is, if I sell the place, how does the next guy know about the top damper? I don't think I would of figured it out if I had such a thing.

And I do believe I've seen a weak draft towards the end of the fire. Hard to tell since the smoke smell was already present. So a liner would probably be needed as well. I think they come with insulation? But then I need to worry about whether the flue is big enough for the fireplace after the liner+ insulation is inserted, correct?

So I'm thinking I need a liner+ insulation to stop the weak draft when fire burns out. And I need the top damper to stop cold from coming in. And I need to prepare a draft before I start a fire. This sounds pretty expensive for the occasional fire. So I definitely need to think about it.

Another thing not mentioned yet is doors for the fireplace. A friend has some that look like bi fold closet doors. Would those work to do the same job as the top damper?

 

[double-d]

The control for the Damper in in the firebox opening. It will be a Stainless steel cable and routed up through the chimney flue, and secured to the inside of the firebox. They should be fairly noticeable so I'm sure the next owner would see it.
Round Liners can be a Pre-Insulated liner but the square liners that I'am aware of would have to be insulated by the home owner and because of the size, sometimes do not have the room for insulation, unless the clay tiles are removed.
Doors will help with cold air getting into the room, but they are not as good as a Top Sealing Damper

 

[Sixwaypwrmudflap]

sd, another option to improve draft might be a flue extender. I have a similar style house, and when I built a fire I had to get the chimney very hot to get good draft otherwise you fill the house with smoke. In an old drafty house smoke is going to the path of least resistance. When I had the chimney cap repaired I added another 12" to the height of the chimney. Getting the chimney just that little bit higher made a difference, the chimney was about level with peak before the repair.

 

[sdhearth]

I got a second opinion today and when the guy checked, there was no downward draft. There was actually a nice upward draft. The guy said the fireplace should be fine and to try to build a draft with newspaper/dura flame log. He also said Vacu stacks may or may not work. It is not guaranteed.

Now I am left scratching my head on how there was such a strong downdraft when the first guy came. I've checked a few times since he left and I believe the draft is getting weaker as the days wears on.The first thing I can think of is that the first guy came at 8 am on a cold day (20 F). And the second guy came at 1 pm on a warm day (40F). I want to discount wind because today was very windy and it should of affected the draft more. But maybe it just depends on the wind direction. The second thing that came to my mind is that the first guy had two guys get on top of the chimney before he showed me the draft. For all I know he had a fan up there to trick me. I will have to check every cold morning until I can find another cold draft before I know for certain.

Now I'm going to wait for a warm front before I build another fire to see if I can get a good upward draft going and hopefully not have any smoke in the house. I don't do it on cold days because if smoke gets in, I need to open up all the windows and it gets pretty cold.

 

[xman23]

Is this a home brew fire box? If so there are more of them that don't work than do.

 

[Destructor]

Was the person who checked the fireplace familiar with fireplace construction and not just the chimney. Often a fireplace and chimney can have beautiful masonry work but the whole system may not be built to the proper proportions. I have a 1950’s cape with the outside chimney, I usually open the damper 10 minutes or so before lighting a fire, I have never had a draft problem even with very gusty winds.


You should have an 8” X 12” flue. That was the standard size most everyone used back then, they usually built the chimney to be 1 foot above the peak. Code Is now three feet but 1 foot was often adequate.


You should try to determine if the throat, smoke chamber and smoke shelf was built properly before you put any effort or money into the chimney. I agree with everything mentioned about the newspaper trick and building a nice kindling fire. That may be all it takes.

 

[sdhearth]

This morning at 8 am, it was 22F and there was a downdraft! The whole area near the fireplace was so cold. So it looks like the downdraft happens due to cold. Will keep checking every morning.

I burned a small piece of newspaper and the downdraft stopped! But I didn't get an upward draft going, at least not a noticable one. But the downdraft was totally stopped. It was much warmer with the damper open after I stopped the downdraft then when the damper was closed in the morning. I didn't burn too much newspaper because it smelled and I didn't want to overdue it. Anyone know of a less smelly way of getting the draft going? I think I am going to try slightly opening a window tomorrow morning and try again.

So now I am back to figuring out what to do about this cold downdraft in the mornings. The choices are: vacu-stack, top damper, fireplace door or one of those fireplace balloons. Will vacu-stack work for a downdraft that only happens in the morning? Assuming it does, I think the most effective solution, is the vacu-stack or top damper because they stop the cold all the way on the top. So I'm going to ask for the cost of a top damper.

One thing I am worried about is leaving the fire to die out over night. Once the downdraft occurs in the morning, It will stink up the house! Maybe the downdraft won't happen in the morning if the chimney was warmed up with a fire the night before. I need to test that. Anyhow, the top damper won't fix that issue as I can't close it before I go to bed. So that means I may need a fireplace door. Is that effective at keeping smells out if a downdraft were to occur? Can I close that as the fire is dying out? If not, it looks like the vacu-stack is my only solution.

 

[jatoxico]

This morning at 8 am, it was 22F and there was a downdraft!

As expected. The warm air in the house is rising and cold chimney is the perfect conduit to allow cold dense air to make up the for the negative pressure.

The choices are: vacu-stack, top damper, fireplace door or one of those fireplace balloons.

You referenced another site so if you read the content you know this is not an easily solved problem. By the time you add a Vacu-Stack or electric draft inducer and some decent doors you're going to be into it for some bucks. I'll say again IMO, that money would be better spent on an insert with insulated liner.

But because you say that's not an option and since you don't want to run the fireplace that often I think I would invest in a good quality top sealing damper or stick a balloon style flue block and call it a day.

 

[sdhearth]

As expected. The warm air in the house is rising and cold chimney is the perfect conduit to allow cold dense air to make up the for the negative pressure.



You referenced another site so if you read the content you know this is not an easily solved problem. By the time you add a Vacu-Stack or electric draft inducer and some decent doors you're going to be into it for some bucks. I'll say again IMO, that money would be better spent on an insert with insulated liner.

But because you say that's not an option and since you don't want to run the fireplace that often I think I would invest in a good quality top sealing damper or stick a balloon style flue block and call it a day.

Yup, only issue (I'm guessing) is that neither of those options allow me to let the fire die out over night. As I expect a downdraft on the ashes of a previous fire will stink up the house. So the vacu-stack or fireplace doors is still my only option if I ever have a fire.

 

[huauqui]

If you are needing to stop the draft from coming down the chimney when you are not using it and your damper doesn't seem to be working well. You could try googling fireplace draft stopper or chimney balloon. There are many easily installed options for stopping the air flow. These however do not help with the downdraft issue when you want to burn. The suggestions to help with that in this thread are what worked for me when I had your situation. You could also try some form of forced air heat being blown up the chimney to help warm it a bit. Something like a blow drier or small electric heater for 10 to 15 minutes prior to having a fire.

 

[BoilerBob]

Yup, only issue (I'm guessing) is that neither of those options allow me to let the fire die out over night. As I expect a downdraft on the ashes of a previous fire will stink up the house. So the vacu-stack or fireplace doors is still my only option if I ever have a fire.

Fireplace doors (only) will not stop the stinky creosote smell from coming down the chimmney.
I had that problem at a previous house, the only fix for me was to block off at top of chimmney and not use it.

 

[bholler]

This morning at 8 am, it was 22F and there was a downdraft! The whole area near the fireplace was so cold. So it looks like the downdraft happens due to cold. Will keep checking every morning.

I burned a small piece of newspaper and the downdraft stopped! But I didn't get an upward draft going, at least not a noticable one. But the downdraft was totally stopped. It was much warmer with the damper open after I stopped the downdraft then when the damper was closed in the morning. I didn't burn too much newspaper because it smelled and I didn't want to overdue it. Anyone know of a less smelly way of getting the draft going? I think I am going to try slightly opening a window tomorrow morning and try again.

So now I am back to figuring out what to do about this cold downdraft in the mornings. The choices are: vacu-stack, top damper, fireplace door or one of those fireplace balloons. Will vacu-stack work for a downdraft that only happens in the morning? Assuming it does, I think the most effective solution, is the vacu-stack or top damper because they stop the cold all the way on the top. So I'm going to ask for the cost of a top damper.

One thing I am worried about is leaving the fire to die out over night. Once the downdraft occurs in the morning, It will stink up the house! Maybe the downdraft won't happen in the morning if the chimney was warmed up with a fire the night before. I need to test that. Anyhow, the top damper won't fix that issue as I can't close it before I go to bed. So that means I may need a fireplace door. Is that effective at keeping smells out if a downdraft were to occur? Can I close that as the fire is dying out? If not, it looks like the vacu-stack is my only solution.

Well from what I can tell you have a typical outside masonry fireplace. When not in use the structure will get cold because it is just masonry with no insulation at all. When it gets cold the air cold air will drop down the flue and leak out around the damper. That is just how it works. It will also be hard to establish a draft in the chimney because you need to get the air in that cold structure warm enough to get it moving up while it is being cooled down by the surrounding masonry. A vacustack will not change this at all. A top sealing damper will help but it will still be cold near the fireplace because that structure will still be cold and warm inside air will go up into the flue get cooled by the masonry and then drop back down. It will not be anywhere near as bad as without the top sealer but it still wont be great. A chimney balloon will make a big difference because it will seal off the flue at the bottom. But the whole structure will still be cold.

So basically a top sealer will help. Doors will help a little bit but not much because they typically don't seal well at all. A vacustack will not help much at all. A chimney balloon will probably make the biggest difference as far as the cold draft but it will not make it easier to start a fire.