Draft questions

[NCPT]

This is a two-part question. Do chimney caps restrict draft and why is smoke coming down my chimney flues? I have three flues, one for the basement woodstove, one for the basement fireplace, one for the living room fireplace. I installed a chimney cap due to heavy rain coming in on my living room fireplace....I installed it last week before i started burning and I never had one last year (this is my 2nd winter here at a new home).

My stove only drafts good when everything is clean and I have to clean the stove often to keep it drafting well, it's on an 8" flue and goes about 20ft up. I am having a brick mason come over to tap into the basement fireplace flue and sealing off the fireplace and hole from existing stovepipe....the basement fireplace flue is 12" and I'm hoping it will draft better.

Installing the cap this year I have noticed smoke coming in the fireplaces both upstairs and downstairs. Is anything in particular causing this?....like the new chimney cap?

Any help and opinions are appreciated.

 

[U&A]

How old is the house? Have you tried cracking a window to aid in a good draft?


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[NCPT]

How old is the house? Have you tried cracking a window to aid in a good draft?


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House was built in 1978 and I have been having to open a door to the other (unheated) half of my basement. Never had to do this before the chimney cap but I'm hoping it's not this much of a restriction to the draft.

 

[MAD MARK]

The chimney cap will not restrict draft.

I would guess that the temps are not low enough. And if the fireplace chimney is not sealed good you will notice a smell with downdraft with no fire in it.

 

[moresnow]

Guessing you will end up adding length to the stove flue. This is a regularly discussed problem on another site Most often the fix is to lengthen your stove pipe to get it above the others. Not what you wanted to hear I am sure.

 

[NCPT]

Guessing you will end up adding length to the stove flue. This is a regularly discussed problem on another site Most often the fix is to lengthen your stove pipe to get it above the others. Not what you wanted to hear I am sure.

Well.....now I am considering taking the cap back to the guy who made it and having him adding a piece of metal to divide all three flues.

 

[NSMaple1]

I don't think all those trees are helping your draft situation any. The cap might have nudged a borderline situation before just a hair over that edge. As it was before, each flue had straight path to the sky. Now they all only have a straight path to the cap, then stuff lingers under the cap before it eventually finds its way up around out then up. More chance for a slight downdraft in one of the other flues to grab that llingering stuff & bring it back down again.

 

[NCPT]

I don't think all those trees are helping your draft situation any. The cap might have nudged a borderline situation before just a hair over that edge. As it was before, each flue had straight path to the sky. Now they all only have a straight path to the cap, then stuff lingers under the cap before it eventually finds its way up around out then up. More chance for a slight downdraft in one of the other flues to grab that llingering stuff & bring it back down again.

Those trees are not quite as close as they look in the pic, but I agree with the cap causing smoke to linger. I wonder if putting a divider in the cap will help?

 

[NSMaple1]

Maybe? I'm not really sure. You might have to come up with a cap for each & extend the stove one higher than the rest as suggested above? Our place has two Class A chimneys side by side, one for basement boiler & other for rarely used first floor fireplace. The boiler one is a foot +/- higher, they each have caps, and we have never had any drafting issues of any kind. But might be apples to oranges - 30' of chimney, and wide open hill top.

 

[NCPT]

The reason I went with one big cap was to prevent water from coming in the center flue which goes to the livingroom fireplace (which happens during heavy rains) plus the mortar on top of the chimney has some cracks. I guess I'll take it back to the guy who made it and let him install the dividers because I want to keep the cap, it cost $350

 

[MAD MARK]

How and where are the location of the basement woodstove and basement fireplace?

$350...thats a lot of money. It doesnt even look that sturdy. Is it at least SS?

 

[Mustang71]

I'm thinking you are getting a back draft down both chimneys because the smoke is some what contained under that cap. When you use the stove you are removing air from your house causing negative pressure and it's probably pulling air into the house through the other 2 chimneys. With that cap on there it pulls the smoke back into the house. I would put in some sort of make up air near the stove. I dont think it's the caps fault. It's good to have a cap on the chimney.

 

[NCPT]

How and where are the location of the basement woodstove and basement fireplace?

$350...thats a lot of money. It doesnt even look that sturdy. Is it at least SS?

They are side by side, so I've got to be pulling air from that open chimney like posted above.

The cap is ss and it is sturdier than it may look in that pic. I thought the guy did a great job and I can be particular.

 

[CaseyForrest]

Its likely a combination of temperature differences between the individual flues, ambient temp and barometric pressure. I don't think its the cap.....

Have you tried getting a small, hot fire going to get the flue hot prior to commencing normal burning?

Our insert has a liner going through a flue right next to our water heater flue and they both exit at the same elevation at the top of a masonry chimney. We have never had an issue with anything coming down the water heater flue. Both have caps.

 

[Mustang71]

We have had customers who started a fire in their wood fire place and then an hour later their co alarm is going off because their furnace or water heater stopped drafting due to the house being in negative pressure and the fire place pulling air down that chimney. These aren't new homes either they are 20+ year old houses that aren't built real tight.

 

[NCPT]

Here is a pic of the top of my chimney. 12" flue on the left goes to basement fireplace. 12" flue in the center goes to living room fireplace. 8" flue goes to woodstove in basement which doubles as the exhaust for the oil furnace....the pipe for the furnace is above the pipe for the stove where it enters the chimney.

For some reason the center flue was busted up and had mortar built up around it. I'm going to put a piece of sheet metal in front of the basement fireplace to prevent my stove from pulling air from it. Also going to pull the chimney cap and try and block off the fireplace flues up top to prevent smoke from going down.

 

[NCPT]

So I have been working on this today. In an effort to keep smoke from coming back down the fireplaces, I pulled the cap and stuffed some oversized insulation just down the tops of the 12" flues. Then I cut a piece of sheet metal and placed it over each flue weighted down with bricks. Then I installed a piece of sheetmetal over the basement fireplace which is directly beside the woodstove. Now I have a fire going and will see if it has made a difference.

I'm thinking of stuffing insulation above the opening in the living room fireplace also. I was kind of shocked how warm the air was coming out the top when I was capping it off...and that's heat from the oil furnace.

Here's a pic of what's going on in the basement.


Here's a pic of the cap.

 

[Mustang71]

I dont think you solved the problem of bringing in fresh air for your wood stove to burn. It's still going to draw air from where ever it can pull it from.

 

[MAD MARK]

One thing I am seeing then, or at least trying to think out loud here.

Both the woodstove and oil furnace share the same flue. When the woodstove is trying to create a good draft I bet the barametric damper opens wide and pulls room air along with the wood stove exhaust.
To test this, get a good hot fire going and see if there is "draft/pull" on the oil furnace damper. If so, then there is the issue. Need to separate them.

If you are done using the fireplace, easy fix. Just put the stove exhaust into it, should use a liner, and it will have excellent draft.

 

[NCPT]

If you are done using the fireplace, easy fix. Just put the stove exhaust into it, should use a liner, and it will have excellent draft.

That's exactly what I'm thinking. Just waiting on the brick mason to punch the hole for me.