windy day downdrafts

[Hoytman]

The first thing I would do is lose the single wall stove pipe and add double wall stove pipe. That’s the same effect as adding more height…which is what I think you need with that high pitched roof nearby. If the double wall also helps “some” then add another section or two to the chimney height.

I would be very careful choosing a cap. The wrong one will cause you more grief than you have now, in my opinion.

 

[farmer_luke]

The first thing I would do is lose the single wall stove pipe and add double wall stove pipe. That’s the same effect as adding more height…which is what I think you need with that high pitched roof nearby. If the double wall also helps “some” then add another section or two to the chimney height.

I would be very careful choosing a cap. The wrong one will cause you more grief than you have now, in my opinion.

The installer said he couldn't get any double wall telescoping pipe. Where the single wall is only in the living space I assume it's not as important that it be double wall compared to an unheated space?

We currently have 9 feet of triple wall pipe on the roof. There's about 9-12 feet of triple wall below that, and 4 feet of single wall below that. We haven't had any trouble with draft once the fire gets going with the 9 feet of triple wall on the roof but we do still get intermittent downdrafts with a cold stove with a South wind. I do think adding more height might fix the problem, I just really don't want to do it. With a taller pipe we'd likely need a second set of braces and I'm afraid it would look like an unsightly contraption up there.

I'm pretty much planning on getting a luxury metals vacuum cap and trying it on the easily accessible liner we have in the masonry chimney which also has the same South wind downdraft issue. If it works there I will get one for the class A pipe. Any thoughts about this brand/type of cap? I'm afraid of potential problems with a wind directional cap.

On a side note it seem like the draft is plenty strong. We almost always burn the stove with the air shut either all the way down or close to it to keep the single wall stove pipe out of the "Too Hot" range. I've checked the magnetic thermometers that are on the stove pipe and they are a little hotter than the infrared indicated but pretty close. When the single wall is about 500 the stove top is about 750.

 

[Hoytman]

That seems excessively high to me for single wall pipe.

People here make quite the claims about the difference double walled stove pipe makes. I have no reservations about this truth.

I just thought the double wall would maybe prevent adding an additional section of class A and an unsightly bracket. It would also be the easiest way to tell if adding more height would help. Would be worth a shot. Lots of online chimney suppliers if your supplier can’t get it.

A lot of old timers didn’t believe in a cap. Some still don’t. My masonry chimney has never had a cap in almost 70 years. Not saying I agree with that or not, but I see pros and cons, mostly benefits to having a cap…but I didn’t and still don’t want just any cap. So, I’m still searching and researching. Like you I’m prone to down drafts, but not from high winds…from living in a narrow valley with hills on three sides. My issue isn’t constant so I’m in no hurry and will likely add a cap when I do chimney repairs.

My pretty extensive research this far on caps led me to the conclusion that there are a lot of custom caps out there to catch customers with no real science behind many designs. For instance some sit high off the chimney exit, some seem far too low. A lot of them are super expensive, and from reading little to no consensus on which ones work best and which ones don’t. I’ve seen a lot in person and in pictures stopped up and iced up with ice cycles hanging from them at -26below. I’m just saying …

…ask around here. Ask Begreen, BHoller, and regular forum folks. What brand, style, etc. Get peoples opinions and experience, keep asking questions and try and make the best informed decision you can.

Some have conical inner designs (like a cone pointing downward) that allow any condensation that might accumulate at the top inside of the cap to drip straight back down into the chimney. Those can be hard to find and $$$. Others seem like a kindergartener designed and built them. They just aren’t all the same, nor do they all work the same. As some have said already, some caps are made for special applications like high wind, condensation at the top, to stop down drafts or swirling winds, etc. The information doesn’t seem to all be in one place either.

My point in all this, be careful what you let someone talk you into.
Just my 2 cents…

 

[moresnow]

Is there a open thimble into the masonry chimney on the main floor? Or is it properly sealed?

 

[farmer_luke]

Is there a open thimble into the masonry chimney on the main floor? Or is it properly sealed?

The thimble on the main floor got sealed when we moved the stove on the main floor.

 

[VintageGal]

Would an outside air kit (OAK) help?

 

[Max W]

This rig with its surface area seems an unlikely solution in your windy location. Also it would need to set lower than your current chimney section(s) and be braced. Looks are important to you as well. A friend whose father was a tin knocker came up with one for me and solved the downdraft problems I was having with my first wood stove. A local resaraunt has a large one on a kitchen stack. Figured I’d just throw it out if only to add to general downdraft ideas.

 

[farmer_luke]

Would an outside air kit (OAK) help?

By outside air kit (OAK) you mean an air kit attached to the stove? There's also something that brings outside air into the home to equalize pressure or provide positive pressure right? I'm not sure about an OAK to the stove. I've looked over my quadrafire 4300 to see about possibly reducing the available fresh air and I'm not super impressed with how the right side shield would seal off the house air from the outside air. I was considering partially covering the spot where the OAK line would go (because that's also the main place the fresh air from the house comes into the stove) to be able to better control the air. It's getting too much air/too much draft on non-South wind days where the wind really blows.

Also, I installed the luxury metals vacuum cap on the liner in the masonry chimney and we had a couple days of strong south winds and I don't think it helped. I didn't try a fire in the basement stove that uses the masonry chimney but I could tell there was an intermittent back/downdraft. Some things I wonder about: is the masonry chimney far enough away from the higher peak to the north that it wouldn't be in the positive pressure area? Wouldn't the class A, where it's 2 or 3 feet above the highest peak be out of the positive pressure area? When we were having South winds around 20 mph I started a fire and it back puffed about three times before it got going and never had a problem once hot. Now the wind has switched to the Northwest and we have the opposite problem, too much draft

 

[farmer_luke]

This rig with its surface area seems an unlikely solution in your windy location. Also it would need to set lower than your current chimney section(s) and be braced. Looks are important to you as well. A friend whose father was a tin knocker came up with one for me and solved the downdraft problems I was having with my first wood stove. A local resaraunt has a large one on a kitchen stack. Figured I’d just throw it out if only to add to general downdraft ideas.

View attachment 305034

That seems similar to the luxury metals vacuum cap I installed, no?

 

[farmer_luke]

I guess what makes the most sense to me is that the house is experiencing negative pressure on South wind days because there are only 3 windows on the South side of the house but 7 on the North side so more air is getting sucked out than blown in. Maybe adding to this is the higher peak to the North of both stove's flues possible creating a positive pressure area around each stove pipe cap (although the class A should be above it). Positive pressure around each stove pipe termination and negative pressure in the house. Bad combo. But I don't really see confirmation of this when I open a window on the South side of the house and start a fire. I would think this would easily reverse any negative pressure in the house but it doesn't seem to help the fire much. The fire still struggles to get going even with the window open. Once hot there hasn't been a problem. We don't have that much South wind when burning the stoves so that's good.

 

[BillBurns]

I have a T on top of my flue/chimney/stove pipe/vent...it keeps rain out, allows a lot of draft, but I need screen in case of critters. I assume ill be flamed for this, but its what it is. I guess it "unsightly" but its on he back of my house, no neighbors, and it was cheap.

 

[farmer_luke]

I have a T on top of my flue/chimney/stove pipe/vent...it keeps rain out, allows a lot of draft, but I need screen in case of critters. I assume ill be flamed for this, but its what it is. I guess it "unsightly" but its on he back of my house, no neighbors, and it was cheap.

Thanks Bill. I appreciate all answers, even the ones that aren't quite up to code. I don't know anything about cap code requirements. I wonder if a T might overheat in the case of a chimney fire? Kind of seems like all caps are a type of T.

 

[begreen]

His system is using stovepipe as a chimney. It is way out of code regardless of the cap.

 

[farmer_luke]

His system is using stovepipe as a chimney. It is way out of code regardless of the cap.

I guess I'm not following. Maybe you have previous knowledge of his setup? I could also be lacking in understanding of terminology. I don't understand what "using stovepipe as chimney" means. My stove has stovepipe and no chimney. :S

 

[begreen]

I guess I'm not following. Maybe you have previous knowledge of his setup? I could also be lacking in understanding of terminology. I don't understand what "using stovepipe as chimney" means. My stove has stovepipe and no chimney. :S

Sometimes people get terms mixed up. Stovepipe is the black pipe inside the room that connects to the ceiling support box. Stovepipe is only permitted for use in the room envelope. At the ceiling (or the wall) the flue system transitions to stainless steel, insulated, class A chimney pipe.

 

[farmer_luke]

Sometimes people get terms mixed up. Stovepipe is the black pipe inside the room that connects to the ceiling support box. Stovepipe is only permitted for use in the room envelope. At the ceiling (or the wall) the flue system transitions to stainless steel, insulated, class A chimney pipe.

I see. So how do you know Bill doesn't have Class A pipe with a T on the top? If that were the case would having the T on the top be a code violation?

 

[begreen]

I see. So how do you know Bill doesn't have Class A pipe with a T on the top? If that were the case would having the T on the top be a code violation?

Stated in previous threads.

This is the first time I recall someone asking this question. I don't think having a class A tee on top of class A chimney is a code violation, but the manufacturer of the class A chimney may have strong objections, especially if this provided a pathway for water to get into the pipe's insulation layer.

 

[baerjo]

We solved one of our issues, the windy downdraft, by installing a Vacu-Stak. Of course the day I put it on was insanely windy which was, uh fun, on a ladder. Either way had zero issues and worked perfectly. Now I get to figure non-windy day downdraft issues, but that's a separate problem. I never knew stoves were such problem children to get working right. Makes TP's seem pretty smart.

 

[begreen]

The installer said he couldn't get any double wall telescoping pipe.

What brand stovepipe is this?