Lets Talk WOOD STOVES, Exhaust and Chimney

Lets Talk WOOD STOVES, Exhaust and Chimney information. Nothing about RHM or Rocket Stoves Please. Talking about a standard wood stove that John Q Public can buy in a store today.

Let me throw this example out there.
You put a wood stove in the middle of your Basement. You run the exhaust pipe up 36" from the stove, then a 90 degree elbow, and horizontal aprox 12 feet to another 90 degree elbow to the outside wall of your structure to a Verticle pipe that runs 15 feet up as a chimney. Would this work properly.
Compare that to an insulated pipe outside.
Lets change the Horizontal pipe to instead of Horizontal we change that to a 5 degree incline to the outside of the structure and then connect to the Chimney.

Is a Chimney really needed? An insulated pipe compared to a Black pipe.

Temp outside is 0 and snow on the ground.
Use real wood. Not pine 2x4 scraps. Use firewood that you cut in the forest last summer. The wood stove stays lit all winter to heat your home.

Any input to advantages and Disadvantages of different types of pipes and chimney pipes.

I am not searching for a specific answer, Just to start a conversation from Experience Firewood Burners who have used different types of pipes for their Wood Stoves. (not RHM or Rocket Stoves)

Thanks

Has anyone seen the H pipes that people put on top of your chimney of a wood stove to increase draw? Anyone used them?

We have heated with wood for forty years...in three different homes with three different stoves and three different stovepipe setups. The earliest eventually setting the shake shingle roof on fire...our fault...too much creasote build up. The next was a bad barrel stove but the pipe went in to the old fireplace chimney and worked OK. Now we have an excellent stove...not quite large enough to heat more than two rooms in super cold weather but good enough...the pipe goes into a tile lined poured cement chimney and up 30 feet...it is a two story house. We burn mostly standing dead oak...white, red and post,some hickory and a few others that we cut on our forty acres. Tops from my husbands woodworking trees and shiitake log tree leftovers get used also This stove draws well and our luxury is the glass front door for viewing the flames from a well placed sofa.

OK I won't mention how much i love my RMH, how well it works, or how little fuel it takes, or how cheap it was to build


seriously, i've had numerous experiences heating with wood and different stove pipe configurations (i didn't know any better)

I have never run a straight horizontal pipe more than about 3-4 feet, but i have seen setups with a slight incline (guessing 1" for every couple feet) running more than ten feet that seemed to do ok, maybe a little smoky, that was a while ago,, more incline is better than less

as for the elbow outside where the pipe turns up--do a t out there so you can monitor and clean regular whatever you burn and whether it's insulated or not--that will be a place where creosote can collect, and caused one of the two chimney fires i've had in my lifetime.

as for insulated pipe-- that really works, especially at startup, but also for continued burning to reduce creosote condensation,, and i've never burned a stove straight through the winter with no breaks,, there's always a milder day when you can let the fire die, clean out the stove, check connections etc, if you are planning to operate the winter start to finish, really make sure everything is right where you want it and top condition. that's a lot to ask of any appliance, and just the fact that you're thinking about uninsulated pipe outside suggests you're working on a budget and looking to economize where possible-- don't--get good stuff at the beginning

that being said, and off the record, i have made quite satisfactory insulated pipes using spun fiberglass insulation and pipes with a 2" difference in diameter,,say 6 and 8--i'd take my time and pack as i connect--ie the 6" inner connect,screw, the 8"outer connect, screw, then pack, this allows me to pack the joint with continuous insulation, and is one place where home packing is superior insulation to double wall sections that have conductive metal joints--i'd do this from the wall thimble right on up to the cap on top--i never did a T out there, so never had to pack one, ,,after the fire i reconfigured the shack and took the pipe through the roof instead of out the wall,

i don't try and connect already packed sections-- i use handfuls at a time and take my time, if it means standing on a ladder outside packing pipes then that's what i have to do,, obviously i don't use the paper or foil backing material

i have used these pipes when i was burning wood in an rv with an old coal potbellied stove and i still have one with the water heater stove in the greenhouse where the pipe goes through the roof

stainless steel double walls are very expensive, and probably worth it, but i was never able to afford them, and that's really the way to go-- home packed pipes are as good as i took care to make them, but stainless is the failsafe mainstay and last longer too

I have exposed that fiberglass to intense heat and the worst i have ever seen was some melting, the other fire i had however was a close call, caused because of temporary connections that never should have been in continuous use with one of these home insulated setups where i didn't connect the pipes properly, insulation got lost, ....

I know that it seems like overkill to have an insulated double wall running up over the roof, and at times for short runs i used to cheap out and go single wall all the way, with a little fiberglass stuffed around the pipe where it went through the wall or roof, and a little metal flashing to keep out the water, but chimney fires are no joke--one of them i used up two fire extinguishers (did i mention to have them on hand) and was shaking like a leaf when i finally realized the danger was past, it was just a little shack, but it was my home, and i damn near burned it down--(that was where the creosote collected in the elbow)

ah, a trip down memory lane, before i became enlightened,,don't know if this is any use to you, but it was sort of fun to write, and if anybody asks i did tell you not to use that home packing insulation method and i warned you of the dangers.

First I did not design my set up but use it. Stove in middle of the house, upper level, with pipe going straight up and out. Metal roof. Single wall pipe to ceiling, triple thru attic. Stove way too big gets plenty warm

sorry about the misunderstanding, did you find any of the information useful?

Bob,

I thought you had a quite a few good points in there I will re-itterate a few in responce to the OP. I've never tallked much about fires and chimneys but I did grow up in a wood burning house and can say this for starters. Design matters. There are wood stoves out there that plain suck. Garbage. Some are supper effective. Many are in between.

First woodstove in basement. I can totally see that working especially if you're house is well designed and insulated. As for exaust pipe - I have never seen a chimney set back 3 feet from the fireplace. I personally would be kinda worried about a 3 foot section of horizontal pipe . Just sounds sketchy to me. I've always seen fires going straight up into the chimney or making a 90 as soon as possible like 10 to 12 inches or so. 15 feet up would make for some mighty high ceilings. I don't know where you live - but at that rate of heat loss into the ambient air I'd be worried about turning you're woodlot into Crete! Better to catch that heat and make sure it doesn't go anywhere than keep your woodstove going full blast all the time. It would be better if you could think of a way to catch and store as much of that heat as possible. I've never seen a stove pipe in at an angle. I could see that working better than a 36 inch horizontal run.

By black pipe do you mean just plane old iron chimney piping? That stuff rust through collects creosote and will burn through. You're going to need to change it every 6-10 years. Less if you get any sort of water leak going on. I've seen those things rust through quick. An turn to dust. Having used it extensivley it would not be my first choice. Insulated pipe is better but looses heat pretty quick (like if you let the fire go out for half the day) Nothing I've seen beat stone. tried and true that - never had the pleasure of having one myself.

I think a chimney is needed in most all situations I can think of. An exception would be if you have a smoke hole. The only practical way I can think of doing this would be with a Mandan style earth lodge. These are pit house with a raised sloped earth bermed wood roof with a smoke hole in the center. I imagine they had skins to close the flaps. I'd have to read some more Merryweather Lewis and see how good his notes were.

Learn your stove. Learn you're wood. and Learn how to burn. Lots of oxygen can be great to start a roaring fire but once its good and going you want to put as much fuel in as possible and lock it down. Proper banking of coals once it burns down can be a big boost too. You don't need to keep a good fire going once its heats up - Just bank the coals and through a bit more fuel on and lock down the air again.

Jeremiah wales Original Poster
Lets Talk WOOD STOVES, Exhaust and Chimney information. Nothing about RHM or Rocket Stoves Please. Talking about a standard wood stove that John Q Public can buy in a store today.

Each time you put an angle in the flue or chimney you reduce the draw. Reduced draw requires greater heat to get enough draw to draw out the smoke.

I have seen it all.
Stoves in basement with 15 feet of horizontal pipe over to a wall and out a chimney
20 feet of horizontal pipes and then some people here have 20-25 feet of Horizontal pipe with several 90 degree angles on their stoves.
Just to put some sense to all of this. I just posted this Talk.
There are a few good Videos on You Tube. I saw one guy who had a barrel stove and made a heat exchanger out of stove pipe. 2 t's 4 90's and two 36" pipes. all just above his stove. Seemed to really increase his heat. It was in a shop, Not a house. Then in another video the guy put what he called an H pipe on top of his exhaust pipe up about 20 feet in the air. It had 4 outlets on it. When the wind blew a little smoke came out of all 4 outlets. But with no wind just came out of 2 of them. He said this overall increased the draw out of his stove. Interesting stuff.

Is there any formula that anyone has heard of horizontal vs vertical rise for stove pipe. Obviously the same formula would not work on a RMH as they are a different animal. But just on wood stoves. Yes there are Crummy Wood stoves out there. Seems like they are more decoration than actual wood stoves.

Judith Browning wrote:We have heated with wood for forty years...in three different homes with three different stoves and three different stovepipe setups. The earliest eventually setting the shake shingle roof on fire...our fault...too much creasote build up. The next was a bad barrel stove but the pipe went in to the old fireplace chimney and worked OK. Now we have an excellent stove...not quite large enough to heat more than two rooms in super cold weather but good enough...the pipe goes into a tile lined poured cement chimney and up 30 feet...it is a two story house. We burn mostly standing dead oak...white, red and post,some hickory and a few others that we cut on our forty acres. Tops from my husbands woodworking trees and shiitake log tree leftovers get used also This stove draws well and our luxury is the glass front door for viewing the flames from a well placed sofa.

Judith, Sounds like you enjoy sitting down and watching the Fire as much as I do. The heat is a benefit too. I use real wood too. Cut it all. Solid wood works the best. Although this winter with this terrible cold in Wisconsin. I had to set my alarm and keep that fire working harder to make sure my home is toasty. It has been -13 several times here for days at a time last month.

Hi,Jeremiah... yeah, we even sometimes 'critique' the flames We also cook on our wood stove six months out of the year....and it simmers my natural dye pots...dries our clothes...warms my seed flats....keeps the muscadine wine at the right temperature.....

i don't want to get into this much more as i can't give formulas since there are so many "it depends" and each formula is more than i want to think about

exhaust temperature influences draft--a cold chimney will smoke back , a warm one won't

height of the chimney influences draft, even the chimney cap, size of the pipe, etc

the draft on the pipe determines how far you can run the horizontal without issues--and at start up i would just assume a smoky start unless you have a primer hole for lit newspaper where the pipe starts back up, and in those cases you can run an exhaust pipe under the floor before heading it back up, by starting the thermosiphon of the hot gasses

for all it's problems, that horizontal pipe can probably double the heat in the room (depending on the stove) and it certainly increases radiant heat to other parts of the room, or even other rooms where it runs through an interior wall thimble and an adjacent room

there are formulas for this, i've seen a few of them, but never really tried to apply them, it was always hit or miss for me

I'm currently heating with a high quality woodstove in my basement and regret my chosen location. For various reasons, I placed the stove against an exterior wall with the flue elbowing (2 45's) into a 2ft length of insulated chimney before T-ing into a 15ft vertical insulated chimney. This arrangement meets the code here but is very much handicapped in many ways. The short horizontal pipe can't help but collect creosote, and combined with the elbows reduces draft noticeably. Add to that the 15ft of exterior chimney and cold climate (zone 1b), as well as the negative pressure of a basement and you have a very good woodstove that performs like a poorly made homebuilt stove. I often stare at the fire and fantasize about how it would be if I'd placed it in the center of the basement with the pipe running vertically up through the warm house and exiting the roof right at the peak. I'd get much better efficiency, require fewer chimney cleanings, have no smoke in the house and sleep better. If I was planning to live here longer, I'd make the necessary renovations to move it, but instead I'm just tolerating it for now.

I would suggest that you not skimp on your chimney and avoid elbows at all costs, if possible. Any cost savings by using black pipe are short-lived and to be regretted down the road.

Great comments. This brings up another question.Outside chimneys vs inside chimneys. ( thru the center of the house.
My home had an inside chimney years ago. But it was removed just before I bought the place. A friend said. Just put a chimney on the outside wall. Its EZ. But I wonder how well it would work. Vs just my stove pipe.

Jeremiah wales wrote:Great comments. This brings up another question.Outside chimneys vs inside chimneys. ( thru the center of the house.
My home had an inside chimney years ago. But it was removed just before I bought the place. A friend said. Just put a chimney on the outside wall. Its EZ. But I wonder how well it would work. Vs just my stove pipe.

For best heating, the wood heater needs to be central. Then you want to run a long horizontal flue to an outside wall? Not sure how that is easier than straight up. If you are putting your stove near a wall anyway, that may be the easy way to go. On the other hand, I have seen the flue run from the centre of a house through a concrete mass (cinder blocks) to the wall and out that way. The mass also acted as a wall between two rooms. The mass also holds the heat for many hours and acts to hold/absorb heat from the sun as well.

Thin wall vs. massive chimney: A massive chimney will pull air out of the house as long as it is warm, a thin wall will stop drawing as soon as it cools down. Thin wall may keep your heat in the house after the fire goes out rather than drawing it out.

We've heated with wood for about 40 years. Generally, you want to avoid horizontal runs. Locate chimney in center of building, it works better there. Outlet must be 2' taller than the roof. Use furnace/retort cement and sheet metal screws on all joints. This is vital! Wood should season at LEAST one year after cutting. Lots to read on the Internet about chimneys and draft.

Drying firewood is a complicated procedure. There are situations and climates that drastically increase or decrease the time required, and the real goal is not a calendar year of waiting but a moisture content of around 20%. Last winter I was able to take freshly cut and split birch and have it down to 25% moisture content in three weeks. The following discussion thread outlines the process and the method of measuring moisture:

http://www.hearth.com/talk/threads/drying-wood-quickly-indoors.61783/

Having a face cord or so of not quite dry firewood indoors helps to alleviate the dry winter air and avoids the need for humidifiers or kettles on woodstoves.

Horizontal runs more than a foot can be problematic and even dangerous. The danger is in maintaining air tight joints and establishing clearances to combustibles. Local codes may vary, but NFPA 211 establishes minimum distances to combustible walls and ceiling...not sure if it's been changed since I retired or not, so check it before you install. A chimney fire in a horizontal pipe would be one of my main concerns. Chimney fires typically extinguish themselves in a few minutes, but some have gone on for hours. There's no way to tell. So, can you imagine a 12' run of single wall pipe glowing red hot for 20-30 minutes...which is not a rare duration? I wouldn't touch that installation for love or money...just too much liability.

So the Mass Crew talks about Horzontal Pipes for long distances in the mass and the Wood Stove Crew talks about No Horizontal Pipes.

Good thread! Attached are some photos of my current setup: an exterior masonry chimney with a Napoleon insert. I wanted to ask a few questions about making this setup as efficient as possible:

We've been burning wood like this for 4 years now, and it's a good setup: one cleaning a year, let the firewood season for a year before burning, works great. It's a little 2.0 cu. ft. firebox so I have to fill it 4 times a day, and it is usually over 200 degrees when I wake up in the morning.

[edit]I've also replaced the cheap, "foam" bricks that go inside the top of the firebox with stainless steel:
http://www.covingtoncreations.com/blog/review-napoleon-1402-wood-burning-insert-custom-steel-baffles
[/edit]

Has anyone boxed in / insulated their exterior masonry chimney? Worth the investment? We are thinking about possibly insulating and finishing off the front porch on our house, which would enclose the chimney for another 8 feet. However, we've still got 20 feet of chimney sticking up above the roof of the porch...

One thing I've found that helps throw off some more heat is the "firebricks" that line the inside of the stove... I bought a bunch of extras and lay them on top of the unit, behind the cosmetic cover panel... these sit on top of the thin sheet metal above the unit's blower, holding a lot more heat in for the blower to "use."

Does anyone have other suggestions? Thanks in advance!

Jeremiah wales wrote:So the Mass Crew talks about Horzontal Pipes for long distances in the mass and the Wood Stove Crew talks about No Horizontal Pipes.

A rocket/mass heater setup can use horizontal plumbing because of the internal chimney's push and clean burning (no creosote).

Insulated Stovepipes inside or just outside the roofline?
What are benefits or none benefits?
One person commented Non-Insulated inside the building and Insulated outside the building.

Metal Insulated Stovepipe Vs Standard Concrete block with the clay liner?

I finally picked up a Wood Furnace. Hot Air type. Complete forced air venting. Now comes time for a chimney...? Chimney, Insulated Pipe. 6" or 8", Where would I used insulated part. Inside the building? Outside the building? One 90 or 2 90's. 30" from the outside wall. So it would only have one horizontal section. Any Comments on experience of what has worked best for you?

Got my furnace hooked up for this winter. I have 30 inch horizontal pipe right out of the back of furnace to outside. One T and then 15 foot straight up. Uninsulated pipe. Just doing it this way, Because it all comes down in May. when a New roof goes on the place. I still get a little smoke back until I get a hot fire going. I am unsure of how to put my final chimney in.

Well with experiments over the past sixty days. I am going to move the chimney back to the center of the house where it was originally. I know I am losing heat going out a window opening. Then When I first put the stove in it still had a lot of ash in the bottom. I kept it in there. The fire would last for eight hours. Choked down. Keep the house semi warm. This small fire caused the Non Insulated outside stove pipe to build up with HUGE amount of creosote. I cleaned it all out.... The stove pipe and all the ash. Now I keep the fire going hot. But I am only getting the wood to burn hot for three to five hours. No Creosote.
I also changed my Chimney pipe style.
First I came out of back of stove. Thirty inch horizontal. a ninety then fifteen feet in air. BAD.. It leaked back moisture into the stove.
Then I came out of back of stove. Thirty inch horizontal. a TEE then fifteen feet in air. Better but still bad. The Tee would build up and still leak back a little
Finally. I came out of back of stove. Thirty inch horizontal. a Tee with a thirty inch stove pipe going down and not sealed. and fifteen feet up in air. BINGO. THat is it.
Just think using a chimney. A Chimney hole is not at the bottom of chimney. It is about one third up from bottom. This gives you some clean out area.

Then for those who will bring up the Dry wood Formula.
Listen there it is a bit Humid here. No matter how dry the wood was at one time. It will always have same moisture content as the air. Inside my wood shed or not. So I have some moisture when burning.

Please if you really burn wood semi full time. Add any comments. If you have only read a book on how to burn wood. Uhh. Don't tell someone how it is done.
Many sites have helpful people who have burned wood at the boyscout camp and never after that. They quote formulas that work in a Lab. Not in real life.
So. Thanks for the help, But if you burn wood a LOT lets keep this information passed on.

I hesitate to pay the huge amount for insulated stainless pipe. I am considering going with a brick chimney again. Seems like they will be about the same price.
Thanks

Quick, and maybe stupid, question! I have a wood stove with a 6" stove pipe. Am I able to connect that with an 8" chimney? I found a complete 8" chimney that will save me hundreds of dollars if so!

Vincent

Hi Vincent

If your 8" chimney is in good condition, yes you can connect a 6" flue to it. There are commercially available adaptors that are designed for this purpose.

Vincent Parkhurst wrote:Quick, and maybe stupid, question! I have a wood stove with a 6" stove pipe. Am I able to connect that with an 8" chimney? I found a complete 8" chimney that will save me hundreds of dollars if so!

Vincent

Yes if it is single wall, but nearly impossible to find an adapter if it is double or triple wall stainless stove pipe.

Jeremiah wales wrote:Let me throw this example out there.
You put a wood stove in the middle of your Basement. You run the exhaust pipe up 36" from the stove, then a 90 degree elbow, and horizontal aprox 12 feet to another 90 degree elbow to the outside wall of your structure to a Verticle pipe that runs 15 feet up as a chimney. Would this work properly.
Compare that to an insulated pipe outside.

Not so well.

The answer lies in that it is single wall stove pipe and located on the outside of the home. By having single wall stove pipe, the smoke going up the chimney will cool because it is outside the home and thus not only creosote up really fast, but also lose draft because it is not getting warm enough air to the top of the single wall stove pipe. This effect is really noticiable on warmish days when the air is heavy and damp, or when burning coal, and a lot of draft is needed to pull air up through teh coal bed.

Triple wall pipe will draft better because it is insulated and retains the heat of the smoke going up the chimney, and keeps the cold at bay...but

A masonary chimney up the center of the house is going to draft the best. It might take a few days of burning to really warm that chimney up, but then thermal mass takes over and it is buffered from hot and cold fluctuations like putting single wall pipe on the outside of a house.

Vincent Parkhurst wrote:Quick, and maybe stupid, question! I have a wood stove with a 6" stove pipe. Am I able to connect that with an 8" chimney? I found a complete 8" chimney that will save me hundreds of dollars if so!

Vincent

Yes but, and it's a big but, the 8" chimney will want to run cold and this will work to reduce the draw. It will creosote up easier. You may bet smoking at the stove when lighting, difficulty lighting, smoke if you run the kitchen and bathroom exhaust fan together, or the clothes drier or if someone opens a window upstairs  etc. We are off grid and our 8" chimney system is on an 8" outlet stove. We light the fire in September and it burns steady through March. We also have a 6"outlet stove in the shop and have experimented with chimneys. We know things about chimneys. And ours is perfected - for us, in our application.
Use the math of pi-r-squared to see the huge volume difference for the 8" and you will see you will be pumping a lot more air and heat up there. Install a baffle in the 8" near the stove and this will help butbwill not prevent things gumming up.
If it is mostly insulated pipe that will help. It is commonly only gets down into the -30s here now, rarely -40 and never the -60s of 40 years ago so trust me when I say an 8" chimney needs a good amount of heat flowing up it in the winter for it to work well though careful installation design makes a world of difference.
You will want to look at the idea of a short hot burn once a day to help the pipe stay cleaner.
Expect frequent cleanings.
And you may have to fake up an adapter for single wall pipe to the inside of the double wall.  Or not. Having a sheet metal crimping tool and a riveter will help with this. You can use off the shelf duravent type single wall bits as raw material. Your insurance company might freak out.

Jeremiah wales wrote:
Compare that to an insulated pipe outside.

Our approach is to use 20 feet of uninsulated stainless steel pipe inside...





...so that it can radiate heat into the house all the way up.

Greg Mamishian wrote:

Jeremiah wales wrote:
Compare that to an insulated pipe outside.

Our approach is to use 20 feet of uninsulated stainless steel pipe inside...





...so that it can radiate heat into the house all the way up.

Us too.  Works great. But we only have 10' of uninsulated 8" pipe inside. Your setup looks great!

I was given a wood stove with a rear flue vent. My home is small with no chimney, and I don't have an outside wall to install it on. It seems this type is for connecting to an existing chimney or to exiit from an outside wall? The only space I have for it is on an interior wall. Can I make it work for me with a T pipe or would the extra horizontal clearance probably put it too far into the middle of the room? I think I may be better off purchasing a wood stove with the flue located on top vs the rear for space reasons. How much additional horizontal clearance will I need for a rear vent style vs top style? Are there other considerations when deciding if the rear vent style I have will work in the interior spot I have?

Meagan:

Use the clearance rules for the type of pipe, but measure to the pipe not the rear of the stove. A rear vent works fine in a house. Elbow or tee. Tee is easier for clean out. Yes, it will take up more space. But if you need it, can fit it and it's free you have to live with it. On an interior wall is nice as a stove in the middle of a room is nicer for heating. Your additional things to think about are mess under the tee during cleaning etc, the bigger stove pad and passing through floors if more than one story.
Plus you will be needing a chimney system. They are expensive. If you value having house insurance then a certified stove and a complete 'one brand only' chimney system are usually needed. Safe chimneys can be constructed out of parts from different suppliers if you have experience  (and usually more economically) but .....

Plenty of clearance data and chimney expertise posted at woodheat.org

Clearance data is here:
https://woodheat.org/clearances.html

Quick question for the group.  My wife and I built a Tiny House on Wheels and moved to Northern Minnesota.  We have a Jotul wood stove, can't remember the model, but its the smallest one they make.  My question is how to vent it.  The house is only 8 feet wide,(and 13 feet tall) but there are sleeping lofts on both ends and the stove is going in closer to the loft for the kids.  My wife is worried about running the pipe up along the edge of that loft and wants to run it out the back of the heater and through the wall, with a T and run it up the side of the house.  Someone told us that was a really bad idea, due to problems with drafting.  Having read through the above posts, as long as we use a double or triple insulated pipe, there shouldn't be a problem, correct?  I know it would be a lot easier to do that, especially at this time of year, as I really don't to be on the metal roof cutting into it right now.

If I am envisioning it like I think, it will draft fine. You will have to cap the bottom of the Tee, or use a 90 elbow instead.

I have a pellet stove in that configuration and it drafts fine even with the power draft off.

That sounds like old thinking. If you are using insulated chimney your drafting will be fine running along the outside.Draft at light up can sometimes be an issue since its cold but that is very temporary. you will need the wall bracket and I find the T fitting with the removable bottom cap ideal.
This install video is pretty typical: