In Room Flue Pipe vs In Chimney Flue: A Matter of BTUs

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billfrommissouri2

New Member
Mar 1, 2010
16
Southeastern Missouri
Hello Forum Members,

Working with a fireplace, what's better –– to have a flue pipe in the room that taps through the masonry into the chimney flue above the mantel, or to have a stove set into the fireplace which runs the flue right through the fireplace box and up the chimney? Doing the second way I'm losing heat in order to have the stove take up less room, to not have an "ugly" black flue pipe in the room and to save myself the trouble of gouging a hole through the masonry wall to hook the in room flue into the chimney flue. Is it worth the hassle to get another 10% of the heat from my stove into the room? With an 80% efficient stove, twenty percent of the heat is going up the flue so shouldn't I have the flue in the room if I possibly can?

I've got a blowerless Morso insert and I am sick and tired of it. Even so, I want to have a stove without a blower if I possibly can. I just don't like the noise. I like to hear the dogs barking outside etc. That is why I'm not really looking at inserts, even though an insert with a blower would by far be the easiest solution.

I feel pretty lame about not being more decisive about this and bringing it to you all. Obviously the right thing to do is to put the g-d danged stove out in front of the fireplace and run the flue inside the room –– Right?

Thanks,

Bill
 
Yup. If you don't want a blower, then having the stove out on the hearth is going to make a sizable increase in the heat convected off of the stove. However,it should be noted that some insert blowers are fairly quiet when run at medium or low speed.
 
The stove will protrude much further into the room. You will have to deal with CTC to the mantel and CTC for the hearth extension.
 
I see double wall in-room flue pipes for sale and I wonder what their point is -- to keep the gases hot? It seem like they are just depriving you of heat.

Please allow me to ask again: will I get more "lots" more heat from the flue by having the flue in the room instead of running directly up chimney? Is a 10% heat gain a good estimate, or is it high or is it low? Should I even care about whether the flue is in the room or running directly up the chimney? Neither of you mentioned the heat from the flue in your responses.

Thanks!

Bill
 
The purpose of double wall stove pipe is to reduce clearance to combustibles. Can't give you a number on what the BTu rating would be in the two different installs. but my guess is there would be a difference.
 
I have double wall flue pipe to my ceiling. It is for a reduced clearance to combustibles. 6" vs. 18" for single wall is huge. The DW pipe is built better with stainless steel as well. I am not concerned about the small amount of heat to be gained by using single wall, I doubt it is 10%. It's not lots. Your stove will be hot and if you need the heat from your flue then you bought a stove too small.

Your biggest issue is aesthetics. Going up above the mantle and then in is much less attractive in front of a fireplace. Has the potential to look like a hack job.
 
Great Responses! Thanks. Just what I was looking for. It's complicated and its a matter of aesthetics and nuance. You guys are dialed in for sure.

Dakotas Dad: great conversion job! It's pretty much what I'd like to do (or pay to have done). Of course my situation is somewhat different. I've got brickwork on my fireplace surround that extends a foot into the room that is structural to a big ol' brick chimney. You seemed to think it was important to get several feet of air space (and hot flue run) above your stove. I as well don't like the idea of tucking the stove under a tight overhang. I believe you've given me some ideas, or at least re-invigorated some old ones that I had discarded. The question that I might need a stone mason to answer is how much brick can be taken away without harming the structural integrity of the chimney.


Thanks again,

Bill
 
Dakotas Dad, may I ask you why went to the trouble of that whole conversion -- which is very beautiful btw -- anyway? Because you didn't like inserts with blowers? Or just cause it was cool and you like building things?
 
billfrommissouri said:
Great Responses! Thanks. Just what I was looking for. It's complicated and its a matter of aesthetics and nuance. You guys are dialed in for sure.

Dakotas Dad: great conversion job! It's pretty much what I'd like to do (or pay to have done). Of course my situation is somewhat different. I've got brickwork on my fireplace surround that extends a foot into the room that is structural to a big ol' brick chimney. You seemed to think it was important to get several feet of air space (and hot flue run) above your stove. I as well don't like the idea of tucking the stove under a tight overhang. I believe you've given me some ideas, or at least re-invigorated some old ones that I had discarded. The question that I might need a stone mason to answer is how much brick can be taken away without harming the structural integrity of the chimney.


Thanks again,

Bill

We were going for a certain look. we wanted it to appear that an old craftsman style fireplace had been converted with the addition of a wood stove. Some of what was done had to do with the clearance requirements for our stove, getting the stove where we wanted it on the hearth, and the need to be able to hook up the pipe to the stove itself, and unhook it for cleaning.
 
billfrommissouri said:
Dakotas Dad, may I ask you why went to the trouble of that whole conversion -- which is very beautiful btw -- anyway? Because you didn't like inserts with blowers? Or just cause it was cool and you like building things?

We didn't have an insert, we had a pre fab fireplace. we wanted a wood stove over an insert or ZC because we wanted (as a side benefit) to be able to heat the house in case of loss of power, which we had exactly 1 year ago for 8 days. We do in fact have a blower on our stove, but it was a kind of "well since we have to have a heat shield" kind of thing. Some of the work we did also had to do with getting the walls protected because of the needs of the stove and trying not to have the stove any farther out into the room then we needed.

We do in fact like building things. and we do think it's cool.
 
billfrommissouri said:
Or just cause it was cool and you like building things?

Sorry, I didn't mean *just*. It's certainly is great look, certainly worlds better than my idea of running my flue pipe in front of the mantle and into the wall. (And how great is it that you like building things!)

Do you use the blower much?
 
We do use the blower almost all the time. A small bit of subjective experimenting tells me it helps add some heat to the room. It could be I just like the background hum.. Since our "chimney" is just a chase that happens to be covered with brick, doing the flue up outside the wall and then into the chimney really wasn't a method we wanted to use, although it does give a good "retrofit" look. It also moves the stove out into the room pretty far, especially if you don't use double wall pipe. Our living room is 14x27, but the stove is centered on the outside wall of the long length, and right across from the TV.. so we wanted to give up no more floor space then we had to. One of the downsides of a very open floor plan with lots of "we live in the woods and need lots of windows to see the woods" design is very limited wall space in the room. It's good for moving heat out of here and into the rest of the house, but very limiting in what you can do furniture wise and stuff. We didn't own a TV when we moved out here, and it took us 3 years to get one, but now the darn thing has center stage in the room and has even cloned itself into the bedroom and basement.

Oh, and we took no offense at the *just*. :)

Oh, and one more thing.. on the ONE remodel I helped with that may be along the lines of what you are starting with (pics help.. this forum loves pics) the brick face in the house was just a veneer, and the chimney, fireplace was monolithic. The brick facade was removed and it was just about a blank slate to work with. Will attach a couple pictures of what was found in that home.. It *may* be what you find in yours.
 

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Dakotas Dad said:
The purpose of double wall stove pipe is to reduce clearance to combustibles. Can't give you a number on what the BTu rating would be in the two different installs. but my guess is there would be a difference.

Double wall will also keep the flue gases hotter. This can improve draft and reduce creosote accumulations which is important when there are elbows involved in the connector and an exterior chimney.
 
BeGreen said:
Double wall will also keep the flue gases hotter. This can improve draft and reduce creosote accumulations which is important when there are elbows involved in the connector and an exterior chimney.

Yes, and much more important than any small increase in heat transfer gained from use of single wall pipe. The whole idea IMO is to get the stove working at it's optimum. Dropping the already low-temp flue gases coming from an EPA stove even further could have a effect that actually lowers the efficiency of the stove itself by decreasing the draft while at the same time creating the conditions for condensation inside the pipe - a real double whammy. Nothing in life is 100% efficient. Get the system working at the peak of its operating capabilities and live with any small losses.
 
So the only way to get that 80% efficient non-cat stove that you wrote about is to lose that 20% to the flue. You won't be able to shift it to a 90/10 relationship by stealing flue heat.
 
Is the masonry chimney located in the center of the home or on an exterior wall? If it's an exterior wall, trying to set a stove in the fireplace without a blower is essentially going to heat that mass of brick and the outdoors. Brick is a relatively good conductor of heat, and will make a great heat sink for a stove that's just cooking away with 30% of it's heating coming out the back of it. A heat shield and a blower will make sure that heat goes where you want it, which is into the room.

If it's a central chimney, you are in much better shape. If you go with a hearth stove, and put it into the fireplace, you are going to want a blower anyway. A block-off plate at the bottom is certainly a big help, but if the stove is set into the fireplace, heat is going to go up from the stove, radiate into the block off plate, and some of that heat is going to be going up the chimney. I've heard some of the blowers on new stoves in stove shops and some of them are nearly silent.

You aren't going to gain much heat from the flue being in the room, and if I'm picturing this correctly, it sounds like you are planning on having a flue pipe dead center in front, blocking the view of your mantle. if you use single wall stove pipe for this, it will also need to be 18 inches out from the mantle. For me with a 1 foot wide mantle, that would mean a stove sticking nearly 4 feet into the room, and a hearth(or at least floor protection) sticking nearly 6 feet into the room.


I can certainly relate to the fact that you want a freestanding stove. I definitely prefer the look and feel of the radiant heat from a freestanding stove, and I have an install similar to the one you are thinking of, which is the stove sticking approximately 65% out of the fireplace opening. If it were cost effective, I would purchase the blower for my stove. The heat shield on the back of the stove currently directs the heat up, which serves essentially to warm my block-off plate, which in turn sends that warmth up the masonry around the sides of my chimney liner. I have a small metal fan that I use on top of the stove in lieu of a blower to combat this effect. It's not quiet.


Blowers don't increase combustion efficiency, but they do increase heating efficiency in our types of installs where the heat from the back of the stove would otherwise be going where we don't want it. Perhaps you could look into a free standing stove and make the volume of the blower a priority in your selection.

Keep us updated on what you decide to do!
 
Pyro Extraordinaire, you mentioned a block-off plate, which I take to be a plate that blocks off back of the fireplace. Isn't there a high R factor material you could use for that such as ceramic fiber board? http://www.fssperry.com/Fiberfrax.htm It's what I'm interested in finding more about.

FWIW, I'm leaning strongly towards Dakotas Dad's stove, the Hearthstone Homestead. I don't have his flair for remodeling - I don't want to tear into my masonry fireplace unless I feel I have to, so I plan to have almost all the stove out in front of the fireplace wall. The Homestead comes with a surround kit that actually cross-sects the rearmost inch or two of the stove, leaving the backside of the stove on sealed off from the room. I guess people with sacrifice the backsides of their stoves if it keeps them from jutting too far out into the room. (The Hearthstone surround set up is show on page 14 of the manual here: http://www.hearthstonestoves.com/assets/files/document_library/Homestead8570Manual.pdf
Maybe the backside of the stove doesn't put off serious heat. I wish I knew more what they're thinking. The dealer I'm working with isn't familiar with the Homestead model and all the Hearthstone reps are at a convention in Florida and the sale they're having on the model ends this week.

So that's where I'm at. Thanks again.
 
Oh dear. More complexities. Obviously a very good thing to do. I just had a vague idea to cram some ceramic flue liner I have up the damper slit -- not a great idea. This will be an early summer project when the heating season is over.

Sill, I'd like to make my fire place less deep - maybe only 4-6" deep in fact, and was thinking of a removable, hight R factor wall. Removable so that you could collect you chimney sweep debris. Maybe I should just leave the fireplace as it is, but I really don't like the way it's got a steel liner, which seems like it would suck up stove heat.
 
It's beginning to look more and more like I should do the standard install with the manufacturer's surround, though I'm not crazy about it. To not do so would be to have to tear out the steel firebox and reconfigure the fireplace, or to leave the fireplace with steel firebox as it is. I've attached an image showing the standard install with surround.
 

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You have an insert now, correct? installed into a wood burning fireplace, and you want to switch to a free standing wood stove. Are you going to remove the insert? it kind of sounds like you are not..?

Could we get a picture of what you have now? Do you have enough hearth to place the stove? Before deciding on a stove, what are the goals for the stove? heat the whole house? Or just suppliment? How big, what kind of floor plan, how old, how well insulated? all of these are very important considerations, and it's pretty expensive if you buy a stove that won't really do what you want it to.

We love our stove, but from reading on here, many do not like the way a soapstone heats. It is apperantly not as quick to heat up as an all steel or cast iron stove, and I know for sure it doesn't get as hot on the surface as steel stoves, at least compared to the couple people I know with cast iron or steel stoves.
 
Hi Dakotas Dad,

It's hard to put into words! Yes we will take out the Morso insert we are now using. I believe we have enough hearthstone (21" or so) for the Homestead to work. I'm just being fussy about heat loss to steel fire place firebox when I put the Homestead right in front of it.

Our heating situation is that yes we want all the heat we can get from wood and we want to cut our baseboard electric bills that we have been using so heavily to supplement our under-perfoming Morso. The down side of doing this is that we will have to OVER heat our 16x23 living room where the fireplaces is to get heat to other rooms in the house. I'm trying to use less electricity. My mood is that I would prefer to take the downside of have a 78º living room (actually we used to enjoy that when we have an old inefficient insert w/blower before the Morsoe) over running the electric. It's a trade off. Our insulation is OK.

The Morso is wasting our wood. I feed it like crazy. And only so much heat (often not enough) comes out of it. It works very well when its in the 40ºs. Not so well in the 20ºs. We used to burn less wood with our old much less efficient insert.

The soapstone appeals to me because it might help with the over heating as far as the more spikey burn of steel and iron stoves by comparison. We'd just have to live with the slow heat up time. Our lifestyle as of date has been for there to be some one (me) at home most all the time to keep the stove burning all the time. I probably do less that 20 fire starts a year. The larger capacity of the Homestead in comparison to the Morso will mean a longer burn time with even fewer starts. But who knows? I may not be home so much in the future.
 

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What is the total square footage you are heating?


The pictures you've provided are very helpful.
From the depth of your hearth, I think a freestanding stove sitting with the back of it partially in the FP opening is a great option for you. I really wouldn't trash the idea of a blower yet. I'm not surprised that dinosaur you're using has a loud blower, but the newer ones are very quiet and efficient. Keep your options open, and ask to run the blowers on high, med, and low on any stoes you look at at a dealer. The dealer may be able to point you in the direction of a model or manufacturer that makes the quietest blowers.

As far as moving the heat, I've seen people have good results with very minimal fan setups by pointing a fan along the floor from the colder region into the warmer region. I've even seen people use the small fans used as PC case coolers to very surprising results.
 
billfrommissouri said:
Hi Dakotas Dad,

It's hard to put into words! Yes we will take out the Morso insert we are now using. I believe we have enough hearthstone (21" or so) for the Homestead to work. I'm just being fussy about heat loss to steel fire place firebox when I put the Homestead right in front of it.

Our heating situation is that yes we want all the heat we can get from wood and we want to cut our baseboard electric bills that we have been using so heavily to supplement our under-perfoming Morso. The down side of doing this is that we will have to OVER heat our 16x23 living room where the fireplaces is to get heat to other rooms in the house. I'm trying to use less electricity. My mood is that I would prefer to take the downside of have a 78º living room (actually we used to enjoy that when we have an old inefficient insert w/blower before the Morsoe) over running the electric. It's a trade off. Our insulation is OK.

The Morso is wasting our wood. I feed it like crazy. And only so much heat (often not enough) comes out of it. It works very well when its in the 40ºs. Not so well in the 20ºs. We used to burn less wood with our old much less efficient insert.

The soapstone appeals to me because it might help with the over heating as far as the more spikey burn of steel and iron stoves by comparison. We'd just have to live with the slow heat up time. Our lifestyle as of date has been for there to be some one (me) at home most all the time to keep the stove burning all the time. I probably do less that 20 fire starts a year. The larger capacity of the Homestead in comparison to the Morso will mean a longer burn time with even fewer starts. But who knows? I may not be home so much in the future.
I'd take the insulation off the stove on the 3rd picture & try burning it, not the insulation!
 
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