recommendations for interior or exterior chimney?

[jabram]

Hey guys, I was looking for your thoughts on advantages/disadvantages on constructing a new chimney on the inside of the building envelope or on the outside. Attached is a photo of our existing brick chimney on the east end of our home. We are planning to build a one story addition on this side of the house so this chimney will need to be torn down. UGH! We will need to construct a new chimney on the addition.
Presently we are burning a Mendota wood hearth which was installed in 1992. This has been a great little unit and we are considering re-installing it in the new addition. I have been trying to find an excuse to purchase something like a Quadra-fire 7100 but my only complaint with the Mendota is the firebox is a little on the small side.
Anyhow, what I'm really wondering about is constructing an interior or exterior chimney. We would like to have floor to ceiling manufactured rock covering the chimney inside. Is there an advantage to constructing the outside wall chimney other than something that adds to the outside appearance?

 

[Corie]

The advantages to constructing inside the building envelope are numerous.


The flue will have less heat loss to the surroundings so you should ideally have less creosote buildup, stronger draft, and increased control over the appliance. Since the flue is "preheated" by the room air, you shouldn't have reversal problems or any another flue related problems that can sometimes go hand in hand with an exterior chimney, as long as you build the new chimney sufficiently tall.


Also, although minor in comparison, you may also get some additional heat storage value out of the increased thermal mass surrounding the flue gases.



All in all if you have the option, you want an internal chimney.

 

[Kenny1]

Others will be better informed than I am, but you may want to check out woodheat.org. They have a number of articals about flues.



http://www.woodheat.org

 

[begreen]

The advantages of having an interior chimney are many. Look at the house of yore when people didn't have central heating. You won't find many exterior chimneys there. The advantages are: better draft, less cooling of flue gas equalling less creosote, far less heat loss to outdoors and most of it instead radiated to the interior of the house and less deterioration due to weather.

 

[tradergordo]

Are you absolutely sure you need to tear down that chimney? Why not build the addition right around it? Then you'll have your interior chimney.

 

[titan]

Do the inside flue,you won't regret it.This summer I'm disconnecting my wall thimble into clay- lined exterior masonry chimney because I'm done fighting with it's heat robbing ability and frequently poor draft.I'll blank off the cap after removing the wall thimble, then rebuild the hearth I really want with double-wall to cathedral ceiling, then enough stainless above the roof to suck a seagull from a garbage truck.

 

[Highbeam]

Too bad as that is an attractive fireplace and chimney. The ivy can grow into the required gap between the house and brick though and actually topple it over time so don't let it get away from you.

The previous owner of my home had the same issue except a single story home and added on to the gable end of the house full height. The exterior masonry chimney is now my interior masonry chimney. The only trick is that the required clearances move from 1" to two inches but maybe elk can speak to that.

Chimneys are expensive to build and if you can keep this one up then that would be good.

In the end, I would like to follow Titan's lead and convert to a freestanding stove and metal chimney. My masonry chimney has some issues that would be very hard to fix without complete demolition or very expensive rennovation.

 

[jabram]

I wanted to thank each of you for sharing your wisdom concerning my chimney question. I have certainly received the message loud and clear that an interior chase & pipe is the best installation for the new addition. I really gained a lot of chimney info from the woodheat.org website. I wish we could leave our existing chimney but think that will be impossible. It is situated on the east living room wall and we are bumping the wall out 16' so the fireplace would be in the middle of the new living room. Can't figure out how to make that work. The large oak tree will have to go also (new firewood!)Anyway, we're only in the thinking and planning phase right now and hope to build next spring so we still have plenty of time to think about every angle.
After reading the chimney articles on woodheat.org, one think I didn't quite understand. When you build your interior chase for the pipe, do you insulate all the chase or just the outside wall? Also do you build and insulate the chase as it runs into the attic space or just run the chimney pipe through the attic?
Again thanks for all the comments.

 

[Rhone]

Others can chime in on your questions, just make sure you read about the "Evil Outside Chimney" from that woodheat.org site if you didn't come across it when there. (broken link removed to http://www.woodheat.org/chimneys/evilchim.htm)

 

[tradergordo]

...so the fireplace would be in the middle of the new living room.

Sounds perfect to me!

 

[whitesjtaa]

Our old house had a woodstove with an exterior metalbestos chimney. The previous owner left us a list of "tweaks" to get the draw started and continued on the stove.

We moved the stove to a center location and reran the chimney through the inside of the house. We no longer have any problems with back draft and have virtually no creosote buildup. Also, the radiant heat from the flue heats the house on the way out.

We recommend an internal flue, if it will work with your house layout. Good Luck.

 

[jtp10181]

Are you planning on putting this new chimney on the one story addition? I have seen this done many times around here and they always have drafting problems. If you look in the manual for a wood unit, that is the "Not Recommended" chimney location. Not only does the wind not flow across the cap very well but sometimes the house itself makes a better chimney than the actual chimney. I have seen this not only with open faced units but also with a Quad 7100 or a HNG Northstar.

 

[jabram]

jtp
Yes, we were planning to locate the fireplace inside the new one story addition. I read the articles on chimney placement on woodheat.org and realize this could be a bad ideal. I think they called it the "stack effect". So, we need to re think our floorplan. The last thing I want to do is spend $5-6,000 on a new fireplace and chimney that will perform poorly. It's tough when you need to design the house around the fireplace but you must also balance the design for traffic flow and space utilization (remember the wife has to be happy with the layout). We are not starting this project until next spring so we have plenty of time to wrestle this around. Thanks so much for all the input. I'm gaining a good education in fireplace/chimney design & operation.

 

[begreen]

ja, It's great that you're thinking this through carefully. Good placement of the stove/fireplace and stack will have a nice long-term payback. Post some sketches of the floorplan. Sometimes it helps to get an outside perspective. Also, what is your range of options for the heater? Must this be a fireplace or could a nice freestanding stove work?

 

[dvellone]

As a stone mason I can offer you my opinion from that perspective. Aside from putting all that nice thermal mass outside of your house rather than inside, you have weathering of the mortar joints to consider. A chimney, unlike a house is much more exposed to weathering ( especially if it's on the prevailing weather side of the house!) and some day will have to be repointed. If you're using weather-graded bricks or stone repointing work isn't too much of a problem although it is tedious and very costly. If you're using "cultured" stone grinding those joints out - which will have to be done to get the proper depth for quality repointing- can severely damage the thin veneer of coloring on the stone. The stone also cannot be cleaned vigorously after the pointing because of the thin veneer. I know you see a lot of this stuff going up outdoors and as a manufactured masonry unit it has it's own strength, but those guys making good money selling it and putting it up aren't going to talk you out of their payday. You've got to see these jobs once the mortar decays which depending on the quality of installation can be as little as 10 years and as many as 40. Though there aren't many masons left who know how to get you to that big number.

 

[jtp10181]

Just thought I would add one more thought on the same issue thats kind of funny. I often get calls directed to me of people complaining about smoking back or poor draft. This is usually how it goes.

Me: Is your house two stories or more?
Customer: Yes
Me: Is the fireplace chimney on a bumped out one-story section of the house?
Customer: ..... yes (how did he know that?)

..... its kind of scary how I can tell just from thier complaints that thier chimney is in such a location. I would definatly stay away from doing that at all costs.

 

[jabram]

ja, It's great that you're thinking this through carefully. Good placement of the stove/fireplace and stack will have a nice long-term payback. Post some sketches of the floorplan. Sometimes it helps to get an outside perspective. Also, what is your range of options for the heater? Must this be a fireplace or could a nice freestanding stove work?

BeGreen-
I have attempted to attach a drawing of our present floorplan. Sounds like we have the new fireplace drawn in the worst possible area. I'm not sure how we could ever move it back into the two story section of the house without the chase going up through our daughters second story bedroom. As for as which heating unit to use, we are still open to all options (fireplace or stove). As I mentioned on my first post I am considering the re-installation of our existing Mendota Hearth. Although 15 years old it still works fine. I wish it had a larger firebox and put out a little more heat. Our present pipe is triple-wall SS and assume it is good shape. Could this pipe be re-used or should new pipe be installed if we use the old Mendota?
I have visited the local Quadra-Fire dealer and was impressed with the 7100fp as well as a Northstar unit that he had in the showroom. Although we like the look of a fireplace (so the wife can have a mantel to decorate) we were also very impressed with a beautiful mahogany Isle Royale in the showroom.
With the addition our house will have about 3200 sq. ft. heated. Look over the floorplan, any suggestions are welcomed! thanks

 

[jtp10181]

If you are dead set on putting the fireplace there here are some recommendations.

You should get an EPA fireplace or stove with sealed doors, otherwise I for-see lots of smoking back.
Build the chase for the chimney as high as possible without it looking too goofy. The higher it is the better chance for a good draw.
Read up about requirements for HVAC return air and things like that, basically keep return air registers away from the fireplace and keep it balanced.
Keep the fresh air run short, this will allow the most possible air in.

There are some other factors with the rest of the house that will go into play. Best was for it to work good is for the house to be loose on the bottom and tight up top. That means the ceilings and top floor is sealed up good and maybe not quite so tight down in the lower level / basement. Can lights in the ceiling can act as alternate chimneys especially if they are the cheaper kind which are not sealed.

Also if you try to move the old fireplace, the chimney for it might not be available anymore. If any of it gets damaged trying to remove it you might be SOL.

You will also need to be careful what you burn, since the draft will probably not be the greatest it will be more sensitive to lower energy wood (like if it has too much moisture).

 

[begreen]

The drawing helps a lot. What is that possibility of a stovepipe or chimney running up somewhere along the wall that separates the livingroom from the stairwell? What is directly above it? If that is a common wall for the bedroom above, the flue might be able to be boxed in.

 

[Gooserider]

What about putting the stove where you currently have the TV unit drawn in? That would possibly let you run the stovepipe straight up and come out not to far from the peak of the roof, or possibly run it at an angle back towards the center of the room and come out about where the current chimney is?

You'd have to find a different place for the TV, (or better, throw the TV in the trash...) but it would be a better location for the stove in that it would get it out of the middle of the space, and put it in a more central position to send heat throughout the house instead of just one part of the room.

Gooserider

 

[heydan]

Here's a free web site to help you work out your floor plan: http://www.floorplanner.com/