Chimney question- converting Zero clearance fireplace

[Agnee]

Hello all,

I have been lurking around these forums for a few days now and have gained a lot of information. I am very impressed with the level of expertise of the members and more importantly, the willingness to share that knowledge so generously. Before I start, let me say that I have seen this topic addresses numerous times with varying results/ends - this time I am hoping to get a "customized" answer to my situation, or atleast varying points of view.

My husband and I would like to convert our Majestic zero clearance fireplace into something that can heat up our living room. Background : Last winter, we lost power for 14 days and by the end of day 4, we broke down and paid a grand for a generator. I got rid of it in summer since I needed the garage space. I am trying to plan for a repeat of the same situation since this coming winter is forecast to be wetter and colder than normal with potential for a power outage. So I am looking for something that will at the least, comfortably heat up our 600 sq feet living area/kitchen- not necessarily our entire house (which is approx 2000 sq ft BTW).

We have narrowed down our choice to a small Jotul F 100 wood stove- but we here is my question:

We have a triple -walled air cooled chimney (about 15-20 feet total) and the dealer told us that it was attached to and RESTING ON or SUPPORTED by the ZC firebox. If we took out the firebox, the chimney would collapse. Hence, if we wanted to install a wood stove, we would have to tear out the existing chimney, replace with a 6 " HT rated version for wood stoves and go from there- cost over $ 5000 easy. He did say that lining it with stainless steel liner was an option but he could not guarantee that the chimney was supported and he thought it may collapse.

I have read multiple DIYs mostly on these forums that have involved replacing a ZC fireplace with a wood stove but have not seen this particular chimney question addressed. Could we install a ceiling support box?

Of course, the easiest and most economical way maybe to get a fireplace insert (we have looked at the Lopi Revere) but we have our hearts set on a wood stove (and the husband does not like blower noise).

Any ideas/comments appreciated! Sorry for the long post. Thanks!

 

[begreen]

As long as the flue outlet is lower than the lintel of the fireplace you should be able to put the F100 on the hearth in front of the fireplace and connect the stove to a 6" stainless steel liner run up the ZC chimney. This probably will require extending the hearth in front of the stove.

 

[Agnee]

Thanks for the reply, Begreen. We are actually willing/wanting to rip out the old ZC unit and make a sort of alcove/ opening with a proper raised hearth for the Jotul- keeping all the clearances kosher of course. Our only confusion is if we can re-use the ZC chimney (with a SS liner)- I have this horrific vision of the whole thing tumbling down the moment we remove the ZC firebox

 

[bholler]

Our only confusion is if we can re-use the ZC chimney (with a SS liner)- I have this horrific vision of the whole thing tumbling down the moment we remove the ZC firebox

You will not be able to reuse it there will be no support. And besides you dont want it anyway it is a major source for drafts. That open outer wall lets air cirulate freely from inside to out. And no you cant put an insert in there either unless both the fireplace and the insert say that it is ok to do so.

 

[qyota]

I'm in a similar boat, Agnee, although my chimney pipe may be different (mine is 7"/9" ASHT Security Chimney pipe). I too don't understand why the pipe can't be supported without the stove. The chimney manufacturer makes support brackets for my pipe, so my intention is to use them. In my case, the pipe is not designed solely for my ZC fireplace, rather it can be used with many types of installations. Yours may not be, unless you can find support bracketry that is manufactured for your pipe specifically.

 

[begreen]

The old chimney will need to come out. It is being supported by the fireplace. The chimney can be removed first, a section at a time. The fireplace then can be removed. An alcove installation for a freestanding stove has special clearance requirements that must be adhered to. The alcove will need a ceiling. This is where the new chimney support will be installed. 84" is a common, minimum, alcove ceiling height requirement, though the F100 has a 60" requirement. Note that the F100 also has a high, alcove hearth floor insulation requirement of R=2.0.

 

[begreen]

I'm in a similar boat, Agnee, although my chimney pipe may be different (mine is 7"/9" ASHT Security Chimney pipe). I too don't understand why the pipe can't be supported without the stove. The chimney manufacturer makes support brackets for my pipe, so my intention is to use them. In my case, the pipe is not designed solely for my ZC fireplace, rather it can be used with many types of installations. Yours may not be, unless you can find support bracketry that is manufactured for your pipe specifically.

When you build out the alcove it will have a ceiling. As long as parts are still available for your chimney pipe you should be able to install a ceiling support box in the alcove ceiling.

 

[Agnee]

When you build out the alcove it will have a ceiling. As long as parts are still available for your chimney pipe you should be able to install a ceiling support box in the alcove ceiling.

Sorry if this is a stupid question, Begreen, but are you saying we could re-use our old chimney with a 6 " SS liner inserted in it? Or are you talking about supporting an entirely new chimney? And thank you for pointing out the alcove hearth requirements....I am hoping to lay a slab of granite on the bottom -maybe over a layer of firebricks? I'm hoping my contractor while have a few ideas to build it up.

 

[begreen]

No, the old chimney must be removed. You will need an entirely new class A high temperature chimney system.

Granite is a poor insulator. It will actually conduct heat and adds nothing noteworthy to the hearth insulation. The slab will need some Micore and Durock NexGen cement board under it to build up protection.

 

[Agnee]

No, the old chimney must be removed. You will need an entirely new class A high temperature chimney system.

Granite is a poor insulator. It will actually conduct heat and adds nothing noteworthy to the hearth insulation. The slab will need some Micore and Durock NexGen cement board under it to build up protection.

Thank you for clarifying about the chimney. Also - I paid a good sum for this slab of granite- I used part of it to make a hearth and there's a second piece that I was hoping to have the stove sit on- can I have it sit on top of the Micore /Durock Next Gen cement board?

 

[begreen]

Yes the micore and cement board can act as an underlayment that builds up insulation value under the granite slab. The micore will provide most of the insulation, but it is soft. The cement board will provide a bit more insulation and will protect the soft surface of the micore below it.

 

[RSNovi]

How do people install class a pipe up the chase? Especially in cases where you need 30' of chimney.


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[bholler]

How do people install class a pipe up the chase? Especially in cases where you need 30' of chimney.

I climb down into the chace and assemble it as you go up. It kind of sucks.

 

[Agnee]

Hello,

Thanks for everybody's input. So of course you'all were right- we are ripping out the old zero clearance fireplace along with the chimney and the dealer is set to install a completely new chimney that is specific for a wood stove- we have chosen to go with the Jotul F 3 CB (a slightly larger model than the F-100). The listed R-value for the hearth is 1.1. We were not able to locate Micore locally, so have decided to go with 3 layers of Durock Next Gen 1/2 inch cement board under a slab of granite- just wanting to check if this is acceptable? this shd build up the R- value to just over 1.1 - am I right? Is there any better way?

Thanks for all help.

 

[qyota]

That's how we did it at our last place...3 layers of durock, and a protective layer on that (we used concrete pavers, but granite is nice too! ;-)

I'm glad your project is underway!

 

[Agnee]

That's how we did it at our last place...3 layers of durock, and a protective layer on that (we used concrete pavers, but granite is nice too! ;-)

I'm glad your project is underway!

Thanks!