Converting an open hearth to stove in (combustible) alcove

[U235]

I had some trouble finding examples of people who had done this conversion. I don’t claim to know the codes where you live - I shared my plans with my local town inspector, got permits, and scheduled inspections at the requested intervals. For me, this was relatively cheap insurance in case I ever need to submit a claim.
This is certainly not the perfect install, but hopefully it’ll give you some ideas for your situation. So come along and see how I turned this:


Into this:

First, we start with the demolition. Removed the mantel, brick surround, and hearth.


Next, removing the 8” uninsulated chimney and the old fire box. The ‘framing’ under the stove was pretty terrifying.



Time to open up the wall, shore up some of the framing, install the new header and frame the ceiling in the alcove. Here is where the clearances are established. Everything inside of this will be non-combustible.


Framed in the new hearth and the basic metal stud structure for the non-combustible wall. I left a small gap at the top to ventilate all the hot air above the stove - although this hasn’t been quite as effective as I had hoped.


Added insulation and used the reflectix stuff as a vapor barrier (this may not count as non-combustible). Not sure, but maybe it also helps keep the heat in/cold out. You can see the floor framing for the hearth with the floor removed.


Next goes the first layer of Durock. I don’t think this is strictly required for code, and it probably reduces the effectiveness of the reflectix but it made sense to me to have a full floor to ceiling barrier - especially considering my choice for ventilation gap framing.



My clearances to the side and back are too tight without creating a ventilated air gap. There are a lot of options to create this gap. There are these single screw ceramic spacers - for my project this would’ve been excessively expensive. You can cut strips of Durock and screw them to the wall. This would’ve been cheaper but a lot of cement board cutting and I wasn’t sure I could hit the studs on the final layer of Durock blind with 4’ screws.
I chose to use skinny metal studs. I have them directly anchored to the wood studs and resting on the top of the foundation. No anchors directly behind the stove (but enough to screw the Durock to). I left the tops open to encourage ventilation air to accumulate at the top of my alcove.




And now the final push to wrap everything in a final layer of Durock. I finished my last cut at 2 am. The installlers arrived at 8 am.




It’s not an illusion. The right corner dips - we pounded in a couple shims before putting on the brick. My stove installer did the brick veneer, chimney, stove, and new chase cap. The stove is a VC Encore 2040-CAT-C.






In the alcove, the transition from double wall black pipe to class A insulated chimney in the chase occurs in this square chimney support. I think that the wood framing could be right against the support but I framed it to maintain a slight gap.


Now I know what you’re thinking, where does the ventilation air come from? My chase is directly above a similarly shaped room in my basement. I cut air holes to allow air flow from basement into cavity under hearth. These will be covered with decorative grills later this year.


I put R30 insulation on top of the ceiling joist and R15 rockwool in between them. Finished the ceiling with two layers of Durock with silicone on the seams.




The front wall is also a ventilated air space. This is the area directly behind where the mantel will be. I used leftover metal stud scraps to create little cooling fins - not sure how much these help.


Finished the Durock to the ceiling and installed a linear diffuser in the air gap. There is a weird pocket cut into my ceiling which does a great drop trapping hot air. I think my next modification will be to install a small ceiling fan in that space. Hoping the low pressure below the fan will help pull more heated air out of the top of the alcove.




And that’s pretty much how it stayed through heating season 1.

 

[U235]

Once the last fire was finished for the season, set to work finishing the aesthetics. My wife wanted a shiplap look for the stove wall. What I came up with was Hardie board 4’x8’ siding cut into strips. This covered the Durock as well as the sheet rock on the rest of the wall.

Painted the siding with exterior paint and mounted the mantle. Magra hearth barn beam.

That’s the setup as it will likely be through my second burning season. Without air freely moving through the alcove, I had some issues early with high stove top temps. I put one of the little heat activated fans on the stove top. Despite not moving enough air to actually seem like it could do anything, I never had STTs above 650. I’ve installed a blower fan for this season, hopeful that it can move a little more heated air out of my “alcove”. My floor plan doesn’t let this be a sole heat source but it definitely keeps the living room warm and helped supplement my heat pump. Auxiliary heat never turned on (even during Christmas 2022 cold snap in the Midwest).

Looking forward to season 2 and many more to come!

 

[begreen]

It looks great but I'm surprised that the inspector signed off on this. What is the shiny insulation behind the cement board?

The manual has an explicit statement in bold print:

NOTE: Installation of the Encore® is not permitted in alcoves.

 

[begreen]

The images all just disappeared. RU editing?

 

[kborndale]

It may be perfectly safe but if you ever had to put in an insurance claim you will not get it. VC states no alcove installation so insurance could care less if your town said it was ok.

 

[U235]

It looks great but I'm surprised that the inspector signed off on this. What is the shiny insulation behind the cement board?

The manual has an explicit statement in bold print:

NOTE: Installation of the Encore® is not permitted in alcoves.

Can you specify where this is located? The word alcove does not appear in the 2040-cat-c install manual or user manual.

 

[begreen]

This is in my copy of the 2018 manual for the Encore 2040

 

[begreen]

I just downloaded the latest revision of the manual. They have eliminated all mention of alcove, but provide no clearances for an alcove installation either. The required side clearance with double-wall stove pipe is 18" to combustibles and 11" at the rear.

This is a highly radiant stove, thus my concern. Without the images I can't tell if the side and back wall spaces are ventilated at top and bottom or not. This is not the same as ventilating the alcove. There is a shiny insulation material used. What is this product and is the shiny material aluminized plastic or actual metal jacket?

 

[Woodsplitter67]

This looks like a fantastic job.. I like seeing people do hands on things like this. Good skills my man..

 

[U235]

The two sides and back are ventilated but I understand your concern. Just shows how difficult this can be. Used a professional vendor/installer, applied for all permits with the town, read the manual a million times. Never would’ve considered to look for guidance in the previous model’s manual.

The shiny stuff is a plastic bubble wrap like material, made for attics. Compressed under the Durock, it might drop my clearances 1/16”.

 

[weee123]

I think it looks great, you did an awesome job.

Never would’ve considered to look for guidance in the previous model’s manual.

Because that wouldn’t make sense to do.

 

[begreen]

The two sides and back are ventilated but I understand your concern. Just shows how difficult this can be. Used a professional vendor/installer, applied for all permits with the town, read the manual a million times. Never would’ve considered to look for guidance in the previous model’s manual.

The shiny stuff is a plastic bubble wrap like material, made for attics. Compressed under the Durock, it might drop my clearances 1/16”.

It's not an appropriate material for a hearth. That layer becomes the nearest combustible, with the Durock not counting. It's better to not have it there at all.

Because that wouldn’t make sense to do.

When the manual has no guidance for alcove clearances, then it's a good idea to check with the manufacturer on this off-label install, especially for a strongly radiant stove. I hadn't updated my docs for the 2040 model since 2018 so this bubbled up. It's indicative of a concern by VC and one that has come up in the past for alcove installations of highly radiant stoves.

 

[U235]

Well. The verdict is in. My insurance has finished their 4 month inquiry - if any fire is confirmed to be caused by the stove, my claim will be denied.

So. Are there any cast iron jacketed steel stoves other than the PE Alderlea and BK Ashford? We like the cast iron look but probably can’t accommodate a primarily radiant stove.

The PE clearly allows alcove install. BK is kind of luke warm. Prohibited in Canada, but in US - “please adhere to minimum safe clearances”. I have two messages submitted to BK to confirm if clearance reduction is allowed with ventilated air gap or if “adherence” means no reduction.

 

[kborndale]

Well. The verdict is in. My insurance has finished their 4 month inquiry - if any fire is confirmed to be caused by the stove, my claim will be denied.

So. Are there any cast iron jacketed steel stoves other than the PE Alderlea and BK Ashford? We like the cast iron look but probably can’t accommodate a primarily radiant stove.

The PE clearly allows alcove install. BK is kind of luke warm. Prohibited in Canada, but in US - “please adhere to minimum safe clearances”. I have two messages submitted to BK to confirm if clearance reduction is allowed with ventilated air gap or if “adherence” means no reduction.

Hopefully @BKVP will chime in with your answer.

 

[KDubU]

Well. The verdict is in. My insurance has finished their 4 month inquiry - if any fire is confirmed to be caused by the stove, my claim will be denied.

So. Are there any cast iron jacketed steel stoves other than the PE Alderlea and BK Ashford? We like the cast iron look but probably can’t accommodate a primarily radiant stove.

The PE clearly allows alcove install. BK is kind of luke warm. Prohibited in Canada, but in US - “please adhere to minimum safe clearances”. I have two messages submitted to BK to confirm if clearance reduction is allowed with ventilated air gap or if “adherence” means no reduction.

Jotul has a couple cast iron jacketed stoves. The F45 and F55.

 

[BKVP]

All,

When testing clearances, the safety test labs would test a corner install. In this test they would get a measurement from side of stove to adjacent wall.

That measurement, say 20", was then assumed to be the same for the opposite side. Now, you have side wall clearances and combine that with ceiling height clearance from top of stove, you now have every clearance value requirement for an alcove.

In 2022, UL said the "assumed same distance to wall clearance" was not sound as once placed into an alcove, all clearances requirements may change.

As no stoves had been tested for "alcove" clearances, a new actual alcove test would be forth coming.

Not speaking for any other mfg, the safety test agencies notified all mfgs of the requirement to retest stoves or remove the alcove clearances from their manuals and labels.

We have not retested to the new alcove test. We do not have a timeline as to when we will retest.

Before doing an alcove installation, it would be wise to double check if the stove you might purchase has been subjected to the relatively new alcove test.

To the OP, as BeGreen pointed out, the material used behind the Durarock is not questionable, it is not a proper material for this type of installation. Whether or not your stove is "alcove approved ", the insurance company will find a way to stamp your claim "denied" because your build was not approved.

As a mfg, we speak with hundreds of consumers each week. We've heard this all before.

BKVP

 

[U235]

Thank you all for your feedback. As I mentioned when I started, I had a difficult time finding guidance on how to do this properly when originally setting off on this adventure. I now know that the bubble wrap material was a poor choice - I’ll reduce my clearances to combustibles accordingly. What I hope everybody who makes it to the bottom of this thread has learned is to reach out to the manufacturer if your alcove install is not specifically listed.If we can keep this thread open a little more, I’ll conclude it with my new stove and all the clearance comparisons.

 

[Dajolu]

I haven't read through all of the posts thoroughly and not sure of your alcove measurements but the Hearthstone Green Mountain series of stoves are approved for alcove installs. The GM 40 may work?