Alcove question for Lopi Evergreen II

[s0ulP@tch]

Hi all! As part of a remodel, we removed the 2-storey ~3'x5' masonry chimney in our home, to be replaced with a class A chimney and a Lopi Evergreen II with the blower kit. So far from what I've read the GreenStart is noisy and gimicky, so we won't get that. It's small enough to fit into an alcove in the space vacated by the old brick chimney and puts out enough heat for our home. We previously had an old Lopi FL that I refurbished with secondary burn tubes (link to build/pictures) and that heated the house just fine. There's a pic here of the insert in the brick fireplace for size reference. There are no bricks left and it's now down to concrete. The fireplace went through the wall, the wall on either side of the brick will be flush with the front of the new alcove. The back will be a bumpout into the next room, with one side flush with the furnace room next to it. All our wood is poplar or maple seasoned to <20% moisture.

My wife wants an alcove with a clean look, as much like painted drywall as possible. On pg 13 of the manual it describes a non-combustible surface as something that's 3.5" thick with a 1" vented gap to combustibles. It mentions stone, brick, or concrete, but none of those lend themselves well to the "drywall" look. Would steel 2x4 studs and concrete board (durock, hardiboard) work just as well? or do I need the serious 3.5" of chunky rock/brick/concrete to be on all sides and the ceiling of the alcove?

I'd also like to install an outlet connected to a light switch so I can turn on the blower without getting near the stove. Is that OK? Any special considerations for the outlet behind the wood stove?

 

[begreen]

A non-combustible wall does not have a rear clearance requirement. That is for combustible surfaces. The description on pg 13 is for a shielded, combustible wall. A non-combustible wall would be entirely built of non-combustibles like cement block or a metal stud wall with cement board on it and then tile. Seeing that a shielded wall is only required for combustibles, if drywall is used, would it be possible to move the stove way from the wall to meet those clearance requirements? If so, drywall is fine. Or the cement wall could be stuccoed to keep it entirely non-combustible. However, if the concrete wall behind is exterior, then it will be a large cold surface without insulation.

Is this just for the back wall? How do the side clearances to the stove pencil out? Are they ok? Also note the top clearance requirement.

 

[s0ulP@tch]

Maybe a picture of the space would help. See below - this is where the old fireplace & insert used to live. We've not modified the space aside from removing all the bricks & mortar.

The alcove opening would face the room I’m standing in and the back of the alcove, facing the Ikea bookshelf and orange dog rope in the next room, would be closed off. The wall cladding facing the other room would preferably be drywall to match the rest of the room. The old shelves on the right (they have some old light blue paint showing) will be removed prior to the alcove installation. To the left side is the furnace room (i.e. on the other side of the wall behind the TV) and could be anything - we don't care if it's uglyish. Obviously where the alcove meets the studs for the 2x4 load bearing walls on either side would have to be fireproofed. We will probably do slate or tile for the floor. The ceiling is ~7’6”, but my wife wants a ~4’6” or 5’ tall alcove so we can use the wall space above it for pictures and maybe a mantle. The stove is 31" tall, and if the top is non-combustible the clearance can be 6" from the top of the stove to the ceiling of the alcove. The side margins pan out with a few inches to spare (as long as the 40" minimum clearance of shielded combustible wall is OK, i.e. the alcove is 42" wide to the inside of the shielding). No exterior walls involved here.



My wife wants the wood stove door to be flush with the finished wall instead of hanging out into the room. So my biggest question is how do I build out the three walls (left, right, back) and the ceiling of the alcove? Can I build a "shielded combustible" wall out of cement board, steel studs, and insulation with a 1" space to combustibles? Or does the shielding need to be some kind of masonry, stone, or concrete?

Does that help clarify my conundrum?

 

[s0ulP@tch]

After doing more reading and re-reading, I think I may have answered my own questions.
Here's the manual page in question.


If I Just line the alcove with sheet rock or tile/brick veneer over cement board and it's unvented behind it, the alcove, according to Lopi/Travis Ind is "combustible." If I have a 1" spaced gap with 3.5" of brick, stone, or concrete shielding, the wall itself might be combustible BUT Lopi considers the alcove, for spacing considerations, to be "non-combustible."

Because the air return ducting seen at the top of the proposed alcove space is lower than 7' (84"), we will need to do an alcove install per the manual. That install is described on pg. 13 above. As part of the alcove build, I will need to purchase an approved chimney and double-wall chimney connector from the top of the page.

Stove measurements:
Stove height: 31"
Stove width: 28"
Stove depth: 20.25"

Alcove size requirements for a combustible alcove if the combustibles (i.e. finished drywall) are NOT shielded with 3.5" of stone/brick/concrete and 1" of vented air:
Alcove height: minimum = 84" or higher
Alcove width: minimum = 50" (28" of stove + 11" on either side)
Alcove depth: minimum = 29.25", maximum = 48"

Since an 84" ceiling cannot be achieved, I'd either have to (a) lessen the alcove depth to get past the lowest drywall and bump the stove out into the room a few inches or (b) build a non-combustible alcove per Lopi's tested requirements in their manual.

Alcove size requirements for a non-combustible alcove (which must have a 3.5" brick/stone/concrete face and 1" vented air gap to combustibles):
Alcove height: minimum = 6" above the stove to the brick-faced ceiling, maximum = 4.5" below the lowest sheetrock (to leave room for brick & gap)
Alcove width: minimum = 40" between the brick faces of left & right walls, maximum = whatever I can fit
Alcove depth: minimum = 27" (6 3/4" clearance with fan kit + stove depth), maximum = 48"

Have I missed or misunderstood anything? Sorry for all the questions - this is the first time I've had to do an alcove install, and it sounds like Lopi's manual has some language ("non-combustible alcove") that is specific to their manual and not what @begreen understands to be a non-combustible wall.

 

[PaulBunyun]

After doing more reading and re-reading, I think I may have answered my own questions.
Here's the manual page in question.
View attachment 282158

If I Just line the alcove with sheet rock or tile/brick veneer over cement board and it's unvented behind it, the alcove, according to Lopi/Travis Ind is "combustible." If I have a 1" spaced gap with 3.5" of brick, stone, or concrete shielding, the wall itself might be combustible BUT Lopi considers the alcove, for spacing considerations, to be "non-combustible."

Because the air return ducting seen at the top of the proposed alcove space is lower than 7' (84"), we will need to do an alcove install per the manual. That install is described on pg. 13 above. As part of the alcove build, I will need to purchase an approved chimney and double-wall chimney connector from the top of the page.

Stove measurements:
Stove height: 31"
Stove width: 28"
Stove depth: 20.25"

Alcove size requirements for a combustible alcove if the combustibles (i.e. finished drywall) are NOT shielded with 3.5" of stone/brick/concrete and 1" of vented air:
Alcove height: minimum = 84" or higher
Alcove width: minimum = 50" (28" of stove + 11" on either side)
Alcove depth: minimum = 29.25", maximum = 48"

Since an 84" ceiling cannot be achieved, I'd either have to (a) lessen the alcove depth to get past the lowest drywall and bump the stove out into the room a few inches or (b) build a non-combustible alcove per Lopi's tested requirements in their manual.

Alcove size requirements for a non-combustible alcove (which must have a 3.5" brick/stone/concrete face and 1" vented air gap to combustibles):
Alcove height: minimum = 6" above the stove to the brick-faced ceiling, maximum = 4.5" below the lowest sheetrock (to leave room for brick & gap)
Alcove width: minimum = 40" between the brick faces of left & right walls, maximum = whatever I can fit
Alcove depth: minimum = 27" (6 3/4" clearance with fan kit + stove depth), maximum = 48"

Have I missed or misunderstood anything? Sorry for all the questions - this is the first time I've had to do an alcove install, and it sounds like Lopi's manual has some language ("non-combustible alcove") that is specific to their manual and not what @begreen understands to be a non-combustible wall.

I just bought and installed a Lopi Liberty. I put it in an existing masonry chimney after opening it up a bit. I believe what begreen was saying is a masonry wall is considered non-combustable traditionally speaking. From my research when doing my project is that I agree with you in that Lopi/T-ind considers a non-combustable install as being 3.5" non-comb material separated by 1" air gap to comb material. If you build it this way then you can abide by the non-comb install clearances is my understanding.

 

[begreen]

Ok, the problem is with Lopi's definition and terminology. There are several NFPA 211 wall shield variations. They have documented the most extreme example of these shielding options and call it non-combustible. That is not quite correct terminology. It is not a truly non-combustible wall. And they chose only to show example "d" from the NFPA shielding options, ignoring "e-h" which offer the same 66% clearance reduction. In doing so, they have made things clear as mud.

NFPA Wall Clearance Reductions

The following table sets forth some of the reductions in wall clearances possible with certain wall construction details. For some further discussion on wall clearances, see: http://www.hearth.com/econtent/index.php/articles/stove_wall_clear

www.hearth.com

You'll have to take this up with Travis tech support to see if common sense and the other NFPA 211 options for 66% reduction are acceptable. For the safest construction, the rear and side wall could be framed with metal studs, clad with cement board on the stove side and drywall on the Ikea bookshelf room side. If there is a 1" gap at the bottom and top of the cement board to allow ventilation behind it, then it qualifies.

Your wife's request makes things much more complicated. The boxing in to a low height above the stove is going to make that cavity MUCH hotter. The manual calls for an 84" ceiling above the stove with no exception. That means that anything above the stove lower than 84" must be 100% non-combustible, not wood framed and then shielded. There are a couple possible ways that this might be done, but I would get signed off approval from the inspecting authority before proceeding.

 

[s0ulP@tch]

Thanks for the NFPA table and suggestions, @begreen! Those are both incredibly helpful. I'll ask Travis if the other NFPA clearance reduction methods are viable options and will clear the installation plan with city inspectors before installing.

Regarding the alcove ceiling height, I don't think you're correct. from pg 13 of the manual:
Alcoves are classified as combustible or non-combustible. Non-combustible alcoves must have walls and a ceiling that are 3 1/2" (89mm) thick of a non-combustible material (brick, stone, or concrete - see Figure 5). This non-combustible material must be spaced and ventilated at least 1" (25mm) off of all combustible materials (walls, ceiling, etc.) to allow air to move around the non-combustible walls and ceiling. All other alcoves are considered combustible.

I agree the ceiling would still get hot, though. I presume angling it up from back to front would assist in washing the heat away through convection, so I'll bring that to the Aesthetics Committee as another thing to consider.

 

[begreen]

The difference with a ceiling is that is the hottest area usually. Some alcoves can really trap heat. Without an external venting of the shield the wood, even behind a single layer of brick, can get hot enough for pyrolysis. I'm not saying it can't be done, but this is a critical issue. A solution is to make the ceiling lid out of completely noncombustible materials, like steel studs and cement board. This needs to be made strong enough to frame in the chimney support box and carry the weight of the chimney system.

For online advice, I want to see drawings and plans of precisely how this will be put together. Any good inspector will want the same.

 

[begreen]

PS: I'd also consider venting the cavity above the stove into the IKEA bookshelf room.

 

[s0ulP@tch]

The difference with a ceiling is that is the hottest area usually. Some alcoves can really trap heat. Without an external venting of the shield the wood, even behind a single layer of brick, can get hot enough for pyrolysis. I'm not saying it can't be done, but this is a critical issue. A solution is to make the ceiling lid out of completely noncombustible materials, like steel studs and cement board. This needs to be done strong enough to frame in the chimney support box and carry the weight of the chimney system.

Yes, I agree this needs to be addressed. I’d rather not use wood studs and originally asked about using steel studs I’ll bring this up with the city inspectors.

Great idea with venting the cavity into the next room! Thanks for that.

So the last thing I’d love input on is an outlet for the fan. I could put it in a corner to ensure it’s at least 11” from the corner of the stove to comply with combustible clearance specs. Of course if I can get it farther away I’ll do that. Any issues you can see there?

 

[begreen]

That should be fine for the outlet. Place it as low as is practical.

A question for the Lopi documentation people is how to make that brick ceiling using their narrow interpretation of NFPA 211.

 

[begreen]

PS: I'd also consider venting the cavity above the stove into the IKEA bookshelf room.

The vent grille should be large enough for the free flow of air, ideally with a lower intake grille to facilitate convection.
PPS: Also, if there is a mantel involved it either needs to be non-combustible or adhere to the stove clearance requirements. Plan structural support for it ahead of time.

 

[EbS-P]

Would it be possible to build a completely free floating non combustible alcove box. Leave a gap from it to all combustibles (eventually somewhere at the top-front and sides it needs to be covered /connected but I don’t have those details worked out yet. Walls don’t have to be 4” think so metal studs sideways would be fine. Frame out the back wall with wood studs but leaving the gap. 2” deep wall ok?
Where would the support box go? I guess the alcove box? Vents where you like. Ceiling probably tile? Stucco? Just ideas/thoughts that might be helpful

Evan

 

[s0ulP@tch]

Here’s how Travis Industries replied to my inquiry:

Hello,
Thank you for your interest in our product. What is needed per NFPA 211 is a non-combustible material such as cement board mounted with a 1” non-combustible spacer allowing a 1” gap top and bottom for air movement. You will need to contact your dealer who should be familiar with local code requirements and NFPA 211 requirements.

Regards,

Glen Payson
Customer Service/Technical Support Department
NFI Certified Master Hearth Professional
Travis Industries, Inc.

So contact local code peeps for signoff, which is on the list of things to do already. Unfortunately, they’re not being overly helpful here.

@begreen good call on the mantle. The wife wants one, but we were thinking of a faux distressed reclaimed mantle, and obviously it would need to be at least 36” from the stove front or top. LMK if that’s insufficient. This was the kind of idea - it’s mostly hollow: https://toolboxdivas.com/mantel-build-rustic-faux-beam-diy/

Roger on the vents - I was already thinking lower intakes would help keep the air flowing.

@EbS-P I don’t think I have the clearance to do a fully (or mostly) detached or floating alcove. I only have a few inches of extra space in width and depth, so I really have two choices: 1) make a shielded alcove, or 2) skip the alcove and put the stove out in the room against the wall. Might be a good discussion for someone with more space though.

 

[begreen]

That is more practical. They really should update their manuals.

The county engineers are going to want to see drawings and specs in order to judge the safety and code compliance of a non-standard installation.

There is a thread on non-combustible mantels. There are several that are exceptionally realistic looking.

 

[s0ulP@tch]

So I spent some time in SketchUp to figure this out. If I use steel studs with 1/2" cement board on the inside of the alcove and a 1" gap between the steel studs and any combustables on the outside, I have barely enough room as long as the inspectors agree that this is just as satisfactory as a 3.5" brick wall with an air gap. There alcove is 42” wide (minimum is 40”) and 27” deep (the precise minimum: 20 1/4” stove depth + 6 3/4” gap since I will get the fan kit).

I'll include an outlet in one of the bottom/back corners that will be run to a light switch nearby so the fan can be turned on or off via switch. Vents will be placed in the bottom & top of the outside wall of the alcove to allow the heat to reach the other room and cool the cement board.

I’ve attached pictures of the SketchUp layers starting with the as-is hole left by the old chimney. There are some posts that will support beams in the basement ceiling and the 1st floor ceiling, and those are colored dark brown (they're pressure treated because the will touch the concrete). I put in a 2x8 to support the faux beam mantle I linked in an earlier post. Yes, it’s wood but it looks nice and will be much lighter than a cement mantle.

Layers are attached below as images. I textured the drywall (straight stripes) and cement board (diagonal stripes) differently so I could tell the inspectors which was which. There cement board extends out to the face of the wall for fire protection.

The alcove ceiling is angled up toward the opening to allow hot air to escape. The alcove is 27" deep and the front of the alcove is 6" higher than the back. Comments welcome on whether that's enough (or more than necessary... the Mrs. wants as flat a ceiling as is feasible). I'll add electrical and get this ready to submit to the city.

There's 30" from the top corner of the stove to the mantle bottom at the moment.

 

[begreen]

That is looking better. Why the big mantle support and why is it wood? Also, why the offset in the chimney? Was there one in the old fireplace chimney too?

 

[s0ulP@tch]

I figured the wood would support the mantle better, and that’s why I put it up higher as well - to get it away from the heat.

The steel chimney will be a new installation. It goes through both floors, and I’ve lined it up with where it will be flush with a wall upstairs above the furnace room. The offset is to realign it with the collar of the stove. We technically could pipe it straight up, but we removed the old masonry chimney to open up the living room upstairs. Putting the new chimney right where the old one was defeats that purpose. This design should draft well and also look nice when finished. That’s the goal. The chimney would go up where the lion toy is in this pic from the main floor. Plywood is over the hole left by the masonry.


The offset is angle doesn’t seem all that bad - is there a risk of affecting draft?

 

[begreen]

The offset will be ok as long as a minimum of 2" clearance is maintained all the way up through the roof. The offset should be supported per mfg. guidelines. The chimney pipe will need a firebreak as it passes through floors. With proper planning, a metal beam should be fine for supporting the mantel. There are heavy gauge studs made in normal dimensional lumber sizes.
Have you checked out this thread?

Non-combustible mantels

Starting a thread for folks that are looking for non-combustible mantels. These are very realistic, but made from concrete: http://magrahearth.com/natural-wood-series-gallery MagraHearth website http://magrahearth.com/

www.hearth.com

 

[s0ulP@tch]

Thanks for the tip on heavier gauge steel beams - I’ll look for those. I have seen the concrete mantels and it’ll be tough to justify $700+ on the mantle. Depends on how badly my wife wants it to be lower

I’ve been trying to do this one by the book, so the chimney manufacturer instructions will be followed. Thanks for helping keep my house from burning down

 

[begreen]

Keep on looking. If the design is for a more contemporary look, then maybe a non-combustible painted mantel would work? They are in the $460 range.

Pearl Mantels Non-Combustible Mantel Shelves

Pearl Mantels - Manufacturers of fine furniture quality wood and MDF fireplace mantels and surrounds, wood and MDF mantel shelves and decorative shelves, non-combustible mantel surrounds and shelves, and cast stone shelves. Distributed in the United States and Canada.

www.pearlmantels.com

 

[s0ulP@tch]

Question about electrical outlet - looks like my alcove isn't quite big enough to get the outlet 11" away from any part of the stove. Are they considered combustible? Is there specific guidance regarding outlet clearances from stoves? I've tried to search for "non-combustible outlets" but keep getting results for fire-rated outlet boxes - nothing seems to be said about the outlets themselves. And is there an issue with running the electrical through the steel stud wall? Will I need metal flex conduit for that?

 

[begreen]

It won't be a problem if placed low, a few inches above the floor. 11" is to the sidewall, 9" to the rear. You could use a metal receptacle cover if concerned. Or mount flush in the hearth floor behind the stove.

 

[EbS-P]

Will I need metal flex conduit for that?

I think so but but you should check. I remember something about no romex in conduits too.

 

[s0ulP@tch]

Many delays later, I’ve finally passed mechanical inspection and am ready for framing. Here’s the progress so far on the alcove.

Found a supplier of 20g (30 mil) steel studs in a 1-5/8” width to give me a little more room. This is heavier metal than the 25 gauge studs at big box stores. There is a 1” gap between the steel studs and where the drywall will connect on the outside, so a total of 2-5/8” between the 1/2” durock and the drywall. The drywall side will be vented top and bottom. The 2x6 metal studs are 33mil structural steel, and I used scraps from the cutoffs to ensure I can secure durock to the back side of the front wall. The structural steel should be sturdy enough to hold up a non-combustible mantle. The electrical pass-through holes were patched with 33mil scraps. The heavy duty steel is strong enough to hold me up while hanging on it, and I’m 185 lbs.

The back of the alcove tapers toward the front to guide the hot air toward the front, where two vents will be installed at the top near the ceiling. The steel studs at the top are 1.5” offset from the studs above for extra protection (so over 3” between the steel studs and the joists).

Electrical is as low as I could get it, and I think it’ll be fine. Used a plastic bushing/grommet to pass it through the metal stud.

What I’ve hated most about this project is bringing something that was built ~9 degrees off of square back to square. I’m happy with the results so far!