NFPA 211 Question

[gtilflm]

Hi. I've been looking through how to get a little bit of a clearance deduction and have looked over this...

I will be using Versetta stone as a "back drop" in a corner installation.

1. For "b", is that meaning that I would have (from outside to inside), siding → sheathing → studs → drywall → 1 in. class fiber or mineral woos batts → 1/2 thick foam board like https://www.homedepot.com/p/R-Tech-...-Rigid-Foam-Board-Insulation-320810/202533656 → (maybe 1/2 in. Durarock) → Versetta faux stone.
2. I also don't see why just using a higher R-value foam board like https://www.homedepot.com/p/R-Tech-...-Rigid-Foam-Board-Insulation-310891/202532856 isn't an option listed on here. Wouldn't the R-7.7 reduce the heat getting to combustibles, and thus be a valid way to reduce clearances?

This will end up being inspected, so I feel that I need to play by the book here.

 

[EatenByLimestone]

Foam board is good at slowing down heat transfer until it catches on fire.

 

[gtilflm]

Foam board is good at slowing down heat transfer until it catches on fire.

Well that sucks.... 😀

Is my understanding of "b" above correct?

 

[bholler]

Hi. I've been looking through how to get a little bit of a clearance deduction and have looked over this...

I will be using Versetta stone as a "back drop" in a corner installation.

1. For "b", is that meaning that I would have (from outside to inside), siding → sheathing → studs → drywall → 1 in. class fiber or mineral woos batts → 1/2 thick foam board like https://www.homedepot.com/p/R-Tech-...-Rigid-Foam-Board-Insulation-320810/202533656 → (maybe 1/2 in. Durarock) → Versetta faux stone.
2. I also don't see why just using a higher R-value foam board like https://www.homedepot.com/p/R-Tech-...-Rigid-Foam-Board-Insulation-310891/202532856 isn't an option listed on here. Wouldn't the R-7.7 reduce the heat getting to combustibles, and thus be a valid way to reduce clearances?

This will end up being inspected, so I feel that I need to play by the book here.

What stove is this for?

 

[EatenByLimestone]

EPS foam is flammable.

 

[gtilflm]

What stove is this for?

Most likely a Lopi Evergreen, but we'd like to build the hearth, walls, etc. to accommodate a larger stove in the future if desired.

 

[bholler]

Most likely a Lopi Evergreen, but we'd like to build the hearth, walls, etc. to accommodate a larger stove in the future if desired.

Many modern stoves don't really allow extra clearance reduction anyway. So you just have to go with the specified clearances

 

[gtilflm]

Many modern stoves don't really allow extra clearance reduction anyway. So you just have to go with the specified clearances

A Lopi technical guy directed us to review NFPA 211 for clearance reduction options. Overall, how do you know if clearance reduction is even an option?

 

[bholler]

A Lopi technical guy directed us to review NFPA 211 for clearance reduction options. Overall, how do you know if clearance reduction is even an option?

The manual doesn't say clearances can be reduced below the specified numbers

 

[gtilflm]

The manual doesn't say clearances can be reduced below the specified numbers

Just looked it up, and it looks like they do allow reductions, which is good news.

 

[bholler]

Just looked it up, and it looks like they do allow reductions, which is good news.


View attachment 312244

Your correct I missed that. But the minimum clearance allowed with nfpa shields is 12 your already below that if you just use double wall pipe so why bother?

 

[gtilflm]

Your correct I missed that. But the minimum clearance allowed with nfpa shields is 12 your already below that if you just use double wall pipe so why bother?

Please correct me if I'm wrong. I believe the most recent NFPA 211 documentation is 2019. I'm looking at https://www.cityofmtcarmel.com/sites/default/files/fileattachments/planning/page/7867/211-19-pdf.pdf. Under 211-31, I'm looking at "Table 9.5.1.2 Reduction of Connector Clearance with Specified Forms of Protection".

All the min. clearances are halved!! I don't see any other appreciable difference between the pic. that I copy/pasted (and that we were talking about) and the data on the 2019 document. Perhaps the pic. I copy/pasted was from an older version of NFPA 211?

 

[bholler]

Please correct me if I'm wrong. I believe the most recent NFPA 211 documentation is 2019. I'm looking at https://www.cityofmtcarmel.com/sites/default/files/fileattachments/planning/page/7867/211-19-pdf.pdf. Under 211-31, I'm looking at "Table 9.5.1.2 Reduction of Connector Clearance with Specified Forms of Protection".

All the min. clearances are halved!! I don't see any other appreciable difference between the pic. that I copy/pasted (and that we were talking about) and the data on the 2019 document. Perhaps the pic. I copy/pasted was from an older version of NFPA 211?

Looks like your correct again. But honestly I would keep it at 12 anyway for a margin of safety and ease of service

 

[gtilflm]

Looks like your correct again. But honestly I would keep it at 12 anyway for a margin of safety and ease of service

Fair enough. I am curious to what could cause the clearances to be halved from one version to the other.... with no other changes. Maybe the more efficient stoves made these days impact that somehow?

Separately, the Lopi Evergreen NexGen Hybrid shows the clearances as follows.



Note the 8" and 4" spec. for the corner install. I know you're still recommending 12", but does the manufacturer's specs. override NFPA 211, or vice versa?

 

[bholler]

Fair enough. I am curious to what could cause the clearances to be halved from one version to the other.... with no other changes. Maybe the more efficient stoves made these days impact that somehow?

Separately, the Lopi Evergreen NexGen Hybrid shows the clearances as follows.

Note the 8" and 4" spec. for the corner install. I know you're still recommending 12", but does the manufacturer's specs. override NFPA 211, or vice versa?

The nfpa guidelines honestly are most often used for older stoves so no they didn't change them because of the new stuff. And no efficiency doesn't effect clearances at all either. I can't explain why they changed them other than they must have retested.

I would go below 12" on corners if allowed for sure but I generally don't go to the minimum.

 

[stoveliker]

Note the 8" and 4" spec. for the corner install. I know you're still recommending 12", but does the manufacturer's specs. override NFPA 211, or vice versa?

My understanding is that yes, mfg specs override the others, because the mfg specs have been tested; the stove has been tested (proved) to be safe with those specs, even if they are more tight than NFPA.

The NFPA specs are for stoves that are not tested (not UL listed, and thus need I believe 3 ft clearance to combustibles all around!, which can be decreased by proper shielding on walls (a 1" vented noncombustible plate in front of the wall, with openings below and above, to allow to convect away the heat from behind the shield)).

 

[begreen]

4" corner clearance with double-wall stove pipe is very good. There is no need to go closer. If there is a blower hanging on the back of the stove make sure there is room to service it.

 

[stoveliker]

One might not even wish to go closer for ease of access, and for convection (getting the heat out of the corner into the room)...?

 

[gtilflm]

4" corner clearance with double-wall stove pipe is very good. There is no need to go closer. If there is a blower hanging on the back of the stove make sure there is room to service it.

Good call! I wouldn't want to go closer than that.

At this point, we're leaning toward the Evergreen, but want to build the hearth/wall to be able to accommodate a larger stove in the future for whatever reason. That's mostly the reason I'm diving into clearance reduction so heavy. Don't want to have to rebuild the hearth, wall, etc.!!

 

[begreen]

Stove flue outlet and clearances vary a lot. It's very hard to predict future stove requirements but increasing the corner clearance distance may help. However, if you switch from an E/W loader to a deeper N/S loader then an offset in the stovepipe may still be required.

 

[stoveliker]

While the hearth could be an issue with a future larger stove, you can always keep the ceiling penetration and add two 30 degree elbows to offset the pipe to the stove exit.

 

[gtilflm]

Stove flue outlet and clearances vary a lot. It's very hard to predict future stove requirements but increasing the corner clearance distance may help. However, if you switch from an E/W loader to a deeper N/S loader then an offset in the stovepipe may still be required.

Hmmm.... Interesting. So, having the smaller Evergreen set up with FURTHER clearances than it has to be would more likely to be a better match (hopefully without offsetting w/ 45's) if we ended up wanting to go with a larger stove in the future. Is that what you're saying?

 

[gtilflm]

While the hearth could be an issue with a future larger stove, you can always keep the ceiling penetration and add two 30 degree elbows to offset the pipe to the stove exit.

Yeah. We're wanting to build the hearth to accommodate a future, larger stove. That's the goal at least!!

 

[begreen]

Hmmm.... Interesting. So, having the smaller Evergreen set up with FURTHER clearances than it has to be would more likely to be a better match (hopefully without offsetting w/ 45's) if we ended up wanting to go with a larger stove in the future. Is that what you're saying?

Possibly, but there is no guarantee. I put in a Jotul F400 with generously exceeded clearances. It was replaced with the Alderlea T6 and due to difference in the flue outlet location of the two stoves I had to offset the stovepipe anyway. It's not a big deal if needed. I put in an oversized hearth so no change needed there. Good thing too, it's inlaid into the floor.