NFPA code for type of heat shield spacers?

[The Dude]

I am hoping someone can end my confusion about spacers for heat shields regarding reduced wall clearance to combustibles. Is there any NFPA code for approved materials that can be used for these spacers? I don't have access to this code book. I am so close to being able to install my stove with this being the last grey area. Is it one of of those things where there are no materials or methods specified, and many solutions will do? I'm hoping someone can look this up for me in the NFPA book. I have heard of the following, but no confirmation if any are required, allowed, or prohibited:

-1" ceramic spacers: seem to be discussed as if they are officially acceptable

-1" pieces of copper tubing: A DIY method that seems similar but a guy at the local stove dealer told me he wouldn't discuss because he never heard about it and wouldn't want to give me the wrong advice that could be the red flag if my house burnt down and the report listed "copper spacers used instead of ceramic"

-Strips of 1/2" cement board, doubled up: seemed like a good idea, so I cut all 20 strips needed. Now I worry these will transfer the heat right into the studs since that's where they will be mounted. Since they are solid vertical strips, this would allow much more space for heat transfer to the studs (if there even is any) than ceramic or copper spacers.

My setup:
Harman TL-300 stove
Modern Drywall & Stud wall
Reduced clearance heat shield of 1/2" Hardibacker cement board to be covered in thin stone, spaced 1" from wall, mounted into studs
One wall is exterior, the other is interior right over a steel I-beam under the floor, so the weight should be okay.
Clearance reductions are based on stove manual and then reduced by NFPA code of 66% reduction.

Thanks!
Tom

 

[summit]

All that you listed will work.. just don;t use wood! cooper, durarock strips, and ceramic all work to satisfy the code requirements.

 

[The Dude]

Thanks summit. That is great news. Do you know what the actual code requirements state? I just hate the idea of following advice assuming that it's code. I did that at first with my chimney installer's information about noncombustible clearance reduction for my wall being 2/3 reduction, and then I realized that I could be putting my family's lives at risk based on what someone else thought was right. I was able to find online the page out of the NFPA on clearance reductions to confirm it. But I can't find anything on spacers. Thanks again.

 

[BurnIt13]

I'll add to the question if you don't mind. I am in the same boat as you and assumed the spacers only had to be "non-combustible". You bring up some good points.

What about 1" square tubing cut into 1" long sections?

 

[summit]

non combustible face, w/ spacers does give you a 2/3 reduction according to nfpa specs... however your local code may be different, and the local code takes authority... that being said, 99% of local code guys have no idea what they are talking about, and most will refer to nfpa 211.

 

[yooperdave]

just want to weigh in on this as i was in the same boat last oct. after much thought, i went with a steel stud. they are used for construction and i got a couple of them for somewhere around $2 a piece. i think they were 10'. they are "U" shaped and i just laid the flat part against the wall (which, incidentally, is tongue and groove pine, clearcoated, with a raw plywood backer). when i attached the shield (cement board) i held it in place, then drilled through the cement board being careful not to collapse the "U" channel of the steel stud. i only used it on the vertical. be sure to allow clearance off the bottom of the floor; i think they suggest no more than 3" and to allow clearance at the top of the spacer; i think they want at least 1".
you can see that due to the flammability of the wall, i was very concerned with the safety. i assure you that i am very satisfied with this set-up. the total cost of the "spacers" and "heat shield" was about $30.

 

[The Dude]

Thanks for the suggestion yooperdave. It seems that would be a good option. I already have the strips of cement board cut, which actually came from three different boards, so I'm in $30 on that already and would like to use them if I can.

In that regard, I'll simplify my question. Summit, thanks for the follow up. Could you or anyone else do me a favor and check the NFPA book and tell me the actual verbiage on spacers? Or if it is available online, could someone send me a link? I'd like to know for sure that the cement board strips are both safe and approved by the code. Hopefully the mentioning "spacers" includes different suggestions including cement board strips. Maybe it prohibits the use of anything other than ceramic spacers, or if it is vague without much specification. I have the notion that there are multiple types of materials approved by summit's two posts, but I still don't know what the actual code is.

 

[begreen]

You folks are overthinking this. The spacer just needs to be non-combustible, period. Personally I like ceramic or the cement board strips more than a metal spacer due to the lower heat conductivity of these materials, but either are acceptable.

 

[BurnIt13]

You folks are overthinking this. The spacer just needs to be non-combustible, period. Personally I like ceramic or the cement board strips more than a metal spacer due to the lower heat conductivity of these materials, but either are acceptable.

I'll be going with the cement board strips as well then. Easy enough to do. I'm surprised that you can use strips instead of pieces. You would think that strips would prevent air from moving horizontally. But then again heat rises, so its most likely going to move vertically anyways.

That pic did teach me something though.....the fasteners cannot be directly behind the stove. Makes sense when you think about it but I didn't know that.

 

[The Dude]

Be Green: thanks for posting that code! That's exactly what I wanted to know. I don't have enough experience to know that I am overthinking it. I'm playing it safe and making sure everything is done right. For instance, I did not know that the spacers should not be directly behind the stove.

I can't get peace of mind knowing that the cement board strips are completely blanketing the underlying studs when I know that ceramic spacers would not do this. Sure, there is air space to the channels left and right of the strips, but I can't see that changing temps on each of these 3" wide strips much more than they would be if I simply double up solid 1/2" sheets of cement board in place of air. Maybe in both cases no significant heat would transfer through to the combustibles. But I don't like the idea of guessing, and all I know right now is that ceramic spacers have such a small surface area compared to those solid vertical strips of cement board, so why shouldn't I just use them? Maybe big strips of anything directly over studs are not even considered spacers. Maybe some people have done tis 100 times for professional installs without one fire. But it can take decades of exposure to char framing to the point of combustion.

No one has ceramic spacers around me except a big stove dealer who had kits of 10 with screws that aren't even long enough for $13. but I was able to order some from the local Tractor Supply which are $8 for 25. $35 with tax for peace of mind is my final conclusion. I say this after screwing down a sheet of Hardibacker to the strips last night. Sorry for wasting everyone's time.

 

[sesmith]

No one has ceramic spacers around me except a big stove dealer who had kits of 10 with screws that aren't even long enough for $13. but I was able to order some from the local Tractor Supply which are $8 for 25. $35 with tax for peace of mind is my final conclusion. I say this after screwing down a sheet of Hardibacker to the strips last night.

Ceramic fence insulators work well. I'm assuming that's what you're talking about here.

 

[begreen]

They sell wall shield spacer kits. More like this: http://www.northlineexpress.com/item/5CO-54230/HomeSaver-Heat-Shield-Screws-and-Spacers-Pack-of-30

I like using the cement board strips because they're easier to install and the wall shield can bear more weight.

 

[yooperdave]

https://www.hearth.com/econtent/index.php/articles/stove_wall_clear

does this help?

 

[The Dude]

Ceramic fence insulators work well. I'm assuming that's what you're talking about here.

Thanks for that info. I just did a google search after you mentioned what they are called in the fencing industry, and most of them are 1-1/2" to 2" long. So I called Tractor Supply who are getting some from another store tomorrow, and the guy said they are closer to 2' long than 1". I have to have it only 1" because of where my chimney is located, which is dictating where my stove will be. Thanks for the links. I'll look into it. One day I'll just do something the easy way.

 

[The Dude]

Just a quick note that the link Be Green included is the same pack as what the stove shop near me, and I thought it was only 10 spacers for $13, 30 pieces total including anchors and screws. Turns out it is actually 30 spacers in there, so I guess I'll go back to the store and buy them. A note for anybody who comes across this in the future...the 2-1/2" screws that come with that spacer kit aren't long enough to go through 1/2" cement board, 1" spacer, 1/2" dry wall, and deep into the stud. I recommend 3-1/2" screws for that. Maybe there is a way to mount the spacers to the wall and then the heat shield to the spacers separately, but I can't figure it out.

I wish I could bring myself to use those hardibacker strips that I already cut as spacers, but I have too much doubt the more I think about it. I read on this forum how one or two people held their blowtorches up to cement board and it would not ignite. I am concerned that the strips will transfer heat to the studs, being only 6" from the rear of my stove. I just did a test to see how easily heat would transfer through it by holding a piece of 1/2" hardibacker a few inches over my electric stove burner with a pair of channel-locks. After 2 minutes or so, only the side facing the heat was hot to the touch. After 4 or 5 minutes, the top was indeed too hot to touch. If this went through one 1/2" piece in 5 minutes, I'd say it's possibly to transfer through three pieces through the course of a burn. I think there is serious significance to the air space preventing direct contact into the combustibles. Strips of the cement board over the studs seem like a completely different concept than small spacers here and there with lots of air all around them.

Another point supporting my fear regarding the cement board spacers is that Durock used to have a set of instructions on how to make spacers with their board, and now the link is dead and I can't find instructions anywhere on their website.

 

[begreen]

That link is dead because they came out with their NextGen product. I suspect they have not tested it for the same application and may not unless the hearth industry and individuals press them to.

 

[nelraq]

An additonal point that hasn't been discussed in this thread:

To The Dude: Does your TL300 stove have the factory rear heat shield installed? If it does, I don't think that you are permitted to further reduce the clearance from combustibles by placing an additional heat shield on the wall.
In other words, you can only reduce the stove clearance ONCE; either by using a heat shield attached to the wall OR by using the factory built rear shield that attaches permanently to the stove.

The above may or may not apply to your jurisdiction, but I'm almost positive that it does in mine.

 

[The Dude]

That link is dead because they came out with their NextGen product. I suspect they have not tested it for the same application and may not unless the hearth industry and individuals press them to.

Great point. I forgot about that. Information you posted in other threads I searched led me to choose Hardibacker over Durock NexGen for my heat shield, contrary to my original suspicion that hardibacker would be less safe because of the cellulose content. So I'll forget about that "supporting evidence" I mentioned.

An additonal point that hasn't been discussed in this thread:

To The Dude: Does your TL300 stove have the factory rear heat shield installed? If it does, I don't think that you are permitted to further reduce the clearance from combustibles by placing an additional heat shield on the wall.
In other words, you can only reduce the stove clearance ONCE; either by using a heat shield attached to the wall OR by using the factory built rear shield that attaches permanently to the stove.

The above may or may not apply to your jurisdiction, but I'm almost positive that it does in mine.

Thank you for this great point. This better not be true for my case! My chimney and hearth were both installed based on the clearance reduction plan. Even worse, the stove would jut out into the entranceway in between rooms if I had to move it out out further. I was aware that you can't double up on clearance reductions, but didn't consider that my stove already had heat shields. It does on the sides and likely the rear.

There is a mentioning of reduced clearances in the stove manual. Here is the exact paragraph. This is the very first thing mentioned on clearances before it goes into detail about different setups.

Clearances
Clearance is the empty space required between the stove or chimney connector and the nearest combustible surface or object, such as walls, ceilings, floors, or furniture. Clearance distances may only be reduced by using methods approved by either the CAN/CSA B365 standard (Canada) or NFPA 211 (U.S.) Contact your building authority for information if you are interested in reducing clearance distances below those presented here.

Here is a link to the manual: Harman TL-300 Install Manual

 

[The Dude]

Hopefully this will be the last annoying question I ask about the code for spacers. The NFPA 211 states "no spacers or ties shall be used directly behind appliance or conductor." I'm putting up my heat shield right now, and wonder if the same principle should be applied to side of the wood stove. I'm not asking for a technical interpretation of the code, but more so of personal advice if the sides let off just as much heat as the rear of wood stoves. I understand stoves vary. Thanks a lot!

 

[begreen]

No worry, this just applies to the midpoint, behind the stove, where the stove pipe goes up.

You'll find that a proper wall shield is more effective than you might think. It really blocks a lot of heat as long as it is ventilated top and bottom.

 

[The Dude]

Thanks Green, you're the best!

 

[KodiakII]

Nexgen is ULC listed as non-combustible and suitable for floor and wall protection..."only in Canada eh...pity". It is what is behind and under my stove. Nice stuff to use compared to the old gen!

 

[joecool85]

Thanks summit. That is great news. Do you know what the actual code requirements state? I just hate the idea of following advice assuming that it's code. I did that at first with my chimney installer's information about noncombustible clearance reduction for my wall being 2/3 reduction, and then I realized that I could be putting my family's lives at risk based on what someone else thought was right. I was able to find online the page out of the NFPA on clearance reductions to confirm it. But I can't find anything on spacers. Thanks again.

That 2/3 quote is true, but you can only go to a minimum of 12" from the wall - no closer. So if you had a 14" clearance requirement and put up proper protection, that would bring you down to 12" clearance, not 4.67".

 

[The Dude]

Joe, can you quote the code that specifies this? I've never seen this or heard it from anyone else in my research and installation process.

 

[joecool85]

Joe, can you quote the code that specifies this? I've never seen this or heard it from anyone else in my research and installation process.

Got that from here: https://www.hearth.com/econtent/index.php/wiki/NFPA_Wall_Clearance_Reductions/