Ceiling heat shield for wood stove

[Ginger Squirrel]

What is a good way to setup the heat shield for the ceiling for a wood stove?  For walls I'm doing cement board, then I will use metal roofing an inch away all around.  For ceiling I'll be doing cement board too, and I can probably use the same roofing material, but I'm thinking of instead to do drop ceiling an inch or so away from the cement board.  Would this be considered a suitable heat shield or does it have to be metal?  If it matters, I will also have an air duct somewhere in the middle, and the heat shield will have a few small openings throughout so air can be sucked into the vent. Something like this (VVV is vent) :

Code Select Expand


Ceiling Joists ->  U   U   U   U   U   U   U  U
Cement board   ->  =========VVV================
Drop ceiling   ->  ____   ____   ____   _____ =  
                                           | =
                                           | =
                            metal roofing->| =
                                           | =
                     [stove here]            =
                  ============================



I'm thinking this may also help reduce too much heat from accumulating in the ceiling. The location of the wood stove is not necessarily where I want the heat, but the only location that was possible to put one, so the duct will pump the heat where it's needed most with a 497cfm inline fan. Of course this needs to be safe in the event that the fan is not running, as well.

As a side note how concerned should I be about having Romex wire runs in that ceiling?  I will probably roxul that part of ceiling before putting the cement board so I'm hoping that will be ok.

[Don P]

Good questions, most revolve around distance to combustibles and the listing of the woodstove.  NFPA 211 is the code reference for those things, there is a free to view online version... Here it is, I think, I'm throttled at the moment;
NFPA 211

[Ginger Squirrel]

I skimmed through it but it's not searchable so I may have missed it, but I don't see much mention on ceiling.  I guess it's probably safe to assume the requirements for ceiling are same as walls?    I guess the question is, are drop ceiling tiles considered a combustible?  I assume this depends a lot on the specific tile.  Quick google search seems to indicate ones made from stone wool are non combustible.  So perhaps those would be ok to use.  Maybe I'll see what HD has and if it even mentions what they're made from.  Worse case scenario if inspector does not like it I can maybe swap the tiles for some precut metal pieces.  Basically I just want something removable as there is an electrical junction box I'll need access to.  I am moving my garden hose and I already moved a few other things so that leaves me with just the junction box to worry about.

As for the romex wire being an issue it looks like the temp rating of it is 90C so I don't imagine the ceiling is going to hit that temp by the time I factor in the heat shield and the cement board.

I'm also going to be meeting or exceeding the distance requirements to combustibles so maybe that alone makes it so I have to worry less about the materials too. 

[doc henderson]

I assume you have a mounting box beginning at the ceiling or below that the stove pipe goes into, and the insulated chimney parts are supported by.  i think distance is the issue and usually ceiling are far enough away.  if you drop too low, then the materials may be below the junction support box, and get too close to the  hot stove pipe.  is the pipe double wall?  all component should have diagrams and nice charts referring the distances by A, B, C ect. to combustibles.  I think a metal vent/grate, going into meatal ducting to suck heat to another spot will be fine.  we live in a trilevel, and we have a through the wall fan to to pull from the stove and into the basement.  it is plastic.  I think the back clearance on our stove with the double wall stove pipe is 10 inches.  we have sheetrock wall and concrete floors.

[Ginger Squirrel]

There's a room above and I didn't want to have the chimney go through a room and then have to deal with working in the attic, so the pipe will be going through the foundation wall to go outside then 90 up along the house then through the soffit.  I will probably use double wall stove pipe, but have not bought it yet.  Chimney will be double wall stainless and be fully outside. (Selkirk).

[beenthere]

Ginger
Pls give us a location where you are at in the world. Will help answer and give suggestions. Click user name and there you can update your profile.

Pipe to surfaces are important. Hope your wood stove mfg. gives those distances for code requirements. Likely you will have to show that info on house insurance paperwork. 

[Don P]

This is the table i was thinking of in NFPA 211. The section on ceiling protection is around pg 48. Manufacturer instructions to trump this generic info.



 

[Ginger Squirrel]

I think some ceiling tiles are made of mineral fibre or similar material, so maybe that will actually count as noncombustible insulation board if I can find the right ones.

If that's the case I should be good to go with my idea then.  Failing that I can always cut some metal panels to fit where the tiles will go, it will give me the desired option to be able to access the ceiling. There will be cement board above the tiles but I will cut an opening for a junction box that can't be moved then just screw the cutout back on. At least if I need to get in there I just need to undo a few screws.

[Old Greenhorn]

It looks like you are trying to see what you can get away with and be within spec. Any tiles you put above the pipe along the ceiling should have a specific fire rating or they really don't count. With a ceiling you get the radiant heat from the pipe, plus the convection flow, and heat rises. SO that ceiling area is going to see more heat than the walls.
Just throwing in a thought here: Those specs are designed for two things, Safe normal operation AND allowing as much time as possible to safely evacuate the building and deal with any fire. Most folks think about the first and not the second. There are a bunch of firefighters here on the forum, either current or retired, and most can tell you how a metal chimney system fails under extreme fire conditions. It isn't pretty. The normal operational heat in a chimney can build on nearby surfaces and sometimes get fairly hot. But when there is an uncontrolled full blown chimney fire working and the pipe is glowing cherry red, the rules of physics change and accelerate. The metal can actually vibrate and 'dance', joints get stressed and poor fasteners can fall out, smoke pushes from every crack and joint. Non approved pipe will melt when it gets hot enough or corroded sections in any pipe can open up. It gets ugly very fast and I have worked too many of these fires.
I am by NO MEANS trying to scare anyone. But when you make your design plans, it is good to have the worst case scenario in your head rather than what will work and satisfy the codes. I can also tell you I have caught several of my chimney systems starting into a fire with that freight train noise or the dark grey/brown  smoke pushing out the top, then joint cracks. It was at that moment every time that I was thankful I overbuilt a little, used 3 new stainless screws on each joint connection every time I cleaned the chimney, and did other things to make it right. I even had a stove take off one time and dance across the floor, literally. The only thing that kept it from puling the stove pipe out of the wall were the joint screws.

So plan well, make sure your are using tested and approved materials within their spec. and then you can have a warm space with peace of mind.
Best of luck.

 Also, keep in mind, we have no idea where your are, requirements vary by country, state, county, and town. You will need some kind of approval from somebody, so it's best to make that call before you spend money, rather than later.

[doc henderson]

remember that heat and temp are related but different.  If you heat up meatal with a torch, you do not blow the flame parallel, but right at the piece.  so any redirection of the heat going up the flue, like a 45 or 90 degree turn will result in a higher temp and faster degrade of that metal.  that is the reason we try to go straight up.  same amount of heat, but faster degrade to the outside of an elbow pipe.  can also affect draft.

[Ginger Squirrel]

I'm in Ontario.  And yeah I want to make this safe, so want to see if this is considered acceptable or not.   Most people just use large sheets of roofing material but I'm just thinking for the ceiling that will be a bit awkward to make it look good especially at the corners because I will have the wall heat shield too, so I'm really not sure how to do the transition especially because of the corrugations.  The ceiling tiles should be easier to transition as I'll just run them maybe half inch away from cement board wall then heat shield will come straight up to it and only have a small gap.

I was also not considering the pipe itself, I guess that will also be putting off lot of heat.  I will probably want to add an extra heat shield around the pipe area as well. I think I've seen some that attach to the pipe so I might want to do that especially for the top one as it will be coming close to the ceiling.

For the tiles I'd be looking at ones that have the A fire rating though it seems harder to find as most of them are made of PVC now.  

I found these that state have class A fire rating but then also say they're made of PVC so not sure how that works?  Is that actually rated?: https://www.homedepot.ca/product/genesis-2-ft-x-2-ft-stucco-pro-re-white-ceiling-panel-carton-of-12/1001413812

I would not want to use PVC though even if it says it's rated as it puts off pretty toxic fumes when it melts.  The more I'm thinking of it, I may just try to find a company that can custom cut flat sheets of metal, and I will use those as the tile in a drop ceiling system, it will accomplish the same thing I want, a flat surface for the ceiling, accessibility, and acting as a shield. Does that sound better?  The drop ceiling tracks are all metal right?  I never actually worked with them before. 

[doc henderson]

I thought the shielding was for the ceiling,  is that not for the pipe going through the wall?  cement board should be good, ceramic tile over that if you like.

[Ginger Squirrel]

Yeah I'm asking about ceiling, the walls will have metal roofing material most likely.  Have not decided that 100% but it will be metal.

Ceiling, walls and floor all will have cement board, the proposed ceiling tile would be on top of the cement board. (with 1" gap)

As for the pipe going through the wall I currently have it opened up right down to the cinder block, have not decided how I will close that up yet but that's something I'll probably leave to the chimney installer.  The stuff I'm doing now is just prep work to get the area up to par. 

[Don P]

Cement block is not combustible, I'd parge and leave that as the finish wall in that area if possible, no other cover needed. The description of wall and ceiling protection sounded like you were not reading or not understanding the need for that 1" space to be freely venting. There is a drawing in the area of where those clearance reductions were, review that section.

[doc henderson]

can you take pics, or do a drawing.  if the turn out the wall is low enough relative to the ceiling, then dry wall is ok.  the picture I have in my head is a wood stove with a stove pipe out the top that at some point turns and goes out the wall.  I do not know how close to the ceiling material that is.  most of the shielding can be done after the fact if needed.  if not needed then you are really talking about "decoration".  My assumption was you are doing all this yourself.  I would have the installer stop by.  Not unusual for an installer to see the job before they start.  The two of you should coordinate and make a plan.  

is the floor carpet or wood?  I have made a hearth area on floor before.  tile over cement board looks nice.  this may turn out simpler than we are trying to make it.

[beenthere]

Agree with Doc, Don, and others that we need a pic of the area you plan to install the stove and heat shield. 
Members here (with lots of experience both the right way and the wrong) can be a lot more helpful to you with more information.

Depending on the situation, how the stove sets, and where on the stove the pipe connection is located, am thinking of two 45° elbows to reach the pass-through the wall connection and stay a good distance away from your ceiling might be an option. 

To be the best help, we need more info.

[Ginger Squirrel]

I know they're kind of stingy on here with where we're allowed to post pics so was not sure if I could post here.  Here's a pic of the area, don't mind the mess, turning into a multi trade job lol.  Recently moved the garden hose out of that area, and also had to move 2 light fixtures.  I also need to move those ethernet cables, they feed the jack on the right which I'll just cover over. Don't need it now that the stove is going there. 

Cement block is not combustible, I'd parge and leave that as the finish wall in that area if possible, no other cover needed. The description of wall and ceiling protection sounded like you were not reading or not understanding the need for that 1" space to be freely venting. There is a drawing in the area of where those clearance reductions were, review that section.

It's not insulated so it will be a heat loss.  I will want to insulate and cover that.  Rest of wall is insulated but I made that opening for the chimney will go.

For the floor, it's drycore (wood) but I laid down cement board and will be tiling over that.  I just want to do ceiling first so I'm not working over new tile.  

[Ginger Squirrel]

(double post, delete)

[KEC]

I'll not try to advise on this installation, but I have a heat shield between my furnace flue and floor joists above and above the wood stove flue pipe and the floor joists above. One is a piece of aluminum flashing, the other is sheet steel. My annual cleaning process includes taking the shields down and washing them to remove all dust and vacuming the  area all around by the joists. Dust is combustable and clean metal disperses heat better.

[Don P]

Do you have the woodstove and install instructions for it? If so there should be tables and sketches of clearances. If not it defaults to what is in 211.

Looking at that, the ceiling is covered by 5/8 drywall or cement board,  then a 1" air space, then metal, inulated panel, whatever. Then 18" minimum clearance, then the pipe is going thru the third block down, leaving 8" to combustibles below the pipe, check the Selkirk manual for their exit instructions. There is a thru the wall kit and instructions for it.

[Ginger Squirrel]

Yeah I have it, and it will be installed accordingly.  I don't remember the distances off top of my head but when the installer was here he figured out how big I need to make the pad and where the pipe will go approximately (will depend on where the rafters are in the soffits). I also have the through wall kit.  I imagine doing the 2 45 degree elbows as mentioned will be the best bet as far as pipe goes. 

Just double checked manual:  (located here if curious: 15-W06 WITH BLOWER | Installation & user manual | Englander) 

For pipe to ceiling it does look like they call for 18" as mentioned.

Corner of stove to wall is 5" for corner installation. 18" in front for floor protection. 

I assume these distances are to the wall itself, and not to the heat shield right? As the heat shield will extend 1" out.

[Don P]

Words are very important here. I believe it will say "to combustibles" which is the ceiling joists or the wall studs. That is not the face of the drywall or the heat shield... but it depends on how it reads exactly.

[Ginger Squirrel]

That's a good point, I keep interpreting that as to "anything" but I guess it can be closer to non combustibles such as the shield itself.