Uncombustible vs Combustible Walls and Roof Eave Questions

[danieltp]

Hello all,

This is my first post on hearth.com - I have been coming to this website for information, especially when we were looking for a wood stove for our home in Austin, TX. Our house doesn't have any real heating system, and Austin can drop down to 30's during the winter especially nighttime. We finally purchased an used 1993 Jotul FireLight, in an excellent shape. Some threads were also helpful with purchasing chimney pipes and stove pipes - this whole wood stove and pipes research took me a while, but wouldn't be possible without some members' input on this forum. Thank you all.

I have two questions and I hope you guys can help me out here, as I'm having a person come in on December 30th to install and I want to make sure I get the installation done right. He was referred to me from a local wood stove store, but I want double check and make sure things get done the right way...

Our wood stove will be "through a wall" installation (with thimble).

1. My roof eave is approximately 14" or 16" from the wall (it's too high for me to get an accurate measurement). Let's assume that it is 14" - the installer recommended that we put a chimney through the eave instead of getting two 30* elbows. My chimney is double walled, 6" inch with 8" external diameter. Is this normal setup? I can imagine this set up being more straightforward and neater, but my biggest concern is safety. I couldn't find anything about the minimum length of eave allowable for chimney pipe to go through it.

2. The manual book says 18" clearance from the back of stove to combustible wall. I have 12" - 16" adjustable stove pipe and I'd like to have the stove set closer to the wall than 18". If we were to take the drywall off, add 1" ceramic spacer, sheet rock and cover it with tiles. How much closer can I get our Jotul to this wall? Second option is to leave drywall there, and add the same ceramic 1" spacer between drywall and 1/4 steel sheet - would this work as well? Would I be able to bring the stove a bit closer to the wall? We already have some homemade welded steel furnishings in our house and they would go with a steel wall behind the stove nicely. It would be nice to be able to set the stove 12" away from the wall, if possible as Jotul Firelight is BIG.

Danke,

Daniel

 

[Simonkenton]

I am not sure about the code, but I can tell you from practical experience of 20 years with this set up, that if you put a free standing metal heat shield between the stove and the wall that your wall will never get too hot. I have installed 2 stoves with a free standing copper heat shield, it looks good and it protects the wall.

Also, in my current house, I have installed a copper heat shield that is nailed to the wall with 3 inch copper nails, in a fashion that keeps the shield 1 inch away from the wall. Also left a 1 inch air space at the bottom of the heat shield to allow convection air flow. I have run my stove in this fashion for 17 years with no ill effect. This is against a log wall.
You probably can't get any research on the copper heat shield, because copper is expensive and nobody but me uses it, but copper has the effect of reflecting about 99 percent of the heat that strikes it. I have installed a free standing copper heat shield at my mom's house, that stands 3 inches behind her VC Resolute. When that stove is cranking at 600 degrees, you can grasp the shield with your hand, and hold on, and your hand will not be burned! The copper shield feels cool to the touch, it must be about 80 degrees.

Hammered copper heat shield at my house, with my Waterford stove. I laid the copper sheet on a big beam, and hammered every square inch of it with a ball peen hammer. The hammered copper looks good.

 

[begreen]

If you have 14-16" on the overhang then going through it makes sense, or it can be notched and boxed.

How will the connector be routed? Straight up or up and then out the wall? If you use double-wall connector pipe AND the stove has a rear heat shield, then the rear flat wall clearance is 12".

 

[DougA]

#2. If the manual says 18" to combustible, then that is the code. Most stoves have a rear heat shield kit that should reduce that. If not, you can make one as suggested but you should have an inspector check what you are doing. I have no idea how strict they are in your area but our's is very strict and if you are not to code, your insurance is invalid. The easier option that I used on my old stove is to go directly from the stove to SS chimney. That way, the insulated SS chimney can be 1" from combustible which worked perfectly for me.

 

[danieltp]

I am not sure about the code, but I can tell you from practical experience of 20 years with this set up, that if you put a free standing metal heat shield between the stove and the wall that your wall will never get too hot. I have installed 2 stoves with a free standing copper heat shield, it looks good and it protects the wall.

Also, in my current house, I have installed a copper heat shield that is nailed to the wall with 3 inch copper nails, in a fashion that keeps the shield 1 inch away from the wall. Also left a 1 inch air space at the bottom of the heat shield to allow convection air flow. I have run my stove in this fashion for 17 years with no ill effect. This is against a log wall.
You probably can't get any research on the copper heat shield, because copper is expensive and nobody but me uses it, but copper has the effect of reflecting about 99 percent of the heat that strikes it. I have installed a free standing copper heat shield at my mom's house, that stands 3 inches behind her VC Resolute. When that stove is cranking at 600 degrees, you can grasp the shield with your hand, and hold on, and your hand will not be burned! The copper shield feels cool to the touch, it must be about 80 degrees.

Hammered copper heat shield at my house, with my Waterford stove. I laid the copper sheet on a big beam, and hammered every square inch of it with a ball peen hammer. The hammered copper looks good.

The copper heat shield looks good and cozy - I'd consider it if we had more copper furnishings around our living room. We have been using steel to make some fixtures (shelves, lighting fixtures and etc). Steel doesn't have the similar reflector property like Copper does? Correct? I'm going to show this picture to my wife, to give her a better idea what "metal surface" behind the wood stove may look like.

 

[danieltp]

If you have 14-16" on the overhang then going through it makes sense, or it can be notched and boxed.

How will the connector be routed? Straight up or up and then out the wall? If you use double-wall connector pipe AND the stove has a rear heat shield, then the rear flat wall clearance is 12".

View attachment 148616

It's good to know that 14" to 16" is more than enough for the chimney pipe to go through it.

The stove pipe will rise 18", 90* elbow, then 12 - 18 inches adjustable stove pipe that will connect to thimble with an adapter. It will go through the wall, connecting to a tee, then straight up to the top of the roof (through the eave). The chimney stove will be going straight up to the eave, just off the center, where the highest point of roof is. The stove pipes will be single wall pipes. The thimble, adapter, tee and pipes outside will be double walls.

When I bought this stove, it came with 19 ft chimney pipe (Superpro) and I had to stay with its brand for the rest of external SS chimney pipe. I called several places and they said they don't sell Superpro Stove Pipes so I went with Metalbests (SP).

Texas codes aren't too strict and I also called my insurance company about the process of getting the wood stove approved. He told me just to call back and confirm that it has been installed (no inspection needed).

 

[danieltp]

#2. If the manual says 18" to combustible, then that is the code. Most stoves have a rear heat shield kit that should reduce that. If not, you can make one as suggested but you should have an inspector check what you are doing. I have no idea how strict they are in your area but our's is very strict and if you are not to code, your insurance is invalid. The easier option that I used on my old stove is to go directly from the stove to SS chimney. That way, the insulated SS chimney can be 1" from combustible which worked perfectly for me.

I looked for Jotul Firelight Heat Shield a while ago - I couldn't find anything. Do the heat shield has to be specific to a model?

 

[begreen]

It has to be specific to the stove in order to pass UL testing for reducing the clearance. On a cat stove I would go for double-wall pipe to keep the flue gases hotter. But if single-wall then you will need the wall shield to extend above the wall thimble in order to continue the clearance reduction. The wall shield must be open top and bottom by at least an inch so that air can freely convect behind it. The wall shield just needs to be non-combustible. You can use cement board and tile it or sheet metal and leave it raw or paint with BBQ or stove paint.

 

[Simonkenton]

Central Texas, huh? I am in Columbus Texas right now in my 18 wheeler, at 4:30 pm, and it is windy and cold as hell. Good day to fire up a wood stove if you had one around here.

 

[danieltp]

It has to be specific to the stove in order to pass UL testing for reducing the clearance. On a cat stove I would go for double-wall pipe to keep the flue gases hotter. But if single-wall then you will need the wall shield to extend above the wall thimble in order to continue the clearance reduction. The wall shield must be open top and bottom by at least an inch so that air can freely convect behind it. The wall shield just needs to be non-combustible. You can use cement board and tile it or sheet metal and leave it raw or paint with BBQ or stove paint.

I just checked my stovepipes - they're double walled, not single-walled as I originally thought.

Let me clarify on what I can do - I take the drywall out, replace the wall with cement board and cover it with a sheet metal or tiles without 1 inch ceramic spacers - I will be able to push the stove a bit closer to the wall, say 12"? Is this doable?

Or do I have to ADD 1 inch spacers, no matter what?

Thank you for your time and help.

 

[danieltp]

Central Texas, huh? I am in Columbus Texas right now in my 18 wheeler, at 4:30 pm, and it is windy and cold as hell. Good day to fire up a wood stove if you had one around here.

Haha - I'm originally from Pennsylvania and many of my family relatives and friends give me a funny look when I tell them that I'm having a wood stove installed in my house in Austin. Many people don't realize how cold it can get during the night time, especially in the hill country area.

 

[DougA]

Anything directly attached to the wood studs, whether it be cement board or tile will NOT reduce your distance at all. The reason is that the cement boards will transfer all the heat to the combustible wood stud wall.

You need to create at least a 1" barrier of air between the cement board (or shield) and the wood studs that has air openings at the bottom and the top to allow air to circulate between the shield and the wood, then the cooler air will and keep the wood cool enough. Whether the barrier is cement board, copper sheet or painted metal, it is treated as identical under the code as far as I know.
I can't answer your distance question as that is out of my range of knowledge.

Just because something acts as a barrier and it 'feels' cool enough is not good enough. I just had an inspector in last week and he wanted an extra metal shield because one small corner of my stove is not covered by the proper rear heat shield and a small piece of wood trim was 12" away. The owner's manual said I was OK and the IR gun read 90 on the wood trim with a 600 fire going but that was not enough to satisfy him. It took me an hour to fabricate a metal shield and now the inspector is happy and it looks like 'factory made'. Most of the people on the forum will tell you that it's always better to err on the side of safety and caution when doing anything with a wood stove. I am shocked that your insurance company doesn't seem to care that much but what do I know? Each winter there is a house that burns down near us that is caused by a wood stove so I want to make sure my house is not the next one.

 

[Simonkenton]

I am tracking you down, Daniel. I am in Laredo now but will pass through Austin tomorrow afternoon on the way to Dallas. Good God, how I hate to drive I 35 from San Antonio to Dallas. Only road in Texas I don't like.

Yes it can get pretty cold in Texas, that wind whipping down from the Arctic, across Saskatchewan and South Dakota, nothing to stop it but a barbed wire fence before it blows into Texas.

 

[danieltp]

Anything directly attached to the wood studs, whether it be cement board or tile will NOT reduce your distance at all. The reason is that the cement boards will transfer all the heat to the combustible wood stud wall.

You need to create at least a 1" barrier of air between the cement board (or shield) and the wood studs that has air openings at the bottom and the top to allow air to circulate between the shield and the wood, then the cooler air will and keep the wood cool enough. Whether the barrier is cement board, copper sheet or painted metal, it is treated as identical under the code as far as I know.
I can't answer your distance question as that is out of my range of knowledge.

Just because something acts as a barrier and it 'feels' cool enough is not good enough. I just had an inspector in last week and he wanted an extra metal shield because one small corner of my stove is not covered by the proper rear heat shield and a small piece of wood trim was 12" away. The owner's manual said I was OK and the IR gun read 90 on the wood trim with a 600 fire going but that was not enough to satisfy him. It took me an hour to fabricate a metal shield and now the inspector is happy and it looks like 'factory made'. Most of the people on the forum will tell you that it's always better to err on the side of safety and caution when doing anything with a wood stove. I am shocked that your insurance company doesn't seem to care that much but what do I know? Each winter there is a house that burns down near us that is caused by a wood stove so I want to make sure my house is not the next one.

Thank you for clarifying - to make sure everything is safe: I'll take the drywall off, install ceramic spacer, add cement boards (w/ one inch opening on top and bottom), and put a finishing touch on the cement board (tile or steel) and keep the Jotul Firelight stove 18" away from the wall. The Jotul Firelight stove is ivory colored and beautiful - I wouldn't mind having it 6" further out and I'll have peace of mind as I have three children.

As for insurance, I was also surprised. Almost too good to be true. I'll call him again once the installation is done and get this in writing to be safe.

 

[Hogwildz]

Why go through all the tearing down of the drywall? Is that 1/2" really worth the added work?
Leave the drywall up, add your spacers, then your heat shield and be done with it.

 

[Simonkenton]

Mr. hogwildz is correct. Sheet rock doesn't burn too good anyway, just leave it in place and get your 1 inch air space.