Thread: Wood stove installaion

Question for anyone that can help answer this. I found fiberglass insulation installed in the flue of the chimney around the 4 in flue pipe for a wood stove. Used to block the draft from putting the metal flue up the chimney. You can see it from looking up the flue from inside the house. This is regular insulation for walls that does not have a paper vapor barrier. I don't normally see this. Most of the time i see a sheet metal cover or foil backed insulation to draftproof the chimney. The stove store that installed it says it is ok because fiberglass insulation is not a fire hazard. Any comments would be appreciated.
thanks
Mark N

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Do you have pics? This sound confusing. Are you talking about an insert woodstove installed into an open hearth fireplace? I'm trying to figure out why anyone would pack fiberglass around a solid fuel stovepipe or chimney. Also, what kind of stove takes only a 4" pipe? Most are 6 or 8"
Thx,
Bob

Yes Bob It is a open hearth fireplace with a wood stove insert. I can see around the insert and the insulation is around where the fireplace damper would be. And it is a 6IN flue pipe. I don't have any pictures. I recommended it to be further evaluated by a licensed Fireplace/Stove contractor. But I recieve a email from the installer that fiberglass insulation does not burn and this installition is ok. I find this hard to believe and would like further information on it.
Thank you
Mark N

Fiberglass should not be in contact with hot metal, so if that is the case here, then there may be some serious fire hazards in your area. Talk to a chimney specialist about this.

Fiberglass is an extremely poor "draft stopper also", it really needs some sort of metal stop installed, taking in to consideration it's location to combustible materials.

Sounds like you are talking about fireblocking. Fiberglass insulation is an approve fireblocking material between for fireplaces.

R1003.19 Chimney fireblocking.

All spaces between chimneys
and floors and ceilings through which chimneys pass shall
be fireblocked with noncombustible material securely fastened
in place. The fireblocking of spaces between chimneys and
wood joists, beams or headers shall be self-supporting or be
placed on strips of metal or metal lath laid across the spaces
between combustible material and the chimney.

R602.8.1.1 Unfaced fiberglass.

Unfaced fiberglass batt
insulation used as fireblocking shall fill the entire cross
section of the wall cavity to a minimum height of 16
inches (406 mm) measured vertically. When piping, conduit
or similar obstructions are encountered, the insulation
shall be packed tightly around the obstruction.

Originally Posted by Wayne Carlisle

Sounds like you are talking about fireblocking. Fiberglass insulation is an approve fireblocking material between for fireplaces.


R1003.19 Chimney fireblocking.

Wayne,

You left out one critical aspect for the above, and that is:
SECTION R1003
MASONRY CHIMNEYS

That section is dealing with *masonry* chimneys and fireblocking between the masonry chimney and framing, not between a flue/vent and the chimney.

Yep but 602.8 #5 refers you to R1003.19 Chimney fireblocking which (602.8 #5) does not specify masonry metal or whatever. It just says that fiberglass insulation is an approved barrier.

5. For the fireblocking of chimneys and fireplaces, see Section
R1003.19.

So in my opinion any fireplace chimney or whatever follows these specifications even though the specific section is for masonry.

Wayne,

You are missing the point, though.

Originally Posted by Wayne Carlisle

So in my opinion any fireplace chimney or whatever follows these specifications even though the specific section is for masonry.

(red text is mine)

Originally Posted by Wayne Carlisle

R1003.19 Chimney fireblocking.

All spaces between chimneysand floors and ceilings through which chimneys pass shall be fireblocked with noncombustible material securely fastened in place. The fireblocking of spaces between chimneys and wood joists, beams or headers shall be self-supporting or be placed on strips of metal or metal lath laid across the spaces between combustible material and the chimney.

What point are you trying to make? Even with the red text I don't know what you are trying to say.

Are you saying that insulation is not allowed as a fire blocking?

Spell it out. I'm just a dumb ol' country boy here.

What I'm saying is that what is under discussion was fiberglass insulation in contact with the METAL flue/vent/chimney which went up inside some other chimney (masonry? don't know), whereas that section is referring to fireblocking OUTSIDE that other chimney in the spaces between the masonry (other) chimney and the framing ... you know, that required 2" clearance to combustible material around the masonry chimney.

The SPACE BETWEEN the OUTSIDE OF the masonry chimney AND THE framing around it but which is not touching it.

I know what you are saying now. You are saying that the problem is that the original post was questioning the use of fiberglass insulation up against the metal flue pipe.

These types of installations are under the mechanical code.

M1801.9 Fireblocking.

Vent and chimney installations shall
be fireblocked in accordance with Section R602.8. which allows fiberglass insulation for fireblocking. Which is what I originally posted.

So in my opinion the fiberglass insulation touching the metal pipe is okay.

If you are saying that you can't use fiberglass insulation as a fireblock and that it cannot touch the metal flue then please provide a section of the code disallowing it.

From what I read it's okay.

What is the problem with the insulation being against the metal flue? As long as it is secured...no problem.

Just my opinion.

Originally Posted by Wayne Carlisle

I know what you are saying now. You are saying that the problem is that the original post was questioning the use of fiberglass insulation up against the metal flue pipe.

These types of installations are under the mechanical code.


M1801.9 Fireblocking.

Vent and chimney installations shall

be fireblocked in accordance with Section R602.8. which allows fiberglass insulation for fireblocking. Which is what I originally posted.

So in my opinion the fiberglass insulation touching the metal pipe is okay.

That is what I am saying is not okay.

First and foremost the vent is required to be installed in accordance with its manufacturer's installation instructions:

From the 2006 IRC. (underlining is mine)

M1803.3 Installation.

Vent and chimney connectors shall be installed in accordance with the manufacturer’s installation instructions and within the space where the appliance is located. Appliances shall be located as close as practical to the vent or chimney. Connectors shall be as short and straight as possible and installed with a slope of not less than 1/4 inch (6 mm) rise per foot of run. Connectors shall be securely supported and joints shall be fastened with sheet metal screws or rivets. Devices that obstruct the flow of flue gases shall not be installed in a connector unless listed and labeled or approved for such installations.

The installation instructions require clearance to combustibles AND insulation.

R602.8 Fireblocking required.

Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space. Fireblocking shall be provided in wood-frame construction in the following locations.

- 4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion.

"with an approved material"

Now go back to the installation instructions to find out what material is approved for that fireblocking.

Where does it say AND insulation? Maybe in the installation instructions? Maybe...maybe not.

So to say that insulation can't touch the metal flue is just an assumption.

The code allows it because it is not combustionable.

I had a wood burning insert installed in my fireplace; large masonry with fire brick, tile flue, working fireplace, 20-30 years ago. I used it to heat the house for over 15 years with the oil furnace only as backup.

When it was installed fiberglass insulation was packed in to seal the opening between the short 6" X 10 X 12" metal stack that went up from the top of the insert into the bottom of the smoke chamber. After 5 years of using the insert I removed it from the fireplace to clean out the smoke shelf. The insulation was only slightly melted at the contact point to the metal. It was still sealing as no smoke was being drawn into the room by the fan.

When I put the insert back in I did fabricate a metal pan to seal the opening which leaked smoke until several attempts were made with furnace cement and hi temp sealants.

My point is the fiberglass worked well and was confined inside a fireplace. If it had ignited it was contained in a 'fireplace' and the worst would be a small amount of smoke sucked back into the house by the fan, which did not happen.

Not saying fiberglass is the best material, just that it did work in my case with no problem.

Originally Posted by Wayne Carlisle

Where does it say AND insulation? Maybe in the installation instructions? Maybe...maybe not.

So to say that insulation can't touch the metal flue is just an assumption.

The code allows it because it is not combustionable.

Wayne,

You have apparently not been following what I've been stating, which is it needs to meet the manufacturer's installation instructions.

Originally Posted by Jerry Peck

Now go back to the installation instructions to find out what material is approved for that fireblocking.

Originally Posted by Wayne Carlisle

If you are saying that you can't use fiberglass insulation as a fireblock and that it cannot touch the metal flue then please provide a section of the code disallowing it.

Now keep in mind that this is from a Type B Gas Vent installation instructions and the post was about a wood stove insert which will (obviously) have different installation instructions - regardless, though, it is up to what is in the installation instructions and this one answers your last quote above: THE CODE SECTION requires installation in accordance with the manufacturer's installation instructions, which, by reference, become code, so here is that CODE SECTION:

(red text is mine)
ROUND AMERIVENT® TYPE B GAS VENT
- 13.Portions of gas vents that may extend through accessible spaces are to be enclosed to:
- - a.Maintain the one (1) inch minimum airspace clearance.
- - b. Avoid personal contact with the vent.
- - c. Avoid damage to the vent.
- IMPORTANT: The enclosure must provide a minimum of one (1) inch airspace to all combustible material and building insulation. Refer to section 2, page 10 for Type B 2x4 and BW clearances.
(yes, the text is one size larger and bold in the installation instructions)

Jerry, I'm following you perfectly. I know the code states per manufactuers installation requirements. However I have yet to find any that require clearances from insulation used as firestop...only clearances from combustionables. Fiberglass insulation without any vapor barrier on it is noncombustionable. Which is also allowed to be used as a firestop.

The proof is how long it took you to find an installation procedure that mentioned clearances from insulation. I even googled the vent you posted the information on and came up with several installation topics. The one I looked at had no mention distances from insulation...just combustionables.

The section you pasted deals with building insulation. This refers to insulation that has a vapor barrier (paper) that is combustionable that is installed as building insulation in the attic or walls. I agree that insulation with a vapor barrier needs to be 1" away as required by the code. The insulation used for firestopping is not being used as building insulation.

REASON FOR EDIT.....To make note that I didn't intentionally make this font big and want to edit it but may take longer to edit than befort you read it.

Here's the link and information. No where does it mention clearances from insulation
http://www.americanmetalproducts.com/vent/amerivent/803900%20Type%20B%20Gas%20Vent%20Catalog%20-%20Edition%203.pdf

Clearances

Underwriters’ Laboratories-listed Minimum Clearance to Combustibles
AmeriVent Description Type Minimum Clearance
4" Oval BW Clearances as determined by use of 40HD hold-down
(when installed in 2x4 stud wall plate, 40PS ceiling plate spacers, and 40FS
with recessed heater) firestop spacers
4" and 5" Oval B-2x4 Clearance as determined by use of firestop spacers at
(when installed in 2x4 stud wall each ceiling level

with

other thanrecessed heater)

4", 5", and 6" Oval B 1"
3" through 30" Round B 1"

Again I know this is a wood stove and may have different installation procedures but I haven't found one yet that will not allow insulation as a fire stop.

(red text is mine)

Originally Posted by Wayne Carlisle

Jerry, I'm following you perfectly. I know the code states per manufactuers installation requirements. However I have yet to find any that require clearances from insulation used as firestop...only clearances from combustionables.

Wayne,

Did you read my post above?

Originally Posted by Jerry Peck

(red text is mine)
ROUND AMERIVENT® TYPE B GAS VENT
- 13.Portions of gas vents that may extend through accessible spaces are to be enclosed to:
- - a.Maintain the one (1) inch minimum airspace clearance.
- - b. Avoid personal contact with the vent.
- - c. Avoid damage to the vent.
- IMPORTANT: The enclosure must provide a minimum of one (1) inch airspace to all combustible material and building insulation. Refer to section 2, page 10 for Type B 2x4 and BW clearances.
(yes, the text is one size larger and bold in the installation instructions)

It says right in those installation instructions (which ARE CODE BY REFERENCE):

IMPORTANT: The enclosure must provide a minimum of one (1) inch airspace to all combustible material and building insulation.

What is it you do not understand about that?

Those vents ARE NOT ALLOWED to have ANY insulation around them and/or touching them.

Bob H., I am sure you can explain it much better than I am - are you out there?

Jerry what is it that you don't understand?

This is not building insulation.

Originally Posted by Wayne Carlisle

This is not building insulation.

Then what is it? Building .... ?

Insulation, for whatever use and purpose, is not allowed to be installed within that 1" clearance space around a vent. That is why they have other firestops.

The code even acknowledges that in that section you keep referring to:

Originally Posted by Jerry Peck

R602.8 Fireblocking required.

Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space. Fireblocking shall be provided in wood-frame construction in the following locations.

- 4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion.

"with an approved material"

Now go back to the installation instructions to find out what material is approved for that fireblocking.

What is it that you do not understand that not all types of fireblocking is allowed to be used in all installations?

Originally Posted by Jerry Peck

Then what is it? Building .... ?

[/left]

Firestop, which the code allows.

Originally Posted by Jerry Peck

The code even acknowledges that in that section you keep referring to:

R602.8 Fireblocking required.

Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space. Fireblocking shall be provided in wood-frame construction in the following locations.

- 4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion.

"with an approved material"

What is it that you do not understand that not all types of fireblocking is allowed to be used in all installations?
[/left]

"with an approved material"

R602.8.1.1 Unfaced fiberglass.

Unfaced fiberglass batt
insulation used as fireblocking shall fill the entire cross
section of the wall cavity to a minimum height of 16
inches (406 mm) measured vertically. When piping, conduit
or similar obstructions are encountered, the insulation
shall be packed tightly around the obstruction.

Wake up Jerry and accept it. You are wrong on this one!

Originally Posted by Jerry Peck

Then what is it? Building .... ?

Originally Posted by Wayne Carlisle

Firestop, which the code allows.

ONLY IF IT IS ALLOWED BY THE MANUFACTURER'S INSTALLATION INSTRUCTIONS.

Originally Posted by Jerry Peck

The code even acknowledges that in that section you keep referring to:

R602.8 Fireblocking required.

Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space. Fireblocking shall be provided in wood-frame construction in the following locations.

- 4. At openings around vents, pipes, ducts, cables and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion.

"with an approved material"

Now go back to the installation instructions to find out what material is approved for that fireblocking.

Originally Posted by Wayne Carlisle

"with an approved material"




R602.8.1.1 Unfaced fiberglass.

Unfaced fiberglass batt

insulation used as fireblocking shall fill the entire cross
section of the wall cavity to a minimum height of 16
inches (406 mm) measured vertically. When piping, conduit
or similar obstructions are encountered, the insulation
shall be packed tightly around the obstruction.

Wake up Jerry and accept it. You are wrong on this one!

Wayne,

Quite incorrect, you are the one who is wrong, so wake up and stop sleep walking.

"When piping, conduit or similar obstructions are encountered, the insulation shall be packed tightly around the obstruction"

A VENT ... IS NOT a "or similar obstructions" to piping or conduit.

You are way off base in your thinking.

"Approved material" would be "approved as provided for in the manufacturer's installation instructions".

Putting insulation ... OF ANY TYPE ... around a vent IS NOT A GOOD THING, nor is it allowed or approved UNLESS SO STATED *in the manufacturer's installation instructions.

It all gets back to the CODE and the code requiring the vents to be installed in accordance with their installation instructions.

I can see that you believe that you are right.

Well in my opinion I am right so go ahead and take the last word. I'll let you have it. I'm not going to reply to anymore of your comments on this subject. We will have to agree to disagree on this one.

I'll look forward to the next discussion where you and I disagree.

Originally Posted by Wayne Carlisle

I can see that you believe that you are right.

Well in my opinion I am right so go ahead and take the last word. I'll let you have it. I'm not going to reply to anymore of your comments on this subject. We will have to agree to disagree on this one.

I'll look forward to the next discussion where you and I disagree.

Are you disagreeing that the installation instructions rule unless the code is MORE restrictive?

That's just basic first day Code Class 101 stuff.

Wow! This has been fun to follow.

Back to basics guys: This is a masonry fireplace and chimney with an insert woodstove installed with either a chimney connector to the first flue tile or a full length liner. We don't know any more than this. We don't know if it is a listed liner, unlisted liner, stovepipe or what. What we are told is that it is contained inside the fireplace and chimney. All your discussion about firestopping and fireblocking applies to the exterior of the chimney. There should be a 1" clearance around exterior chimneys/ 2" clearance around interior chimneys, both with firestopping and fireblocking around the exterior of the chimney per the code.
Now, as to this insert, the code does not really anticipate this condition. You normally are concerned about insulation invading stated clearances for air cooling. Fiberglass insulation is a grey area. It cannot pass ASTM E-136 but it would probably pass the other parts of the NFPA definitions concerning "combustible" versus "noncombustible" materials. Still, whether combustible or noncombustible, it cannot violate stated clearances.
So, our question boils down to whether or not the connector from an insert stove located inside the firebox of a combustion chamber and connected to the chimney would present a problem or not. Personally, this is the most common way these stoves are installed in the US .......if you get anything at all blocking off around the damper opening. Back in the early 80s there were some systems where sheetmetal was precisely fitted around the connector to a liner such as a Ventinox VDSK (Ventinox Damper Sealing Kit). This was two pieces of sheetmetal that slid around the pipe and was clamped to the damper frame then caulked to seal it.
The biggest problems I see with using fiberglass to pack this gap are:
1) odors
2) air infiltration and exfiltration or not sealing. Aside from cold air, if this insulation is being relied upon to prevent room air from entraining up the stack, it will fail and you will get either exfiltration or possible infiltration with smoke and CO. This can also lead to creosote formation and chimney fires. Also, fiberglass is used to make AC filters so you know it does not stop air flow.

If the insulation has a urea formaldehyde binder, it will offgas and stink. It it gets damp, it can smell like someone urinated on it. It will set off a combustible gas sniffer btw.
It is very hard to get insulation batts packed into place and keep them there. Now, when you cook fiberglass above a few hundred degrees, the binder, regardless of formulation will decompose causing the filaments to collapse and lose shape. Some binders will fuse or calcine into a hard brittle matrix. If you have treated cellulose insulation in contact with moisture, the borax or phosphate salts will leach out leaving the material untreated. You can see the salt trails on firestops and where it dribbles down pipe when this happens.

So, as long as its in the damper frame and not against the side of a chimney or vent, I don't see it as a fire hazard. However, I would still recommend using a sheetmetal plate to block it off and caulk to the throat. Of course, you need to follow the listed instructions for the liner and appliance.
HTH,

Thank you Mr Harper. That was the response i was looking for. It makes very good sense. I will pass this info on to the clients with your permission.
Thanks again
Mark Northrup


And Mr Peck thanks again as always i enjoy the posts that you submit here it makes people think and prove their reasoning not just state it.
And being a serious home inspector i like to know both sides and the facts as they come out of the disscussion.
Cheers

Just ran across this stove hearth information, it's well organized, and I'd like to use it as a basic reference, but though it would be as good idea to ask Bob H., Jerry P. and others to look it over if they have time, to check for significant errors or omissions.

Hearth Design | Hearth Wiki

Michael, a few points. First of all, treat any information you get from that site with a bucket of salt. The site owner has a habit of giving out homespun wisdom that goes against codes and standards especially in his discussion forums.

The article in question relates strictly to floor protection. Several points here:
The issue of stove boards listed to UL1618 has caused the creation of a task force to revise this std. to reflect the difference btw "ember protection" and "thermal protection". Dale Feb sits on that Cmte, which is making progress. Also, previously, floor protection was always stated in terms of k factors. Just recently, we have gotten the mfrs to begin stating their protection requirements in terms of R. This is because building suppliers don't know the k factor of their insulating materials, much less know what a k factor is.

Bottom line is that all installations should be cross-checked against the mfrs. listed instructions and the applicable building codes. Note that NFPA 211 carries the force of law in very few communities. Usually, only in cases where there is a lack of clearly applicable codes that have been adopted into law will a court default to 211.
HTH,
Bob

Thanks. That sort of concern is why I asked.