tearing roxul up and using it to insulate the entire length of the flue?

[ozibit juice]

Hi, does this sound like it could work? i'll give you a little info on my situation first

i'm going to install a 5.5" liner in my 20' chimney.
there is not enough room for a insulation wrap. as is, the 5.5" will be slightly touching two sides of the chimney wall. I live in a remote location that does not have pour down insulation available. getting it shipped up here will cost at $100-200 per bag for a $60 bag of insulation.....so yeah.

I have lots of Roxul rock wool left over from home renovations, would it be a reasonable idea to tear it up into small pieces and simply pour/drop it down the sides of the liner? i am already planning on using it along with a sheet metal block off plate below so their will be something for the roxul to rest on as i pour it in the chimney.

Thoughts?

 

[oconnor]

The base material in roxul would be fine but roxul isn't the right product for this job. When it gets heated to high temps the binders in the product will off gas and it will stink. It's only meant to slow fire spread in a wall not to be constantly exposed to flue liner temps.

 

[xtrordinair]

if you tear it up small enough maybe.what about vermiculite do you have access to that .I have done quite a few chimney liners with good results

 

[ozibit juice]

i've heard about vermiculite and perlite, where would i get them from? it seems that only garden stores have perlite but i don't think that is the same as regular perlite?

 

[aaron1]

Would this home depot planting-style vermiculite work?

 

[xtrordinair]

search the web or your local hearth store .I cant remember the grade off the top of my head .I can look tomorrow when i get to work and post it up for you.

 

[PLAYS WITH FIRE]

That is what I did. I was going to use pour in but decided not to. I used my sweep rods to pack in place to keep my liner straight. It seems to work ok and have never had a oder from it and my liner seems pretty straight. If it's what you got, use it.

 

[oconnor]

The problem is guys that it's just not an approved use of the product. We all go thru great lengths to ensure our stoves are installed to code and that we follow instructions about clearances, but then we shove a product that isn't tested for exposure to routine 1200f temps down our chimneys. It makes zero sense to me.

 

[PLAYS WITH FIRE]

There many folks here including myself with Roxul stuffed in their smoke shelves. They have not had problems....both Roxul and the blankets are rated for 2100+ temps, you are right. It does not say it's specifically used for this so to each their own. I've had mine this way for almost 2 years with no ill effects so, for me, it's ok.

(broken link removed to http://www.roxul.com/files/RX-NA_EN/pdf/Technical%20Data%20Sheets-%20updated/COMFORTBATT_CDAwithSS.pdf)

(broken link removed to http://www.chimneylinerdepot.com/articles-2/chimney-liner-articles/chimney-insulation/)

 

[oconnor]

Roxul isn't rated for 2100f temps. Basalt rock wool melts at that temp. Ceramic wool blankets are actually tested at that temp, as are the loose fill insulations like perlite. The testing roxul goes through is a fire stop test in a built wall.

Also keep in mind that in order for a chimney to meet code, the liner needs to be installed according to the manufacturers instructions. That means that the only technically correct way to insulate it is the way the manufacturer had it tested during compliance testing.

I too used roxul as my lower block off plate. It works, but has discoloured significantly were it is in contact with the flue. If I had a chimney fire, I would expect to need to replace it as it would likely be melted where it was in contact with the liner.

It could be an interesting mess around a liner packed with rock wool after a chimney fire. The approved methods would stand up to the incident and only need an inspection of the liner for integrity.

Just some things to think about.

 

[PLAYS WITH FIRE]

I think if it got hot enough to melt the Roxul, you'd have more problems than just melted Roxul, maybe....

 

[mellow]

ROXUL® products are stone wool insulations made from basalt
rock and slag. This combination results in a non-combustible
product with a melting point of approximately 2150°F
(1177°C), which gives it excellent fire resistance properties.

(broken link removed to http://www.roxul.com/files/RX-NA_EN/pdf/Technical%20Data%20Sheets-%20updated/COMFORTBATT-USAwithSS.pdf)

 

[BrotherBart]

Roxul isn't rated for 2100f temps. Basalt rock wool melts at that temp. Ceramic wool blankets are actually tested at that temp, as are the loose fill insulations like perlite. The testing roxul goes through is a fire stop test in a built wall.

Also keep in mind that in order for a chimney to meet code, the liner needs to be installed according to the manufacturers instructions. That means that the only technically correct way to insulate it is the way the manufacturer had it tested during compliance testing.

I too used roxul as my lower block off plate. It works, but has discoloured significantly were it is in contact with the flue. If I had a chimney fire, I would expect to need to replace it as it would likely be melted where it was in contact with the liner.

It could be an interesting mess around a liner packed with rock wool after a chimney fire. The approved methods would stand up to the incident and only need an inspection of the liner for integrity.

Just some things to think about.

The minute you put a cap or insert adapter on a liner that isn't from the same manufacturer you are not code or warranty compliant either. Your house and stove will melt before that Roxul does.

 

[oconnor]

ROXUL® products are stone wool insulations made from basalt
rock and slag. This combination results in a non-combustible
product with a melting point of approximately 2150°F
(1177°C), which gives it excellent fire resistance properties.

(broken link removed to http://www.roxul.com/files/RX-NA_EN/pdf/Technical%20Data%20Sheets-%20updated/COMFORTBATT-USAwithSS.pdf)

I've been around this bouy before, and you don't have to agree with me. The details you quoted are under the general description, not the specs for the product. There are mineral wool products designed for insulating chimneys, and they are tested in the applications they are advertised for - none of them are available in USA or Canada - most are sold in the EU.

Here is the details on a Roxul product (Enerwrap 80) intended for constant exposure to heat - note the difference between melting point and service temperature.

Properties

• Fire resistance properties, non-combustible
• Designed for high temperature applications
• Melting point of approximately 2150°F (1177°C)
• Service temperature of 1200°F (650°C)
• Lightweight and flexible
• Can be fabricated and laminated
• Excellent thermal resistance
• Water repellent yet vapor permeable material

In my opinion, you should not use an untested product around a flue liner.

If you are curious, call Roxul (1-855-876-3755) and tell them you want to use COMFORTBATT in constant exposure to 1200*F temperatures, and see what they recommend. Let me know what they say.

 

[oconnor]

The minute you put a cap or insert adapter on a liner that isn't from the same manufacturer you are not code or warranty compliant either. Your house and stove will melt before that Roxul does.

Both statements may be true, that doesn't make a Roxul product the right product to insulate a flue.

BB, what clearance reductions is a user going to get when they stuff Roxul down the gaps with chimney rods? How much will they need to use to get a benefit from their effort?

When they use a tested product, they get answers to these questions. When they do their own thing, they are on their own - which is ok when they have the details and knowledge to make the risk vs reward decision. That is why I pass on these details.

 

[mellow]

I personally wouldn't use it to insulate mine. I used a wrap specifically made for my application, so I can understand where you are coming from.

What I don't get is the discoloration you say happened to your Roxul, I have had Comfortbatt as a soft block off plate for a couple years now and it looks the same as day one and it is all around my flex liner the first few feet from the insert which receives the most heat.

What I do find interesting in the MSDS for the Roxul comfortbatt is this statement:

10.3 Thermal decomposition products:
Primary combustion products of the cured urea extended phenolic formaldehyde binder, when heated above 390 °F (200 °C), are carbon monoxide, carbon dioxide, ammonia, water and trace amounts of formaldehyde. Other undetermined compounds could be released in trace quantities. Emission usually only occurs during the first heating. The released gases may be irritating to the eyes, nose and throat during initial heat-up. Use appropriate respirators (air supplied) particularly in tightly confined or poorly ventilated areas during initial heat-up.

To me that reads that it is OK to use in continuous heat applications, but they do not give that number in writing.

I do agree that you need to use something that is tested for this purpose, would it work, more than likely if you are in a pinch.

 

[oconnor]

Mellow - The MSDS is for all Roxul products, so it would include those intended for constant heating. It wouldn't include the technical details for applications. That's the frustration with engineering documents, you almost need to be an engineer to sort thru them. (Disclamer - I'm not an engineer, but spent a lot of time as a testing officer in the Air Force reading these damned documents)

 

[mellow]

That is a good point. It was a pain just to find the MSDS.

I do agree after one chimney fire the Roxul would need to be removed. Not sure how much of a pain that would be as I have not been able to get the stuff hot enough to melt.

 

[ozibit juice]

good discussion, what i'm hearing is that roxul is not specifically made for this application and that it's anybodies guess as to the value if will provide by doing it this way. but on the other hand it will provide an unorthodox way to insulate the chimney and there is not much safety concerns with the exception being of temporary off gassing during the first little while?

I honestly would use something like perlite or vermiculite if i could get my hands on some here. or maybe just dont bother insulating?

 

[aaron1]

My chimney liner supplier emailed me and said "You can use Thermix or any vermiculite based insulation is acceptable for use with our product." when I asked about how I should insulate it. What vermiculite-based insulations are there available? Just plain old bags of vermiculite?

 

[Brian26]

I had a ton of extra Roxul leftover from when I did my block off plate. I decided recently before even reading on here about the topic to stuff the extra around my liner from the bottom and top. The whole liner is packed tightly with it now. I had a 6 inch uninsulated liner in a 7 by 13 exterior flue. I had great draft and was burning quite clean in the uninsulated liner after inspections. The Roxul that was above the stove in my block off plate and touching my liner looked like the day I put it there.

I know it's not to code per say but I have had great results. I just went up and did a cleaning and inspection as it was mild here in CT this weekend before the cold comes back. Drastically cleaner liner than without the Roxul stuffed in. Especially at the top. Not sure if its related but I seem to get much better secondary burning as well. I have definitely noticed a big improvement. This is with a Drolet 1800 insert.

Do it at your own risk as I know its not approved but I had great results so far. Its also cheap. I still have a ton of the $40 bag of Roxul leftover.

 

[tcassavaugh]

sometimes you got to make do with what you have. living in a remote area surely has offered some challenges that you have had to improvise on. this sounds like it might qualify for one of those instances.

 

[Snotrocket]

The problem is guys that it's just not an approved use of the product. We all go thru great lengths to ensure our stoves are installed to code and that we follow instructions about clearances, but then we shove a product that isn't tested for exposure to routine 1200f temps down our chimneys. It makes zero sense to me.

If your flu temps are regularly 1200F you're doing something seriously, seriously wrong. Like burning gasoline in your stove.

The roxul will be more than fine insulating your liner.

 

[branchburner]

i've heard about vermiculite and perlite, where would i get them from? it seems that only garden stores have perlite but i don't think that is the same as regular perlite?

This thread is a few weeks old now, but if you are still looking: big bags of perlite are often sold (or can be ordered) by masonry supply houses. The stuff is dirt cheap.

Bear in mind, you will still be in the same situation that Brent spoke of, with a technically unnapproved insulation, but I believe with a better one. In stuffing bits of rock wool down, they are sure to be unevenly spaced, leaving an uneven distribution of liner/insulation contact. (if you do use perlite, you will still want a dense plug of rockwool above the blockoff to help ensure the perlite never sifts down through.)

From a safety point of view, if a liner is within an existing clay tile that is sound and to code, I think there are many acceptable options to improve draft and reduce creosote by insulating. The liner/insulation is being installed to improve stove performance, not to meet minimum safety requirements. But if the liner is put in because it is required to bring a flawed chimney and/or clay tile up to code, I would insulate strictly by the book with an approved application.

 

[rkofler]

I also decided to stuff roxul down from the top. Used a piece of wood to pack it in. I am definitely noticing a difference in heat output, and keeping the stove warmer, longer. Or maybe it's all in my head...