Insulating a flue

[Wood Scrounge]

I have a fireplace insert that has a 6” flex SS pipe running up through the large masonry chimney. It currently has a steel plate with rock wool I made up, laying where the fireplace damper used to sit. This has worked well, but when I clean the flue pipe I have to take the plate out and then put it back in. It’s such a tight fit that the process is very cumbersome and time consuming. I was thinking about taking the plate out and putting something at the top of the chimney around the flue pipe, my problem is rock wool is very expensive and I really can’t afford it right now. Someone mentioned that plain yellow fiberglass insulation won’t melt to over 1000 degrees. Does anyone know if that is true? Or have any other ideas that don’t involve big money?

 

[Wood Scrounge]

I found this chart from here: http://www.engineeringtoolbox.com/insulation-temperatures-d_922.html

if Fiberglass can handle 1000 degrees it should be fine at the top of my chimney. being that the flue pipe thermometer never has gone above 500, or am I missing something, is this a question for my local fire department?

 

[CrappieKeith]

Please do not use fiberglass insulation. Ijust talked to a fireman who just put out a house fire...single wall pipe torched the insulation and started studs on fire.

 

[Wood Scrounge]

well I don't understand how, but I guess I was right to be cautious

 

[Wife'nHubby]

I have a fireplace insert that has a 6” flex SS pipe running up through the large masonry chimney. It currently has a steel plate with rock wool I made up, laying where the fireplace damper used to sit. This has worked well, but when I clean the flue pipe I have to take the plate out and then put it back in. It’s such a tight fit that the process is very cumbersome and time consuming. I was thinking about taking the plate out and putting something at the top of the chimney around the flue pipe, my problem is rock wool is very expensive and I really can’t afford it right now. Someone mentioned that plain yellow fiberglass insulation won’t melt to over 1000 degrees. Does anyone know if that is true? Or have any other ideas that don’t involve big money?

I'm not understanding why you have to remove the plate. Are you talking about a block off plate? Does your liner go from your stove all the way up to the top of your chimney?

Regarding the type of insulation to use: No, fiberglass is not correct. Check with your stove shop for the proper insulation.

Shari

 

[Wood Scrounge]

on the back of the insert is a 45 that connects to the SS flex pipe, I had made a steel plate to block the air going up the chimney and attached rock wool to the plate. The problem is when I clean that flue I have to slide the insert out a few inches in order to disconnect the 45 from the insert. The plate will not allow me to slide it out so I have to take it out (major pain to put it back).

Rock wool is the correct insulation it costs quite a bit of money, and I am poor right now.

 

[Wife'nHubby]

on the back of the insert is a 45 that connects to the SS flex pipe, I had made a steel plate to block the air going up the chimney and attached rock wool to the plate. The problem is when I clean that flue I have to slide the insert out a few inches in order to disconnect the 45 from the insert. The plate will not allow me to slide it out so I have to take it out (major pain to put it back).

Rock wool is the correct insulation it costs quite a bit of money, and I am poor right now.

Unless your stove design allows cleaning the chimney from the interior of the stove then your process is just the nature of the beast as they say unless you can speak to a stove installer to determine an easier way to clean. BTW Good to hear you ARE cleaning!

Not to chagrin anyone, but that's why we went with a free standing stove, hearth mounted, and verified how to clean the chimney with stove in place before we purchased.

Shari

 

[Wood Scrounge]

if I wasn't dealing with that plate it would be a piece of cake.
I found a guy that has Rock Wool for $65, still think it's steep but if it saves me from the grief it will be well spent.

 

[wapacz]

I guess the question is how much you need. It seems you can buy some higher end stuff in small quantities off the net.

 

[pook]

if I wasn't dealing with that plate it would be a piece of cake.
I found a guy that has Rock Wool for $65, still think it's steep but if it saves me from the grief it will be well spent.

check for "binders" in the kwool & rated temps for application + get more opines about fglass.
Around 1980, I built a furnace from a cast iron tub so to burn 4' slabs without cutting. After experimenting to get it to burn right, I covered the tub with fglass. The binders in the fglass stunk but evaporated off eventually. The tub would glowed orange hot under the fglass. The fglass turned to glasslike but never burned----the tub cracked eventually so I took it back to the dump.

My inverted tub/slab burner had a pipe fitted into the drain which extended into the tub to where the exhaust hole was. At its hot/sweet spot , the end of the pipe looked like a flamethrower as the woodgas was combined with the secondary air from the pipe.

 

[CrappieKeith]

check for "binders" in the kwool & rated temps for application + get more opines about fglass.
Around 1980, I built a furnace from a cast iron tub so to burn 4' slabs without cutting. After experimenting to get it to burn right, I covered the tub with fglass. The binders in the fglass stunk but evaporated off eventually. The tub would glowed orange hot under the fglass. The fglass turned to glasslike but never burned----the tub cracked eventually so I took it back to the dump.

My inverted tub/slab burner had a pipe fitted into the drain which extended into the tub to where the exhaust hole was. At its hot/sweet spot , the end of the pipe looked like a flamethrower as the woodgas was combined with the secondary air from the pipe.

TO ALL: After reading much of the information provided by Pook above, it seems to be misinformed and even dangerous in some cases. Please disregard any posts made by him before this post. I have informed him and will inform you all, if you are giving out bad information knowingly you will be banned from this site and if somebody gets hurt by your poor information, you could be personally liable. This could include jail time or be at the very least financially liable. You are personally liable for anything you say on here or any other website!!! Since there seems to be so many posts with poor/dangerous information, I feel it has to be on purpose as nobody can believe many of the things that have been said, which includes the poster.
Thanks!!! Have a Happy, warm Holiday to everyone!! Also, Thanks to all that try to help others on here and have a genuine interest in making this a site full of good/useful information.
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[Phil_Marino]

Please do not use fiberglass insulation. Ijust talked to a fireman who just put out a house fire...single wall pipe torched the insulation and started studs on fire.

I'm not sure what you mean by "torched" the insulation. But, assuming you're smart enough not to use insulation with attached paper, fiberglass insulation will not burn. Glass is essentially melted sand.

And, it won't even melt until you get to about 2500F. ( close to the melting point of steel).

Phil

 

[Wood Scrounge]

I'm not sure what you mean by "torched" the insulation. But, assuming you're smart enough not to use insulation with attached paper, fiberglass insulation will not burn. Glass is essentially melted sand.

And, it won't even melt until you get to about 2500F. ( close to the melting point of steel).

Phil

I agree the numbers seem to say it would be ok, but I have enough people telling me it's wrong including the local fire chief, I will err on the side of caution.

my thinking is there may be other chemicals on the glass (why is one pink and one yellow) but I really don't know I will use the rock wool (rotten cotton, Mineral wool).