Mineral Wool (Roxul) vs. Kaowool for smoke shelf cavity

[Benchwrench]

Hi guys,

back again for another question dealing with my upcoming insert install.

I want to provide a block off plate at the damper area and have a need to know which insulation product should be applied to fill the void stuffed around my liner at the smoke shelf area that will have a blocked off plate cover ?
It seems it will take a fair amount of product, but which insulation is needed?
note: This application needs a fire rated product since it is going to be in direct contact with my liner

Thanks in advance,
Bench

 

[EJL923]

I was looking for the answer to this exact question. I think some will recommend either. I know Roxul isnt rated for it, but many people use it without a hitch. Roxul is more readily available though. I am putting in Roxul. I believe Brotherbart stuffed roxul in up top and down bottom on his liner with no issues. Hopefully he'll chime in.

 

[FyreBug]

I have used Roxul on mine as well and no issues.

 

[Sisu]

I have Roxul at the top and bottom of the fireplace where my insert is installed. No issues at all. Roxul is cheaper, thicker (get a better R-value), and I think is a bit safer to work with (larger respirable fibers vs kaowool's small ceramic fibers).

 

[mhrischuk]

Stuffed mine with Roxul.

 

[joefrompa]

Using Roxul as well as a permeable block-off plate. Prevents alot of air movement.

One of my family members is a real hardcore DIYer. He challenged me one day and pointed out that the melting point of spun-glass (fiberglass) insulation is essentially the same. I.e. He stuffed unfaced insulation around his insulated liner and had no problems even with routinely overfiring his stove to 900 degrees stove top (which he recognized was not good, but he was using alot of pallet wood). His reasoning was that you don't see 1000+ degree temps on the surface of the liner).

I'm sure there may be reasons, but I thought I'd share this.

 

[mhrischuk]

I always thought glass is stone.

 

[joefrompa]

I always thought glass is transparent

Seriously though, yeah, I don't personally know why fiberglass can't be used for 1000-1200 degree surface temp areas. Maybe it's the binding agents used int he manufacturer of the fiberglass and they offgas toxicity compared to rockwool? I don't know.

 

[Loco Gringo]

20+ years ago I workied in an oil refinery and we used kawool as insulation on pipe and in furnaces. The boxes then stated that it was a "suspected" carcinogen. Is this no longer on the packaging? I would/will go with the roxul to be honest. But still use respiratory protection and seal it off from getting into our home. I just dont trust any of these products floating around in the air within our home. I also did a lot of asbestos abatement and I worry about that so maybe Im just paranoid.

 

[ddddddden]

Man, Gringos get all the good jobs!

 

[ddddddden]

+1 on nasties, including formaldehyde, outgassing from fiberglass. OTOH, Corning has a new line called EcoTouch. "99% Pure" or somesuch.

 

[glenlloyd]

Stuffed mine with Roxul.

Is it reasonable in a situation such as yours to use some sheet metal pieces to help support the insulation blanket? My install is going to be very similar to yours, flexi insulated liner with the old damper assembly completely removed. I was worried about the insulation falling down onto the insert. I would prefer to seal the unit at the old damper opening and potentially not have to deal with the face plate for a while since I need custom fit pieces.

thx

Steve A

 

[mhrischuk]

There is stainless steel wire holding it up. I think that picture was before i put the wire up.

I hammered in some masonry nails... first I stuffed the smoke chamber as you can see in this first picture. I got about three full batts in there.

Then I cut pieces to fit.... two more layers and wired them up. They were holding themselves up but definitely needed the wire.
I don't think a metal blockoff plate would do much more in this case.

 

[glenlloyd]

There is stainless steel wire holding it up. I think that picture was before i put the wire up.

I hammered in some masonry nails... first I stuffed the smoke chamber as you can see in this first picture. I got about three full batts in there.


Then I cut pieces to fit.... two more layers and wired them up. They were holding themselves up but definitely needed the wire.
I don't think a metal blockoff plate would do much more in this case.

You're right, didn't realize you had used the SS wire to keep it in place. A good idea for your install but my old firebox masonry is not something I could nail into without possibly making it crumble and fall apart.

I'll have to re-examine my install plan and figure out what options I have. My liner kit should be shipping today (I hope) and that gives me five days to round up and finalize my install but I'm still leaning toward a series of steel panels that provide support for the insulation.

thanks for clarifying that

Steve

 

[RK05]

Are you going to see that much of a benefit with filling the cavity compared to just covering the bottom and top of the chimney with insulated block off plates?

 

[mhrischuk]

Are you going to see that much of a benefit with filling the cavity compared to just covering the bottom and top of the chimney with insulated block off plates?

My thinking is if you replace an airspace with insulation you have essentially created a very thick insulated plug that has a r value that is through the roof if you calculate the thickness x r value per inch. This Roxul is r15 at 3 1/2". I have it stuffed in there probably 2 feet up. 24"/3.5"= 6.8. That would be 6.8 thicknesses. 6.8 x R15 = R102

So yea, I think it's plenty. Not sure if a metal plate would make any difference. Certainly wouldn't hurt but I didn't feel like I needed it.

 

[glenlloyd]

Are you going to see that much of a benefit with filling the cavity compared to just covering the bottom and top of the chimney with insulated block off plates?

My thinking is if you replace an airspace with insulation you have essentially created a very thick insulated plug that has a r value that is through the roof if you calculate the thickness x r value per inch. This Roxul is r15 at 3 1/2". I have it stuffed in there probably 2 feet up. 24"/3.5"= 6.8. That would be 6.8 thicknesses. 6.8 x R15 = R102

So yea, I think it's plenty. Not sure if a metal plate would make any difference. Certainly wouldn't hurt but I didn't feel like I needed it.

Ordered a bag of that stuff today, Lowes says it'll be here by the 10th. Should be right around the same time the liner arrives I hope. Magnaflex said they ran out of insulation so my liner has been delayed over a week now. I was told that it should ship today or tomorrow and that puts it into town after the weekend. I told the retailer I was not happy about the delay, that not only do they not answer emails but they jacked the price up while I waited for their tech support to not respond to my email. Had I known they weren't going to respond I would have ordered right away and saved $130...the price went up $130 between the time I emailed them and when I finally ordered.

Look forward to getting this all stuffed into place before the weather heads south....which looks like it won't for at least another eight days...which is good for my outside painting projects and new storm windows!

Steve

 

[RK05]

Sucks about the price increase...

If you could take a bunch of pics of your install. I'm pretty sure I know how I need to go about doing mine whenever I get the money to do it but its always nice to see others progress.

 

[ddddddden]

It might have been the end of a special, rather than a price increase. I bought my Insulflex around this time of year, and it was 15% off until the end of the month. . .but yeah, sucks that you were not informed. Did you talk to theheatelement at gmail? He took good care of me.

 

[glenlloyd]

Sucks about the price increase...

If you could take a bunch of pics of your install. I'm pretty sure I know how I need to go about doing mine whenever I get the money to do it but its always nice to see others progress.

Yeah, I pulled up the product on Wednesday, the kit was $453 (sale price) and sent them an email hoping that I would hear by Friday morning so I would order before the weekend arrived. By Monday I hadn't heard (they publish a 'we respond within 24 hours' banner on their website) so I called them for an answer, which took all of two minutes and still didn't resolve my situation since they couldn't 'price' a chimney top plate greater than 15" square...about $100 more was what they said. After I finally got the unacceptable response I went to order the product and it wouldn't let me add it to the cart at the old price. I had to reload the page and that's when the price jumped to $585 for the same kit, still marked 'sale price' on their site. So I ended up waiting for five days to order to not only get an unacceptable response to my question, but also pay another $13x for the same kit.

As for the install I will make every attempt to document it with photos. I have the existing early 20th c damper assembly partially removed. It had to come out completely as it was too small for any liner to squeeze through even with the door fully open. Fortunately it's been coming apart (screwed / bolted together) without any hitch, I've only had to grind off one screw. Once that's out of the way everything will go right in.

Thanks for this thread, I wasn't sure where I was going to locate an appropriate insulation material. I suppose I could have gone with the local avalon retailer if I absolutely needed to, but being able to get the Roxul at Lowes was a nice surprise, I'll get more of it than I would at the Avalon retailer for less $ and I'm already sort of over-budget on this.

steve a

 

[ddddddden]

Yeah, $585 is the regular price for 25'. . .still a good deal, IMO. You'd be hard pressed to get a liner kit + insulation for much less, and you're not going to have to monkey around with wrapping it.

 

[glenlloyd]

Yeah, $585 is the regular price for 25'. . .still a good deal, IMO. You'd be hard pressed to get a liner kit + insulation for much less, and you're not going to have to monkey around with wrapping it.

Well it's the insulflex 20' kit, site says regular price is $7xx. Yes, I agree, it's a good product and the price is ok, but the circumstances of the whole deal leave a lot to be desired. $585 might be regular price for a non-insulflex 25' kit.

steve

 

[mhrischuk]

I'm wondering if the $453 price was a mistake. That's what I got my Insulflex for and it was shipped for free. I thought at the time that was awful cheap. I bought the 20 foot kit which included the cap, liner and appliance connector. The place I bought it from now has the price at $599.

 

[glenlloyd]

I'm wondering if the $453 price was a mistake. That's what I got my Insulflex for and it was shipped for free. I thought at the time that was awful cheap. I bought the 20 foot kit which included the cap, liner and appliance connector. The place I bought it from now has the price at $599.

I think you were the one who turned me on to the magnaflex / insulflex liner option..thx

The 20' wasn't the only one that had a price increase, it would appear that a large chunk of the product range got a bump.

I agree, for $453 the insulated option was a fantastic buy, in fact who makes the same product at that price? I haven't found anyone else that does pre-insulated liner like this and I don't think I have the patience to deal with a flex liner I would have to wrap and then try to squeeze into my 10" wide opening.

At this point I just want the product here.

thx

steve

 

[mhrischuk]

I can tell you this much, It seems to be high quality stuff so even at $580 or so it's a great deal compared to the hand wrap systems that look to run in the $800 range plus the added labor. Plus you have a nice aluminum flex tube protecting the insulation during the install and after it's installed.

I was especially surprised at how they prepare the end of it at the factory so the appliance adapter slips right on.