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rock wool

lukes | Posted in Energy, Heating & Insulation on January 22, 2011 11:55am

Why do Canadian contractors love rock wool insulation. If the fire resistant factor is a good reason, does it need to be covered after installation? I have crawl spaces that need to be insulated but was told foam or fiberglass would need a fire rated covering.

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  1. User avater
    digdug18 | Jan 22, 2011 12:22pm | #1

    If you use spray foam, alot of them do have fire ratings, and those that do not, you do need a spray on coverying, easy to apply though.

    Tigerfoam.com says right on the front page of their site that it is E-84 fire rated.

    1. User avater
      lukes | Jan 22, 2011 01:42pm | #2

      what does an E-84 rating mean? will it need to be covered?

  2. JohnWalker | Feb 05, 2011 12:02am | #3

    FWIW I saw them demonstrating Roxul Plus rock wool at Home Depot (Vancouver, Canada) some time ago. About the only thing they guy could show me is how fire proof it is - a torch won't ignite it (or melt it). Fibreglass is still king here though.

    What i know about it (from my own little research only):

    -very fire resistant/proof.

    -very dense - less air convection through the product means more realistic R rating.

    -because of the density it can be installed below grade (ie outside the foundation wall) and at the same time provide a drainage plane.

    -less iritating to work with.

    -slight price premium to FG.

    -made from mining/metal production by-product(s) (slag?). Its "green-er" but I am still a teeny-tiny bit unsure what ~might~ off gas. (In my case I was considering it for floor insulation in a staple up radiant system where it would be continually heated to a high temperature than if in a wall assembly.)

    (I am not familiar with your local code(s) but I would suspect its the floor framing system that needs a fire rated covering as FG on its own doesn't require one here.)

    John

  3. rf_engineer_5 | Feb 05, 2011 11:05pm | #4

    If you put up roxul, I believe you do not have to cover it with drywall.  It can be used for insulation but also has good sound deadening properties. 

    I am not well versed in what E-84 flame spread really means.  For tigerfoam though, the material is considered organic and will burn at 200°F (see their datasheets on the website).  I take this to mean that it should be covered with something.  It really depends on what the local building code guy will say to you.  That is the best advice I have for you.  I used one of the tigerfoam kits for the rim joist.  I do not have it covered right now.  If there is a fire, I am pretty sure that I have many things to catch on fire alongside of the foam that will be a problem.    BTW, I would never do the tigerfoam thing again for the rim joist.  While I am not knocking the product, the cost and prep time made it not worth it to me. 

  4. Unsworth | Feb 18, 2011 01:50pm | #5

    Sound Attenuation Mineral Wool Insulation

    We use it alot in high rise construction because it is super fire resistant and deadens sound much better than standard fiberglass insulation.

    R-4 (about) per inch.  so 2x4 wall r-19, 2x6 r-23

    It is semi rigid and won't slump down over time.

    Pretty easy to install, but wear long sleeves, powder up, safety glasses, and N-95 or better mask is a must.  It can be cut with a break away blade, knife, or razor.

    Comes in 24" or 16" X 48" seimi rigid sheets with varing thickness.

    If you look on Roxsul's website their is a test building they torch and you see the fiberglass melt, but the mineral wool is fine.  This type of insulation is used in heavy industry, masonry stove, commercial projects, and kilns because it is super fire resistance.  I can't see a typical residential fire wiping this stuff out.  With deck to deck double layer 5/8 type X drywall on each side of the wall it will be rated as a 2 hour fire wall.   Firemen and families rejoice.

    Foam products are worse in this respect because they actually become fuel for the fire after they have reached the temperature and exposure to a fire.  Foam emits toxic gas while burning.  Their rating is only telling you at what point it will burn, not that it won't.  If I were to insulate an exterior wall with foam, I would definately use 5/8 type X Firecode drywall over it.

    A correction to the fellow above, this stuff is not more comfortable to work with that fiberglass.  We call it the rotten cotten and it will make you scratch yourself like a junky .  When its hot out and you work with it all day.  Not so bad once you get used to it.

    Will not feed mold, and can get moist without completely failing.

    Made primarily by Therma Fiber (USA) and Roxsul (Canada).

    Leeds credit because of the large portion of recycled content, up to 80%.

    Sound attenuation type really works well, although it certainly is not sound proof.

    Cost will vary according to supplier, location, and bulk.  It should cost around 65 cents to 85 cents per square food of 5.5 inch thick, or so I've read.  I've heard it is about twice the cost of fiberglass, where as spray foam can a lot more.  I just used to install the stuff, not buy it.

    I have not been impressed with the foil face on this product, it seems thin and cracking.  Instead I would use drywall with foil on the backside.  I think USG might make it.

    Mineral Wool is a great product for homes and the price of the upgrade won't break the budget.  When I build my own place it is definately going in.

    I've been looking for a good section detail for an exterior wall that incorporates fiber cement siding over a rainscreen, over 30 lbs tar paper, over 2" XPS, over 15 lbs tar paper, over 5/8 plywood, over 24 OC 2x6 framing with mineral wool in the bays.  My problem is in an area like upstate NY or southern New England ect., what kind of vapor barrier would would be used on the inside.  I am not crazy about foil or 6 mil plastic because they can never be install perfect and I think would create a double vapor barrier when used with the exterior XPS.  Plus, any punctures or failed tape over time will let in moisture in the winter and become trapped in the cavity causing rot and mold.  Spray foam between the stud bays would be good, but would be super expensive and involve of outside contractor or buying or renting equipment.

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