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R-15 ComfortBatt Fire Resistant Stone Wool Insulation Batt 15 in. x 47 in.

  • Maintains R-Value year after year
  • Fire Resistant & Water Repellent
  • Ease of Installation - Cuts Easily & Friction Fits
  • See More Details

Frequently Bought Together


Product Overview

Roxul ComfortBatt R-15 Fire Resistant Thermal Home Insulation. Whether you are building new or renovating your home, use Roxul ComfortBatt Thermal Home Insulation in your exterior walls, attic, ceiling and floor frames for top thermal performance. With its high density, non-directional fiber structure and unique flexible edge, Roxul ComfortBatt is designed to deliver a better fit providing heating and cooling energy savings.
  • For 2 in. x 4 in. exterior wood frame walls at 16 in. on center, attics and crawl spaces
  • Resistant to water, rot, mold, mildew and bacterial growth
  • Bag coverage: 59.7 sq. ft.
  • Completely fills wall cavity to eliminate gaps and voids
  • Friction fit batts conform to normal variations in stud centers caused by distortion or warping
  • Flexible edge springs back, expanding the batt against the frame studs to provide a complete fill
  • Made from natural rock
  • Greenguard gold certified for indoor air quality
  • Click here to learn more about Eco Options and Energy Efficiency
  • Installation Breakdown:

    basement wall R-15 installation breakdown

  • Buying guide and insulation calculator:

    insulation buying guide
    Insulation calculator button

Info & Guides

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Coverage Area (sq. ft.)
Product Length (ft.)
3.91 ft
Product Thickness (in.)
3.5 in
Product Width (in.)
47 in


Bag Size
48 ft. x 16 in. x 24 in.
Batt/Roll Size
3.91 ft. x 3.5 in. x 47 in.
Compatible Install Surface
Coverage Area per Bag (sq. ft.)
Faced or Unfaced
Insulation Features
Friction Fit
Insulation Location
2x4 Wall,Attic,Basement,Ceiling Insulation,Crawlspace,Floor
Insulation R-Value
Insulation Type
Mineral Wool Insulation
Number of Bags
Pieces Per Bag
Pieces per Pallet
Product Weight (lb.)
Roll or Batt

Warranty / Certifications

Warranty Information

Questions & Answers


insulating a shed . should this insulation be faces to prevent irritation.is it acoustic also.

Asked by glen April 5, 2021

Faced or unfaced it could irritate your skin if it touches it during install so long sleeves are a must. Once up, you should cover it (thin sheathing or sheet rock depending on your use for the shed) or it will grab onto dust, dirt, etc in the shed. In my opinion this product does cut down noise better than fiberglass, but if that’s your primary need for it, use the Roxul product intended for sound deadening instead.

I want to reduce the noise from a sump pump located in a utility room in our basement. The utili...

Asked by Bob February 11, 2021

Use roxul safe and sound. Then quite rock. Sheetrock

Can this be used as pillow stuffing?

Asked by Martyjanetty October 31, 2020

No! Mineral wool or fiberglass need to be sealed off from breathing organisms, like people and animals. Inhaling small fibers causes many health problems.

If I'm installing this in the ceiling of an outbuilding/studio--not a residence--will it become a...

Asked by Wolfcreeker October 29, 2020

Dear WolfCreeker: Any type of insulation can become tunnels and nesting areas for rodents -- if they can get access. This is typically a problem is ventilated and unsealed attics, where whatever insulation was installed can become a 'home' for rodents. Your studio probably doesn't need an attic. I am also an artist, and an open space above would be better than a ceiling. You could add triangular windows on one or both sides, for more light. This isn't expensive. So if you have an insulated roof, you can fill the rafter bays with rock wool (R-4.1 per inch), and rodents will not be able to access it. This is also true for the walls; you can fill the stud bays with rock wool If your studio is in a part of the country with cold winters, you could add 1" or 2" layer of polyiso foam board on the surface of the rafters and studs. This would add R-6.5 or R-13, would 'break' all of the 'thermal bridges' created by the wood framing, and would allow you to air seal the surface. Seal all of the joints and perimeter, to block air leaks. DAP 230 or HVAC mastic work well for joints and small gaps. Use the 'Window and Door' version of Great Stuff spray foam for larger gaps. Foam board is flammable, however, and must be covered by an approved 'thermal barrier', e.g. 1/2" drywall. The floor also needs insulation, if you live in an area with cold winters. Fill the joist bays with rock wool or Foamular XPS foam board. Finally, air sealing is almost as important as insulation R-value. Seal every seam, gap etc. HVAC mastic is a good option for small gaps; use the 'Window and Door' version of Great Stuff for larger gaps. You could also 'wrap' the exterior walls with Henry Blueskin self-adhesive film.and cover the roof with Grace Ice & Water Shield. Neither are expensive. In addition to air-sealing, these products protect against water leaks and damage. For windows, I recommend Marvin fiberglass framed, Low-E, argon filled, two or three paned. Fiberglass is much stronger than vinyl, and the cost difference is negligible. Marvin makes custom fixed pane versions, e.g. for the triangular windows near the peak of the roof -- and awning / casement versions for ventilation. (Classic double-hung windows do not seal effectively.) I hope this info is helpful, and your project is successful! Mark

can I put this in my chimney between the flue pipe and the chimney to stop the downward draft

Asked by KEITH September 22, 2020

Dear Krunne: Yes, but pack it tight. Rock wool is made from rock so it is very flame resistant. I hope this is helpful. Mark

is this suitable for under floors as insulation? Also does it contain abestos of formaldehyde? ...

Asked by Person July 29, 2020

Dear Person: If "under floors" means insulating the floor joists in your crawl space or unheated basement, then yes, rock wool is ideal. You can also order versions to match the depth of your joists, e.g. for 2x6 and 2x8 joists. Use Simpson insulation wire to hold the batts in place. See: Simpson Strong =-Tie Model # IS16-R100, Home Depot Internet #100375163, UPC Code # 044315396618 Store SKU #594333 RockWool does not contain formadehyde or asbestos. It is made from molten rock, so it cannot be 'recycled' but does not pollute the environment. I hope this is helpful, Mark

Does this product contain Formaldehyde? Is it printed on the packaging?

Asked by Roger March 11, 2020


What is the best way to use this in a cathedral ceiling application for a finished attic/loft spa...

Asked by Moesenfreunde February 11, 2020

Dear Moesenfreunde: Thanks for including the photo. First, you need to create ventilation channels that run from the soffit vents along the bottom edge of your roof to the ridge vent at the top -- so that air can travel up along the underside of the roof deck, and not be blocked by new insulation. These channels are easy to assemble with 1" thick XPS Foamular foam board, with narrow pieces of foam board along the edge of the rafters as standoffs - to create a 1 1/2" air space. Or you can purchase pre-made air channels; see: ADO Model # UPV1448010, Home Depot Internet #202541345. I recommend creating your own with 1" Foamular foam board; this is quick and easy, the channels are stronger and will add R-5 to your final assembly. These air channels will ventilate your roof deck and eliminate the potential for rot. Second, mount rock wool batts in the rafter bays, over the air channels. Rock wool is much denser than fiberglass, so make sure you don't crush the pre-made air channels if you use them. Use Simpson insulation wire to hold the batts in place. This product is available for 16" or 24" spans. See: Simpson Model # IS16-R100, Home Depot Internet #100375163, Store SKU #594333 Third, mount 1" or 2" polyisocyanurate foam board on the surface of your rafters. This will add R-6.5 to R-13 to your roof / ceiling, plus break all of the 'thermal bridges' created by the (previously) exposed wood rafters, and allow you to effectively air-seal the ceiling. Screw the foam board panels to the bottom of your rafters, over the rock wool. Carefully seal all of the joints and edges to block air leaks. HVAC mastic works well for joints and small gaps. Use the 'Window and Door' version of Great Stuff spray foam for larger gaps. All of these products are sold by Home Depot. As for a reflective / radiant barrier, you could apply one to the roof-side of the foam panels used to create the air channel. This would only be marginally helpful, however, and only if you have hot summers in your location. I hope this is helpful. Mark

how many 47" pieces per vat

Asked by ronnie January 9, 2020


I am looking to insulate a basement wall that is attached to my garage. There is sheetrock on th...

Asked by d926 December 13, 2019

Dear D926: Rockwool is an excellent insulation solution for walls, and you do not need a vapor barrier. Modern building science shows that walls need the ability to slowly dry to at least one side. Because your adjoining room is in a basement, the concrete floor is also a 'thermal bridge' that steals heat. Is the floor insulated? If not, this is a good step. Here are some tips for insulating a basement that may be helpful. All of the products are available at Home Depot: (1) Make sure there are no cracks and leaks in the concrete walls. Fill and seal cracks with Sikaflex Model # 7116110, Home Depot Internet #300934565 Store SKU #652010 If moisture is coming through the wall, apply damp-proofing to the surface. Products like Drylok can provide an important layer of moisture protection. See: Drylok Model # 28615, Home Depot Internet #202610896 Store SKU #1000531519. This product will minimize diffusion from the soil through the foundation. (2) Use 2" thick Foamular XPS foam board against the concrete walls. XPS does not absorb moisture; a 2" thick layer will provide R-10 insulation plus a strong vapor retarder. (3) Using foam board compatible glue, fasten sheets of foam board to your concrete walls. Apply a thick bead around the perimeter of each sheet, to create an air seal when it is pressed against the concrete wall. See: Loctite PL300 Model # 1421941, Home Depot Internet #202020476 Store SKU #780400. You can lean a 2x4 against each sheet to hold it in place while the glue sets, or pin them in place with a RamSet. After all of the sheets of foam board are installed, seal all of the joints and edges to block air leaks. DAP 230 works well for joints and small gaps; the 'Window and Door' version of Great Stuff foam is good for larger gaps. (4) Build your new 2x interior wall in front of the foam board. Use pressure treated (PT) lumber for the sole plate. If water leaks could occur and the floor may be damp, install a piece of Veranda cellular PVC trim on the floor first, to lift the sole plate off the concrete and keep if from rotting; leave small gaps every few feet for water to trickle through under the DriCore panels noted below. Use a RamSet to drive nails into the concrete, or drill holes for expansion bolts. We use bolts in areas with high stress, e.g. near doorways, stair landings and the ends of pony walls. See: RamSet Model # 00022, Home Depot Internet #100091715 Store SKU #107708. Be sure to wear ear and eye protection when you use a RamSet. (5) Insulate and seal the rim joist pockets: Install 2" thick pieces of Foamular 250 in the pocket at the end of each floor joist -- to insulate and seal the rim joist. Seal the edges with the 'Window and Door' version of Great Stuff foam to block air leaks. Then fill the rest of the end of each bay with rock wool. (6) Run your electric lines to receptacles and lights. Fire block (seal) the holes in the studs with 3M Fire Block sealant. See: 3M Model # FB 136, Home Depot Internet #100390499 Store SKU #191728 DO NOT use any type of spray foam, even if it says "Fire Block" on the label, e.g. Great Stuff. These spray foam are actually very flammable. Informed building inspectors can fail an inspection if they find spray foam used for fire blocking. (7) Fill the stud bays with rock wool. See: Owens Corning Model # UB-40-P3D-15--47--121, Home Depot Internet #304633821 Store SKU #1003061505 (8) If there is any possibility of a water leak into your basement, install DriCore panels on the floor first. They have a rubber surface on the bottom with channels that water can trickle through. Make sure, of course, that you have a drain with a dry well or sump pump for the water to escape to. Carefully seal all of the joints and edges of the DriCore panels to block air / moisture leaks. Then install 1" of Foamular on top of the DriCore, and seal the joints and edges. Cover the Foamular with 3/4" plywood as the subfloor / nailbase for your new flooring. Run the plywood 90 degrees from the direction of the foam board, with a 1/2" gap around the edge for expansion. Again, seal all of the joints and edges. See: DriCore Model # CDGNUS750024024, Home Depot Internet #202268752 Store SKU #361018. We installed DriCore at a recent project as a fail-safe, even though the basement was dry. Water leaked in unexpectedly through a window during a downpour, and DriCore saved the new floor. If you are certain that there is no possibility of a water leak into your basement, install 1" thick Foamular 250 on the concrete floor -- and seal the joints and edges. Cover this with 3/4" plywood, running 90 degrees to the foam board panels. Leave a 1/2" gap around the edge to allow for expansion. Again, seal all of the joints and edges. (9) Also read up on fire blocking, which many people overlook. This is required at the top of basement walls, along the walls, at the top of stairs, etc. Do a Google search for "How to Firestop Your Basement" from ContractorKurt. Roxul rock wool is a good solution. You can stuff it into the gap at the top of the wall and into the end of floor joist bays. To seal holes created for pipes and wiring, use fire resistant caulk, e.g. 3M Model # CP-25WB+, Home Depot Internet #100166701 Store SKU #163096.. DO NOT use the "Fireblock" version of Great Stuff foam; as noted above. I hope this is helpful. Mark

R-15 ComfortBatt Fire Resistant Stone Wool Insulation Batt 15 in. x 47 in. - page 2

Customer Reviews

  • 4.9
    out of 554 reviews
  • 99% recommend this product
Filter by:
Showing 1-10 of 554 reviews
The best product!
I have replaced all of the old 1955 insulation in my home and i am working on the last room right now.I'm using R14 for 2 x 4 application inside my walls.I am so glad that i'm using Roxul as it has already shown to lower my heating bills and the accoustics changed right away.I don't hear much noise outside anymore.It is so easy to install and it's not itchy,i'm cutting the pieces with a bread knife.Thanks guys for a great product!
by Andreas
This should make regular fiberglass insulation obsolete
I'm remodeling my 1950 mid century modern home one room at a time. I started with the hardest room to heat & cool, knocked out the old plaster & had the room sprayed with rigid & soft foam. The guys rushed the job & left some thin spots and even bare wood showing thru. I wanted to fill voids with Roxul but could not find it anywhere in Oklahoma so I hung the drywall anyway. Since then I've found a dealer 30 miles from me that can order it. I've since used Roxul in my sun room & garage. I like it better than the foam & I can easily install it myself.
by Dogwalker
I used this to replace old fiberglass batts in my upstairs. It is very nice to work with, and fil...
I used this to replace old fiberglass batts in my upstairs. It is very nice to work with, and fills the wall cavities completely without gaps, unlike the fiberglass batts that were there. It really shines around electrical outlets and obstructions that you would typically have a very hard time filling well with anything but dense pack. I used the mineral wool insulation knife, but you can just as well use a long bread knife or even an electric meat carving knife. Any serrated blade. I had odd stud spacing and was able to use whole batts combined with vertically 'ripped' batts to fit the cavities. A straight edge is handy. Wear a dust mask.
by DaninHouston
Better Conformance to Joist Spacing
Fiberglass batts depend on springback to original shape, from large compression in packaging. That springiness then results in buckling if a bit oversize for the space. Rockwool doesn't do this. Lost contact with confining surfaces destroys insulation value.
by Attic Access
130 year old church restoration, ideal product
Installing comfort batt insulation in the walls and floor of a 130 year old William Critchlow Harris church/cottage upgrade. As this structure is a 'balloon' design, fire concern was paramount. Simple installation even with so many cuts, and huge long term benefits. Ideal application for your product.
by Michael
I am happy with this product.
I like it when i get asked what i'm putting into my walls.I let friends know that this product is safe to handle and not itchy.I'm using a bread knife to cut pieces to fit.I've got peace of mind knowing it's not going to grow mold,it's fire resistant,easy to install and i won't hear as much outside noise in my home.Right now i am installing this product and i am 3/4 completed.
by Andreas
We won't use anything but this product in our builds!
We do both custom and high volume manufacturing for tiny homes on wheels. It's important to us that the products we spec out to use are easy to install and work effectively for our applications. This product does exactly that. Sounds carry far and wide even in tiny homes. So, when we have new families moving into a small space, this product makes an excellent noise dampener in between closed off rooms to provide an element of privacy where it can normally be hard to find. Nevermind its obvious positives, this product is just far superior at the end of the day. It's our gold standard for each home that we send out of our shop and it makes us proud!
by Tina the Contractor
Ive been a fan of Roxul aka "Rockwool" ever since Mike Holmes Introduced it to his show Holmes on Homes. Had to wait a couple of years before it came to the States but when it did, i was elated!!! I got to try the water test and burning it, and boy was it amazing, just as described and show. I will never ever use the pink insulation ever again!! Re-insulating that garage picture i sent you in 90degree heat, after done that garage kept a temp of 70 degrees, i was extremely impressed!! ROXUL HEAD 4 LIFE!!!!!!!
by Coach
I've used Roxul ComfortBatt throughout my entire house for all...
I've used Roxul ComfortBatt throughout my entire house for all the exterior facing walls. They make a huge difference in terms of thermal insulation and vapor barrier (just remember to also use the 3 mil+ poly over). The product is very cost effective when you're on a tight budget.
by WilliamC
Remodel - exterior wall on interior of family room - I like the properties of this product for it...
Remodel - exterior wall on interior of family room - I like the properties of this product for its density (some sound acoustical value) and that it is mineral rock wool packed into 4 foot batts. NOTE: these batts have NO vapor barrier. where vapor barrier is needed (typically exterior/garage walls), I added a barrier film to the interior side of the wall where remodeling by using Certainteed "Membrain" vapor management film (remember, "paper to the people side of the wall!"). The Roxul product is easy to install in the wall cavity and with a serrated insulation knife very easy to cut in around boxes and blocking. It provides a solid fill in the wall void and has very little "dust or raveling. the batts are slightly wider that the standard stud spacing making it easy to simple push them into the void without stapling or fastening (and has a full contact seal). Be sure to match the spacing of studs or joists to the width of the batts (typically studs or joists are 16" or 24" spacing) and to the depth of the space (3 1/2 inch or 6 inch.. depending on studs or joist size. When encountering a wire crossing the stud cavity I simply cut the batt parallel to the wire , pushed the batt under and over the wire (make sure it goes behind the wire in the wall void). provides a complete "air pocket-free" seal. Also, these batts are rated at R-15 for 2x4 stud cavity providing more insulating value (fiberglass batts are typically R-13 for 2x4 cavity). it is thought that rock wool also discourages rodents but I have no proven evidence that it does and have seen where they chewed through some old rockwool batts (non Roxul products) on other projects. Today's products may have been treated to deter rodents but it is not advertised as such to my knowledge. easy to use, quick to install, clean wall finish when done.
by rlhLIttleton
Showing 1-10 of 554 reviews