Rockwool Comfortboard 80 is a modular rigid stone wool insulation board made from rocks. If you’re going for a big-bad-wolf-proof building, Rockwool should be on your list to consider for insulating your exterior walls. Rockwool isn’t perfect for every application though, it can be expensive, heavy, and challenging to install.
Here, we cover the major benefits of Rockwool, its shortcomings, and what other options are available to insulate your walls in your home or commercial project.
Rockwool has a number of things going for it. Here are some of the benefits of choosing Rockwool Comfortboard 80 to insulate your project:
Made from natural and recycled raw materials
Excellent fire resistance with no smoke production or flame spread
Termite and insect resistant
High compressive strength
Provides acoustic sound absorption
Rockwool Comfortboard 80 is designed for use on the exterior side of the wall for continuous insulation. It’s installed with 3-inch washers and nails, and is attached to sheathing over a vapor barrier or house wrap. Other applications can include foundation walls and under concrete slabs.
Rockwool is a great option for some projects, however this type of insulation isn’t always the best for every application. Some of the shortcomings of Rockwool Comfortboard include:
It’s heavy, at over 50 lbs. per 4’ x 8’ board at 2” thickness, which makes installation laborious.
At R4.2 per inch, Rockwool Comfortboard 80 is a middle-of-the-road option when it comes to thermal R-value performance.
Rockwool Comfortboard 80 can be difficult for homeowners to obtain because it is not typically stocked in big box stores, so it can be a challenge to obtain, and pricier to purchase.
Luckily, there is an alternative to Rockwool Comfortboard 80. Polyiso is a comparable option to Rockwool when it comes to installing insulation on walls. Taking it a step further, polyiso outperforms Rockwool when it comes to installability, thermal performance, and price point. If you’re looking for a less expensive, lightweight alternative to Rockwool—without sacrificing on performance, consider polyiso.
Polyiso can be installed in the same locations and applications as Rockwool as a continuous insulation, but with significantly less weight bearing on your installers and your walls. Since polyiso is made out of foam, it’s inherently lightweight and can be carried and maneuvered easily by a single installer without suffering from the fatigue of lifting heavy Rockwool boards, which may require two installers per board, or smaller board sizes.
It’s hard to beat the thermal performance of polyiso. At R6 per inch, it’s one of the best thermal insulation options for walls. With polyiso products like Rmax Durasheath® building envelope insulation, you can achieve an R21.8 with just 3-½” thickness, whereas achieving this same R-value with Rockwool Comfortboard 80 requires over 5” thickness.
Polyiso insulation is affordably priced at just over a dollar per square foot for a two inch thickness. Rockwool, on the other hand, can be quite pricey at nearly two dollars per square foot at the same thickness. Since you’re getting less thermal insulating power for the same thickness, that’s a double whammy.
Polyiso is more readily available for purchase by ordinary homeowners, because it is available at building supply stores. Rockwool Comfortboard 80, on the other hand, can be a specialty item that is not stocked in stores and often requires a special order and larger quantities.
Polyiso has a unique advantage over most other wall insulation types, including Rockwool Comfortboard 80—it can be tailored to meet your project’s needs by applying an appropriate facer. Because polyiso not only accepts, but requires a facer during production, it gives you the choice between different performance properties that you want to incorporate.
For example, if you’re looking for an air and vapor barrier, you can find an all-in-one solution with Rmax’s ECOMAXci® FR Air Barrier. Rockwool, on the other hand, is vapor permeable and requires a second product to add vapor protection.
Here are more polyiso insulation products that are available as an alternative to Rockwool Comfortbatt 80:
ECOMAXci® FR Ply: Fire-Resistant Plywood Faced Polyiso for Cladding Attachment
R-Matte® Plus-3: Aluminum faced polyiso available at your local big box retailer
Thermasheath®: Reinforced aluminum faced polyiso boards
Thermasheath®-SI: Structural composite insulation with aluminum facers
Rmax has been in the insulation business for decades and has honed and perfected its evolving product line to meet building codes and customer needs. We have a full lineup of insulation solutions to help you meet your project’s requirements and get your next job started off on the right foot.
Talk with one of our experts today today to get help choosing the right insulation for your project!
Exploring alternatives to traditional building materials is a critical part of the construction process. Should you continue to use what you know has worked in the past, or is there something better out there? If you’re considering mineral wool insulation for your next project, it’s time to evaluate the pros and cons and know your options.
Mineral wool insulation is a building material used in construction to thermally insulate the building envelope as an alternative to fiberglass insulation. Builders realize the benefits of mineral wool insulation over fiberglass in several areas, including:
Higher R-Value
Better Acoustic Blocking
Superior Fire-Resistance
Like fiberglass, mineral wool typically comes in batts, but carries a little more stiffness and dimensional stability than fluffy fiberglass batts or rolls.
The minerals in mineral wool can come from volcanic rock as a raw material source. Another common raw material used to make mineral wool is called slag, a byproduct of molten metal production. Slag is a mixture of impurities and flux that escape the molten mixture during the melting process.
The raw materials in mineral wool are spun into fibers, glued, pressed, and formed together—to create cotton candy-like wool batts that can be installed in areas of the building envelope, like the cavities between studs in a stud wall.
When selecting the right type of insulation for your project, it’s important to weigh the pros and cons of each material. Let’s cover the advantages and disadvantages of mineral wool insulation.
Mineral wool is stiffer than fiberglass, which makes it easier to cut with precision and install to fit a space perfectly. On the other hand, since the material is much more dense than fiberglass, it is also much heavier. This can make the installation process a little more challenging due to the added weight of the material.
In terms of insulating value, mineral wool carries an R-value of just above R4 per inch, meaning that it requires 3.5” to achieve R15. It is an improvement over fiberglass, which carries an R-value of under R3 per inch, for an R13 at the same thickness of 3.5”.
When space matters, mineral wool carries a slight edge on thermal performance over fiberglass with the added benefit of enhanced sound blocking. However, there are other insulation options on the market today that provide significantly higher thermal insulating values than mineral wool.
Mineral wool is more expensive than fiberglass and it can be more difficult to procure with fewer options available at local contractor supply warehouses. However, mineral wool can be tailored during the manufacturing process to meet specific needs and is available in various options, including:
Soundproofing
Fire-resistant
Fire and Sound
Increased Thermal Performance
Other types of insulation can introduce additional properties, but it’s generally the facer that is changed rather than the insulating material itself. Mineral wool is unfaced.
The disadvantages of mineral wool include price, availability, lackluster thermal performance, and limited installation applications. If you’re looking for an alternative to mineral wool, polyiso is a valid consideration. Unlike mineral wool, polyiso is a rigid foam insulation—so it is both lightweight, and easy to work with.
Polyiso comes in boards that can be cut to fit by hand. The modular sizing makes installation fast and easy, to decrease your cost of labor. Polyiso is also widely available from manufacturers in various thicknesses ranging from ½” up to 6” and it can be doubled up in multiple layers to meet thermal R-values with ease.
Polyiso outperforms mineral wool in thermal performance with a steady R6 per inch for polyiso. That means it only requires 2.5” of polyiso insulation like Rmax Durasheath® to meet R15, while it takes 3.5” of mineral wool.
When it comes to installing wall insulation, why limit yourself to the wall cavity or to using expensive furring to hold mineral wool in place? With polyiso, you can achieve continuous insulation on the outside of the stud cavity simply by fastening the insulation directly to your walls underneath your cladding.
You can also turn your continuous insulation into an air and vapor barrier with inventive polyiso products like the ECOMAXci® FR Air Barrier, which has glass fiber reinforced aluminum facers to limit moisture and vapor permeance, as well as air flow.
While there are some clear benefits of mineral wool insulation, there are an equal number of drawbacks. Get help choosing the right products for your next build by reaching out to the experts in insulation. We can help you pick a solution that meets your design criteria and fits within your budget.
