We’re going to give you the full low-down on mineral wool batt insulation and what you should know before buying, and also whether it gets a pass or fail as a sustainable building material.
Is Mineral Wool a Good Insulator?
Mineral wool batt insulation was designed to be installed in wall cavities, floors, ceilings, and attic spaces.
The first thing people usually look for with insulation is the R-value per inch. The R-value is essentially the ability for something to resist heat flow, so the higher the R-value per inch, the better. So, a home with a higher R-value in its walls, basement, and attic, will make sure it stays nice and warm in the winter, and nice and cool in the summer.
And as far as a batt goes (which is the format this material comes in) mineral wool gets high praises because it achieves close to an R-4 per inch. For a typical 2x6 framed wall, you’ll achieve an R-value of 22 with the insulation alone.
Mineral wool also resists pests, fire, and moisture — very few insulation materials have all these benefits wrapped into one package.
What is Mineral Wool?
Mineral wool insulation is made from spinning slag which is a waste product in the production of steel. It can also be made from natural rock or a combination of molten slag and natural rock and even glass. Typically, mineral or stone insulation is made with 90% recycled content.
Is Mineral Wool Insulation Safe?
One of the historical pitfalls to mineral wool batts has been that it typically has a binder to hold the fibers together, and these chemical binders have historically been made of volatile organic compounds like formaldehyde. The insulation would off-gas these chemicals, which ends up being dangerous for anyone installing the product, and also have an impact on the indoor air quality for the homeowners.
In recent years, VOCs (or volatile organic compounds) are less of a concern since there’s been a general move to using low or no VOC binders, which mitigates those pitfalls. But they’re still around so you’ve gotta pay attention when picking your mineral wool.
One way to know for sure that you’re getting a mineral wool batt that has low or no VOCs is by looking for the Greenguard standard or an equally rigorous emissions standard right on the packaging.
What Is the Best Mineral Wool Insulation?
Owen’s Corning and Rockwool are two of the most recognizable brands on the market in this category, and both have newer low-VOC versions that are Greenguard Gold certified (just be sure to check the packaging before buying).
Mineral wool typically has a higher density than common fiberglass insulation, so it also has better sound-blocking properties.
How Much Does Mineral Wool Insulation Cost?
Other alternatives to these types of batts are cotton, cellulose, and sheep’s wool. Generally speaking, mineral wool batts are priced over fiberglass at $1.50 to $1.70 sq. ft. for a R-22 batt and are also priced under more natural alternatives like sheep’s wool.
How Does Mineral Wool Insulation Impact the Environment?
It’s important to consider the production of mineral wool. At its core, mineral wool typically takes waste from other sectors such as steel and glass (using as much as 90% recycled content to create) and transforms that waste into something useful.
The most notable part of the manufacturing process is the combustion necessary to melt these waste products so they can be spun into wool, as well as the addition of chemical binders.
So while mineral wool has a good amount of embodied energy during manufacturing, it’s actually much lower than other forms of insulation — it’s about half of fiberglass and one-fifth of polyiso and EPS as far as embodied energy used. Still, it is much higher than more natural alternatives like cellulose, which is just one-fifth the embodied energy of mineral wool. Sheep’s wool and hemp batts would also score much higher on the low embodied energy scale.
Because of its compressibility, mineral wool batts are very transportable, as they can be compressed to about a ninth of their uncompressed size. And we can’t forget insulation’s purpose in the first place — to address comfort and minimize the heating and cooling requirements for our homes (thus reducing our carbon footprint).
On the waste side, the packaging is usually minimal with recyclable plastic covering, and any additional waste would be from offcuts of the batts themselves. And since it resists moisture, fire, and insects, you can expect mineral wool to have a long lifespan.
Is Mineral Wool Insulation Healthy?
Mineral wool batts are impervious to moisture, which means you don’t need to worry about mold or mildew or necessarily throwing out the insulation in the event that it gets wet. Perhaps the greatest health implications are present during installation, and even though formaldehyde may be excluded from newer versions, it is a good idea to wear proper eyewear, masks, and gloves during the installation process.
Is Mineral Wool Insulation Sustainable?
So back to our original question of whether this building material gets a pass or fail on the sustainability side — from us at Rise, it gets a pass! And this is a good thing as it is one of the most widely available insulation materials out there, perhaps second to fiberglass insulation.
If you love learning about sustainable home improvement, check out buildwithrise.com for hundreds of articles, rebates, photos, and inspiring videos.
