A split picture showing Rockwool insulation on the left side, and Cellulose insulation in a bag on the right with the words Rockwool vs. Cellulose written in the middle.

After several months in a row of especially high energy bills, you’re finally ready to upgrade that weathered insulation in your attic or basement. You did a bit of cursory research and narrowed down your choices between Rockwool and cellulose insulation. Which is the better pick?

Determining whether Rockwool or cellulose insulation is right for you comes down to factors like price, R-value, and how DIY-friendly the insulation is. For example, Rockwool has a higher R-value but requires a professional to install, which cellulose does not always.

If you’re looking for even more information to help you make an educated decision on insulation, you’ve come to the right place. In this guide, we’ll examine the materials, R-value, and cost of both Rockwool and cellulose insulation. This will help you choose which insulation option suits your home the best. 

Rockwool Insulation – What You Need to Know 

What Is Rockwool?

Starting with Rockwool, also known as mineral wool, this form of insulation is named after its production process. To make Rockwool insulation, rock materials such as ceramic and slag are drawn together. Spinning molten mineral rocks like basalt is another way to produce Rockwool. 

These recycled materials (most mineral wool insulation is 90 percent recycled) produce loose-fill insulation that looks a lot like fiberglass but is stiffer and less likely to cause injury. You can purchase Rockwool insulation in batts as well.

Although you don’t see it as often compared to the other two types, Rockwool insulation is also available in spray form. 

The thermal insulation of mineral wool is a given, but an added benefit that many homeowners later realize is that Rockwool is excellent at reducing street noise as well. You’ll experience more relaxing days in your home without so many outside sounds creeping in. 

Rockwool insulation is thicker than fiberglass but still installs the same way – cut to form and sit in between the studs.

What Is Rockwool’s R-Value?

If you’re contemplating Rockwool insulation for your home, then you must know its R-value. That value depends on how much space the insulation covers. A 2×4-inch application of Rockwool has an R-value between 13 and 15.

A larger surface area of 2×6 inches increases the R-value between 21 and 23. For 2×8-inch areas, the R-value is 30 to 32. Areas of insulation that are over 2×10 inches have an R-value of 38. 

How Much Does Rockwool Insulation Cost?

Before you proceed with getting your home insulated with Rockwool, do you need a big budget or does a small one suffice? According to Homewyse, the materials for 1,069 square feet of Rockwool insulation cost between $1,841.50 and $2,542.20. 

The cost of tools, which includes job supplies, is $28.40 to $32.30. Installing Rockwool insulation can take up to 10.7 hours, says Homewyse. That means you have to tack on labor expenses to the above costs, anywhere from $394.33 to $991.87. 

Altogether, your project tally for Rockwool insulation in an attic or basement that’s 1,069 square feet is $2,264.33 to $3,566.37. 

That’s only if the insulation has an R-value of 11. If you want a higher R-value, then that requires premium materials, which then drives up the labor costs. All said, now you’re looking at project costs between $3,964.53 and $5,907.36. 

Keep in mind as well that the greater the surface area in square feet for the insulation, the higher the costs of installation will be. Even though Rockwool is available in spray foam, you cannot install it yourself. 

A man with gloves and a facemask on installing beige-colored Rockwool insulation inside an open wall.

Rockwool Insulation Pros and Cons

As an overview, here are the pros and cons of Rockwool insulation. 

Pros

  • Rockwool uses primarily recycled materials, so it’s something you can feel good about adding to your home.
  • The insulating qualities of Rockwool are excellent, and it’s a great sound absorber as well.
  • Mineral wool has a good R-value.
  • Capable of handling temperatures up to 1,800 degrees Fahrenheit, Rockwool won’t begin burning right away if a fire occurs in your attic or basement.
  • Rockwool is available in batts, loose-film, or spray foam. 
  • Installing Rockwool is simple due to the rigidity of the insulation. Unlike fiberglass, there’s no need to wire or staple Rockwool insulation into place. 

Cons

  • The denseness of Rockwool makes it heavy, so handling it is not necessarily convenient. 
  • Mineral wool is considered a very costly form of insulation, especially compared to fiberglass. Rockwool might cost up to 50 percent more! 

Cellulose Insulation – What You Need to Know

What Is Cellulose?

The second form of insulation we want to discuss today is cellulose. 

Cellulose insulation is comprised of plant fibers. You can select between one of four types of cellulose: low-dust, stabilized, wet-spray, and loose-fill cellulose insulation. Let’s go over each of these types now.

A picture of grey loose-fill blown in cellulose insulation with a top-down view. It's sitting in between two wood studs.
Loose-fill cellulose insulation usually gets blown in the walls or a building cavity using a blower machine (that you can rent at your local building store), or you can pack it into areas if needed also.

Low-Dust Cellulose

Cellulose insulation, coming from plant fibers, can be sort of clumpy and dusty, not unlike cat litter. The low-dust variety of this insulation includes a dust dampener or oil to lessen the amount of dust being kicked around by your insulation when it’s installed and in use.

If you’re allergic to paper dust or if you have asthma, we’d recommend low-dust cellulose. It will make breathing conditions in your home better.  

Stabilized Cellulose

We’ve talked about attic insulation a lot throughout this guide, and that’s one of the primary uses for stabilized cellulose. Roofing insulation is another. 

By combining the stabilized cellulose with water, it creates a paste-like consistency. You don’t need as much stabilized cellulose when it’s made this way. The sticky consistency of the insulation can also prevent settling. 

Wet-Spray Cellulose

 The most popular form of cellulose is wet-spray or spray foam cellulose. When new walls are erected, this cellulose is mixed with a moisture retardant and water. The moisture retardant prevents mold. The water holds the cellulose together.  

The seal created by spray foam cellulose is secure, which inhibits issues with settling and prevents the insulated cavity from filling with air. However, the insulation must dry for at least 24 hours before wall construction can continue. 

Loose-Fill Cellulose 

The last type of cellulose is loose-fill or dry cellulose, aka blown-in cellulose. This option is viable if your home has long since been constructed but you want to add insulation to structures like the attic. In many cases, loose-fill cellulose is applicable in homes are being built as well.

Settling occurs more often with loose-fill cellulose at a rate of 30 to 40 percent. That can impact the R-value, as the thicker the cellulose is, the higher its R-value. 

Unlike the other forms of cellulose, water does not play nicely with blown-in cellulose. 

What Is Cellulose’s R-Value?

Like we did with Rockwool, let’s now go over the R-value of cellulose insulation depending on the surface area. For spaces that are 2×4 inches, the R-value is 11. Increasing the area to 2×6 inches boosts the R-value to 17.

For areas that are 2×8 inches, the R-value of cellulose is 23 and for 2×10-inch areas, the R-value is 30. 

As we stated above, the thickness of cellulose insulation can change its R-value, as can one type of cellulose compared to another. 

How Much Does Cellulose Insulation Cost?

Since we’re sure you’re very curious, it’s time to examine the price of cellulose installation courtesy of Homewyse.

A man in full PPE protective gear standing on an attic floor installing loose-fill grey cellulose insulation in between the wood trusses.
You can see how the loose-fill terminology comes in – you buy it in bags and can blow it into place or scoop it, and set it yourself. When settled and packed in, it forms a really efficiency blanket in that wall or attic floor, or wherever else you might want to install it.

For a 534-square foot area that’s insulated with blown-in cellulose and has an R-value of 19, the cost for materials is $251 to $587. The supplies for the job cost $20 to $23 while labor is anywhere from $285 to $346. It takes about four hours for installation, making this a quicker job than getting Rockwool installed. 

The equipment for blown-in insulation adds another $30 or $49 to your tally. That brings the overall project costs to $586 or $1,004. Even if you doubled that price for double the square footage, getting cellulose insulation installed would only cost $1,172 to $2,008, which is a fraction of Rockwool insulation prices. 

It is worth mentioning that if you have prior insulation that you want to remove, this will take a little over four hours for the pros to do and will set you back $315 to $382. Disposing of any debris can tack on $207 to $235 extra as well. 

Cellulose Insulation Pros and Cons

Are you still debating whether cellulose insulation is the right option for your home? Here are some pros and cons that will make your decision easier. 

Pros

  • Cellulose insulation is available in four forms, giving you the versatility to choose the best type of cellulose depending on which part of your home that you’re insulating. 
  • You can get cellulose insulation retrofitted without having to remove the whole wall of your home. 
  • Cellulose insulation is far more affordable than Rockwool. 
  • When you choose cellulose insulation, you’re making a good choice for the environment since it’s built from recycled materials.
  • This form of insulation is DIY-friendly, especially spray foam cellulose. 
  • Cellulose insulation is fire-retardant and often mold-retardant as well.  

Cons 

  • Compared to mineral wool insulation, cellulose insulation has a lower R-value.
  • Some forms of cellulose insulation can settle, which creates space for air to leak in your attic. 

Rockwool vs. Cellulose Insulation: How to Choose

Now that you’re much more well-informed on Rockwool and cellulose insulation, how do you select the right material? Here are some factors to keep in mind.

Consider the R-Value

In some parts of the country, a higher R-value is far more important than it is in others. For example, if you live in a northern state where the winters are freezing cold, the last thing you want is cold air leaking into your basement or attic. The whole house will be icy.

A diagram of the R Value Insulation formula in grey, blue, and yellow accent colors.

Likewise, if you’re in a southern state where the climes are usually hot, you must pay more attention to your insulation R-value. The insulation material must be suitable for blocking out heat so your home isn’t a sweatbox.

The R-value difference between Rockwool and cellulose insulation is quite large, so keep that in mind. 

Calculate the Price

Every homeowner likes to save money. In the last two sections, we gave you the average costs for both mineral wool and cellulose insulation. As that information showed, Rockwool is more expensive than cellulose by a good margin.

You’ll recall that we stated earlier that mineral wool is also higher-priced than fiberglass. It’s one of the more costly insulation materials, so you’d need a sizable budget if that’s the direction you decided to go in. 

DIY or No DIY

If you’re one of those DIY fanatics who has built your home from the ground up (well, not literally, but almost), then you’ll probably want to tackle your home’s insulation as well. Luckily here for both types, DIY’s will have some good news.

You can easily spray cellulose foam into nooks, crannies, and corners of your attic or basement. You can even rent blower equipment if you really want to get into things. Of course, you can just as easily let a professional install the cellulose installation, but you will pay more.

Rockwool cellulose installs differently but as you can see from the pictures, it comes in large sheets that you can cut. If you’re confident in yourself with cutting these big sheets and putting them in yourself, this should be no problem! 

Both types of insulation mentioned here would arguably be much safer and less messy than the popular spray foam insulation option as well.

Conclusion 

Rockwool and cellulose are two of the most popular forms of insulation, but you only need one. If your budget is larger, Rockwool is a great pick. It offers noise reduction as well as fire retardancy and thermal insulation.

Cellulose comes in more forms and is DIY-friendly as well as more cost-effective. It can settle though, which can be problematic in some instances. 

If you’d like to explore more information on different types of insulation as well – we’ve got some great info on things like the different types of insulation and whether it can make you sick, or comparing fiberglass vs. spray foam insulation as well.

We hope the information in this guide helps you decide how to insulate your home! 

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