Rockwool Insulation: Your Complete Guide

Rockwool insulation is extraordinary. The insulation protects your home from heat loss during cold weather. When it’s hot outside, the insulation keeps your house cool. It is energy efficient and can help you save money.

Rockwool Insulation

The insulation is found in many homes and is durable. We’ll learn about rockwool insulation and how it is used. Perhaps you can learn something useful about this special insulation.

What Is Rockwool Insulation? 

Rockwool is a material that is known as mineral wool. The material is made from rocks, not wool

Real rocks are heated to around 3,000 degrees Fahrenheit to the point of liquefaction. When melted, the rocks look like magma and are pressurized before being spun to create long strands.

So it looks like cotton or fiberglass insulation but it’s made of rocks. The rocks are spread thin throughout the insulations. It doesn’t mean they are no longer rock hard, making for durable insulation. 

Why Use Rockwool Insulation

Why Use Rockwool Insulation

Rockwool insulation has many benefits.

Here are the most common advantages that it offers:

Rockwool Insulation Factors

  • Sustainable – contains 75 percent recyclable materials. 
  • Efficient – those who switch to rockwool often report lower energy bills.
  • Fire-resistant – it withstands high temperatures before it melts. 
  • Water-resistant – it resists and repels water. 
  • Soundproof – it’s a great noise muffler. When used in walls and ceilings, it can reduce the sound transfer between the indoors and outdoors.
  • Doesn’t degrade – made with rocks, so it’s stronger. 
  • Mold-resistant – yes.
  • Easy-to-install – doesn’t require staples.

Where To Put Rockwool Insulation

Where To Put Rockwool Insulation

The great thing about rockwool is how you can install it in the same places as fiberglass.

The most common places or rockwool insulation: 

  • Ceilings
  • Attics
  • Crawlspaces
  • Walls
  • Floors/Basements 

Where Not To Install Rockwool Insulation 

You might be wondering, but it can go anywhere. 

Well, we will go more into the details later when comparing it to other insulation but again, the short answer is that it is more expensive than other insulation. Is it worth it? That’s the question we need to address.

Rockwool Insulation Vs. Other Insulation Types

Rockwool Insulation Vs. Other Insulation Types

When looking at the pros and cons, it’s best to compare it with other products. 


The R-value is the insulation based on thickness. Some areas need a thin layer of foam while others need six or eight inches of protection. A high R-value is a positive indicator that means the insulation has strong insulating qualities. The highest R-rating is 45.

  • Rockwool – 3-4 per inch, range of R13 to R38.
  • Fiberglass – 2-3 per inch, range of R11 to R37.
  • Cellulose – 3-4 per inch, range of R11 to R30.
  • Foam – 3-5 per inch, range of R3 to R25.
  • Natural Fibers – 1-3 per inch.


When it comes to eco-friendliness, it will depend on the recyclable materials in the product.

  • Rockwool – 70-75% recycled.
  • Fiberglass – 20-40% recycled. 
  • Cellulose – 80-90% recycled. 
  • Foam – depends on brand.
  • Natural Fibers – usually 100% recycled. 
  • Bonus: denim – 100% recycled. 


There are many insulation options available at different prices.

  • Rockwool – $1.50 to $2 per square foot.
  • Fiberglass – $0.50 to $1 per square foot.
  • Cellulose – $1 per square foot.
  • Foam – $0.30 to $2 per square foot.
  • Natural Fibers – $0.50 to $3 per square foot.


When it comes to fire protection, rockwool insulation is the best.

Here are the temperatures each insulation can withstand before it melts or catches fire:

  • Rockwool – 1,500 degrees Fahrenheit. 
  • Fiberglass – 1,000 degrees Fahrenheit. 
  • Cellulose – 800 degrees Fahrenheit.  
  • Foam – 700 degrees Fahrenheit. 
  • Natural Fibers – depends on the material.


Rockwool is water-resistant.

Here’s a quick rundown of water-resistant insulation. 

  • Rockwool – water-resistant.
  • Fiberglass – yes, after resin application. 
  • Cellulose – yes, after protectant is applied. 
  • Foam – high-density, closed-cell. 
  • Natural Fibers – sometimes.


Thicknesses, size, and installation options are insulation qualities to consider.

How To Install Rockwool Insulation 

How To Install Rockwool Insulation 

Installing each type of insulation is unique. For example, spray foam requires a special sprayer while fiberglass requires staples.

Step 1: Fill Gaps With Foam/Caulk

Fill in any gaps in the area where the insulation will go. Start with caulk around windows, doors, and other spaces that are half an inch wide. You can use expanding foam for larger cracks and gaps. 

Step 2: Don Gear

Rockwool won’t irritate your skin or throat like fiberglass insulation. However, don’t inhale it. You’ll need to wear a mask and goggles. 

Step 3: Install In Floors And Walls

Start from the bottom and outside of the house. The exterior walls, crawlspaces, and basement ceilings. Cut each piece and install it.

You won’t need staples. Add the insulation in the hole and cut any obstructions with a utility knife.

Step 4: Install In Ceilings And Attic 

It will fit in the slots with ease, even without ceiling covering. 

Enjoy Your New Rockwool Insulation

Install In Ceilings And Attic 

Frequently Asked Questions (FAQ)FAQ

Does rockwool need a vapor barrier?

The insulation is un-faced, so it doesn’t have kraft paper or a foil barrier. You might need a separate permeable membrane to act as a vapor barrier.

You will need to add a vapor barrier with a cement board. Place the barrier behind the board. This will stop the moisture from penetrating into your walls.

Can rockwool insulation get wet?

The insulation is moisture resistant. If it gets wet, let it dry and check on it once a month to make sure it doesn’t have mold. 

Is rockwool recyclable?

Yes, it is. If you have leftover pieces, you can recycle them too.

Rockwool Insulation Conclusion

It would be hard to find better insulation for your home. When you sell your home, it will be more appealing to potential homebuyers.