Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Rockwool and fiberglass insulation are the most commonly used insulation in commercial and residential buildings. In this article, we are going to learn how they are made, their main differences as well as the pros and cons of “Rockwool insulation vs fiberglass”.

Ownes corning and Rockwool are the two most popular brands out there in these types of insulation.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Actually, Rockwool insulation is usually called mineral wool insulation but in fact, they are both mineral insulation. They are just made up of different minerals, one is made up of stone and rock and the other is made of glass.

What is Rockwool?

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Rockwool is the mineral wool insulation, which is made up of stone and rock. Its main ingredients are recycled stone wool waste, coke, slag, and basalt rock.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Basalt rock, slag, and the briquettes of recycled waste are ground down washed, and melted with coke at 1500 degrees Celcius or 2700 Fahrenheit to form molten lava & the liquid is spun into fiber.

A binding solution made of phenol, urea, formaldehyde resins is added to the fibers to help them stick together and oil is sprayed to enhance water repellency. Rockwool is generally available in comfort batt, comfort board, and safe ‘n’ sound.

Comfort batt is a semi-rigid product used inside homes on walls connected to the exterior.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Comfort board is a compressed rigid product used outside homes for continuous insulation.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Safe ‘n’ Sound is used in interior partitions.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Pros

  • Great as an acoustic insulator
  • Good water repellent
  • It has a good NRC rating
  • Class A fire rating
  • It has greater dimensional stability
  • It is stiffer, denser, and thicker
  • Lower thermal drift

Cons

  • Heavier
  • Expensive
  • Not environmentally friendly
  • Harmful to health

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What is fiberglass?

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Fiberglass is also a mineral wool insulation, but it is made up of glass. Its important ingredients are recycled glass called cullet, limestone or calcium carbonate (CaCO3), soda ash or sodium carbonate (Na2CO3), and sand or silicon dioxide.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

All the ingredients are heated in a furnace to 1700 degrees Celsius or 3000 degrees Fahrenheit to form liquid sand or glass & the liquid is spun into glass fiber.

They are naturally white or brown in color but a pink polymer glue is sprayed on them and giving them the color that we know.

The most popular fiberglass manufacturer is Ownes corning, their Eco touch insulation is available in blown-in loose-fill, rolls, batts, and also in rigid boards.

Fiberglass batt

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences
Fiberglass Batt

Fiberglass rolls

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences
Fiberglass Rolls

Fiberglass loose-fill

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences
Fiberglass Loose-fill

The Batts can either be unfaced, faced with craft paper to control moisture transmission, or a foil vapor retarder for walls connected to the exterior.

Unfaced

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences
Unfaced

Faced with craft paper

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences
Faced with craft paper

Foil vapor retarder

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences
Foil vapor retarder

Pros

  • Inexpensive
  • Light in weight
  • Fire resistance

Cons

  • It is fluffy
  • It doesn’t maintain its shape either vertically in walls or horizontally in attics so its thermal drift or loss of R-value over time is significant

Let’s look at some of the other differences between Rockwool insulation vs Fiberglass insulation,

Rockwool Insulation Vs Fiberglass Insulation

So let’s see the other differences of Rockwool insulation vs Fiberglass insulation,

1. Working Principle

The working principle for both the stuff is the same, Each fiber of this stuff makes a pocket-like structure and traps the air in this structure.

Basically, these pockets create resistance in the flow of air and prevent air from going from one pocket to the next, and this thing makes them a good sound absorber as well as a good insulator.

Both of these insulation types operate on the insulating property of air trapped between the fibers that’s why it’s recommended to fluff up the insulation after taking it out of the bag, when the batts are compressed they lose trapped air and the R-value is drastically reduced. The loss of R-value over time is called thermal drift.

2. R-Value

R-value indicates thermal resistance or heat resistance capabilities of any stuff. Every material has a different R-value.

The R-value is calculated according to the thickness per inch of any stuff. If the R-value of any stuff is 3.3 then it means that 1″ thick material has a thermal resistance capability of 3.3.

The higher the number of R-values, the greater the thermal resistance. The R-value of the Rockwool ranges between 3 to 3.85 and the R-value of the fiberglass ranges between 2.5 to 3.7. As we observed that Rockwool has better insulation capability than Fiberglass.

3. Pricing

Six pieces of the 16 inch by 48 inch (16″ * 48″) R-30 Rockwool insulation cost 61$. The equivalent 16 inch by 48 inch (16″ * 48″) R-30 fiberglass insulation cost 64$ but it contains 11 pieces.

Rockwool insulation is almost twice the price of fiberglass insulation since Rockwool is three times denser and it is also heavier.

Now we are just a few steps away to complete this article Rockwool insulation vs fiberglass insulation so stay tuned with us.

4. Weight

A single bat of R-30 Rockwool weighs 6.6 pounds, while an equivalent batt of R-30 Fiberglass weighs only 3 pounds.

The thicker and denser material is always heavy in weight and you all know that the thicker, denser, and heavier materials always have the better capability to reduce the noise effectively.

The high density of Rockwool equals more trapped air and better sound absorption properties than fiberglass.

5. Dimensional Stability

Stone wool or Rockwool is stiff if it’s compressed it just bounces back to its original shape. It has greater dimensional stability and lowers thermal drift.

Fiberglass, on the other hand, is fluffy, it doesn’t maintain its shape either vertically in walls or horizontally in attics so its thermal drift or loss of Rvalue over time is significant. It is a marketed R-30 product but we do not get the result as per the value mentioned.

6. Hydrophobic

Rockwool insulation is naturally hydrophobic or waterproof because it is made up of basalt rock, the oils added to the fibers to improve water repellency.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

Fiberglass, on the other hand, isn’t waterproof it can absorb water and moisture become compacted, and lose all insulating properties.

Rockwool Insulation Vs Fiberglass Insulation: 10 Best Differences

The resistance to moisture means that stone wool doesn’t promote rot, corrosion, fungi mildew, or bacterial growth, unlike fiberglass.

7. Fire Resistant

Rockwool is naturally fire-resistant up to 2000 degrees Fahrenheit because it has a high melting point.

If you live in an area prone to fires, it is recommended to use continuous insulation on the outside of your home. In such cases, you can use a comfort board to protect the structure of your building.

Fiberglass is not as fire-resistant. It will burn the craft paper or foil even quicker. Both Rockwool and fiberglass are pretty easy to use.

8. Easy To Use

Rockwool can be cut with a serrated bread knife, while fiberglass can be cut with a utility knife. It is easier to install because the dense, firm batts, friction fit into place and don’t require any stapling both on the walls and the ceiling.

Fiberglass on the other hand is floppy so it needs to be secured with staples or wire.

9. Health Safety

You must wear gloves, long-sleeved shirts, and a respirator when handling both these materials. If it touches your bare skin tiny shards of rock or glass will be embedded in it and cause rashes.

You must not inhale these fibers because they will be stuck in your lungs and your windpipe and will cause respiratory issues in the long run. Once they are installed however and hidden behind sheathing or drywall there isn’t any risk to your health.

10. Vapor Permeability

Vapor permeability is the ability to allow the movement of water vapor molecules through the material but Rockwool is vapor permeable, if it is used as continuous exterior insulation it allows your facade to breathe and dry out.

Fiberglass is also vapor-permeable but you have to be careful with the orientation of the foil or paper-faced batts. They must face inward in cold climates and outward in warm climates.

These all are the main differences between Rockwool insulation vs Fiberglass insulation.

Hope this article Rockwool insulation vs fiberglass insulation will guide you in the right direction.

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