If you’re debating between Rockwool and fiberglass insulation, you’re not alone. Both are popular choices, but they offer different benefits depending on your home’s needs.
Rockwool, made from melted basalt rock, is denser and highly resistant to fire, moisture, and pests. Fiberglass, the more common pink insulation, is lightweight, flexible, and generally more affordable. The cost of Rockwool typically runs between $1.50 and $2.00 per square foot installed, while fiberglass averages between $0.60 and $1.20 per square foot. However, Rockwool tends to last longer and insulate better over time.
Choosing the right insulation can make your home more energy-efficient, comfortable, and even quieter — all while lowering your utility bills. In this article, we’ll compare Rockwool and fiberglass insulation across key factors like durability, fire resistance, and installation difficulty so you can choose the best option for your home.
Rockwool vs. Fiberglass: Key Differences
Insulation Performance
Both materials provide solid thermal insulation, but Rockwool’s higher density gives it an edge. It has an R-value of about 4.0 per inch, while fiberglass ranges from 2.2 to 3.8 per inch. This means Rockwool does a better job at keeping heat inside during the winter and blocking heat in the summer.
Fire Resistance
Winner: Rockwool
Rockwool is naturally fire-resistant and can withstand temperatures over 2,000°F. This makes it an excellent choice for fire safety, especially in attics or areas near fireplaces and furnaces. Fiberglass won’t catch fire easily but can melt around 1,100°F and may contain paper-based backings that are flammable.
Moisture and Mold Resistance
Winner: Rockwool
Since Rockwool is made from stone fibers, it naturally repels water and prevents mold or mildew growth. Fiberglass, while not highly absorbent, can hold moisture if exposed, which can lead to mold over time.
Pest Resistance
Winner: Rockwool
Rockwool’s dense, inorganic structure makes it unappealing to rodents, insects, and other pests. Fiberglass, while not a preferred nesting material, can sometimes attract rodents in unfinished areas like attics.
Soundproofing
Winner: Rockwool
If you want a quieter home, Rockwool’s high-density structure absorbs sound better than fiberglass, making it ideal for bedrooms, media rooms, and shared walls.
Ease of Installation
Winner: Fiberglass
Fiberglass is lightweight and flexible, making it easier for DIY installation, especially in irregular spaces. Rockwool is denser and harder to cut, requiring a serrated knife or specialized insulation saw.
Cost
Winner: Fiberglass (Budget-Friendly), Rockwool (Long-Term Investment)
Fiberglass insulation costs $0.60 to $1.20 per square foot installed, while Rockwool typically runs $1.50 to $2.00 per square foot installed. Rockwool is more expensive but it provides better insulation and longevity, making it a worthwhile investment for energy savings.
Lifespan & Long-Term Performance
Winner: Rockwool
Rockwool lasts about 30 years and maintains its structure over time. Fiberglass lasts about 25 years but can sag and lose effectiveness faster, especially in humid environments.
Final Verdict: Which One Should You Choose?
Choose Fiberglass if you want a more affordable, easier-to-install insulation that still provides good energy efficiency for standard home applications.
Choose Rockwool if you want maximum insulation performance, better fire protection, and superior soundproofing—especially if cost is not a major concern.
