Insulation Showdown: Rockwool vs Fiberglass for Walls, Ceilings, and Floors
By Graham Mann | Published: 12/20/2025
Compare Rockwool and fiberglass for walls, ceilings, and floors — R-value, fire resistance, moisture handling, soundproofing, and cost.
Insulation Showdown: Rockwool vs Fiberglass for Walls, Ceilings, and Floors Rockwool(https://www.rockwool.com/north-america/) and fiberglass are two popular insulation materials for walls, ceilings, and floors, but they serve different needs. Here's a quick breakdown: - Rockwool: Made from volcanic rock and steel slag, it offers better thermal performance (R-15 for 2×4 walls vs. R-11 to R-13 for fiberglass), excellent fire resistance (up to 1,800°F), and superior soundproofing. It's water-repellent, durable, and eco-friendly, but costs more ($0.62–$3.10/sq ft). - Fiberglass: Made from melted glass fibers, it's lightweight, flexible, and budget-friendly ($0.30–$1.50/sq ft). It performs well in dry spaces but absorbs moisture, reducing effectiveness. Fire resistance is lower (up to 1,000°F), and it may sag over time. Quick Comparison: | Feature | Rockwool | Fiberglass | |---| --- |---| | R-Value (per inch) | 3.0–4.1 | 2.2–2.7 | | Fire Resistance | Up to 1,800°F | Up to 1,000°F | | Moistu...
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