Rock Wool vs Fiberglass Insulation: Complete Comparison

When you are sourcing insulation for a building project, the two names you will hear most often are rock wool (stone wool, mineral wool) and fiberglass (glass wool). Both are fibrous insulation materials, but they are made from different raw materials and perform very differently in fire, heat, and moisture.

This guide compares them side by side so you can choose the right material for your project — and ask your supplier the right questions.

What Is Rock Wool Insulation?

Rock wool is made from natural basalt rock melted at temperatures above 1450 °C and spun into fine fibres. At Taishi, the fibres are produced with a pendulum-process layering technique that creates a uniform, high-strength structure. The result is a rigid or semi-rigid board with excellent fire resistance, thermal performance, and acoustic absorption.

What Is Fiberglass Insulation?

Fiberglass (glass wool) is made from recycled glass and sand melted at high temperature and spun into fine fibres. It is light, soft, and a very cost-effective thermal insulator — which is why it dominates in HVAC ducts, roof void insulation, and other applications where fire rating requirements are lower.

Key Differences at a Glance

Property	Rock Wool	Fiberglass (Glass Wool)
Raw material	Natural basalt rock	Recycled glass, sand
Fire rating	A1 non-combustible	A2 (limited combustibility) or B1
Maximum service temperature	Up to 750 °C	Up to 250 °C
Thermal conductivity	≤0.040 W/m·K	0.030–0.040 W/m·K
Acoustic absorption	Excellent, dense fibre structure	Good
Water repellency	Hydrophobic treatment available	Hydrophobic treatment available
Typical density	50–200 kg/m³	10–48 kg/m³
Relative cost	Higher	Lower

Rock Wool vs Fiberglass: Fire Safety

This is the biggest difference. Rock wool is A1 non-combustible — it does not burn, does not spread flames, and does not produce significant smoke. This is why building codes around the world require A1 or A2 materials for exterior wall insulation on high-rise buildings, and why rock wool is the default choice for steel structures, cold storage, and industrial plants.

Fiberglass melts at around 650 °C and begins to lose its structure well below that. It is acceptable for many interior applications, but it is not a substitute where fire resistance is a regulatory requirement.

Which One Should You Choose?

Choose rock wool when:

The project requires A1 non-combustible insulation (high-rise exterior walls, curtain walls, fire-rated partitions)
The application reaches high temperatures (industrial furnaces, boilers, pipe insulation above 250 °C)
You need high compressive strength or dimensional stability (sandwich panels, load-bearing cavities)
Acoustic performance matters alongside thermal performance

Choose fiberglass when:

Budget is the primary constraint and fire rating requirements are low
The application is lightweight void filling (roofs, partitions, HVAC ducts)
You are insulating areas that will never be exposed to fire risk

Factory-Direct Rock Wool from Taishi

Taishi Rock Wool operates 800,000 tonnes of annual capacity across seven production bases in China, producing exterior wall boards, curtain wall boards, sandwich panel strips, blankets, and pipe sections. We export through Geyuan Insulation (Shandong) Co., Ltd. with a full range of test reports and export documentation.

Browse our rock wool product range or request a quotation — we reply within 24 hours with factory-direct pricing.

Buyer questions we get most

Is rock wool better than fiberglass for fire performance?

For fire-rated assemblies, rock wool is usually the choice: it melts at a higher temperature and our range is A1 non-combustible, while glass wool is typically specified for ducts, roofs and acoustic fills.

Which one is cheaper?

Glass wool is lighter and generally cheaper per cubic metre. The comparison only becomes fair when both products are quoted at the density and thickness the specification actually requires.

Can both be used in the same building?

Yes, and they often are — glass wool for ductwork and metal roofing, rock wool where a fire rating, compressive strength or acoustic mass is required.

About this guide

Who maintains it

This guide is maintained by the Taishi Rock Wool export team in Shandong, China — factory-direct rock wool and glass wool from seven production bases with a combined capacity of 800,000 tonnes a year. Technical questions go straight to the factory rather than to a trading desk: WhatsApp +86 175 6050 1246 or email cliu32626@gmail.com.

Standards and sources referenced

GB/T 25975-2018 — Chinese national standard for rock wool and its products; our production and test reports follow it.
EN 13162 — European product standard for mineral wool, including how thermal conductivity (λ) is declared.
EN 13501-1 — fire classification of construction products; class A1 means non-combustible.
ISO 8301 / ASTM C518 — steady-state thermal conductivity test methods behind any quoted λ figure.
ASHRAE Handbook—Fundamentals — definitions of thermal conductivity and R-value used here.
EURIMA — European Mineral Wool Manufacturers Association, technical guidance on mineral wool performance.
Insulation Institute (NAIMA) — industry technical resources on insulation performance and specification.

Last updated: September 23, 2026

Rock Wool vs Fiberglass Insulation: Complete Comparison