# Rockwool vs Glass Wool for Soundproofing in India: Density (48/64/96 kg/m³), NRC & 2026 Price Comparison

**Date:** Oct 12, 2026 | **Read Time:** 10 MIN | **Category:** MATERIALS

> **Summary:** Comprehensive engineering comparison between Rockwool (stone wool) and Glass Wool for Indian soundproofing projects. Discover optimum density, moisture handling, fire safety, and 2026 prices per sq ft.

When designing soundproof drywall partitions, false ceilings, home theatres, and recording studios in India, mineral wool insulation inside the air cavity is the primary engine of acoustic absorption. However, consultants and contractors frequently debate between two dominant materials: Rockwool (stone mineral wool manufactured from volcanic basalt rock) and Glass Wool (manufactured from recycled silica glass). Which material delivers superior Sound Transmission Class (STC) ratings? What density (48 kg/m³, 64 kg/m³, or 96 kg/m³) is optimal? How do they perform in humid Indian coastal climates? Here is Boho Acoustics' definitive technical comparison.

## Manufacturing & Material Composition: Basalt vs Recycled Glass

Rockwool (Stone Wool) is produced by melting natural basalt volcanic rock and metallurgical slag at temperatures exceeding 1,500°C, then spinning the molten rock into fine, entangled mineral fibers bonded with thermosetting resins. This produces a dense, rigid or semi-rigid fibrous matrix with exceptional natural mass.

Glass Wool, on the other hand, is manufactured by melting recycled cullet glass and silica sand at approximately 1,100°C and spinning it into fine glass fiber filaments. Glass wool fibers are naturally lighter, more flexible, and resilient, resulting in lightweight blankets or low-density batts.

Because basalt rock is inherently denser than glass, Rockwool is readily manufactured in higher densities (48 kg/m³ to 144 kg/m³), whereas Glass Wool is typically produced in lower densities (16 kg/m³ to 48 kg/m³).

## Acoustic Performance (NRC & Cavity Sound Isolation)

In stud partition cavities and ceiling plenums, fibrous insulation absorbs resonant sound waves and eliminates the 'drum effect' (cavity resonance) by converting acoustic particle velocity into microscopic thermal friction.

For mid and high frequencies (500 Hz to 4,000 Hz), both 48 kg/m³ Rockwool and 32 kg/m³ Glass Wool achieve stellar Noise Reduction Coefficients (NRC 0.90 to 1.00). However, at critical low frequencies (63 Hz to 250 Hz) - where subwoofer punch, traffic rumble, and diesel generator vibrations dominate - Rockwool's higher fiber mass and flow resistivity provide superior low-end damping.

In a standard double-stud drywall assembly (with double 12.5mm gypsum on each side), filling the 100mm cavity with 64 kg/m³ Rockwool yields an STC rating of 56 to 58 dB, outperforming 24 kg/m³ glass wool by 3 to 5 dB in the low octave bands.

## Moisture, Humidity & Indian Monsoon Durability

In coastal and tropical Indian cities such as Mumbai, Chennai, Kolkata, and Goa, relative humidity regularly exceeds 85% during monsoon months. Moisture behavior is a paramount selection criterion for acoustic longevity.

Rockwool fibers are naturally hydrophobic (water repellent) and do not absorb ambient moisture. If water accidentally splashes on Rockwool, it drains freely without causing fiber slump or loss of acoustic thickness, preventing mold and mildew growth.

Glass Wool, while treated with water-repellent binders, is more hydrophilic and susceptible to moisture retention if vapor barriers are breached. Saturated glass wool loses its loft and sags inside vertical drywall cavities, creating acoustic voids where sound bypasses the insulation.

## Fire Resistance Standards (NBC 2016 & BS 476 Compliance)

Fire safety is non-negotiable in commercial auditoriums, multiplexes, high-rise residential towers, and corporate office fitouts under the National Building Code of India (NBC 2016).

Rockwool possesses an extraordinarily high melting point (> 1,000°C), classifying it as non-combustible (Euroclass A1 and Class 0 under British Standard BS 476 Part 4/6/7). It acts as an active fire barrier, providing up to 120 minutes of fire containment without releasing toxic fumes.

Glass Wool has a lower melting point (around 550°C to 600°C). While fire-retardant (Euroclass A2/B), glass wool fibers will melt and disintegrate significantly faster during intense structural fires, reducing its effectiveness as a passive fire barrier.

## Cost Analysis & 2026 Price Comparison in India

Pricing in the Indian market is determined by raw material costs, density, thickness (typically 50mm or 100mm), and facing types (unfaced, black tissue, or reinforced aluminum foil FSK facing).

Glass Wool (16 kg/m³ to 24 kg/m³, 50mm thickness) is the most budget-friendly option, retailing between ₹22 and ₹45 per sq. ft. It is widely utilized for basic HVAC duct thermal insulation and large-scale industrial PEB shed roofing.

Rockwool (Stone Wool 50mm, 48 kg/m³ density) ranges from ₹55 to ₹85 per sq. ft. For heavy-duty acoustic decoupling and home theatre wall cavities, 64 kg/m³ Rockwool ranges from ₹85 to ₹125 per sq. ft., while high-density 96 kg/m³ slabs for equipment enclosures range from ₹135 to ₹195 per sq. ft.

## Frequently Asked Questions

### Which is better for soundproofing in India: Rockwool or Glass Wool?
Rockwool is superior for soundproofing. Its higher density (48 to 64 kg/m³) provides greater airflow resistivity and low-frequency bass absorption (63-250 Hz) compared to glass wool. It is also completely hydrophobic, making it far more durable in humid Indian climates.

### What is the best density of Rockwool for home theatre soundproofing?
For partition wall cavities and false ceilings, 48 kg/m³ to 64 kg/m³ density (50mm thickness) delivers the optimal balance of gas-flow resistivity and structural damping. Densities above 96 kg/m³ become overly rigid and reflective for interior absorption.

### Is Rockwool safe to use inside home bedrooms in India?
Yes, provided it is properly enclosed within airtight drywall or wrapped in acoustic non-woven fabric. Once sealed behind gypsum boards with acoustic caulk, mineral fibers cannot migrate into room air. Look for CE-marked, bio-soluble stone wool complying with IS 8183.

### How much does 50mm 48 kg Rockwool cost per sq ft in India in 2026?
Standard 50mm thick, 48 kg/m³ unfaced Rockwool slabs cost between ₹55 and ₹85 per sq. ft. in India. Slabs with black glass tissue facing (used behind perforated wooden panels) cost ₹75 to ₹110 per sq. ft.