Mineral Wool vs Foam for Soundproofing: Which Is Better? (2025 Comparison)

Mineral Wool vs Foam for Soundproofing: The Definitive Comparison

When choosing soundproofing materials, the debate between mineral wool and acoustic foam is one of the most common questions. While both are used in acoustic applications, they serve fundamentally different purposes and deliver vastly different results for soundproofing.

This comprehensive comparison explains the key differences, performance characteristics, costs, and which material is right for your soundproofing project.

The Critical Difference: Soundproofing vs Acoustic Treatment

Before comparing materials, understand this fundamental distinction:

• Soundproofing (sound isolation): Blocking sound from entering or leaving a space—requires mass and density
• Acoustic treatment: Controlling sound quality within a space (reducing echo and reverberation)—requires absorption

Key takeaway: Mineral wool is for soundproofing. Acoustic foam is for acoustic treatment. They are not interchangeable.

Mineral Wool for Soundproofing: Complete Overview

What Is Acoustic Mineral Wool?

Mineral wool (also called rock wool or stone wool) is a dense, fibrous insulation material made from molten rock or slag spun into fibers:

• Density: 45-100 kg/m³ (acoustic grade is 60kg/m³+)
• Thickness: Typically 25mm-100mm for acoustic applications
• Structure: Dense, rigid slabs or batts with high mass
• Purpose: Sound absorption within cavities + adds mass to block transmission

Acoustic Mineral Wool Products

• 100mm acoustic mineral wool slabs – High-density (60kg/m³) for maximum sound absorption
• 75mm acoustic mineral wool slabs – Ideal for standard stud wall cavities (60kg/m³)
• 50mm acoustic mineral wool slabs – Space-efficient option (60kg/m³)
• 25mm acoustic mineral wool slabs – Professional sound absorption for shallow cavities

How Mineral Wool Works for Soundproofing

1. Absorption: Dense fibers trap sound energy within wall/floor/ceiling cavities
2. Damping: Converts sound energy to heat through friction
3. Mass: High density (60kg/m³) adds weight to block sound transmission
4. Broad-spectrum: Effective across all frequencies (low, mid, high)

Mineral Wool Performance Data

• Sound absorption: Excellent (NRC 0.85-1.0 depending on thickness)
• Sound blocking: Good when combined with mass layers (membranes, boards)
• Frequency range: Effective 125Hz-4000Hz+ (all frequencies)
• Fire rating: A1 non-combustible (excellent fire safety)
• Moisture resistance: Hydrophobic, won't absorb water
• Lifespan: 50+ years, doesn't degrade or settle

Mineral Wool Applications

• Wall cavities in stud walls and party walls
• Floor joists for impact noise reduction
• Ceiling voids for airborne and impact noise control
• Building Regulations Part E compliance projects
• Professional soundproofing in homes, studios, offices

Mineral Wool Cost

• 50mm slabs (60kg/m³): £8-12 per m²
• 75mm slabs (60kg/m³): £10-14 per m²
• 100mm slabs (60kg/m³): £12-18 per m²

Acoustic Foam: Complete Overview

What Is Acoustic Foam?

Acoustic foam is lightweight, open-cell polyurethane foam designed to absorb sound reflections within a room:

• Density: 20-35 kg/m³ (very lightweight)
• Thickness: Typically 25mm-100mm
• Structure: Soft, spongy, often with wedge or pyramid patterns
• Purpose: Reduce echo and reverberation within rooms (NOT soundproofing)

How Acoustic Foam Works

1. Surface absorption: Traps high-frequency sound waves in foam cells
2. Reflection reduction: Prevents sound bouncing off walls
3. Echo control: Reduces reverberation time in rooms
4. Limited frequency range: Only effective for mid-high frequencies (500Hz+)

Acoustic Foam Performance Data

• Sound absorption: Good for high frequencies (NRC 0.4-0.8)
• Sound blocking: Virtually none (too lightweight)
• Frequency range: Only effective 500Hz-4000Hz+ (mid-high frequencies)
• Low-frequency performance: Poor (cannot control bass below 250Hz)
• Fire rating: Varies (often flammable, check fire rating)
• Moisture resistance: Poor (absorbs moisture, can degrade)
• Lifespan: 5-15 years (degrades with UV exposure and moisture)

Acoustic Foam Applications

• Recording studios (controlling room acoustics, not isolation)
• Home theaters (reducing echo for better sound quality)
• Podcasting booths (improving recording clarity)
• Music practice rooms (reducing internal reflections)
• NOT suitable for: Blocking neighbour noise, soundproofing walls, Part E compliance

Acoustic Foam Cost

• 25mm foam panels: £15-30 per m²
• 50mm foam panels: £25-45 per m²
• 100mm bass traps: £40-80 per m²

Head-to-Head Comparison

Which Should You Choose?

Choose Mineral Wool If You Need To:

• Block noise from neighbours (walls, floors, ceilings)
• Reduce traffic noise entering your home
• Soundproof bedrooms, home offices, or living rooms
• Meet Building Regulations Part E requirements
• Control impact noise (footsteps from above)
• Create professional soundproofing in studios or music rooms
• Block low-frequency noise (bass, rumble, traffic)

Recommended products:

• 100mm acoustic mineral wool for maximum performance
• 75mm acoustic mineral wool for standard stud walls
• 50mm acoustic mineral wool for space-limited applications

Choose Acoustic Foam If You Need To:

• Reduce echo and reverberation within a room
• Improve recording quality in home studios
• Control reflections in home theaters
• Enhance speech clarity in podcasting booths
• Improve acoustics in music practice rooms

Important: Acoustic foam will NOT stop neighbour noise, traffic noise, or footsteps from above.

Use Both Together For:

• Recording studios: Mineral wool in wall/ceiling cavities for isolation + foam on surfaces for acoustic treatment
• Home theaters: Mineral wool for soundproofing + foam for controlling internal reflections
• Music rooms: Mineral wool to contain sound + foam to optimize internal acoustics

Common Misconceptions About Foam

Myth 1: "Acoustic foam soundproofs walls"

Reality: Foam is too lightweight (20-35kg/m³) to block sound transmission. It only reduces echo within the room.

Myth 2: "Egg boxes work like acoustic foam"

Reality: Egg boxes provide minimal acoustic benefit and are a fire hazard. Use proper materials.

Myth 3: "Thicker foam blocks more sound"

Reality: Thickness helps with low-frequency absorption but doesn't add sound-blocking mass. Density matters more than thickness.

Myth 4: "Foam on walls stops neighbour noise"

Reality: Neighbour noise requires soundproofing (mineral wool in cavities + mass layers), not surface foam.

Professional Soundproofing System Example

For effective soundproofing of a party wall:

1. Build independent stud wall 50-100mm from existing wall
2. Fill cavity with 100mm acoustic mineral wool (60kg/m³)
3. Apply 4mm acoustic barrier membrane (7kg/m²) to studs
4. Install 30mm acoustic SilentBoard finish
5. Seal all perimeters with acoustic sealant
6. Optional: Add acoustic foam panels on finished wall for echo control

Performance: 55-65 dB sound reduction (transformational)

Cost: £80-120 per m² (materials + installation)

Why Mineral Wool Is Superior for Soundproofing

Density and Mass

• Mineral wool (60kg/m³) is 2-3x denser than foam (20-35kg/m³)
• Higher density = better sound blocking
• Essential for Part E compliance

Broad-Spectrum Performance

• Mineral wool controls all frequencies (125Hz-4000Hz+)
• Foam only works for mid-high frequencies (500Hz+)
• Low-frequency control essential for traffic, bass, footsteps

Fire Safety

• Mineral wool is A1 non-combustible
• Foam is often flammable (fire hazard)
• Building Regulations require non-combustible materials in cavities

Durability

• Mineral wool lasts 50+ years without degradation
• Foam degrades in 5-15 years (UV, moisture, age)
• Mineral wool is moisture-resistant, foam absorbs water

Cost-Effectiveness

• Mineral wool: £8-18 per m² depending on thickness
• Foam: £25-80 per m² depending on thickness
• Mineral wool delivers better performance at lower cost

Conclusion: Mineral Wool Wins for Soundproofing

For soundproofing applications—blocking neighbour noise, reducing traffic noise, meeting Part E requirements, or creating quiet spaces—acoustic mineral wool is the clear winner. Its high density (60kg/m³), broad-spectrum performance, fire safety, durability, and cost-effectiveness make it the professional choice for sound insulation.

Acoustic foam has its place in acoustic treatment (reducing echo in studios and home theaters), but it cannot soundproof walls, floors, or ceilings. For effective soundproofing, always specify high-density acoustic mineral wool (60kg/m³+) combined with mass layers like acoustic membranes and acoustic boards for professional results.