Acoustic Insulation Materials: A Comparison

Choosing an acoustic insulation material involves balancing several factors: noise reduction performance across relevant frequency ranges, physical compatibility with the existing assembly, moisture behaviour in Canadian climate conditions, fire rating requirements, and installation constraints. No single material performs best in every category, which is why many effective soundproofing assemblies use a combination of materials.

The materials most commonly used in Canadian residential acoustic insulation are mineral wool, cellulose, fiberglass, and various acoustic foam products. Mass-loaded vinyl (MLV) is distinct from these in that it functions primarily as a mass barrier rather than an absorber, but it is frequently used alongside the above materials.

Mineral Wool (Rock Wool / Stone Wool)

Mineral wool is manufactured from basalt rock or industrial slag, spun into fibres and formed into rigid batts or semi-rigid boards. It is the material most frequently specified for acoustic applications in Canadian residential construction, for several reasons:

• Higher density than standard fiberglass batts, which improves absorption across a broader frequency range
• Dimensionally stable — does not settle or compress significantly over time
• Inherently fire-resistant; does not require added flame retardants to meet building code requirements
• Moisture-resistant and will not support mould growth
• Good acoustic performance at mid and lower frequencies, where wall noise complaints commonly originate

Products such as Roxul Safe'n'Sound (now branded as Rockwool Safe'n'Sound) are widely distributed through Canadian building supply retailers and are specifically marketed for interior partition acoustic applications. The product is tested to ASTM E84 for fire behaviour and provides a listed STC contribution when used in specified assemblies.

Mineral wool costs more per square foot than standard fiberglass batts, but the performance difference in acoustic applications is measurable. In a standard 2x4 stud wall, switching from fiberglass to mineral wool batt insulation can increase the assembly STC by 4 to 6 points, with no other changes to the wall construction.

Cellulose Insulation

Cellulose is produced from recycled paper fibre, typically newsprint, treated with borate compounds for fire and pest resistance. It is available in loose-fill form for blowing into cavities and attics, and in dense-pack form for filling enclosed wall cavities under pressure through small access holes.

The dense-pack method is particularly relevant for retrofitting existing walls without full demolition. A contractor drills small holes (typically 2 to 3 inches in diameter) through the existing drywall or exterior cladding, inserts a fill tube, and blows cellulose into the cavity until it reaches the design density. The holes are then patched.

Acoustically, cellulose performs comparably to mineral wool in wall cavities, particularly at mid-range frequencies. Its higher density when dense-packed — typically 55 to 65 kg/m³ compared to 32 to 48 kg/m³ for mineral wool batts — contributes to effective airborne noise absorption within the cavity. The material's fibrous structure is also effective at damping resonance within enclosed air cavities.

Fiberglass Batts

Standard fiberglass insulation is the most widely installed cavity insulation in Canadian residential construction. Its acoustic performance, however, is lower than mineral wool at comparable thicknesses due to its lower density (typically 8 to 12 kg/m³ for standard batts versus 32 to 48 kg/m³ for mineral wool acoustic batts).

Fiberglass is adequate for providing some acoustic benefit in wall and ceiling cavities, and its low cost makes it a default choice in new construction. In dedicated acoustic applications where performance is the priority, it is generally not the first choice. Higher-density fiberglass products do exist and perform better than standard batts, but they typically cost more than standard mineral wool and do not match mineral wool's fire performance characteristics.

Where fiberglass is already installed in an existing assembly and the budget does not permit full replacement, adding a resilient ceiling or secondary wall treatment can achieve acceptable acoustic results without removing the existing insulation.

Acoustic Foam

Acoustic foam — open-cell polyurethane or melamine foam in wedge, pyramid, or flat panel form — is frequently misunderstood in the context of home soundproofing. Foam panels are effective at absorbing sound within a room (reducing reverberation and echo), but they provide little resistance to sound transmission through walls, floors, or ceilings.

The distinction is between sound absorption (reducing reflections inside a room) and sound isolation (preventing sound from passing through a structure). Acoustic foam addresses the former; it does not meaningfully address the latter. A recording studio lined with acoustic foam is quieter inside because of reduced reflections, but it is not significantly more soundproof to outside noise than before treatment.

In Canadian residential applications, acoustic foam is appropriate for:

• Home recording or podcasting spaces where internal acoustic quality matters
• Home theatres where reflection control improves the listening experience
• Reducing echo and flutter in home offices used for video conferencing

It is not appropriate as a primary treatment for noise transmission between rooms or units.

Mass-Loaded Vinyl (MLV)

Mass-loaded vinyl is a flexible, dense sheet material (typically sold at 1 lb/sq ft or 2 lb/sq ft) that adds mass to an assembly without significant thickness. It can be attached to existing walls, floors, or ceilings and then covered with drywall or other finishes.

MLV works as a limp mass barrier: its flexibility and density prevent it from coupling efficiently to the structural frame, so it vibrates somewhat independently and absorbs sound energy in the process. It is most effective in the mid and upper frequency ranges and provides less improvement at low frequencies (below 200 Hz).

Common Canadian applications include:

• Adding to the back of existing drywall before applying a second layer
• Wrapping mechanical ductwork to reduce duct-borne noise
• Floor underlayment beneath hardwood or laminate flooring
• Pipe wrapping for drain noise reduction (particularly effective for ABS and PVC drain stacks in multi-unit buildings)

Material Comparison Summary

Material	Primary Use	Acoustic Role	Fire Rating	Moisture
Mineral Wool	Wall & ceiling cavities	Absorption	Inherently non-combustible	Resistant
Cellulose (dense-pack)	Retrofit cavity fill	Absorption	Treated with borate	Sensitive if wet
Fiberglass Batts	General cavity insulation	Moderate absorption	Non-combustible facing required	Can retain moisture
Acoustic Foam	Room acoustics (absorption)	Absorption only — not isolation	Varies by product	Not moisture-resistant
Mass-Loaded Vinyl	Surface barrier layer	Mass / barrier	Varies by product	Generally resistant

Frequency Considerations

A common challenge in Canadian urban soundproofing is low-frequency noise: bass from music systems, mechanical hum from HVAC equipment, and low-frequency traffic noise. All acoustic insulation materials lose effectiveness at lower frequencies. Below 100 Hz, the wavelengths involved are long enough that thin material layers have minimal impact.

Addressing low-frequency noise requires mass and decoupling at a scale that is difficult to achieve in standard residential construction. Double stud wall systems with significant air gaps, and floating floor assemblies with heavily loaded resilient mounts, can reduce low-frequency transmission, but complete elimination of bass frequencies is not achievable in most residential retrofit projects without major structural changes.

References

• NRC Canada — Canadian Building Digests on Acoustic Performance
• ASTM International — Test Standards for Acoustic Materials