Quieter Rooms Start With the Right Insulation

Open-cell spray foam fills wall and ceiling cavities completely, absorbing airborne noise between rooms. Serving the Twin Cities metro.

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What Does Soundproofing Insulation Do?

Soundproofing insulation is material installed inside walls, ceilings, and floors to absorb and slow the transfer of sound between spaces. At Spray Foam Insulation Plus, our go-to soundproofing material is open-cell spray foam, which expands to fill every gap in a wall cavity and uses a soft, fibrous cell structure to absorb airborne sound, including voices, television, and music. Combined with proper air sealing, it reduces the noise that travels through shared walls and floors across the Minneapolis-St. Paul metro.

Open-cell spray foam is one of the few materials SFI Plus installs primarily for soundproofing rather than thermal performance. We rarely use it for energy purposes, but for sound control between rooms it is our first recommendation.

Understanding Noise

Airborne vs Impact Noise: What Insulation Actually Fixes

Not all noise travels the same way. Knowing the difference helps you set realistic expectations and choose the right solution.

Airborne Noise

Voices, television, music, and similar sounds travel as pressure waves through the air and then through walls and ceilings. Insulation in the wall or ceiling cavity absorbs this type of noise. Open-cell spray foam excels here because it fills the entire cavity and its soft structure absorbs sound energy rather than transmitting it.

Impact Noise

Footsteps, dropped objects, and structural vibrations travel through the building frame itself. Insulation in the cavity does very little for impact noise because the sound bypasses the air and travels directly through the structure. Reducing impact noise requires decoupling (resilient channel, floating floor systems) in addition to insulation.

The Material Advantage

Why Open-Cell Spray Foam for Soundproofing?

How Open-Cell Absorbs Airborne Sound

Open-cell spray foam expands to 100 times its liquid volume, filling every corner and gap inside a wall cavity. Unlike fiberglass batts, which can leave voids and compressed sections, open-cell foam leaves no gaps for sound to travel through freely. Its open, sponge-like cell structure absorbs sound energy, converting it to a small amount of heat rather than letting it pass through. It seals air leakage pathways at the same time, which matters because air gaps are the primary route for sound between rooms.

STC and NRC: Honest Numbers

Sound Transmission Class (STC) measures how much a wall assembly reduces airborne sound. A standard uninsulated wall scores around STC 33. Adding open-cell spray foam to the cavity typically brings a wall assembly into the mid-to-high 30s to low 40s range, depending on the wall construction and thickness. STC 50 or higher, which most people would describe as quiet, requires added mass (extra drywall layers) and decoupling in addition to insulation.

Material Comparison

Open-Cell Spray Foam vs Other Soundproofing Materials

Each material has a different role. Here is an honest comparison of your main options.

Open-Cell Spray Foam

Best for: interior walls and ceilings where airborne noise is the issue. Fills the cavity completely, seals air leakage, and absorbs sound well. SFI Plus’s primary soundproofing recommendation.

Mineral Wool (Rockwool Safe n Sound)

Good density for absorbing mid- and high-frequency airborne sound. Does not seal air gaps the way spray foam does, so flanking paths remain. A solid choice when the wall is already tight and sound absorption is the main need. SFI Plus installs both open-cell foam and mineral wool, and will recommend the right fit for your project.

Fiberglass Batt

Provides some airborne-sound reduction but leaves voids at edges and around obstructions. Lower density than mineral wool limits absorption at lower frequencies. Works better as a thermal insulator than as a primary soundproofing material.

Dense-Pack Cellulose

High density provides good airborne-sound attenuation in existing wall cavities. Can be blown into walls without opening them, making it useful for retrofits. Does not seal air gaps as completely as spray foam.

Residential Housing

Professionally installed insulation reduces drafts, improves energy efficiency & year-round comfort.

New Construction

Expert installation for new build homes, working with contractors who hit optimal energy performance targets.

Multi-Family Units

Insulation for apartment complexes, condos, and multi-unit buildings.

Agriculture & Pole Barns

Specialized insulation services for agricultural buildings, workshops, and metal pole barn structures.

Attic Insulation

Energy-efficient insulation solutions for attics including one and a half story homes, split level and knee wall improvements.

Basement & Crawl Spaces

Targeted insulation for attics, basements, and crawl spaces to eliminate air leaks & moisture issues.

Where It Helps Most

Where Soundproofing Insulation Makes the Biggest Difference

Interior Walls Between Rooms

Shared walls between bedrooms, home offices, and living areas are the most common request. Open-cell foam fills the cavity completely, cutting the voice and television noise that batts leave behind.

Floors and Ceilings Between Levels

Between-floor assemblies carry both airborne noise (voices from below) and some impact noise (footsteps from above). Open-cell foam in the joist bays addresses the airborne component.

Home Office

Remote work makes call privacy a real need. Insulating the walls and ceiling of a dedicated office keeps your calls in and household noise out.

Home Theater and Media Rooms

A dedicated media room is one of the highest-return applications for soundproofing insulation. Combined with proper door seals, open-cell foam keeps bass and dialog inside the room.

Nursery and Bedroom

Light sleepers and young children benefit from quieter bedrooms. Insulating shared walls and the ceiling below a noisy room above can make a meaningful difference.

Multi-Family and Shared Walls

Party walls between units, between-floor assemblies in duplexes and apartment buildings, and common-area corridors all benefit from soundproofing insulation.

Honest note: soundproofing insulation reduces noise, it does not make a room silent. For near-silence (STC 50+), you also need added wall mass, structural decoupling, and sealed flanking paths. We will tell you exactly what open-cell foam will and will not do for your specific situation before any work begins.

Our Process

How the Soundproofing Installation Works

Step 1: Assess the Noise Path

We identify whether the noise is airborne or impact, trace the path it travels, and confirm which walls, ceilings, or floors are the right treatment points.

Step 2: Material and Scope Recommendation

Based on the assessment, we recommend open-cell spray foam, mineral wool, or a combination, and give you a clear scope with honest expectations about the result.

Step 3: Installation and Coordination

We install the insulation and, if drywall needs to be opened and closed, coordinate with your contractor or refer you to a trusted partner.

Want Ballpark Pricing? Call and the Owner Answers.

We don’t publish per-square-foot prices because material costs change quickly. Call and you talk to Travis, the owner: straight answers, current ballpark numbers in minutes, and a firm quote after he sees your project. No call center, no pressure.

Call Travis: (612) 730-9417
Common Questions

Frequently Asked Questions

Yes, for airborne noise. Insulation in a wall or ceiling cavity absorbs sound waves and reduces the amount of noise that passes through. The reduction depends on the wall assembly and the material. Open-cell spray foam, which fills the cavity completely, performs better than fiberglass batts in most wall configurations.

Spray foam significantly reduces airborne noise through walls and ceilings. It does not make a room soundproof in the sense of blocking all sound. For very high sound isolation (STC 50+), you need additional mass and structural decoupling in addition to insulation.

Sound Transmission Class (STC) is a single-number rating of how much a wall or floor assembly reduces airborne sound. Higher is better. A wall at STC 33 is relatively easy to hear through; at STC 42, normal speech is difficult to understand; at STC 50+, loud speech is faint. Most residential walls with open-cell foam land in the mid-30s to low-40s range, depending on construction.

Open-cell spray foam fills the cavity completely and seals air gaps, making it the better choice when the wall has any gaps or penetrations. Mineral wool has higher density and can perform similarly for mid-frequency sound in a tight wall assembly. We recommend open-cell when air sealing is also a goal, mineral wool when the wall is already well-sealed and acoustic absorption is the primary need.

Insulation alone does very little for impact noise such as footsteps, because that sound travels through the structure rather than through the air. Reducing impact noise requires decoupling: resilient channel, floating floors, or similar structural separation. We can advise on what is realistic for your situation.

In some cases, blown-in insulation can be added to an existing wall cavity through small holes. This is a less thorough approach than open-cell foam (which requires opening the wall or installing from one side), but it can help. We assess each situation and explain your options before recommending a path.

Yes. We work with property managers and owners on multi-family buildings including apartment buildings, duplexes, and condos. Party walls, between-floor assemblies, and corridor walls are all common projects.

Prices follow material costs, so a number published today could be wrong next month. Call and you will talk directly to Travis, the owner. He can usually share current ballpark and per-square-foot ranges over the phone, then give you a firm quote after seeing your project.

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Honest assessment. Open-cell spray foam specialists. Serving the Twin Cities metro.

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