Acoustical Test

Rooms are noticeably quieter with INSU-GREEN Cellulose Insulation, which deadens the transfer of sound from one room to another.

INSU-GREEN Cellulose Insulation Provides Better Sound Control


  • INSU-GREEN cellulose insulation outperforms all other insulation systems for sound attenuation

  • Can Have a STC Factor of Up to 80

  • Easy To Install

  • Does Not Irritate Skin

  • Mold and Fungus Resistant

  • Insect and Rodent Repellant

Clients who choose insulation get the added value of superior sound control. It is widely used to help limit exterior noise intrusions as well as for limiting noise between rooms. Understanding how insulation can help control sound provides insight into this important performance feature that can help to limit noise from outside or between rooms inside the home.

Noise Reduction Coefficient (NRC)

Noise Reduction Coefficient measures the build-up of noise within a space. A NRC number index rating is used to measure the sound absorption quality of a material. INSU-GREEN Insulation products have an NRC rating that can range upwards of .80 or higher. What this means is INSU-GREEN Insulation can absorb 80% or more of the sound it comes into contact with.

Sound Transmission Class (STC)

Sound Transmission Class measures the sound transmission between spaces. A single number rating is used to measure a structure’s ability to impede sound transfer. The higher the STC rating, the more effectively a wall, floor or ceiling controls sound transmission. Noises can be heard through a wall with an STC rating of 30, but should much less audible through a wall with a rating of 60. Cellulose Insulation may be used to achieve STC ratings as high as 80.

Using insulation can control sound from outside a home or building and between rooms when added to interior walls. There are many applications including even helping to make a garage home recording or music rehearsal studio more sound proof.

The added value of sound control provided by INSU-GREEN insulation is just one more way consumers can benefit from the enhanced performance and value only INSU-GREEN insulation can provide. Request it from your builder or contractor and discover the benefits of a quieter living environment.


The Applications

Dry Cellulose (Loose Fill)

Dry Cellulose is generally blown into new or existing walls or ceilings. During installation by this method, the material will settle by as much as 20 per cent and must therefore be permanently supported.

Spray On Cellulose (Wet Spray)

Spray applied cellulose is used for insulating new stud framed walls (drywall) or ceilings during construction. The only difference between this application and the dry cellulose method is the addition of water, and sometimes with an adhesive, to the cellulose while spraying. Wet spraying helps seal cavities against air infiltration and eliminates settling problems.

Cellulose Panels (Batts)

Celulose panels are commonly installed in sidewalls of residential or commercial structures, but can also be installed in rim joists, attics, floors or other hard to insulate areas. They are also very functional where traditional loose fill or sprayed-in cellulose insulation is not practical

Sound Transmission Class (STC) Rating

Building Component STC
1/4-inch plate glass 26
3/4-inch plywood 28
1/2-inch gypsum board, both sides of 2x4 studs 33
1/4-inch steel plate 36
Concrete block: Autoclaved aerated 45
3-inch concrete wall 47
6-inch reinforced concrete slab (4-1/8" thick) 44
6-inch concrete block wall 42
8-inch reinforced concrete wall 51
12-inch concrete block wall 53
12-inch brick 56
2x4 wood studs (16" o.c.) with 1/2" GWB both sides 33-39
1-5/8" inch steel studs (24" o.c.) with 1/2" GWB both sides 39
3-5/8" inch steel studs (24" o.c.) with 1/2" GWB both sides 40-44

Changes in STC and Apparent Loudness

Changes in
STC Rating
Changes in Apparent Loudness
+/- 1 Almost imperceptible
+/- 3 Just perceptible
+/- 5 Clearly noticeable
+/- 10 Twice (or half) as loud
STC Privacy Afforded
25 Normal speech easily understood
30 Normal speech audible but not intelligible
35 Loud speech audible and fairly understandable
40 Loud speech audible but not intelligible
45 Loud speech barely audible
50 Shouting barely audible
55 Shouting not audible
60+ Superior soundproofing; most sounds inaudible

STC Guidelines for INSU-GREEN Cellulose Insulation

General guidelines for controlling noise between spaces:

  • INSU-GREEN cellulose insulation outperforms all other insulation systems for sound attenuation. In a typical 2 x 4 wall with a single layer of 1/2” drywall on each side (Tested STC):
    • INSU-GREEN cellulose STC 41
    • Fiberglass or mineral fiber STC 38
    • Icynene STC 37
    • The installed performance in batt insulation systems is typically well below that of their tested STC values
  • Metal studs perform better than wood studs by about 5db.
  • Staggering the studs or using dual studs can provide a substantial increase in sound isolation.
  • Increasing the size of the air space in a wall or window assembly will improve its sound isolation.
  • Resilient channel can improve the STC ratings of an assembly and is necessary to improve the Impact Insulation Class “IIC” in floor / ceiling assemblies.
  • A wall must extend to the structural deck in order to achieve optimal isolation. Walls extending only to a dropped ceiling will result in poor sound isolation.
  • Sound will travel through the weakest structural elements, which, many times, are doors, windows or electrical outlets.

The STC of wall assemblies filled with INSU-GREEN cellulose insulation can be estimated by using the table below. Start with an uninsulated 2 x 4 wall and than add the other components to achieve the overall STC for the wall assembly.


STC Additive Estimator for Cellulose Walls

STC Wall Component
27 Starting Wall: Uninsulated wood studs 2 x 4 16" o/c
+3 Studs 24" o/c
+5 Metal studs
+3 1/2" Gypsum
+4 1/2" Type X gypsum
+4 5/8" Gypsum
+5 5/8" Type X gypsum
+2 3/8" Plywood
+3 1/2" Plywood
+4 5/8" Plywood
+3 3/8" OSB
+4 1/2" OSB
+5 5/8" OSB
+8 3 1/2" INSU-GREEN Cellulose
+14 5 1/2" INSU-GREEN Cellulose
+3 Resilient Channel

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