Home Insulation: Insulating for Sound

Today’s lifestyle is often a loud one. Modern appliances and amenities coupled with today’s high ceilings and hardwood floors help create beautiful indoor environments, but also contribute to noise levels that impact a family’s quality of life. Improving your home’s acoustic comfort with sound insulation can reduce stress and improve overall health and wellness.

What does insulation do for noise?

Acoustic insulation is one of the best ’quieting’ technologies available. A good noise control insulation package not only increases the comfort of your home but also adds to its value. In fact, one of the most economical ways to improve the acoustic comfort of your home is to install fiberglass or mineral wool acoustic insulation—at the time of construction, if possible.

Noise can affect family health

Throughout dozens of studies, noise has been clearly identified as an important cause of physical and psychological stress—and stress has been directly linked with many common health problems. That means that noise can be associated with many of these disabilities and diseases, which include heart disease, high blood pressure, headaches, fatigue and irritability.1

Understanding sound transmission

The Sound Transmission Class (STC) is a single number rating used to indicate the effectiveness of an entire construction assembly (partition, wall, floor/ceiling) in resisting the passage of airborne sound. The higher the STC rating, the better the sound insulation performance of the construction.

STC

AUDIBILITY OF LOUD SPEECH FROM OPPOSITE SIDE OF WALL
25 Easily understood
30 Fairly understood
35 Audible but not intelligible
45 Must strain to hear
48 Barely audible
50 Inaudible

Recommended STCs for your home

For residential partition walls, the recommended STC depends on the particular type of room. For bedrooms, an STC of 52 is good. Living rooms, bathrooms and kitchens should be a minimum of 55.9.

Considering Impact Sound

In addition to the STC rating which concerns airborne sound, floor and ceiling assemblies are also rated for impact sound resistance. Impact sound is structure-borne sound transmitted when one body strikes another, such as in the case of footsteps and falling objects. A single number, the impact insulation class (IIC), is used to describe impact sound performance. As with STCs, a higher number indicates better performance. The current International Building Code requires a minimum IIC rating of 50.10.

Solutions for acoustic comfort

An easy and economical method for increasing the sound transmission loss of a wall is to install sound absorbing acoustic insulation in the wall cavity. Installing fiberglass or mineral wool insulation batts between rooms such as bedrooms and adjoining bathrooms, or between a recreation room and a den or study will keep the noise level between rooms.

Breaking the Vibration Path

An even more effective way to increase the STC rating is to use resilient channels between drywall and studs or joists. Properly installed resilient channels will break the vibration path, which will help reduce sound transmission. Typically, the drywall is screwed to a flange on these channels – not to the studs. By combining insulation, gypsum board mounted on resilient channel, and two layers of 1⁄2 inch gypsum board on one side, a very good STC rating of 52 can be achieved.2

Where to insulate for acoustic control

Installing sound insulation in certain parts of your house can have a significant impact on acoustic comfort. Key areas for insulation include:

  • Exterior Walls
  • Interior Walls
  • Ducts

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Exterior Walls

All exterior walls should be designed and built to meet or exceed the energy code and have an STC rating of not less than 36.17 Exterior walls should be constructed with resilient channels and fiberglass or mineral wool insulation filling the stud cavity. In addition, all exterior penetrations and joints between building components should be sealed as required for thermal performance. This will also improve the acoustical performance.

Interior Walls 

All interior walls between living spaces should have an STC rating of at least 36.18 The basic guideline for installing insulation in wall cavities is to fit the ends of batts snugly against the top, sides and bottom framing.

Ducts  

Duct design should be given special consideration when planning a home’s layout since ducts can easily transmit sound. Installation of sheet metal ducts, lined with sound-attenuating duct liner insulation, or using fiberglass duct board systems will reduce transmission of unwanted sound, including fan noise through the duct. Sealing the joints in the duct system will also improve the acoustic performance and energy savings.

Best Practices for Sound Control

There are best practices for acoustic insulation that you and your insulation contractor or builder should follow for optimal results.

Get the checklist

  • Insulate heating and air conditioning ducts by using fiberglass flex ducts, fiberglass duct board or by wrapping or lining the ducts with fiberglass insulation.
  • Install thick carpeting and padding throughout your home to help reduce impact sound.
  • Caulk around windows and use weather-stripping at the bottom of your exterior doors.
  • Use solid wood or mineral core doors where privacy is required.
  • Install acoustic ceiling panels.
  • Double or triple pane glass and storm windows can help reduce sound transmission through windows.
  • Select quiet, high quality appliances.
  • Install telephones, doorbells, intercoms or audio built-ins on interior walls only – never on common walls or corridor walls.
  • Caulk holes made by wiring that penetrates connecting structures with elastic non-hardening caulk or dry packing.
  • Seal openings around ceiling fixtures so that they are airtight.
  • Make use of plants, draperies and wall hangings throughout your home. The more “soft” objects in a room, the more sound will be absorbed.
  • Minimize window sizes facing noisy areas.
  • Ask your builder to develop a well-planned layout to minimize the noise of flowing water. Insulate walls containing drainpipes.
  • Ask your builder to seal under all bottom plates as the walls are being built.
  • Ask your builder to avoid undercutting doors, if possible. Frequently, doors must be undercut to get proper air circulation for the HVAC. A simpler solution to ensure proper circulation is to keep doors open when rooms are not in use or provide transfer registers.

References:

  • U.S. EPA, Office of Noise Abatement and Control, “Noise: A Health Problem,” p.23
  • National Research Council Canada “Gypsum Board Wall: Transmission Loss Data,” R.E. Haliwell, et. al., Tests TL-93-176, TL-93-166, TL-93-188. March 1988.