Acoustic underlayment is used anywhere a higher level of isolation is required in both STC ratings and IIC ratings.  The materials used in acoustic underlayment are usually recycled rubber, cork, a combination of rubber and cork, and foam.  Other underlayment includes adding Green Glue between the existing sub-floor and a new layer of sub-floor or “mass-based” rigid underlayment usually made of concrete type materials.  The higher performing underlayment (rubber, cork, or a combination) are usually required in multi-family housing and other commercial applications to achieve a field test IIC rating of 45+ and a lab test IIC rating of 50+.  Most condominium structures and large commercial buildings use thick concrete floors and steel framing so these ratings are achievable with an underlayment of minimal thickness–typically around 2mm depending on the flooring used on top of the underlayment.  For example, tile floors will require a thicker underlayment as they will generate considerably more noise than a vinyl floor or even a hardwood laminate.  Learn more about soundproofing at soundproofingschool.com.

Different Ratings For Underlayment

STC ratings largely cover the higher frequencies like speech, radio, and sounds from the TV (not including sub-woofer).  IIC ratings is a way to calculate the level of isolation in relation to impact noise or structure-borne noise which would include footfall, a chair dragging along the floor, or other common noises typically caused by every day living.  The IIC rating is important because a floor can have a sufficient STC rating, say in the low 50’s, but won’t do much at all for isolating impact noise.  With that said, IIC ratings can be very misleading in most cases because it is a rating for the entire system and not just for the material added to the current construction.  Most IIC tests include several inches of concrete, a layer of Gyp-Crete or similar, and usually an acoustically rated ceiling on the underside including either steel stud framing or resilient channel.  So the solution for this dilemma, to cut through the bogus claims of 70+ IIC is to find out the Delta IIC rating.  The Delta IIC rating, or usually written as ?IIC, is a rating for what the material truly isolates on its own.  Like every sound rating the Delta IIC can be misleading as well as performance of a product on a concrete sub-floor will vary from the performance of a product on a wood floor.

If Many Ratings Are Misleading Then What Should I Do?

Unless you can verify the materials used in a test then you can either trust the person trying to make the sale on the product or educate yourself on what type of materials and methods can actually isolate sound.  For walls and ceilings the best way to isolate sound is to decouple the room you are in from the existing structure as much as possible.  The same is true for floors, but the cost of doing this in floors, at least properly, can be ridiculously expensive.  The next best option is to dampen the connection between the flooring and the sub-floor.  To do this you really only have two options.  You can either use a resilient underlayment or add a layer of sub-floor to the existing construction with a damping glue between the existing sub-floor and the new layer of sub-floor.

Using Green Glue To Dampen

Adding the second layer of sub-floor with a damping glue like Green Glue will definitely provide some great results.  The only problem is that installation can be very complicated and limited to certain floor constructions.  One of the limitations is that you can only properly add a layer of sub-floor and Green Glue to the existing sub-floor if the existing sub-floor is wood and not concrete.  This is because the new layer of sub-floor will need to be screwed into the existing layer of sub-floor so that the Green Glue can properly compress between the two layers of sub-floor.  Another limitation of using Green Glue and an extra layer of sub-floor is simply the labor of installing another layer of sub-floor.  It really isn’t much of a DIY project, at least not for a novice, and can be pretty close to impossible to accomplish in a retrofit situation if you don’t have the space to setup a table saw to cut the sub-floor to fit your existing floor.  So adding a layer of sub-floor and using Green Glue is a great option and can be very affordable in comparison to rubber underlayment if all the labor is done yourself or free by someone else.  SIDE NOTE: Have you ever read a paragraph that used the word ’sub-floor’ more than this paragraph?

Using Rubber To Dampen

Solid rubber is without a doubt the most resilient underlayment available.  In fact, 2mm of rubber underlayment is equal to 6mm of the next best performing underlayment which is cork.  Rubber underlayment usually comes in 4′ wide rolls in either 25′, 30′, or 50′ lengths and 2mm, 3mm, 5mm, 6mm, 8mm, and 12mm are the most common thicknesses of rubber underlayment.  The advantage rubber underlayment has over Green Glue is that it can be used on wood floors, concrete floors, wherever, and installation only involves rolling out the underlayment and taping the seams together.  You can glue it down, but you definitely don’t have to and really you shouldn’t glue it down if you are using a floating floor on top of the underlayment.  Acoustical underlayment manufactured from sustainable recycled rubber composite, offers optimal sound reduction while remaining impervious to the elements for life.  Unlike natural cork, recycled rubber remains permanently resilient and will not embrittle with air exposure.  Recycled rubber underlayment can be used with most all wood flooring installations, including glued down, nailed down and stapled down.  It is also specified for use beneath ceramic tile, cork floors, carpets and a variety of resilient sheet and tile floors.  As is the case with acoustic cork, whenever you are installing flooring by a method other than free-floating, the underlayment must be attached to the sub-floor as opposed to simply laying it down.

Using Cork To Dampen

True acoustic cork underlayment will provide a high level of sound reduction as long as the cork used is 6mm or thicker.  Acoustic cork underlayment is spec’ed for use under all types of flooring including glued, nailed, and stapled down installations.  With some flooring types (typically hardwoods and hardwood laminates) you may need to install a moiseture barrier under the cork.  Most manufacturers will accept a 6mil plastic sheet as a moisture barrier.  Be sure to consult the manufacturer before installing your flooring over cork without a moisture barrier.

Cork is also a very affordable build-up material that can be used to create level transitions from tile, hardwood, and carpeted surfaces.  As with rubber underlayment, whenever you are installing flooring by a method other than free-floating, the underlayment must be glued to the sub-floor instead of utilizing a free floating installation of the underlayment.

Conclusion

The only effective way to isolate impact noise and reduce sound transmission between floors is to use an underlayment that can properly dampen.  Rubber underlayment will always perform better than the rest and also has several other advantages in regards to longevity and providing a quality moisture barrier.  Cork underlayment is a very cheap product that can perform well as long as you have a really thick cork.  A 6mm cork will only perform as well as a 2mm rubber underlayment, but that may be all you need for your project.

Does the QuietBox Work?

The QuietBox definitely does allow you to use recessed lighting in your ceiling without reducing the acoustic integrity of your ceiling.  The QuietBox is made of 3/4″ MDF which is a very thick and dense material that provides a significant amount of mass to improve isolation.  The product that really helps the QuietBox isolate sound is Green Glue.  The Green Glue is applied liberally at a rate that is the equivalent of 3 tubes per 4′ x 8′ sheet of material.

If you are using double layer drywall and Green Glue on your ceiling then the QuietBox will perform as well as your ceiling.  If you are installing sound clips on your ceiling then the inclusion of the RSIC-DC04 clips will help maintain a consistency in your theme of decoupling.  In terms of sound isolation, think of the QuietBox as an extension of your ceiling.  The level of performance the QuietBox provides will in no way negate the isolation performance of your ceiling.

How Do I Install A QuietBox?

Our QuietBox is attached directly to your joists using RSIC-DC04 clips.  These RSIC-DC04 clips are included with each box and very easy to attach to both the joist and the QuietBox.  The attachment of the QuietBox is very simple, but does require electrical work to bring power to the recessed light.  We can only provide installation help in regards to the box itself.  Please click the link below to review the steps to installing a QuietBox.

READ OUR IN-DEPTH QUIETBOX INSTALLATION GUIDE

QuietBox Product Specs

Recessed Lighting Specified For This Box

We chose the Halo line of lighting products because of the affordability and availability nationwide.  Halo products are available at almost every electrical wholesale supply house and every Home Depot or Lowe’s in the United States.

For 6″ Lighting: Halo 6″ H7ICT and Halo 6″ H7ICAT.

If you do not have the Halo 6″ light that we have specified then make sure your 6″ light fits the specifications of the light to the left.  The QuietBox allows for 8″ of height within the box.  Allow for 1/2″ of this 8″ to remain a gap between the back of the light and the interior layer of drywall.

For 5″ Lighting: Halo 5″ H5ICT and Halo 5″ H5ICAT

If you do not have the Halo 5″ light that we have specified then make sure your 5″ light fits the specifications of the light to the right.  The QuietBox allows for 8″ of height within the box.  Allow for 1/2″ of this 8″ to remain a gap between the back of the light and the interior layer of drywall.

For 4″ Lighting: Halo 4″ H99ICT

If you do not have the Halo 4″ light that we have specified then make sure your 4″ light fits the specifications of the light to the right.  The QuietBox allows for 8″ of height within the box.  Allow for 1/2″ of this 8″ to remain a gap between the back of the light and the interior layer of drywall.

The RC Assurance Clip acts as an impenetrable washer that puts extra space between the channel and the joist.  The snap on clip works with any resilient channel but is specifically designed for use with RC Deluxe from Dietrich.  RC Assurance Clips are used with resilient channel to eliminate the possibility of short circuiting your resilient channel installation.

RC Assurance Clips will not improve the performance of a successfully installed resilient channel system, but will ensure that your resilient channel installation is a success.  Almost every resilient channel installation will have at least one short and most installations will typically have short circuits in 15% or more of the connections.  While decent results can be accomplished with resilient channel, if you have multiple short circuits then the benefit of the resilient channel will be completely negated.

Developed a number of decades ago, resilient channel is one of the first sound isolation products used.  The popularity of resilient channel has been reduced significantly with innovations such as resilient sound clips and Green Glue, but resilient channel remains pretty popular in some parts of the United States.  One of the reasons resilient channel has become less popular is a huge and common issue with the installation of resilient channel.

The typical design and UL assembly calls for a fastener of 1”.  The typical installation utilizes a 1.25” or 1.5” fastener, mostly to aid in the “grab” of the screw to the channel.  This minor modification assures that 15% of the connections or more will be compromised and that the performance of the system will short circuit the low frequency transmission effectiveness of the system.  Now that lab tested 52 becomes a field 42.  The resilient channel needs another 0.375” to assure that connections are limited between the gypsum board and the joist assembly.  The RC Assurance Clip provides that space.

How Many Would I Need?

Each stud or joist that your resilient channel crosses will require an RC Assurance Clip.  The number of clips you need will depend on the spacing of your studs or joists and the spacing of your resilient channel rows.  Framing is typically 16″ on center and resilient channel is typically spaced 24″ on center.

Use this table below to help decide the number of clips you need.  Choose your framing spacing off to the left and the spacing for the resilient channel from the top row.  Then take your total square footage of all the areas where resilient channel will be installed and multiply it by the corresponding number below.  That will be a pretty good estimate of how many clips you will need.

So if you are putting resilient channel on an 8′ tall wall that is 12′ wide then you will need approximately 50 RC Assurance Clips if you space your resilient channel 2′ on center from floor to ceiling.  A quick calculation for how many clips you need can be accomplished by taking the total square feet of your wall or ceiling where you are installing the resilient channel and divide by two.

How Do I Install These Clips?

• Resilient channels should be RC Deluxe as manufactured by Dietrich. Lawn Care Service in Boise, Star, Meridian, and Eagle Idaho.  Or equal dimensionally manufactured product.Nominal dimensions are:

  a. 2.5” overall width
  b. 0.50” thickness dimension
  c. 0.50” screw area for the RC Channel to the joist
  d. 1.50” screw area for gypsum board to RC Channel
  e. 25 gauge galvanized steel

• RC Assurance is a spacer that is used in every location where a resilient channel is connected to a joist.
• RC Assurance is designed to snap on to the 0.50” FLANGE of a resilient channel with the pinch point on the top and bottom. The 90 degree leg points down toward the open area of the resilient channel.
• Spacing for Resilient Channels varies from UL Assembly & may be between 12.0” on center to 24.0” on center. Please consult your project specifications for proper spacing.
• Layout all resilient channels, following the recommended guidelines of the Gypsum Contractors Association, UL & the project specifications.
• FASTENING THE RESILIENT CHANNEL TO THE JOIST WITH RC ASSURANCE™
  For installation with RC Deluxe from Dietrich, snap enough RC Assurance onto the flange of the resilient channel to fasten the entire 12 foot section, one for each joist connection; RC Assurance will lock & slide to the proper position. Use a 1 3/4” Type “S” bugle head screw to fasten the assembly to the joist. Complete the installation of the channel leaving a small (0.125”) gap between the structural wall elements & the butt end of the resilient channel. Where possible, utilize the screw holes in the resilient channel but where alignment with the center of a joist does not work screw through the resilient channel to fasten to the joist.
• SEAMING RESILIENT CHANNEL
  Most assemblies require a 4.0” overlap of resilient channel butt ends. For this application, slide the two flanges into the RC Assurance & screw through both pieces to fasten to the joist.
• CONNECTING GYPSUM BOARD TO RESILIENT CHANNEL
  Consult the UL Assembly specification or the project specification for the type of screw to install. Typically, Type “S” or Type “W” bugle head screws are required. RC ASSURANCE is typically installed with 1.25” Type ”S” screw for the first layer of gypsum board and with a 1 7/8” Type “S” screw for a second layer.

DOWNLOAD THIS INSTALLATION GUIDE AS A .PDF

Conclusion

You only have one shot at attempting to isolate sound.  If you decide to go with a resilient channel system and you short circuit the channel then your efforts will not be effective.  RC Assurance Clips are very affordable and only add a cost of about fifteen cents per square foot to your project.  The benefits of the RC Assurance Clips is huge compared to the minimal cost which is why this clip is a must if you are planning on installing resilient channel on your project.

Click here to purchase RC Assurance Clips from our store.

A typical exterior wall is made up of a layer of drywall, 2″ x 4″ framing, R-13 insulation, a layer of OSB sheathing, and either siding, stucco, or brick.  Exterior walls will also of course have windows and a door every now and then.  The STC rating of your exterior wall will not be much better than your interior walls.  An STC rating for a regular interior wall will be somewhere in the low to mid 30’s while your exterior walls are usually in the high 30’s to low 40’s.

The first thought by most customers is to purchase a ’save-all’ sound isolation product to make all their troubles go away.  Whether you buy Green Glue, resilient sound clips, mass loaded vinyl, heavy exterior doors, ’soundproof’ windows, specialty insulation, or whatever other product someone is willing to sell you; your efforts will not be successful if you don’t incorporate multiple methods to improve sound isolation.

Deal With Your Weakest Links First

Exterior doors typically perform decently because they are usually solid wood and sealed very well from the exterior elements.  So while the doors aren’t the best for isolating sound, they are not usually the weakest link.  Windows, on the other hand, can transmit sound almost as well as they transmit light.    The average STC rating of a window is in the high 20’s, about 1/2 the isolation properties of your exterior wall, ouch!

Replacing your windows with ’soundproof’ windows may help performance, but you will have a major construction project to undertake.  You will need to essentially remove a 4″ or so perimeter around the window to remove the existing window and install a new window.  If the exterior of your house is rock, brick, or stucco then this can be a major project.  Avoid this headache and high cost by adding a second window on the inner part of your window frame.

Adding a second window will increase isolation in two ways: 1) by adding an air gap between the exterior window and the newly installed interior window and 2) by adding an extra path for sound to have to travel through.  Simply adding a second double pane window you will increase the STC rating between your two windows to the mid to high 40’s.  At that point your windows will perform better than your thick exterior walls!

There are several companies that sell windows that can be used for retrofitting on the interior side of your windows sill.  Run a Google search or humor the Microsoft guys and try their new Bing to find a company near you that sells retrofit windows.

Watch the video below to see the effect of adding a second window to your window installation.

Now, Let’s Improve the Rest of Those Walls of Yours

Your windows now have an STC rating of almost 50, yipee!  Now you need to continue on fixing your new weakest link, your walls…

As I mentioned before, your exterior wall STC rating is likely somewhere in the high 30’s to very low 40’s.  The most basic way to improve your walls at this point with minimal demolition would be to add a layer of 5/8″ drywall with Green Glue at a rate of 2 tubes per 32 square feet.  Adding the Green Glue is simple, the hardest part will be to hang, tape, and texture the drywall.  Adding the Green Glue and additional layer of drywall will bring your STC rating up to the low to mid 50’s and will improve low frequency isolation significantly.

Now your walls will perform just as well as your windows and without major investment into your project this is likely as good as it will get.  You can add decoupling to this scenario to increase isolation, but this will involve removing the wall’s current layer of drywall.

If you would like to go this far then you will need to remove the drywall to avoid a triple leaf effect and then add resilient sound clips with hat channel to your studs.  After removing the drywall, rather than using clips you can also build another 2″ x 4″ wall in front of the current exterior wall, insulate the newly framed wall, and then hang a layer of drywall on the new wall.  This will improve the performance of your walls quite a bit more than a layer of Green Glue ever could and even better than a resilient sound clip system could.  The problem with this though (other than having to sacrifice another 6″ or so of floorspace) is your wall will be big and beefy with a great STC rating, but your freshly installed second window will still be rating in the high 40’s.

If your double stud wall has a rating of around 70 STC and your windows are high 40’s STC, then your final STC value for your wall will be much closer to the window rating than the uber-high double stud wall rating.

Conclusion

If you want to keep exterior noise out of your sanctuary then start by improving your weakest links.  Improve your windows and make sure you have a quality exterior door that is well sealed.  If that does not satisfy your appetite for sound isolation then add a layer of drywall with Green Glue or a similar damping compound (ie, Decibel Drop, QuietGlue, QuietRock) in between.  Don’t forget to get your windows cleaned in the treasure valley area by Clear Impressions Idaho.  Boise Window Cleaning

Still have questions?  I guess we didn’t explain the topic well enough.  Let loose, ask us a question or two.