Every passing car and truck is a reminder of why you were able to purchase your place for such a low price.  Dealing with exterior noise is obviously a very common issue–especially for those living in major metropolitan areas.  There are all sorts of products and wall constructions that can severely reduce exterior noise, but if you don’t treat the weakest points then you will end up with one expensive (and still pretty noisy) exterior wall.

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 floor space) 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.

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

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