Reducing Exterior Noise

Introduction

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 do not 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 an occasionally a door. 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. If you treat just one area, whether with Green Glue Compound, 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 unless you address every issue in your wall.

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 are not 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, less than 1/2 the STC rating of your exterior wall.

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. Replacing your windows will definitely provide you with the cleanest look and a proper window design can yield pretty good results for a window.

You can avoid this construction headache if you prefer by adding a second window on the inner part of your window frame. By simply adding a second double pane window you will increase the STC rating between your two windows to the high 40’s and low 50's range with minimal construction. 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 search 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.

Finish the Wall

Now that your window has been properly isolated we can move onto 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 Compound at a rate of 2 tubes per 4' x 8' sheet of drywall. Applying the Green Glue Compound is really simple, the hardest part will be to hang, tape, and texture the drywall. Adding the Green Glue Compound 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, such as the GenieClip, with furring hat channel to your studs. Beyond this recommendation you could frame in a double stud wall that will cause you to lose at least another 7" of floor space. 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. As a rule of thumb, a wall can rate about 10 to 15 STC points higher than an opening such as a window or a door without major degradation of the wall's overall rating.

To us, the best bang for the buck is adding a second window to the existing opening and treat your wall with just another layer of drywall and Green Glue Compound. If your wall does not have any windows or doors installed on it then consider upgrading your wall using either a double stud framing technique or resilient sound clips like the GenieClip. The added performance of clips over Green Glue Compound in a wall without windows or doors is huge.