Four Basic Principles To Follow In Your Project

Decoupling With Resilient Sound Clips

When building a new wall, opt for (in order of effectiveness) double stud walls, resilient sound clips, staggered stud walls, and resilient channel (in a distant fourth for multiple reasons). The performance of a double stud wall with a 3" gap and high performing sound clips are about the same in mid to high frequency isolation and very similar in low frequency isolation. The most common resilient sound clips would include GenieClips, Green Glue Clips, and RSIC-1 clips. When implementing decoupling, you should also understand that adding mass has a large effect on low frequency performance. As a result, the effect of adding mass to a decoupled wall is much larger than that of adding mass to a conventional wall. We always recommend to hang two layers of drywall on any wall or ceiling that is decoupled. The added cost is minor compared to the improved performance.

Most often clips are used on the ceilings while the walls are built as a double stud wall or staggered stud wall. Retrofitting for a double stud wall requires that you remove the existing drywall before building the second set of studs. The second set of studs should be spaced at least 2" from the existing wall framing. Double that gap and you will raise performance by about 5 STC points, double the gap again and raise your results by another 5 or 6 STC points. Resilient sound clips will perform better than staggered stud walls in field tests and the cost per square foot will be similar or less than staggered stud walls. Read more about decoupling here, Understanding Decoupling.

Damping with Green Glue Compound

The most effective way to improve the damping for your project is to use a damping glue between two layers of drywall. The most commonly purchased damping glue is without a doubt Green Glue Compound. Using a damping glue reduces the severity of resonance problems, and it reduces the ability of structures to conduct vibration. Reducing vibrations will keep sound from traveling through your framing and to the rest of your house/building. Using Green Glue Compound is the same concept as products manufactured by QuietRock or Supress, but the formula in Green Glue Compound is lab tested to be more effective in terms of sound isolation and more cost effective as well. There are also other types of damping that are often used in sound isolation. For instance, our VibraDamp Pipe Wrap which is used to dampen vibrations in drain pipes and also on anything made of sheet metal. The VibraDamp Pipe Wrap is actually a very versatile product that provides basic constrained layer damping on any plastic or metal surface with basic peel and stick installation. Read more about damping here, Understanding Damping.

Increasing Mass with Extra Layers of Drywall or MLV

Adding more mass to the wall helps. To make a big improvement though you have to make a big change in mass. For example, to improve sound isolation by about 10dB you would have to quadruple the number of drywall layers on your wall. From one on each side, to four on each side. Mass makes a much larger improvement when combined with other techniques such as decoupling. Products like our Mass Loaded Vinyl will be a much more effective solution for adding mass to your walls, ceilings, and floors compared to adding extra layers of drywall. Each layer of 1 pound TotalMass Barrier (1/8" thick) is estimated to be equal to the effectiveness of four layers of 5/8" drywall in terms of sound isolation.

Absorption with Insulation

If there is no insulation in your walls, add some. This will help only slightly if the drywall is not decoupled or damped, but will still help. The rule of thumb with insulation is to make sure to at least use some. Think of an empty wall cavity as an empty drum, if you hit the drum, sound will travel easily through the wall. If you fill the drum with insulation, sound will still travel, but it will be muffled. We recommend using standard fiberglass insulation that fits the wall cavity or ceiling cavity you are working with. Additional improvements are seen from using R-19, or even thicker, but these improvements are progressively smaller, and generally don't help with low frequencies. Use something, but you can save yourself money by not spending exorbitantly on extremely thick insulation or exotic types of insulation. Better yet, take the money you saved, and put it towards something else (like one of the other 3 areas of improvements). In general, anything thicker than R-19 is into the realm of diminishing returns.