Alternative Mass loaded vinyl installations
There is more than one method for installing mass loaded vinyl to obtain maximum effect. The standard of the industry is to install the MLV directly to the stud or joist framing using an industrial stapler or heavy-duty roofing nails that have the large plastic heads. This method is known as the membrane or septum method. The MLV works well when placed on a wall or ceiling in a membrane fashion. It should never be sandwiched between layers of drywall unless you can provide a dead air space where in the MLV can resonate or move with the sound waves. This can be accomplished with the use 1" furring channels that will allow the MLV to resonate between 2 layers of drywall. For more information on installing mass loaded vinyl over existing drywall, please call or e-mail us before you purchase or install this material. You have a choice of 1lb or 2lb mass loaded vinyl. Obviously the 2 Lb would be more effective (32STC) as opposed to (26 STC) for the 1lb, but it is more costly and that extra cost may not be necessary. A lot depends on your soundproofing issues. Shipping on the 2 LB mass loaded vinyl can also be a factor. It is always better to pick up these materials at the source whenever possible. There is not a lot of information on the Internet in regards to the installation of mass loaded vinyl, hopefully we will be able to separate the fact from fiction. If you are constructing new walls using the staggered stud method, it would be beneficial to actually weave the vinyl in and out of the staggered stud assembly itself. This picture gives you a rough idea of how this would look. The key to weaving MLV (or any barrier material) is to seal the vinyl as best as possible at the seams and around the perimeter. In the case of a horizontal weave (the most common weave) it is best to overlap the seams by at least 1" and seal that overlap with acoustical caulking as well as a quality seam tape. The weaving of MLV also aids in the defusing of sound waves. The weave also allows the vinyl to resonate or move with the sound. As you know, it is important that the MLV be able to resonate in order to work to it's full potential. You can also use the weave on a standard stud wall provided there is no drywall installed on either side of the studs (just to open studs). This weaving method can be hampered however by stud cross members, so it is best to have only vertically installed studs if you are planning to do the weave. If you weave the MLV on a normally studded wall, there also may be problems with the drywall sitting level on the studs. If your studs are 16" on center, then every other stud will have 1/8" of increased width compared to the studs that don't have the MLV woven on top of them. To keep the drywall even on both sides, a sound isolation tape can be adhered to every other stud that that is not covered with the woven MLV, this will make all of the stud surfaces flat and even and the drywall will rest evenly on the studs. From the feedback of our contractors in the field, we have discovered that the more a wood structure is dampened, the better the soundproofing will be in a wall or ceiling assembly. This is especially true for impact noise from above. There are many ways to dampen a wood frame assembly and some are more effective than others. Some contractors have used blown-in cellulose in order to dampen the joist or stud structures, but cellulose has no mass and though it will help to a degree, it is much less effective than using blown-in closed cell foam. We have obtained the best results by installing Roxul mineral wool in the stud and joist cavities. Roxul is a mineral wool sound insulation that also maintains the R factor of thermal insulation. The Roxul can be used along with standard fiberglass insulation in order to completely fill the joist or stud cavities. Once the cavities are filled with the mineral wool you are ready to add the mass loaded vinyl. The MLV will be stapled or nailed directly to the studs or joists. The MLV needs to be like a membrane across the stud or joists. Once this is complete you will need to caulk the seams as well as the entire perimeter of the vinyl membrane, and then tape the caulked seams. It is not necessary to tape the perimeter but caulking this area is essential. Once the sealing of the vinyl is complete, all that is left is to install the drywall. For the best soundproofing, we recommend installing 2 layers of ½" drywall. If this is not possible, then 1 layer of 5/8" fire code drywall will suffice. This has been a brief description on alternative methods of installing mass loaded vinyl. I hope this little article has helped clear up the misconceptions about the installation of MLV.
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