If you have ever been inside a moving cargo van, you probably noticed the loud vibrations of the sheet metal panels and wheel wells. In order to decrease unnecessary noise, we decided to install a sound dampening material. Not all van builds complete this step as it is not mandatory for a sturdy build, however since we like to chat as we drive, we decided this would help us to hear one another.
How it works:
Good soundproofing is actually a three-step process.
- Reduce vibration with a sound dampening material (using a butyl mat such as Kilmat)
- Apply a sound absorbing material (closed cell foam)
- Use a barrier to trap remaining sound from escaping (Mass loaded vinyl)
In this step, we will be installing the Kilmat butyl mats to the walls, floor, and ceiling of the Sprinter van. The scientific explanation for how the butyl mats work is that the chemical components convert audible sound energy into heat energy which is then disbursed. Scott would love to talk all day about the science behind this stuff, so if you are curious, just leave a comment below.
A helpful analogy is adding extra mass to a trampoline. Just like the extra mass that you have added dampens the oscillations in the trampoline, the butyl sheets dampen the reverberations from the thin sheet metal.
We decided on the Kilmat brand. It is more affordable than comparable products, but is just as effective and is easy to apply. We purchased 2 boxes of 80 mil butyl to cover the sides of the van, ceiling and wheel well. Because the floor has less of an issue with resonance, we were able to use one box of a thinner (and slightly cheaper) 50mil butyl.
We had already sanded, primed and applied undercoating to the interior of the van (See our article on rust proofing the van). Because of this step, we were ready to apply the Kilmat sheets directly to the siding. If you do not prime and undercoat the interior, you may have to use acetone and a cloth to remove any excess oils and dirt before applying the Kilmat sheets.
The Van Build Process: Applying the Sound Dampener
Starting with the walls, we began applying the self-adhesive 80mil butyl. The sheets do not necessarily need to cover 100% of the metal to dampen the sound, as long as the center is covered. However, the more coverage you have, the greater the difference it will make. Because we only purchased two boxes of the 80mil, we were conservative with the material and concentrated the sheets toward the center of the panels.
Make sure that you press the sheets firmly, using the roller to eliminate any and all air bubbles. The great thing about Kilmat, is that the design has a built-in quality control. The sheets themselves kind of resemble the texture of corn on the cob. When applied properly, the textured sheet should become smoother like aluminum foil.
After finishing the sides and ceiling, we moved on to the floor using the lighter 50mil butyl. Using a box cutter, we cut the sheets into appropriately sized pieces to fit into the many grooves, nooks, and crannies. After the major areas were covered, we still had plenty of 50mil sheets left over. We decided to use the remaining sheets as a secondary moisture barrier in areas of high traffic. We applied the sheets on the floor near the sliding door, the back swinging doors, and what will be the kitchen area.
After finishing the floor, we opened the second box of 80mil butyl to completely cover the wheel well. Because this area tends to generate the most noise, it is very important to completely cover these areas.
Sound Absorber and Barrier
The sound absorber (closed cell foam) and sound barrier (MLV) must be applied next to each other. Basically, the MLV is one solid sheet of vinyl that prohibits sound waves from passing through. The foam provides a cushion (thereby reducing any audible vibrations) between the vinyl and whatever it is resting against.
We wanted as much of the interior stuff (insulation, foam insulation, furring strips) to be under the MLV as possible. Therefore, the foam and MLV was not installed until after the insulation and framing. That tutorial will be posted soon.
With the sound dampener step complete, we are now ready to move onto installing our moisture barrier.
- Be sure to roll all of the air pockets out of the Kilmat sheets. In order to maximize effectivity, the sheets must be rolled flat.
- Make sure that it is warm enough outside to apply the Kilmat, otherwise, it is very difficult to roll out the butyl. (It must be at least 50 degrees for proper application.) When we used the sound dampener, it was chilly February weather at 30 degrees. As a result, the mats were incredibly difficult to smooth out. We were forced to use a heat gun in order to heat the mats to a state where they were more malleable. (Note: We did apply the Kilmat to another area about 2 months later when it was significantly warmer. This time, the sheets were super simple to roll out.)
- The Kilmat sound dampening sheets really do make a big difference. Prior to installation, knocking on the sheet metal siding would give you a long echoing vibration. With the Kilmat sheets now applied, the sound has become more of a low thud. As long as you aren’t trying to apply the mats in super cold weather like us (which the instructions clearly tell you not to do), we highly recommend Kilmat
***Disclaimer: We are not professional woodworkers, electricians, or builders…but Scott is a physicist, so he thinks he is all of those. When converting a van into an RV, there are countless options for materials and methods. We just wanted to share what methods worked best for us. 🙂