Sandwich Panel Idea.

Innovations · Post by **Innovations** » Sun Aug 01, 2004 7:47 am

One of my quests has been to come up with a design for a DIY freestanding re-assemblable vocal/practice booth. The goal is to be about a third as expensive as kits like "Whisper Room", as good or better islolation, and able to be built with common tools from materials available from just about any home improvement store.

Stud walls really aren't high on the re-assemblabe scale so I have been looking at some sort of panel system that would still be able to have a mass-spring-mass arrangement. After a lot of complicated ideas that still had way too many flanking paths (screws, spacing blocks, etc) I thought about a glued sandwich panel.

From the outside in:

3/4" Medium Density Fiberboard. glued to:
3/4" Expanded Polystyrene (Styrofoam) glued to:
7/16" OSB board (or maybe 1/2" MDF)
2 layers of 5/8" Gypsum Board laminated to the OSB.

So, what I am asking of the collective experience here is...

Is using styrofoam as the spring layer an idiotic idea? Will there be much advantage to the fact that by using a sandwich panel that the spring will be nothing but styrofoam (no studs). Would there likely be an advantage to using thicker styrofoam, say an inch or an inch and a half instead of three quarters?

knightfly · Post by **knightfly** » Sun Aug 01, 2004 10:06 pm

From what I understand, EPS, being a closed-cell foam (or styrofoam too, for that matter) would not act as an air gap but more as just another layer in a laminated single panel. You would get some advantage of different media layers attenuating sound a bit, (different speed = diffraction at each interface) but this would be nowhere near the effect of a low gas-flow resistance material such as compressed fiberglass or rockwool.

I too have been "brainfarting" this quest for a while, but so far nothing I've considered seems to fill the bill... Steve

cadesignr · Post by **cadesignr** » Mon Aug 02, 2004 12:59 am

Hey Inno, I asked the same thing a year ago. To me a vocal booth is simply a box. A crate. Made of panels, no frame. If you could seperate the two mass leafs of the panel by some sort of perimeter iso seal, like a giant refridgerator door seal or something, so the inner panel floats.....well, you get the idea...my whole point was to design a TWO leaf box sort of like a double wall assembly, but easy to assemble ...cheap....good STC performance.....ha!! But as usual, physics has the last word.

fitZ

http://johnlsayers.com/phpBB2/viewtopic ... highlight=

Innovations · Post by **Innovations** » Mon Aug 02, 2004 7:59 am

knightfly wrote:From what I understand, EPS, being a closed-cell foam (or styrofoam too, for that matter) would not act as an air gap but more as just another layer in a laminated single panel. You would get some advantage of different media layers attenuating sound a bit, (different speed = diffraction at each interface) but this would be nowhere near the effect of a low gas-flow resistance material such as compressed fiberglass or rockwool.

I too have been "brainfarting" this quest for a while, but so far nothing I've considered seems to fill the bill... Steve

Well that is what I was afraid of. Unfortunately compressed fiberglass or rockwool doesn't have the structural rigidity to act as a mid layer in a sandwich panel. if it could have worked it would have been cool...just assemble the panels in 4x8 sheets and then circular saw through all three layers at once.

I am beginning to think that the perfect solution, if I had a clue where to find it, would be paper honeycomb, since it could have strength yet would act as an air gap,

cadesignr · Post by **cadesignr** » Mon Aug 02, 2004 3:19 pm

Hey Inno, I worked all day on this. I've got some ideas to toss your way, but they are not quite done. Tommorow. In the mean time, I think your on to something.
http://www.kineticsnoise.com/arch/pdf/sr.pdf

fitZ

cadesignr · Post by **cadesignr** » Mon Aug 02, 2004 3:37 pm

Here is the baby Inno. This is the KEY to do it. Use the honey comb on the floor. Use this to suspend interior MDF wall and ceiling panels from exterior MDF shell and 2x2 frame. I'll post some sections tomorrow. It's an idea anyway.

fitZ

cadesignr · Post by **cadesignr** » Mon Aug 02, 2004 4:14 pm

Well, here is a quicky detail, section at top and vertical corner. Tommorrow, the floor, HVAC, DOOR.
fitZ

Innovations · Post by **Innovations** » Tue Aug 03, 2004 6:32 am

The only problem is that at about $5 per clip delivered and needing about eight clips per sheet this gets to be by far the most expensife material component of the entire assembly.

edit...

I noticed that the installation instructions on these clips specify that each clip should hold up to 36 pounds. Now I notice that the shear strength of 1pcf EPS is 18 to 22 psi. This gives me the idea of using strips along the edges and a few squares in the center, glued, to hold the two layers apart and then fill the rest of the center with an inch of 703.