Exterior wall, width limited. What do you think?

One thing to consider; which is better, perfectly proportioned space that you can't use because of noise problems, or slightly smaller space that's usable 24/7? If you don't have any more space to expand your envelope OUTWARD, those are your two choices; even tho the "magic Bullets" approach like MLV, Quietrock, etc, may improve TL somewhat in a given wall thickness, I've yet to see any of them that are even close to cost-effective... Steve

Thanks Steve. That I guess sums it up. We either have to scale down the room a little bit or make it larger but where it is we are going to pay through the nose to achieve the level of isolation we are looking for. I started with the staggered wall with double 5/8" but ran of our room quickly. I greatly appreciate your comments and your insight. Michael Lee Draftsman

I have NEVER seen any test data indicating QueitRock etc is cost effective. Neither for any hybrid type either.

I'm not married to the Quietrock idea it's just they they have an exterior sheathing that paired with their interior product they claim they can get to STC-54 with it. I'm just starting to look into it and have no claim to expertise. Just with the limitations, it was worth the review. The only reason it might be cost effective is from a labor standpoint. I think the cost of materials is more but you only apply one layer to each side vs the exterior and RC, Rock, Viny, Rock layer on the inside to get close the the same STC they are claiming. Again, I'll be doing a lot more research on their product before this is over. I'll want to see some independent information to support their positions. Thank you for all the great links. The 4" concrete has its advantages but I'm not certain if that's the direction the owner wishes to go. Michael Lee Draftsman

From what I can see, the 5-1/2" concrete wall will do as good or better than using two layers of "quiet rock" product, and at approximately HALF the cost - that's why I brought it up... Steve

celotex isn't a high mass product, and having only that on the outer leaf of your wall will weaken the isolation considerably. Using MLV will agravate any moisture problems and help you grow mold

- I know about the Celotex but when I started the project, we had an exterior and an interior wall. Due to size contraints, I only had 1/2" left for exterior sheathing and 1/2" OSB wasn't very good either. At least the Celotex breathes a little. I agree about the vinyl, hugh moisture trap. If we were to use that product, one side of the structure had to breath if the other side couldn't. Just my reasoning.

If you're going to use a mass-air-mass wall, I would use 3/4" OSB on the outside, unfaced insulation, preferably 3-4 PCF mineral wool, and two layers of 5/8 gypsum wallboard on the inside over Resilient Channel - the OSB has more mass than celotex and is stronger against racking - the wall I just described would have an STC of 60-61, with its low end at 25 dB @ 50 hZ, roughly. The concrete is still better... Steve

I was thinking of 3.5" of Owens Corning CB-300 insul if that's okay. Let me know if the mineral wool is better and what products you prefer (brand wise). Thanks again for your time and expertise. Did not want to proceed with construction drawings until we had worked out all these details. Your guidance is appreciated. Michael Lee Drafsman

knightfly wrote:

From what I can see, the 5-1/2" concrete wall will do as good or better than using two layers of "quiet rock" product, and at approximately HALF the cost - that's why I brought it up... Steve

I appreciate the advice. I will definitely consider it if we cannot make the walls any larger. LOVE that program. Seems quite unique.... Michael Lee - Draftsman

Hello Gents.....quick relative question Steve. Is there anything that says you CAN NOT use a layer of 5/8" drywall BEHIND the OSB on an exterior wall, IF you use a visqueen layer between the two? Woudn't that increase the mass of the exterior leaf? Just a thought. fitZ :?

Rick, not sure about the gyp behind sheathing yet; will try to find time tonight at work to check the IBC on this; meantime, I'm still digesting stuff on vapor barriers and all the misinformation and WRONG code rules, etc - here's one reason why - http://irc.nrc-cnrc.gc.ca/cbd/cbd175e.html Michael, here's the link to that freebie Insul calculator; the real one costs over $1000, but is 'way ahead of the old demo. Still, lotta bux if you're not doing this professionally. Oops, lost it; I'll post it later when I have time - I'll come back to this tomorrow nite after I'm out of the coma... Steve

Michael, here's the link to that freebie Insul calculator; the real one costs over $1000, but is 'way ahead of the old demo. Still, lotta bux if you're not doing this professionally. Oops, lost it; I'll post it later when I have time -

I found the demo but the version I have doesn't allow me to change the Gypsum Board to anything else. It's crippleware. You must have an different demo version... Oh well. Actually, I start my new position as Project Manager tomorrow so I might get the 30-day demo through my new firm if the boss is okay to the idea. I think that would be a great tool to have around anyway with all the AV rooms in these high end homes. Thanks for everything Steve... Michael Lee - Draftsman

I found the demo but the version I have doesn't allow me to change the Gypsum Board to anything else.

You can change the physical properties of the material to effect concree etc. Twisted thinking: Andre

Sorry, didn't have time to explain some of the "tweaks" - if you click on Material Constants, you can change the density from 690 to about 2000 - then, change the layer thickness to whatever amount of concrete you want to simulate; the results are within 1-2 dB of published results for concrete walls. You will NOT get the same results by just adding 12.5mm layers to get 6" of material. IF you drop the density from 690 down to about 600, you can model plywood fairly close. Be sure and change the panel size at the top of the window; it's set pretty large, and will affect results. I usually set this to 1.2 x 2.4 meters. You can't change the insulation type, so you're stuck with that; you can do two different materials per side of the wall, but only one layer of one and several layers of the other. Doing this, you can approximate using a layer of 1/2" wallboard between two 5/8; only it will look like the 1/2" is on one side of the two thicker layers - the coincidence graph will still reflect the changes. The setting for steel studs is apparently calculated for NON-structural, or 25 gauge, studs; it returns essentially the same result as resilient mounting, and the only reason this would be true is if you used the lighter more flexible studs. There are probably a few other tricks I've either not found or not remembered; if you want more, you can always cough up $1200 for the full newer version; they've discontinued the personal version that used to be about $200. I asked Keith at Marshall-Day if they intended to produce a new personal version, and he said they didn't think so. Hope that helps... Steve

There are probably a few other tricks I've either not found or not remembered; if you want more, you can always cough up $1200 for the full newer version; they've discontinued the personal version that used to be about $200. I asked Keith at Marshall-Day if they intended to produce a new personal version, and he said they didn't think so.

Daggone greedy Aussies. I guess too many sound engineers were opting for the lesser cost version. I wonder how many $1,200 packages they'll sell in comparison? We'll tinker with the values. Thanks again! Michael Lee - Draftsman