Exterior wall concept

Thinking about this outer wall design here and could use some guidance. I have been studying these docs http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir832.pdf http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir693.pdf http://www.nrc-cnrc.gc.ca/obj/irc/doc/p ... /ir761.pdf The walls will be 2x6 wood studs on 24" centers, 7/16ths osb sheer membrane on outside. 14 ft high walls Then as i described in an earlier post, 2x3 strapped horizontally on the 2x6 to make for a 9" outer wall. So lets say that is one leaf for now and will get one or 2 layers of 5/8ths Drywall over the sheer membrane outside. (The floor inside is all cement slap (4") and it is not monolithic, the footings are separate.) Then the inside of the structral wall will remain open(no drywall on the 2x3) and a secondary steel stud wall (on 16" centers?) will go up which on the one face only(inside studio) will get 2 layers of 5/8ths Drywall. How is that looking for meeting my 65 stc? Also I need to decide on insulation for the outer wall sooner than later. Does the idea of using fiberglass for the 9" wall and Mineral fiber for the inner wall make sense or should i go all Mineral? From what i can see in these papers there isn't a ton of difference in the 2 for this application. Only that for airborne transmission, which i believe is what we are mostly dealing with here, that the insulation is important to have in there. The design of the thing is based largely on this room (see pic), dimensionally sort of proportionate but smaller 40'x60', but i think i will opt to keep the Cntrl room the same size as this one. Minus the bright room and dead room as well, i will figure out a solution for the residual parallelness's. Am i out to lunch mostly, partially? I still have not done my tests, but i fully intent to! The building has to go up regardless and it ain't gonna be no cement bunker :) , i only have so much dough. Plus this isn't a 14hour a day, nonstop operation. I track full bands maybe once a month max, loud bands maybe 2-4 times a year. The rest is mixing and piddling about. So there has to be a compromise between what is perfectly correct and what is my situation in reality.

it looks like you will be on your way to meeting your STC 65 goal. are you planning on beefing up the ceiling the same as the walls? the ceiling is going to be large and sound leaving that way could end of traversing further than the wall leakage. on the plus side, you could have a significant air gap between the outer and inner ceilings and that will not only help with the HVAC ducting etc but also the isolation. are you intending to support the inner isolation ceiling on the inner isolation walls? if so, i'd consider wood framing or use heavy steel for the inner isolation wall to ensure it can support that load.

What about using a hanger system for the ceiling? I was thinking of these http://www.kineticsnoise.com/arch/icw/index.aspx Also on that topic, lets say i did add an interior wall (ceiling), what is my best approach with those trusses? Because, am i not potentially creating a triple leaf if i add drywall to the inner side of the trusses and THEN add an addition leaf hanging or supported from the other inner leaf walls? Or is the truss system considered on leaf?

i would certainly consider the trusses and if you only have the roof and then in the inner ceiling, you have your double leafs. depending on how much space you can leave between them will determine how much you might need to do to the outer roof to match the isolation on the walls. you can nest the trusses - side to side like the roof for the live room and booths, and front to back for the CR so you have the slope moving up and away from the front if the CR. let's say you have the exterior 14' walls and go with interior 11' walls, 6/12 (?) on the exterior trusses (which have to support the snow :shock: and suspended ductwork, fire suppression, plumbing, etc ), and 4/12 on the interior ones (which support the drywall mass and electric and treatments).

gullfo wrote:

i would certainly consider the trusses and if you only have the roof and then in the inner ceiling, you have your double leafs. depending on how much space you can leave between them will determine how much you might need to do to the outer roof to match the isolation on the walls. you can nest the trusses - side to side like the roof for the live room and booths, and front to back for the CR so you have the slope moving up and away from the front if the CR. let's say you have the exterior 14' walls and go with interior 11' walls, 6/12 (?) on the exterior trusses (which have to support the snow :shock: and suspended ductwork, fire suppression, plumbing, etc ), and 4/12 on the interior ones (which support the drywall mass and electric and treatments).

Some of this is hard for me to understand. Did you mean to say you consider the trusses one leaf? Just to stick with this ceiling leaf thing for a minute....Are you suggesting NOT lining the inside of the trusses with drywall, leaving them open to the roof, then attaching drywall only to the inside of the inner additional ceiling? Then adding mass to the roof to meet the final goal? That would conform with the other wall design concepts wouldn't it? But in order to stop more lows would it not be advantageous to add 1-2(even 1/2 inch) layers of drywall to the inside of the trusses as well just to add more mass at a different point? The air space in the truss is quite large(see pic) 3-4 feet. So how much more do i need?

Just to be clear on the ceiling structure. The building dimensions are 40'x60' and the scissor trusses run the length of it. So the front of the CR faces the center of the peak of the ceiling.

thinking like this. or just go with the high level ceiling and use angled false ceiling and hangers for trapping.

gullfo wrote:

thinking like this. or just go with the high level ceiling and use angled false ceiling and hangers for trapping.

That is interesting, i hadn't thought of a set of trusses for the CR. I thought i would keep the ceiling 13-14' and use the space(6 feet or so) above that for tapping. What is the advantage to this 90 degree concept? I believe i have seen you mention it in other threads.

gives us the option for an angled isolation ceiling to maximize the available height. if you go with the flat surface it may provide other options for ducting etc overhead and then just create an angled false ceiling inside and use that space for trapping.

I have a question regarding using rockwool insulation. Is it, and if so how is it beneficial to use rockwool in one or both leafs over fiberglass pink in a 2 leaf wall/ceiling system? Would the different densities be an advantage to use one and one(pink/RW)? Can i calculate which frequencies it would help by the thickness of the rockwool, for example 27 cm of rockwool (from what i understand) would absorb to 318hz (math 344sos/1.08m=318hz). Would that hold true inside the wall where it deals with residual frequencies post mass or is the absorption altered somehow? It seems superfluous to use rockwool over pink fiberglass in the walls if it only adds to the lower midband absorption which isn't a problem with the double leaf system anyhow. Thoughts?

use the light insulation in the gap between the inner isolation and outer walls and ceiling. use the heavier insulation inside for treatments. the lighter insulation in the air gap has been shown to do better @ LF than you would expect versus simply calculating it as if it was working within the room as an absorber. using the lighter insulation inside behind rigid insulation is an option where you can benefit from it.

Thanks Glenn :)

Here are a couple SU models. This is the basic layout and the building dims. Thoughts?

of course the CR will have it's angles etc, the thick walls around it represent allotted space for treatment, there is also 3 feet at the back of the CR which is hard to see in the pic allotted for treatment, the actual interior is something like 18x21'. What are peoples thoughts on going with a reflective back wall? Do you think this is a big enough CR to handle that approach. The ceiling could sit around 14 feet. I would sure like that as the CR in my world gets used for a ton of recording.

what is that 4' space on the side of the CR? for the CR, first and foremost its for critical listening so you can make the correct mix decisions. secondly if the room is acoustically pleasing, you can also use it for recording. you could conceptually make the room work as a CR and then use gobos to adjust if acoustically for performances in there. same (type) gobos could be used in the live room as well. I'd plan on making the dry booth larger so you could accommodate multiple people / instruments / amps if needed.

The 4' space is just extra space for treatment or maybe a spot for the tape machines. It came about when the kitchen wall was splayed. As for a dry booth i am leaning toward using part of the amp room for it instead of the little one in the corner. Although i like the idea of that little one as a simple 1 person vocal booth. Something about having the talent down the far end in their own private space is appealing, they(mostly) don't do as well when they are too close to the CR or being watched too close.

if there is an option to change the mechanical room from 10x10 to say 9x13 just to break up the modes there. seems weird but if that room is attached to the building (which hopefully you were considering it on a separate slab and decoupled) then not reinforcing noise levels in that room can lead to overall more quiet... (as a general rule making all rooms quiet/acoustically pleasant is a nice feature to add whenever you're building from scratch and have the option to do so) if it's separated then no problem.

The present state is that the footings are in and the slab(s) will be poured in the spring after framing etc.(concrete costs in winter are outrageous) The mech room has been approached like the rest of the building, the footings are separate from the slab, meaning the 10x10 slab inside is yet to be poured but the footings and framing are in place. So yeah too late to change but i see your point. It is one room removed from the CR and main room and even the dry room if i decide to use the end of the amp room, so hopefully it will be cool. The framing unfortunately is not decoupled. But given what will be in the room(wood fired boiler and oil boiler) i can't see the noise being an issue coming from the room. There is no fan noise from a furnace it's infloor heating. I'm not installing air conditioning, i just plan to implement a fresh air exchange system using inline fans.

2(two) topics with questions comin at ya.... Windows- what are your thoughts on quad pane windows with different thicknesses of glass, one being plexi glass for the exterior walls? That in mind, given i will need to build the detached walls on the inside of the main rec room, and i have 3 windows to deal with there, what about 2 double pane windows? Or would one quad(outer) and a double or even single (inner) be better? Combination? The windows glass sizes are 14"x72"

Diffusion- In the main rec room(see pic) i want to start designing some form of diffusion for the ceiling. Seems to me i can frame the inner ceiling leaf into diffusion with a bit of thought. And then layer it with Fir. The v(inverted) angle of the inner truss doesn't seem conducive to diffusion, i have read that i can expect a focus of sound in the trough. I have read i need one 7th of the sound wave length in the irregularities in the surface i plan to make a diffuser. So my question is, is there a way, given the dimensions of the room, to decide what frequency areas i should be focusing my ceiling diffusion at, or should it be just focused on lows and low mids at the ceiling position and evenly scattered? Ceiling will sit @ roughly a 16ft average.

seaweed wrote:

Windows- what are your thoughts on quad pane windows with different thicknesses of glass, one being plexi glass for the exterior walls? That in mind, given i will need to build the detached walls on the inside of the main rec room, and i have 3 windows to deal with there, what about 2 double pane windows? Or would one quad(outer) and a double or even single (inner) be better? Combination? The windows glass sizes are 14"x72"

the plexiglass is very light and won't do much for isolation. you're generally better off with 2 single panes - they can be laminated - of 3/8" and 1/2" respectively. thus preserving double leaf and avoid triple and quad leaf. in general (also) matching the mass of the glass to the mass of the walls will reasonably ensure you don't create a weaker point with your windows.

seaweed wrote:

Diffusion ...snip... Ceiling will sit @ roughly a 16ft average.

assuming the ceiling is doing it's isolation thing and is effectively a live ceiling (acoustically), i'd consider trapping the peak ala super chunk and some slats (widely space). then a couple of options - scatter absorption to make the ceiling diffusive and absorber the mid-high bits somewhat; hangers below the super chunk and hanging polys - create broad band absorption and some space coupling effects and the polys are diffusive; same w/ hangers and hard panels (as in another thread); or using numeric diffusers suspended on different levels to create pseudo QRD.

gullfo wrote:

they can be laminated - of 3/8" and 1/2" respectively. thus preserving double leaf and avoid triple and quad leaf. in general (also) matching the mass of the glass to the mass of the walls will reasonably ensure you don't create a weaker point with your windows.

Do you mean to laminate the 3/8ths to the 1/2" or laminate the 3/8's to the 3/8ths until the required thickness is reached, then the same for the 1/2" 2nd pane? Is there a way to calculate how thick the glass panes should be to match the wall stc?

gullfo wrote:

seaweed wrote:

Diffusion ...snip... Ceiling will sit @ roughly a 16ft average.

assuming the ceiling is doing it's isolation thing and is effectively a live ceiling (acoustically), i'd consider trapping the peak ala super chunk and some slats (widely space). then a couple of options - scatter absorption to make the ceiling diffusive and absorber the mid-high bits somewhat; hangers below the super chunk and hanging polys - create broad band absorption and some space coupling effects and the polys are diffusive; same w/ hangers and hard panels (as in another thread); or using numeric diffusers suspended on different levels to create pseudo QRD.

Do the slats lay on top of the superchunk? Does the space behind the slats(superchunk area) need to be sealed at the slat edges? I like the plan in your pic best. But i should be clear that the detail you have there would all be on the inner side of the inner trusses as the soundproofing would consist of 2 layers DW on the inner side(roomside) of the trusses, then this diffusion/absorption. Given the slope of the 4/12 inner trusses, how far down from the peak to the outer walls does the diffusion etc need to go? Does sound mostly focus up near the peak and that is where the work should be done or do the middle ceilings and at the edges at the wall connection need to be addressed too?

Do the hangers function as low end diffusion?