Help with Planning & Building of my Recording Studio

OK!! I think I've finally found something that works. The boxes don't have as many sudden changes in direction as the previous ones I had drafted but I believe these will work great. You'll see that I had to angle the outlet a little in order to have them spaced out as much as possible. Here are a few pics to show what I mean. Here's another example of a bigger box that has a few more changes in direction. I might try and use those for the Live Room since I've got a bit more room to work with. Let me know what you think :) Francis,

Not exactly how I pictured them, but those should work as well! My only question is how will you get your AHU hooked up to those? Greg

Not exactly how I pictured them, but those should work as well!

I think so as well. After having measured everything this design was the best I could do width wise. Even length wise I had to shrink them down from the second design above. The slopped ceilings are really a challenge but I'm happy with the results of the boxes. I'm happy that I was still able to make them bigger than the min requirement as this should help me with reducing velocity. The internal pathway is 8" x 10" (80in2) and the outlet sleeve is 8" x 12". That's 20in2 more than the minimum for the CR and with that size I can maintain a ceiling height of 8ft. As for the Live Room I'll try and use the second design above. That design has a few more changes in direction but have the same internal pathway and 15in2 more CSA than the minimum required.

My only question is how will you get your AHU hooked up to those?

Here's a quick picture of my original idea. I'll be running supply and return branches in between the inner leaf walls of the rooms. Basically the ducts will run all the way up against the ceiling from the floor and then run parallel with the support beam (on both sides supply on one side and return on the other) over the silencer box and then down to connect in the middle with some adjustable elbows. I'm currently adding more details to my sketchup plan that shows the framing details of the walls and ceilings, along with the ducts. I'll post pics once I've got that done. Cheers! Francis,

Here are a few pics to show what I mean.

Looks like it should work fine, but I would double up on the baffle thickness at entry and exit: Imagine tracing a straight-line path directly from the duct entry point to the register outlet point, and seeing how many obstructions you hit, and how thick they are. If all you find is one thin layer of MDF, then you should do something about that! :) - Stuart -

Thanks Stuart! I'm glad you think these will work!

I would double up on the baffle thickness at entry and exit: Imagine tracing a straight-line path directly from the duct entry point to the register outlet point, and seeing how many obstructions you hit, and how thick they are. If all you find is one thin layer of MDF, then you should do something about that!

I'm sorry, I'm not sure i get what you mean by this. Are you saying the far end corners at entry point should have some sort of 45 degree angle on them and same at the exit point? Any change you can draw over my pictures to show what you mean? Francis

Great work dude! Greg

Thanks man! I'm getting better and better with sketchup so it's not all wasted time haha. I'm really glad things are starting to line up. Next steps for me is to redo all my Equivalent Length calculations and confirm all is good and hopefully start building the two silencers for the Control Room this weekend. Quick note fresh-air wise, I think I've found a suitable HRV unit that can be hooked up to my future ducts. https://www.venmar.ca/106-air-exchangers-k10-hrv.html. I'll be going shopping at some point but this doesn't stop me from making some progress with the Control Room. I'm also still trying to understand what Stuart meant by:

double up on the baffle thickness at entry and exit: Imagine tracing a straight-line path directly from the duct entry point to the register outlet point, and seeing how many obstructions you hit, and how thick they are. If all you find is one thin layer of MDF, then you should do something about that!

I drew some lines as Stuart mentioned but I'm not sure what I'm suppose to be looking at and also not sure which baffles should be thicker....do you mean the wood needs to be thicker/doubled up or the duct liner? Thanks,

In case I did understand what was being recommended, I drafted yet a few other examples of the silencer box I plan to use. The last one on the right is the one posted about above for the CR. The two others have longer pathways where the baffles really doesn't allow for a straight line to be drawn from inlet to outlet register. I'm thinking the design in the middle is suitable and "should" work fine but if you feel the last one on the left is even better then I'll just do that haha. I also went to pickup some 10" round ducts and fittings to make sure everything will fit and line up as planned. I'm going to start marking down on the floor where all the bottom plates will go so that I can have an idea of where the ducts will run. Enjoy the weekend folks! It's -47 with the windchill here in Ottawa..I'm going to try and stay warm and maybe start to build me some silencer boxes. 8) Cheers, Francis,

I'm also still trying to understand what Stuart meant

The baffle dividers themselves can be 1/2" MDF, but if you had an entry and exit right next to one another like my design: Then as you can see, I doubled up my 1/2" MDF where the sound could possibly make it's way through directly to the outlet. I personally don't see where there would be an issue like this in your design short of your exterior shell needing to maintain the mass of your leaves (two layers of 5/8" drywall = ~1" MDF).

In case I did understand what was being recommended, I drafted yet a few other examples of the silencer box I plan to use. The last one on the right is the one posted about above for the CR. The two others have longer pathways where the baffles really doesn't allow for a straight line to be drawn from inlet to outlet register. I'm thinking the design in the middle is suitable and "should" work fine but if you feel the last one on the left is even better then I'll just do that haha.

The left one looks like the cross sectional area around the ends of the baffles shrinks down due to the angled top. Corners like that are where you can benefit from oversized cross sectional area to help with pressure drop. I think the middle design would be great!

Enjoy the weekend folks! It's -47 with the windchill here in Ottawa.

Woah! I'm in Canada too but we are only at -6 and with wind chill feels like -11 which is way too cold for my liking! Get warm dude! Greg

Ok! I see what you're saying! Thanks man! So I'll use the middle design then :) So I just realized something, most of the time when there's talk of any lumber and sizes...1" is really 3/4", and a 2 x 4 is really 1.5 x 3.5. I bought some 3/4" (actual size) MDF as that's the thickest they had at the store. Do I really need to go to exactly 1" thick? If so would I be safe to just add an additional 1/4" glue over the 3/4" all around?. I guess worst case I'm sure I can make use of the 3/4" MDF somewhere else in the studio....maybe a desk haha. Francis,

I have a quick question about my duct design, I'm fairly sure I know the answer to this but I'll risk asking it anyways because I want to be sure 100%. Here's a quick sample of how I plan to run my ducts to the silencers. As you can see I have two separate branches coming out of the rectangular trunk. Each branch is for a different room. I'm wondering if I could potentially run just one single 10" branch to the top of the ceiling and split up there versus down at the trunk level. I would save on materials but I'm concerned that I might risk taking away isolation since the path from one room to another is shorten quite a bit if the sound was to travel inside the ducts. Does this make any sense and if so does it matter if I run a single or double duct run/branch up to the ceiling? Thanks Francis,

I bought some 3/4" (actual size) MDF as that's the thickest they had at the store.

Here in Alberta, the thickest MDF I can find is 3/4" as well. I bought a bunch of 1/2" sheets that I will glue together.

Do I really need to go to exactly 1" thick?

Assuming your inner leaf is two layers of 5/8" drywall, then yes, you do need 1" of MDF in order to match the surface density of your leaf. You could totally add the extra 1/4" of MDF to make a total of 1" thick. Or like you said, build a desk out of the 3/4" material and get a bunch of 1/2" sheets like I'm doing. Either way, you end up with 1" total.

As you can see I have two separate branches coming out of the rectangular trunk. Each branch is for a different room. I'm wondering if I could potentially run just one single 10" branch to the top of the ceiling and split up there versus down at the trunk level. I would save on materials but I'm concerned that I might risk taking away isolation since the path from one room to another is shorten quite a bit if the sound was to travel inside the ducts. Does this make any sense and if so does it matter if I run a single or double duct run/branch up to the ceiling?

I wouldn't worry about the sound getting from one room to the other through those ducts as your silencer boxes will take care of that crap. The benefit to running two separate round ducts in parallel like that is that you are doubling the cross sectional area which will halve the static pressure. This will also lower the velocity which will result in less air/duct noise. If you tried to move that same amount of air (CFM) up the wall like that in a single duct and maintain that same amount of cross sectional area, you'd need do it with a rectangular duct which adds way more static pressure and even the entry/exits to/from that rectangular duct would add crazy pressure drop. Again, this dual round duct idea you have is great.

Here's a quick sample of how I plan to run my ducts to the silencers.

Do you have any pointers about making those amazing looking duct corners? They're so smooth and flawless! Mine are HORRIBLE. Greg

Excellent! Much appreciated Greg Thanks! I'll go looking for either 1/4" MDF or end up buying a bunch of 1/2". I'll see what I can do.

Do you have any pointers about making those amazing looking duct corners? They're so smooth and flawless! Mine are HORRIBLE.

Sure thing man! I had a hard time figuring out the same but I ended up finding this link below with shows you how to create a 90 degree elbow. I tried real quick to make 45s but for some reason was having issues. https://forums.sketchup.com/t/90-degree ... ow-to/5599 If you have any issues, let me know, I'll gladly create some and share the files with you if you want. Just tell me which size you're looking for. Cheers, Francis,

Hey guys, I'm working some more on my sketchup model and I'm considering maybe doing inside-out walls and ceilings since I think I could make it work but I wanted to make sure that there's clear added benefits of doing this versus conventional wall construction with the drywall on the inside of the room. What are your thoughts on doing this? I would think the main reason why it's a good thing is that the insulation is exposed and probably helps a lot with sound absorption versus having one big solid mass to have the sound bounce on right? Not to mention having to put the added treatment on top of the drywall surface. My other question is would you recommend doing so in both the Control Room and Live Room or is that "design" mostly for specific rooms? looking forward in hearing your inputs have a great day! Francis,

I wanted to make sure that there's clear added benefits of doing this versus conventional wall construction with the drywall on the inside of the room. What are your thoughts on doing this? I would think the main reason why it's a good thing is that the insulation is exposed and probably helps a lot with sound absorption versus having one big solid mass to have the sound bounce on right? Not to mention having to put the added treatment on top of the drywall surface.

For ceilings you pretty much always want it to be insulation and you can add devices to liven up the room if need be. Plus, acoustically speaking, inside out ceilings allow you the maximum height which is the biggest draw back in home studios. For walls, inside out will give you a bigger room (acoustically). Sometimes this is a bad thing as it could cause your room to fail the room mode calculator tests. I know in my control room, I can't really go bigger due to the ceiling height. So, I'm using a combination of traditional and inside out walls to get a more square room that passes all of the tests. For the rear/back wall of a control room, you basically always want it to be stuffed with insulation and/or hangers. Also, you want it as deep acoustically as you can get it. This is a good candidate for inside out. The same can be said about your front wall. For your side walls, I think it's safe to say use either or.

My other question is would you recommend doing so in both the Control Room and Live Room or is that "design" mostly for specific rooms?

And like control room side walls, live room walls can be either or. Again, inside out will give more space which is very much desired in a live room. Now, with traditional walls, you will have a lively room that you have to deaden/dampen to your desired response. So, start live and tame it. If you go inside out, you could leave your stud bays empty and have a similar effect. Or, you could fill them with insulation and start with a dead room and liven it up with acoustic treatment devices/materials. From a construction stand point, standing up inside out walls is dangerous and difficult. For exterior walls, you need to fix your vapour barrier to the back side of the wall. The other major difference is this: Aesthetics. Do you want drywall with devices hung on them? Or you do you want fabric with built in devices and/or devices hung on it? Personally, I hate drywall mudding and would rather stretch fabric over studs and cover up the seams with wood and things like that. Granted, this will cost more than some muds and frustration. Greg

Gregwor wrote:

I wanted to make sure that there's clear added benefits of doing this versus conventional wall construction with the drywall on the inside of the room. What are your thoughts on doing this? I would think the main reason why it's a good thing is that the insulation is exposed and probably helps a lot with sound absorption versus having one big solid mass to have the sound bounce on right? Not to mention having to put the added treatment on top of the drywall surface.

For ceilings you pretty much always want it to be insulation and you can add devices to liven up the room if need be. Plus, acoustically speaking, inside out ceilings allow you the maximum height which is the biggest draw back in home studios. For walls, inside out will give you a bigger room (acoustically). Sometimes this is a bad thing as it could cause your room to fail the room mode calculator tests. I know in my control room, I can't really go bigger due to the ceiling height. So, I'm using a combination of traditional and inside out walls to get a more square room that passes all of the tests. For the rear/back wall of a control room, you basically always want it to be stuffed with insulation and/or hangers. Also, you want it as deep acoustically as you can get it. This is a good candidate for inside out. The same can be said about your front wall. For your side walls, I think it's safe to say use either or.

My other question is would you recommend doing so in both the Control Room and Live Room or is that "design" mostly for specific rooms?

And like control room side walls, live room walls can be either or. Again, inside out will give more space which is very much desired in a live room. Now, with traditional walls, you will have a lively room that you have to deaden/dampen to your desired response. So, start live and tame it. If you go inside out, you could leave your stud bays empty and have a similar effect. Or, you could fill them with insulation and start with a dead room and liven it up with acoustic treatment devices/materials. From a construction stand point, standing up inside out walls is dangerous and difficult. For exterior walls, you need to fix your vapour barrier to the back side of the wall. The other major difference is this: Aesthetics. Do you want drywall with devices hung on them? Or you do you want fabric with built in devices and/or devices hung on it? Personally, I hate drywall mudding and would rather stretch fabric over studs and cover up the seams with wood and things like that. Granted, this will cost more than some muds and frustration. Greg

Hi Greg, I'm trying to understand how doing inside out walls and ceilings saves you space as the airgap between the leaf supporting structures needs to be bigger than traditional walls in order to get the same amount of TL... so either the inside out walls need to go further into the useable room space or the outer walls need to be moved further out. I can imagine maybe saving around an inch or so but not much more... Does that make sense? Paul

I'm trying to understand how doing inside out walls and ceilings saves you space as the airgap between the leaf supporting structures needs to be bigger than traditional walls in order to get the same amount of TL... so either the inside out walls need to go further into the useable room space or the outer walls need to be moved further out. I can imagine maybe saving around an inch or so but not much more...

It saves you space because most of your treatment can then go in between the studs / joists, rather than being hung on the drywall. Considering that acoustic devices can easily be 3 to 6" inches thick, having most of that tucked inside the wall, between the studs, saves you space. Especially for the ceiling, where joists are likely to be 8" deep or more, you can get virtually all of your treatment into the joist space, so the lower face of the joists becomes your visible ceiling, while the actual ACOUSTIC ceiling is 8" higher... - Stuart -

Hi all, Things have been a bit slow the last couple of weeks due to a combination of me getting sick and having to deal with condensation issue in the studio. I went to take some measurements last week and noticed I had some frost build up in the corners of my room (where the ceiling meets the floor). Long story short, I had to remove the vapor barrier panel (Enermax) and take out the ceiling insulation to realize that the contractor failed to install insulation baffles in each corner of the room. Just about done fixing this so I'll be getting back to framing and planning some more. In terms of progress made, I did frame the structural box around my main supply trunk as seen on the pics in previous posts and wrapped it all with roxull insulation. Pics to follow shortly. I also started building the silencer boxes for the control room. I just ripped all the pieces and will be assembling everything in the coming days. Still trying to find some duct liner so I'll be shopping around this week. I had a few questions regarding figuring out the resonant frequency of my walls and ceilings as well as the air gap between two leaves. 1) Am I right to assume that walls and ceilings should have the same resonant frequency? 2) I'm trying to use Greg's TL spreadsheet in order to calculate everything but I'm stuck due to my slopped ceilings. The slopped walls on each side of the rooms is the roof so I suppose the roof acts as my outer leaf correct? If that's the case then my outer leaf construction is as follows: Asphalt roof shingles -> 5/8" OSB sheathing -> 16" roof scissor trust filled with 12" of roxull insulation) -> 1/2" vapor barrier panel (Enermax). I'm wondering how I could possibly plug in these numbers into the spreadsheet? 3) If using the spreadsheet is not an options for me I suppose I can use the following equation and add the extra mass of my outer leaf as part of m1 right? So I'd need to figure out what the (kg/m^2) is for roof shingles and add that to my calculation right? 4) From what I've read this is the basic formula for calculating my resonant frequency correct? Fc=c[(m1+m2)/(m1m2d)]^.5 One thing that I'm wondering is since "c" is a constant for if the cavity/gap is insulated or not, in my case my outer leaf has a 16" roof trust but only 12" of it is insulated. Does that change anything? Would i need to use a different constant for this? 5) I'm having a hard time understanding the air gap requirements for inside out ceilings and walls. Building inside out walls or ceilings would mean that I'd need to increase air gap in between the two structures correct? Say I have two normally constructed 2x4 walls with a 2" gap in between them....this really would mean that I have 3.5" + 2" + 3.5" of space between the two leaves right? And so if I would do inside out for say one of the inner leaf wall, that would mean I'd only have 3.5" + 2" of space between and therefore I'd need to increase the air gap between the two walls an extra 3.5" in order to maintain the same air gap as a normally constructed wall right? I'm starting to think that in my case with the type of room I have I'll be doing inside out ceiling (which isn't very big) and then stick to regular construction for the slopped walls and side knee walls. I hope this makes sense :/ I'll upload some new pictures soon! Cheers and have a great week! Francis,

1) Am I right to assume that walls and ceilings should have the same resonant frequency?

If possible, yes. But don't forget that the place where the resonant frequency is higher, is the place the defines your limit on isolation.

Asphalt roof shingles -> 5/8" OSB sheathing -> 16" roof scissor trust filled with 12" of roxull insulation) -> 1/2" vapor barrier panel (Enermax). I'm wondering how I could possibly plug in these numbers into the spreadsheet?

Why is the vapor barrier on the OUTER leaf? You live in a cold climate, so the outer-leaf will always be colder than the inner leaf in winter. Therefore, your vapor barrier should be up against the INNER leaf, not the outer leaf. It should always be on the warmer surface, never the colder surface, and never in the middle of the wall. If your building code does require a vapor barrier, then double-check this, to make sure you have it in the right place! If you were just finishing the attic without an inner leaf, then that would be fine, but you are not doing that: You are creating a new inner-leaf, and that's where the vapor barrier should be.

One thing that I'm wondering is since "c" is a constant for if the cavity/gap is insulated or not, in my case my outer leaf has a 16" roof trust but only 12" of it is insulated. Does that change anything? Would i need to use a different constant for this?

The constant refers basically to the resilience of the characteristics of the air. It takes into account the density of the air and the speed of sound in the cavity. The speed of sound changes due to the presence and type of insulation, but does not change due to the depth. So there is one constant of your cavity is empty (no insulation), and another if it is filled with insulation. If you only fill it part way (not the complete cavity depth), then the constant is somewhere in between those two. But to answer your question: the constant only changes due to insulation: not due to cavity depth. Here's the full equation, with explanation:

5) I'm having a hard time understanding the air gap requirements for inside out ceilings and walls. Building inside out walls or ceilings would mean that I'd need to increase air gap in between the two structures correct?

You need enough distance across the gap from the surface of the outer-leaf sheathing to the surface of the inner-leaf sheathing. That's all. As long as that distance is correct, and the mass is correct, and you are using the correct constant, then the MSM resonant frequency will be correct.

I'm starting to think that in my case with the type of room I have I'll be doing inside out ceiling (which isn't very big) and then stick to regular construction for the slopped walls and side knee walls.

... and then you will have to waste substantial space inside the room to add your treatment on top of the wall surfaces, and you won't be able to cover all of the wall surfaces anyway. Your ceiling area is very small, and I doubt that it will be nearly enough to provide what you need.

I'll upload some new pictures soon!

Looking forward to seeing those! - Stuart -

But don't forget that the place where the resonant frequency is higher, is the place the defines your limit on isolation.

Ok noted! When you refer to "the place" do you mean either the outer or inner leaf? because I fairly confident that the density of my inner leaf will likely be higher than the outer leaf.

Why is the vapor barrier on the OUTER leaf? You live in a cold climate, so the outer-leaf will always be colder than the inner leaf in winter. Therefore, your vapor barrier should be up against the INNER leaf, not the outer leaf. It should always be on the warmer surface, never the colder surface, and never in the middle of the wall. If your building code does require a vapor barrier, then double-check this, to make sure you have it in the right place! If you were just finishing the attic without an inner leaf, then that would be fine, but you are not doing that: You are creating a new inner-leaf, and that's where the vapor barrier should be.

When the construction was done, I had no choice to install a vapor barrier so yes the vapor barrier is currently on the warm side of the outer leaf. (inside the house) I know that's the code around here. I don't see how putting it up against the inner leaf will change anything? Do you mean on the warm side of the inner leaf? If that's the case then my HVAC ducts would be exposed to the cold as well no? It would also introduce cold air in between the two leafs no? I'll have to check with local building codes but I'm curious to know how this is done. I'm also wondering how this would work with inside out walls/ceilings...I can't see having two layers of drywall then the stud cavity filled with insulation and then the vapor barrier. I'm sure I'm missing something since having the vapor barrier on the warm side of an inside out inner leaf would defeat the purpose of doing inside out no?

The constant refers basically to the resilience of the characteristics of the air. It takes into account the density of the air and the speed of sound in the cavity. The speed of sound changes due to the presence and type of insulation, but does not change due to the depth. So there is one constant of your cavity is empty (no insulation), and another if it is filled with insulation. If you only fill it part way (not the complete cavity depth), then the constant is somewhere in between those two. But to answer your question: the constant only changes due to insulation: not due to cavity depth.

Ok right! I wasn't referring so much to the cavity depth but more the fact that my roof cavity is only 90% insulated versus 100% like a wall would be. I think I'll be fine with using an in between figure.

You need enough distance across the gap from the surface of the outer-leaf sheathing to the surface of the inner-leaf sheathing. That's all. As long as that distance is correct, and the mass is correct, and you are using the correct constant, then the MSM resonant frequency will be correct.

So really when we talk about "the air gap or space between leafs" that's really the distance from surface to surface correct? So when using and filling out Greg's spreadsheet...the input box for the gap is actually the distance from the stud to stud and not what you're referring to from surface to surface correct? Sorry about all the confusion...I'll figure this out eventually haha :| Here's a few pics to show my roof composition...note that I'm using a 1/2" fiber board vapor barrier and not the conventional 6mm polyethylene. Let me know if you have any questions or need additional details and I'll provide. Also note that the current gap between the roof and inner leaf wall is not accurate and just an example. I will make the final adjustments to the plan once I figure the right air gap between the two leafs as well as if I decide to go the inside out method. Thanks again for taking the time to read and answer my questions. Cheers, Francis,

Ok noted! When you refer to "the place" do you mean either the outer or inner leaf? because I fairly confident that the density of my inner leaf will likely be higher than the outer leaf.

Stuart is referring to the area of your room in general where your resonant frequency is the highest. As an example, say you have four walls and a ceiling and your walls have a 3 foot gap between sheathing. Your ceiling only has a 1 inch gap between sheathing. Assuming your sheathing surface density all around is equal, your ceiling MSM system will have the higher resonant frequency that Stuart is referring to. Since the resonant frequency is directly related to the transmission loss, he's stating that the amount of transmission loss your ceiling is offering is now defining your rooms isolation limit.

When the construction was done, I had no choice to install a vapor barrier so yes the vapor barrier is currently on the warm side of the outer leaf. (inside the house) I know that's the code around here. I don't see how putting it up against the inner leaf will change anything? Do you mean on the warm side of the inner leaf? If that's the case then my HVAC ducts would be exposed to the cold as well no? It would also introduce cold air in between the two leafs no? I'll have to check with local building codes but I'm curious to know how this is done. I'm also wondering how this would work with inside out walls/ceilings...I can't see having two layers of drywall then the stud cavity filled with insulation and then the vapor barrier. I'm sure I'm missing something since having the vapor barrier on the warm side of an inside out inner leaf would defeat the purpose of doing inside out no?

If your walls are built inside out, your vapour barrier is ALMOST in the right spot. If your insulation is pushing out your vapour barrier the same distance as your required "gap", then the vapour barrier will be pressed firmly against your inner leaf sheathing. This is fine. Chances are it's not pushing it out though. If that's the case, rip down the vapour barrier, try to add the correct thickness of insulation to fill your "gap", hold that insulation up with something like string stapled to the outer leaf studs. Then as you build your inside out walls on the floor, install the vapour barrier to it and stand up the wall. The vapour barrier will be directly against the cold side of your inner leaf drywall. That's where it should be.

So really when we talk about "the air gap or space between leafs" that's really the distance from surface to surface correct?

Correct.

So when using and filling out Greg's spreadsheet...the input box for the gap is actually the distance from the stud to stud and not what you're referring to from surface to surface correct?

Correct. And when you choose inside out configuration, the calculator eliminates that leaf's contribution to the gap. Example: If you chose both leafs as inside out, even if you chose 2x6 wood studs, the total gap size would only be the value that you entered into the gap cell.

note that I'm using a 1/2" fiber board vapor barrier and not the conventional 6mm polyethylene.

That's the weird part of the discussion. That needs to be touching the cold side of your inner leaf drywall. Either move it or ditch it and use conventional barrier. Greg

Still trying to find some duct liner so I'll be shopping around this week.

The cheapest and best (absorption coefficients) I can find around my area is the Owens Corning QuietR Rotary. I can get 100 feet of it at Alltherm Services Inc here in Edmonton for: 47” $292.41 48” $298.63 Hope you can find some in Ontario! Greg

When you refer to "the place" do you mean either the outer or inner leaf? because I fairly confident that the density of my inner leaf will likely be higher than the outer leaf.

Neither! As Greg noted, this is not about your inner-leaf or your outer-leaf, but rather about your MSM SYSTEM! The two leaves do not just act alone: they also act together, as a resonant system, and that's what matters most: the frequency of that resonant system. That's far more important than the resonant frequencies of the individual leaves. You really do need to do the math here, to make sure that your MSM resonant frequency is low enough that you will get the isolation you need, for the frequency range where you need it. Don't guess or assume!

yes the vapor barrier is currently on the warm side of the outer leaf. (inside the house) I know that's the code around here.

There is no "warm" side of the outer leaf! The outer leaf is exposed to the weather on the other side, so it is ALWAYS cold in winter. It's the INNER leaf that is warm. You don't seem to be getting the point here: I'm sure what you have there is correct for your building code FOR A NORMAL HOUSE, but it is not correct for a studio. With a normal house, you would just put drywall on the studs, directly in contact with the vapor barrier, and that would be your inner-leaf. No problem, because the vapor barrier will then be warmed by that inner leaf, since it is direct contact. But when you build a studio, your inner leaf is a long way away from that vapor barrier, and is NOT touching it: it is not going to keep it warm.... That's the problem here.

I don't see how putting it up against the inner leaf will change anything?

The leaf itself will keep it warm, because the barrier is in direct contact with the leaf. If you just leave it hanging in the middle of the cavity, then NOTHING keeps it warm... it will get very cold... and thus the warm moist air that diffuses through your inner-leaf into the cavity, will condense on the nice cold surface of the vapor barrier... that liquid water then creates the perfect conditions for mold to grow... inside your wall, where you won't even know it is there, .... until the damage is already done.

Do you mean on the warm side of the inner leaf?

The inner leaf IS the warm side of the cavity! That's why the vapor barrier needs to be up against it, in contact with it, so it can be kept warm. If it is warm, then the humidity in the air that diffuses through the inner-leaf will NOT condense on it.

If that's the case then my HVAC ducts would be exposed to the cold as well no?

Your HVAC ducts are not vapor barriers!

It would also introduce cold air in between the two leafs no?

I don't understand that: How would the vapor barrier "introduce cold air in between the two leafs"? I don't see how that is possible.

I'm also wondering how this would work with inside out walls/ceilings...

Simple: you apply the vapor barrier in such a way that it will be in contact with the inner-leaf. That's all.

.I can't see having two layers of drywall then the stud cavity filled with insulation and then the vapor barrier.

Neither can I! That would be the WRONG way to do it. The vapor barrier MUST BE I CONTACT with the leaf itself, not separate from it.

I'm sure I'm missing something since having the vapor barrier on the warm side of an inside out inner leaf would defeat the purpose of doing inside out no?

Why? I don't understand that.

Ok right! I wasn't referring so much to the cavity depth but more the fact that my roof cavity is only 90% insulated versus 100% like a wall would be. I think I'll be fine with using an in between figure.

OK, then use a number that is a bit lower than the constant for insulation. The relationship is not linear, though.

So really when we talk about "the air gap or space between leafs" that's really the distance from surface to surface correct?

Correct. If you could shrink yourself down small enough to fit in the cavity, then it is the distance you would see as you look around you: sheathing surface to sheathing surface, across the cavity, regardless of any studs, insulation (or vapor barriers!) that might also be in there.

I'm using a 1/2" fiber board vapor barrier

Do you have a link to that product? fiber board by itself is not a vapor barrier: it would only be a vapor barrier if it had some type of semi-permeable coating on one face. - Stuart -

Thanks for the replies guys!

Stuart is referring to the area of your room in general where your resonant frequency is the highest. As an example, say you have four walls and a ceiling and your walls have a 3 foot gap between sheathing. Your ceiling only has a 1 inch gap between sheathing. Assuming your sheathing surface density all around is equal, your ceiling MSM system will have the higher resonant frequency that Stuart is referring to. Since the resonant frequency is directly related to the transmission loss, he's stating that the amount of transmission loss your ceiling is offering is now defining your rooms isolation limit.

Thanks Greg! This all makes sense now.

Neither! As Greg noted, this is not about your inner-leaf or your outer-leaf, but rather about your MSM SYSTEM! The two leaves do not just act alone: they also act together, as a resonant system, and that's what matters most: the frequency of that resonant system. That's far more important than the resonant frequencies of the individual leaves. You really do need to do the math here, to make sure that your MSM resonant frequency is low enough that you will get the isolation you need, for the frequency range where you need it. Don't guess or assume!

Thanks Stuart! I'll make sure to do the math as you said! Once I run the numbers for the ceiling, slopped ceiling/walls, side walls, front and back walls as well as the floor and will post results.

If your walls are built inside out, your vapour barrier is ALMOST in the right spot. If your insulation is pushing out your vapour barrier the same distance as your required "gap", then the vapour barrier will be pressed firmly against your inner leaf sheathing. This is fine. Chances are it's not pushing it out though. If that's the case, rip down the vapour barrier, try to add the correct thickness of insulation to fill your "gap", hold that insulation up with something like string stapled to the outer leaf studs. Then as you build your inside out walls on the floor, install the vapour barrier to it and stand up the wall. The vapour barrier will be directly against the cold side of your inner leaf drywall. That's where it should be.

So if I understood correctly, doing everything right would mean for example that my attic slopped ceilings and inner leaf slopped wall composition would be as followed (Outside to Inside): -----------------------------------OUTER LEAF ----------------------------|------REQUIRED GAP---------------------|--------------INNER LEAF -------------------------------| Asphalt Shingle -> 5/8 OSB sheathing -> 2x16" open web scissor roof trust (insulated) -> required gap of MSM system (insulated) -> vapor barrier -> double 5/8" drywall -> 2X4 stud wall (insulated) Here's a quick picture to show what I think is required. I used a random gap just to show the insulation filling out the gap space but the pics show what I'm understanding in the composition above. Now if I remove the vapor barrier (enermax) from the current walls and ceilings of the room and put it up against my inner leaf wall....this would mean that my main hvac trunk and ducts would be exposed to some cold air and I guess now that means that I would need to insulate my ducts with duct liner? This leaves me with the question and please don't shoot me...but what would be the impact of leaving the vapor barrier where it is now and just add the gap and insulation directly against the vapor barrier and then the inner leaf wall? It just seems like a crap load of work for me to do just to have more insulation before the vapor barrier. I've done some research about double stud wall construction and as pointed out by you guys, there's usually some OSB sheathing that's taped and sealed on the cold side of the inner wall and that basically replaces the vapor barrier. I'm just having a hard time understanding the difference of leaving it on the warm side of the outer wall. I'm also wondering doesn't having the vapor barrier against the inner leaf add another/extra leaf? Again thanks for you patience and time Francis,

Doh!! I posted too quickly...I wrote my last post before I saw Stuart's response. Sorry about the confusion...here's my response to Stuart's post.

There is no "warm" side of the outer leaf! The outer leaf is exposed to the weather on the other side, so it is ALWAYS cold in winter. It's the INNER leaf that is warm. You don't seem to be getting the point here: I'm sure what you have there is correct for your building code FOR A NORMAL HOUSE, but it is not correct for a studio. With a normal house, you would just put drywall on the studs, directly in contact with the vapor barrier, and that would be your inner-leaf. No problem, because the vapor barrier will then be warmed by that inner leaf, since it is direct contact. But when you build a studio, your inner leaf is a long way away from that vapor barrier, and is NOT touching it: it is not going to keep it warm.... That's the problem here.

I apologize for not wording it properly. I should have used wall instead of leaf...I keep thinking they're the same but I understand that the leaf is only a surface. I should have said the inside of the outer wall. If I understand correctly the vapor barrier has to be in contact with the inner leaf (for either single or double wall construction) correct? So if I end up building my slopped ceilings or walls normally (not inside out), then my vapor barrier would need to be on the studs inside the room and the double drywall (inner leaf) would go directly over it right?

The leaf itself will keep it warm, because the barrier is in direct contact with the leaf. If you just leave it hanging in the middle of the cavity, then NOTHING keeps it warm... it will get very cold... and thus the warm moist air that diffuses through your inner-leaf into the cavity, will condense on the nice cold surface of the vapor barrier... that liquid water then creates the perfect conditions for mold to grow... inside your wall, where you won't even know it is there, .... until the damage is already done.

Ah ok! This explains it very well Thanks! I suppose this confirms what I said just above where the vapor barrier has to be in direct contact with the inner leaf to keep it warm. Im curious though...wouldn't building say an inside out room be harder to heat that inner leaf? I only say this because the inner leaf would be "hidden" under/behind the insulation. I won't lie...finding out all of this really sucks haha. Just when I thought things were going smoothly... :( Oh well....part of the adventure I guess lol This basically means I need to remove all the enermax panels in that room.

The inner leaf IS the warm side of the cavity! That's why the vapor barrier needs to be up against it, in contact with it, so it can be kept warm. If it is warm, then the humidity in the air that diffuses through the inner-leaf will NOT condense on it.

Got it! 8)

Your HVAC ducts are not vapor barriers!

Ok, so all this has me thinking what this means for my HVAC ducts. The original plan was to run everything in between the inner and outer walls. Does this change anything the fact that the ducts will be behind the vapor barrier? I was planning on having all ducts surrounded in roxull insulation so I suppose the colder area in between the walls wouldn't be that bad if the ducts are insulated on the outside.

How would the vapor barrier "introduce cold air in between the two leafs"? I don't see how that is possible.

Sorry I was thinking about the cold in general and not really air. I know it's not the vapor barrier that cause/introduce cold but more the fact that because the barrier is further away on the inner wall that the area between the two would get colder since the barrier in my case is what seals the room. So taking away the barrier is un-sealing the room but now understand that I'd be re-sealing everything but just further away on the inner leaf.

Simple: you apply the vapor barrier in such a way that it will be in contact with the inner-leaf. That's all.

That sure is simple! lol Got it! The vapor barrier would still need to be directly against the insulation right? no air gaps anywhere?

Quote: I'm sure I'm missing something since having the vapor barrier on the warm side of an inside out inner leaf would defeat the purpose of doing inside out no? Why? I don't understand that.

Bad explanation from my part. I was thinking that in inside out wall/ceiling the vapor barrier needed to go on the inside of the room therefore I thought the barrier would act as another leaf. Again, I hadn't understood that the barrier would be directly part of the inner leaf.

OK, then use a number that is a bit lower than the constant for insulation. The relationship is not linear, though.

Excellent will do and will post results. I've added new materials (asphalt shingles) and wood structure item/sizes (roof truss) to the spreadsheet and looks to be working but I will do the calculations manually as well just to confirm the math is good. Say Tunned! 8)

Do you have a link to that product? fiber board by itself is not a vapor barrier: it would only be a vapor barrier if it had some type of semi-permeable coating on one face.

Sure thing, Here is the link to the product https://bpcan.com/produits/enermax-insulation-vapor-barrier-panel/ and this is the link to the product's installation instruction. https://bpcan.com/wp-content/uploads/2017/01/1214353en-ca0mdpenermaxinsulationeng.pdf I have a few questions regarding how to properly calculate the density of my outer leaf (referring to Fc=c[(m1+m2)/(m1m2d]^.5) My outer wall composition of the roof is: Asphalt Shingles (2 layers) -> 1//2" OSB Sheathing -> 18" open roof truss. Question is do I include the Asphalt Shingle as part of the density of my outer leaf? or is the OSB the only material surface I should use? I'm wondering the same about my outer walls. The composition is 3/4" Pine Board & Batten siding -> 1x3 furring strip -> House Wrap -> 1/2" OSB Sheathing -> 2x6 stud wall. Do I just use the sheathing or the pine siding should be part of it? Again, I can't thank you both enough for all this help! Wouldn't be able to plan this properly without you guys! I really hope to be able to pay it forward someday! Cheers, Francis,