My long, one-car garage studio, construction phase

[Bigsby]

Thanks for the reply, Brien! I'm not sure about perm ratings, but I can describe for you the construction as it currently exists:
Outer leaf: cedar siding, 7# siding paper, one layer of 5/8 densglas sheathing, the original 1x8 sheathing, which I caulked and filled, and then one "beef-up" layer of 5/8 drywall between the studs. There is r-13 fluffy, unfaced insulation that fills the gap between the inner and outer leaves.

Inner leaf: two layers of 5/8 drywall with green glue between. Roxul safe 'n sound used for treatment between the studs.

The roof leaves are a bit different, as I created scissors trusses in place in order to get more ceiling height, and I needed to have proper ventilation for the roof. It is a three leaf system, which I couldn't avoid.

Outer roof leaves: composition roofing, 30# felt, osb. Then r-19 insulation between the scissors trusses with two layers of 5/8 drywall

Inner roof leaf: r-19 insulation with 2 layers of 5/8 drywall with green glue between. The inner roof leaf is not framed inside out.

I have a Fantech fan at my inlet, no fan at the outlet. The air moves quite well through the room using static pressure. I will have a 9,000 btu mini split as well. The entire studio is roughly 260 square feet, with a vaulted ceiling that goes from about 8 feet to about 10 feet.

Does this info give you a feel for the perm rating? Thank you so much for your help!

[Bigsby]

Another quick question: what about painting the interior of the inner leaf, framing and all, with a vapor barrier paint? Glidden has a product called vapor barrier primer sealer that has a perm rating of .6, which seems as good as plastic. Does this sound like a viable solution?

[xSpace]

Actually that is a dangerous marketing term Consider if the user already has an actual vapor barrier on the back/cavity side of the wall and then applies this primer to the interior side, what you create is a double vapor barrier. You have effectively built a "lock" that vapor can not get out of but can get inside of since gas moves with the ease of any pressure available.

So if you have an existing VB on the cavity side of your wall do not use this primer, please.

[Bigsby]

Yeah, I see your point, Brien. This product could definitely be dangerous for someone painting their wall who doesn't know if they already have a VB!

But in my case, there is no vapor barrier anywhere in either leaf structure, and my perm rating, as far as I understand it, is very high (ie: very permeable) with two layers of 5/8 drywall with green glue between on my inner leaf.

So in my case, don't you think using this vapor barrier paint (all seams/joints/cracks of framing and drywall of inner leaf caulked before application) over the entire inside-out wall, framing and all, could be a good solution to my problem? After paint, I would then treat the room per my original plan, but without plastic over the rock wool.

So the inner leaf would be as follows: drywall/exposed framing, then VB paint, then rock wool, then cloth, and in some areas, slats as well.

What do you think? As always, thank you so much for your invaluable advice!

Mark

[xSpace]

Your paint should be in the class of "vapor retarder".

A vapor barrier, a true Class 1 barrier is indeed aluminum which is why I use the aluminum can reference.
Your perm rating is the total rating of ALL the materials from the last piece on the outside to the last piece on the inside of the structure, it is not simply whatever is on the inside or whatever is on the outside.

Poly Plastic is a Class 2 barrier but has much the same properties as in the permeability of the material and is cheaper than aluminum, so that is why we use it.

These are the properties of a vapor barrier.


Now a retarder is different. It does not stop nor should it stop the migration of condensation but allows the passage...and that passage has to be allowed.

If you have a VB on the backside of your sheetrock which means the plastic is attached directly to the stud face then if gas does get into the sheetrock and HITS the poly plastic BARRIER then it HAS to have a path back out. So if you place a true barrier, even though .06 is not true as is this paint perm rating, on the back side then it cannot get out.

And gas as with sound you cannot think in linear terms, it does not move in a straight line but will find the path of least resistance. All it requires is pressure and there is always pressure either externally or internally.

In your case, I would forget about the requirement for a vapor barrier. Where it should be placed if needed, you no longer have access to.

Move along and make certain you have good HVAC return air.

[Bigsby]

Hi Brien--
Sorry if I'm beating a dead horse here; I'm just trying to understand this. Are you saying that I should not apply the vapor-retarding paint to the room side of the inner leaf because if any moisture gets between the leaves (either from outside the building or from any potential flaw in my vapor retardant paint job) it will not be able to dry to the inside because the paint is blocking it from doing so? And it is better for me to let it dry to the inside than seal it off from the interior moisture and let it dry through the outer leaf, depending on the natural drying process to keep the structure healthy? Just to reiterate, this is my entire wall composition:

Outer leaf: cedar siding, 15# siding paper (6 perms), one layer of 5/8 densglas sheathing (17 perms), the original 1x8 sheathing which I caulked and filled (?perms) then one "beef-up" layer of 5/8 drywall (50 perms?) between the studs. There is r-13 fluffy, unfaced insulation (?perms) that fills the gap between the inner and outer leaves.

Inner leaf: two layers of 5/8 drywall with green glue between. Roxul safe 'n sound (116 perms) used for treatment between the studs. *the perm ratings that I was able to find were obtained from various tables I found on the Internet--how accurate they are, I can't say....

Forgive me for being slow on this--I know you've already tried to spell this out for me, but just so I'm clear: since I don't have access to the cavity side of my inner leaf, you're saying it would be counter-productive to paint the inside (room side) of it? There currently is no VB in either leaf. I guess I thought that the paint would help to keep the moisture from inside the room from getting through the drywall into the wall cavity. By the way, here's a link to the specs on the paint:
http://duspec.com/DuSpec2/document/Docu ... tId=934445

The Dept. of Energy website (http://energy.gov/energysaver/articles/ ... -retarders) says that

"Vapor barrier" paints can be an effective option for existing homes in colder climates

I just keep coming back to this possibility as my only option other than tearing my inner leaf apart! But I suppose when they talk about "existing homes" they might be referring to ones whose outer leaf isn't sealed as much as mine is.

One more point of clarification, because I'm not clear on the quote below:

If you have a VB on the backside of your sheetrock which means the plastic is attached directly to the stud face then if gas does get into the sheetrock and HITS the poly plastic BARRIER then it HAS to have a path back out. So if you place a true barrier, even though .06 is not true as is this paint perm rating, on the back side then it cannot get out.

And gas as with sound you cannot think in linear terms, it does not move in a straight line but will find the path of least resistance. All it requires is pressure and there is always pressure either externally or internally.

The above quote seems to be referring to a wall built in the normal way, not inside out, with a VB behind the drywall. In this case, I completely understand that I would not want to add a VB paint to the inside, effectively sandwiching the drywall.

So if you place a true barrier, even though .06 is not true as is this paint perm rating, on the back side then it cannot get out.

In this last sentence, did you mean to say front side instead of back side? If so, that makes more sense to me, since I think of the front side as being the room side and the back side as the side facing the outer leaf.

I hope I'm not being overly tedious--maybe there are others out there with the same questions I have. I'm just feeling like I've spent countless hours and a lot of money building something that is going to become a mold trap!

Thank you!
Mark

[Bigsby]

Ok, well, after obsessing over this vapor barrier issue for a few days and doing a bunch of homework, I've decided to move forward. I'm confident that I'll be okay as long as I make sure to have fresh air supply, stale air exhaust (which I do) and return air dehumidification (which I will). Thank you, Brien and Stuart for your input on this.

Stuart, I'm realizing I left some of your questions about my build unanswered, so here you are..

Maybe it's just the angle that the image is taken, but to me it sure looks like there is drywall on there, in the cavity:

Yes, I can see why you would think that, Stuart, but there is only drywall for the CR leaf, which was built inside out (left side of the picture) in that cavity. The LR wall is actually the only wall in the LR that is not inside-out, in order to give me decent-sized spring between the LR and CR.

It also looks like the framing goes right through, connecting across the gap, and there doesn't seem to be any drywall on the live-room side of that leaf.
But like I say, maybe that's just the angle. Please post your actual SketchUp model, so we can take a closer look.

leaf detail.png

There isn't any contact between the framing of the inner leaves for the CR and LR, nor is there any contact between the Framing of both those leaves and the outer leaf. However, the Sketchup artist (me) who created this image is sorely lacking in Sketchup skills, so that point is not entirely clear. Rest assured, there are no flanking paths, with the exception of the door jamb between the LR and CR. I Built that straight through following Rod's advice in his book.

Just want to clarify something here: you DO have insulation in the MSM cavity too, right? That cavity must have BOTH insulation AND ALSO the vapor barrier. I, not talking about the insulation that is part of the treatment inside the room, but rather the insulation that must be in the wall cavity. You need that for both thermal and acoustic reasons. How much insulation do you have in there, and how did you attach it?

Yes, there is insulation between the leaves, which is r-13 fiberglass. It is held in place by rows of string that are stapled across the studs, and it fills the cavity, gently touching the back side of the inner leaf drywall.

I think that's it, for now. Time for more caulking.....

[Soundman2020]

the Sketchup artist (me) who created this image is sorely lacking in Sketchup skills,

OK, that would explain it!

It looks like you are good to carry on, then!

- Stuart -

[xSpace]

Sir, you want a typical interior primer and two finish coats of paint. You do not want a "vapor barrier" type paint, you want a "vapor retarder" type paint and that is ANY typical interior paint.

Your want for a vapor barrier is over, the time for proper placement has come and gone. So do yourself a favor and get a typical interior primer and paint and let the HVAC do the business of protecting the structure.

[Bigsby]

Yep. Thanks, Brien, that's the plan.

[Bigsby]

Making slow progress, as usual. I primed and painted the CR for my vapor retarder per Brien's advice, and have built most of the framing for the treatments: slats and bass traps.

Here's the view to the front right of the CR:

CR front right.jpg

...And the front left of the CR. This will be filled with insulation, then cloth, then slats. I realize that this may affect my imaging in the low end, but I need all the absorption I can get in this small room!

CR top left.jpg

Here's a couple views of the back wall, which will be super chunks:

CR rear left.jpg

CR rear right.jpg

As you can see, the ceiling is vaulted. I'm working on a plan for a hard-backed cloud that will extend from the front of the room to behind the listening position angled at around 15% from its low point at the front of the room.

I'm about to start building the soffits, which will be angled at 38%, putting my ears at the listening position at 40% from the front of the room, which I'm hoping is close enough to the 38% ideal. My walls are splayed at 8%.

I currently have Alesis M1 MkII monitors, and, although money is tight, I'm wondering if I should bite the bullet and buy something a bit better, before I complete the soffits. I realize I could replace them down the road, but I'm not really excited about re-doing all that work, creating new baffles, boxes, etc, not to mention the height might need to be different. My current monitors have no shelving compensation on them, although I could plug the ports on the front (Alesis suggests this for placement up against a wall--seems it could help for soffit placement as well).

So, a couple questions:
Do things look ok at this point? Any red flags I'm not seeing?

Any suggestions for monitors would be appreciated. I'm really torn on this front. I just want to do the best I can with my monitoring--it might be a bit short-sighted to put so much into the build and then have monitors that don't cut it. I've considered anything from keeping what I have for now to getting JBL LSR2325p's, JBL LSR 4328's, on up to Adam a7x's, or Genelec 1031a's.

One thought about the JBL LSR 4328's: while I'm going to treat this room as much as humanly possible, I suspect that I will still be fighting low end issues at the end. I know that doing the best I can on treatment is the first priority, but does anyone have opinions on the supposed "room correction" abilities of these speakers? I've read a lot of reviews; some glowing and some critical. I guess I'm considering them in the hopes that they could compensate a bit for some of the remaining low-end issues once I've done everything I can to treat the room.

Bottom line: my plan is to run the REW software tests on the room before I do any treatment, and it seems I should settle my monitor decision before I start running tests (BTW, if I ended up with the JBL LSR 4328's I would not engage the compensation software until after I had done everything possible treatment-wise to the room).

As always, thank you so much for any and all feedback!

Mark

[Soundman2020]

I'm about to start building the soffits, which will be angled at 38%,

38%? Or 38°? Two different things....

putting my ears at the listening position at 40% from the front of the room, which I'm hoping is close enough to the 38% ideal.

That's fine. 38% isn't a "rule": just a good starting point.

I currently have Alesis M1 MkII monitors, and, although money is tight, I'm wondering if I should bite the bullet and buy something a bit better, before I complete the soffits. I realize I could replace them down the road, but I'm not really excited about re-doing all that work, creating new baffles, boxes, etc, not to mention the height might need to be different.

There are designs for soffits that allow you to replace the speaker at a later date, based on a removable "module" that the speaker sits in. If you make that big enough and position it low enough, then there's a lot of room for adjustment later. You only need to build a new module for each new speaker, and slide that into the soffit. It is a possibility, but it is also a lot of work, even so!

My current monitors have no shelving compensation on them, although I could plug the ports on the front (Alesis suggests this for placement up against a wall--seems it could help for soffit placement as well).

hmmmm..... doesn't give you much adjustment, does it? What happens if you need 5 dB but your "sock in the hole" only gives you 3? Or 6?...

Do things look ok at this point? Any red flags I'm not seeing?

Do you have the final version of the SketchUp, with everything in place? If so, then please post it here.

Any suggestions for monitors would be appreciated. I'm really torn on this front. I just want to do the best I can with my monitoring--it might be a bit short-sighted to put so much into the build and then have monitors that don't cut it. I've considered anything from keeping what I have for now to getting JBL LSR2325p's, JBL LSR 4328's, on up to Adam a7x's, or Genelec 1031a's.

Personally, for me, that's a no-brainer: I'd go with the A7X's. I'm a big fan of Adam, and I love their ART technology: there's just nothing else that gives you the clarity and crispness of those highs. Their mid-range drivers are decent, middle-of-the-road, nothing special, but those tweeters make up for that, hands down. That would be my choice. Second on the list (for me) would be the Genelec's

But don't take my word for it: go listen before you buy! Go find a show room someplace that has both of those, and listen to the same test samples (your own, that you know really well) on both sets in quick succession (hopefully with instant A/B switching), and choose the one that makes the most sense for you.

but does anyone have opinions on the supposed "room correction" abilities of these speakers?

I sure do have an opinion on those! Junk. Hype. Plain and simple. The issue is very easy to understand: the biggest problems in home studios are modal issues. Modal issues are TIME domain issues: they occur due to energy that is "stored" by the resonance of the room modes, and released again over a long period of time. "Room correction" is a FREQUENCY domain solution: it can do nothing at all about problems that occur in time. Think of it this way: If a room mode is excited by, for example, a low G on a bass guitar, then the energy at that frequency (98 hz) builds rapidly, and the room mode "rings". The bass player cuts off the note with his hand. The speaker stops moving. But the mode carries on ringing, for several hundreds of milliseconds... the speaker cone is dead still, not moving at all, but the sound is still bouncing around the room, decaying slowly. So I ask one simple question: what can the equalizer do to stop that ringing? The answer is clear. Zilch! Nada! Nothing! Zero! The speaker cone is not moving, so the equalizer has no sound to work with, and it can do nothing at all to damp that mode. The ONLY thing that will stop that mode, is acoustic damping. There is nothing at all that can be done electronically to "correct" a room. In fact, there is nothing that can be done acoustically to "correct" it either! The only thing that can "correct" a room, is a very large bulldozer!!! But at least acoustic treatment can damp the modal behavior, so that it is not too obnoxious. In a suitably treated room, that "ringing bass G" will be damped within a short enough period that it sounds natural and pleasing. Room EQ cannot do that.

What EQ CAN do, is to compensate for deficiencies in the signal path and the speakers themselves. That is useful, if your speakers or amp are not up to much. And EQ can also "balance" the apparent levels in the room.... disguising the differences in frequency response due to modal response to a minor extent, as the very last resort, the final "tweak" of the room. But it can only do that for one single listening position in the room, and even then it does so at the expense of all other listening positions. So if you are the one and only person in the room, then it can help to "fake" an improvement for where you are sitting... but if there are other people in the room, they will now hear worse sound, more unbalanced, more modal, since they are not at the position being "corrected".

So that's my take on "room correction": basically it's worthless. The only time I'd use it is in a room that has already been treated as well as possible, to do some minor tweaking of any remaining low-end issues, as well as to treat problems with the speaker themselves. And I would only do it for a room that isn't meant to have more than one person in it.

Yeah, I know that the vendors of "room correction" devices tell you that you can take several measurements in the room, then average them, but that's garbage too: Think of it like this: there was an optimal solution for the mix position alone, but by taking more readings in other places, you are making the correction WORSE for the mix position. Why would you want to do that?

Excuse the rant!

I guess I'm considering them in the hopes that they could compensate a bit for some of the remaining low-end issues once I've done everything I can to treat the room.

mmmmmmmmmmaybe.... But like I said above: ONLY for one single position in the room. But even so, I would not lock myself into a specific "room correction" speaker. Rather, I would use a general purpose digital equalizer, and adjust is as necessary. Or better still, let REW adjust it. I'm not sure if you are aware of this, but that actually is the original purpose of REW. The name stands for Room EQ Wizard, and its original purpose was to automatically analyze a room and adjust any typical digital equalizer. It grew from there to be the best acoustic analysis tool that I have seen, but it still has the basic functionality of doing that. It supports something like a dozen common equalizers, from several different manufacturers, and can either adjust them directly via Midi, if they have that capability, or it can list the needed adjustments for you to do manually. If I were going to do "room correction" (!), I would entrust the job to REW plus a good digital equalizer. Then I can simply update it if I ever do change the speakers, just by running REW again. That way I can buy any good quality speaker that I want, even if it does not include "room correction" capability. That makes the speakers less expensive for the same quality, or better quality for the same price... You only pay for the equalizer once like this, instead of paying for it again each time you buy new speakers....

Bottom line: my plan is to run the REW software tests on the room before I do any treatment,

Yes! Very smart move! As soon as the shell of the room is finished, set up your speakers and measurement mic, and do that important first "baseline" test. Then you have a reference against which you can test each stage of treatment, so see how it is doing and what is still left to do.

(BTW, if I ended up with the JBL LSR 4328's I would not engage the compensation software until after I had done everything possible treatment-wise to the room).

Or REW: REW actually predicts the outcome of the adjustments, and shows them to you on the waterfall plot! And it lets you add your own "tweaks" to that, also updating the predicted waterfall and frequency response graphs, so you can see if maybe you can do an even better job that it can!

What's not to like about REW? Even the price is very likeable....

- Stuart -

PS. Did I mention that I'm not a big fan of "room correction" devices?

[Bigsby]

Stuart, thank you so much for your reply--I can tell you're working overtime on this site (not to mention having a life), so I always really appreciate your feedback! A few answers....

Yes, I meant 38 degrees, not percent, for the soffit angles

As far as the monitors go, I've decided that I do need to upgrade--I didn't need much convincing. My frontrunners right now are the Adam A7x's and the Sonodyne SM 100AK's. I've got quite a bit more research to do in order to decide (not to mention listening), but I really want to build my soffits around speakers that I have confidence in. The Adams have a great reputation, and I know that you, Stuart, are a big fan--I don't think I could go wrong if I went that route. Given their "trapezoidal" shape, the Sonodynes present some challenges for soffit-mounting, but the reviews I've read on them are quite impressive. If anyone here has them, I'd love to hear about it!

You confirmed my suspicions about "room correction" technology--notice that I always use quotes when I use that term--I will cross that option off the list. I haven't downloaded REW yet, and as such, I didn't know about all it was capable of, just that I need to get it soon and start testing. And for the record, Stuart, I appreciate any of your "rants."

Before I get to that point, I need to install my inner-leaf doors in the CR, as well as the window, which brings me to a question: I think I'd like to angle the glass on the CR side so that I will be able to see better into the LR. My thinking is that the lighting will usually be lower in the LR than in the CR. However, I'm concerned that that will mess with my symmetry for the CR, as the wall opposite the glass won't be angled down. Perhaps I should just install the glass straight and deal with any resulting (visual) reflections? Any thoughts on that?

Here's a bird's eye view of the CR; the window isn't shown, but it will be located to the right, looking into the LR:

Control room vapor barrier.jpg

On a related note, I want to upload my final Sketchup file, but I've switched everything over to Apple since I started this, and I haven't been able to get my Housebuilder plug to work (hence the lack of a window in the picture above). I've been trying to figure out how to create the vaulted ceiling as well, but I'm just not that good at Sketchup. I'll keep working at it...

[Soundman2020]

I think I'd like to angle the glass on the CR side so that I will be able to see better into the LR. My thinking is that the lighting will usually be lower in the LR than in the CR. However, I'm concerned that that will mess with my symmetry for the CR, as the wall opposite the glass won't be angled down

Do you mean angled vertically, or horizontally? In other words, tilted forwards so the top is out of line with the bottom, or angled sideways, so the left edge is out of line with the right edge?

Either way is fine, if it will help with your sight lines. I'm not convinced there would be a symmetry issue either: The glass obviously should not be at the first reflection point, so it will probably be roughly alongside your head, which I think is far enough back that it won't make much difference at the mix position (unless the window is very large). I wouldn't be too worried about it. Worst case, if you build it and find that you do have issues, then you could hang something on the opposite wall at the same angle, to re-create the symmetry.

Perhaps I should just install the glass straight and deal with any resulting (visual) reflections? Any thoughts on that?

If you have to angle it, then go ahead and angle it, and we'll figure out a way to deal with any problems, if they arise.

but I've switched everything over to Apple

Well, that explains it all, doesn't it? Now we understand the source of you frustration!!!

(Sorry, couldn't resist!)

I've been trying to figure out how to create the vaulted ceiling as well, but I'm just not that good at Sketchup.

You can use the "rotate" tool locked to the vertical plane, and rotate your joists and drywall to any angle you feel like.

- Stuart -

[Bigsby]

Hi--
After your last Apple comment, Stuart, I became determined to get my Housebuilder plug to work! And I finally realized that I had unzipped the files in the wrong folder. Problem solved!

So I'm going to take some time to edit my plan so that it accurately reflects things as they stand now. There really haven't been many changes since I started building, but I'm sure when it comes time to interpret REW results it will be important to show everything exactly as it is.

As far as the window goes, my thought was to angle it on the vertical axis, so that it leans toward me from the top, but I'm not adamant about that.

Anyway, once I have an updated plan, I'll post it.