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PostPosted: Mon Mar 30, 2020 10:39 am 
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Hi all, I think this is my first post here on this forum, so hopefully this isn't too much.

I've been planning a studio build in our basement for about 2 years now and have a few questions. I'm sure there will be more as time passes, so I'll try to keep them in this thread.

I'm mostly done doing demo of our old basement rec-room (some old insulation is still in). I'm going to split the room into two rooms and am going to reclaim our former furnace room to use as a closet/isolation room (mostly for guitar amps I think). All the room dimensions are less than ideal. There's low ceilings, the control room will be small, there's a big fireplace, two 4'x6' windows, and a couple doors in the "live room". I'm just going to try to make the best of these issues.

I'm planning on doing 2 layers of drywall + Green Glue in the "control room" and on outside walls (this room borders a laundry room). Then the plan is to decouple the walls in the other rooms using either genie clips + channels or hushframe rafts + furring strips (has anybody used these?). These rooms would also have 2 layers drywall + Green Glue. All rooms would have joists/studs stuffed with insulation. I've been working in sketchup on a model and am currently trying to figure out the HVAC.

Rules checklist:
1/2/4. I've been searching here and over at gearslutz, but it seems like I have a few specific issues to iron out.

3. Location updated (Seattle, WA)

5. I need to get a sound level meter, and will edit this post when I get one, but the plan is to play rock music fairly loud in the "live" room, although for recording will probably just be a drum set and maybe an amp. Sorry, this is a bad answer. Ideally the live room will be as sound proofed as possible without doing double studs or drastically modifying the current framing of the house. I don't seem to bug my neighbors, but would like to make sure I don't...and also my wife upstairs who does hear the playing :)

6. The ceiling joists in our basement are around 7'7"3/4 high. The rec room mentioned above is an odd "L" shape. Hopefully the pictures below will give a better sense of the dimensions. There's a large fireplace in the "live room" that connects to the fireplace in our upstairs living room. There's some pretty odd framing here and there. The house is a 1951 rambler with a brick facade. There is a large window (6' x 4') in each room, but I've had them replaced with newer windows with laminated glass, so hopefully that will help. I'm not opposed to creating some sort of second window layer in the "live room". Right now everything is stripped to the studs.

7. Not floating the floor in the construction sense, but will probably use "floating" flooring (vinyl plank) for the "live room" :)

8/9/10/11. See drawings
12/13/15. done.
14. Budget is max $20K, but hopefully I don't hit that if I do most of the work myself.

Actual questions:

1. Since the control room will probably not make nearly as much noise and there's some odd framing*, I thought it would make sense to not worry about decoupling this room. It's below our dining room and there's no bedrooms near by. *Odd framing: there's a beam made out of 6 2x10's that currently makes a border between the side room and the main part of the rec room. This would be hard to decouple without sacrificing more real estate than I'm comfortable with. The Laundry room adjacent to the "Control Room," and the "Live Room" will both have Mitsubishi mini-split systems in them. Would it make sense to run a fresh air system like this: air from laundry room > through wall > baffle box > into "control room" > baffle box > through wall or ceiling > baffle box > "live room" > baffle box > through wall or ceiling > baffle box > hallway connected to laundry room?

2. Regarding baffle boxes, I'm a little confused about the sizing of the inlet and outlet holes. Should they be the same or should the outlet be twice as big (2 times cross sectional area)?

3. If the outlet hole is 2x size of inlet and I'm using two baffle boxes on each side of a leaf, does the second baffle box get even bigger? Or is the only hole to get that big the one that outlets into the room?

4. Should returns be sized larger than fresh air inlets?

5. Is the fireplace going to negate any decoupling, or is it still worth trying?

6. Has anybody used "Hushframe Rafts"(a product over at the isostore)? Do these work?

Thanks for taking a look.


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PostPosted: Tue Mar 31, 2020 4:08 am 
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Hi,

So, you say the control room will not be decoupled and yet I see 3 of the walls are decoupled from the outer brick walls? That wall on the left is the only wall which is not decoupled? Is that right?

Regarding the fireplace, if the fireplace is active and cannot be blocked up then yes, there's really no point in trying to decouple the rest of the room from the outside world. You would end up having a massive hole in your isolation which would make your isolation void.

However, you could still achieve some isolation between the control room and live room if you build it like you've shown in your plan, the only problem is your left wall is shared between the control room and live room, which is a major flanking point.

If you can't build another decoupled wall on that left side of the control room then I would at least build another decoupled wall on the left of your live room. If the live room outer walls and inner walls all connect and are sealed at the fire place then the hole in the middle of the fireplace will not meet the cavity between your inner and outer walls. There will still be some flanking but you'll have some isolation between your control room and live room.

If it were me, I would just build it properly though - at least the live room and iso booth. Fully decoupled framing everywhere and block up the fireplace.

Paul


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PostPosted: Tue Mar 31, 2020 4:39 am 
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Hi Paul, thanks for taking the time to respond.
Quote:
I see 3 of the walls are decoupled from the outer brick walls?

That's just the standard brick facade construction. Typically there's about an inch between the outer sheathing and the brick. I didn't do that, that's just existing construction. It's not decoupled though, I just don't have the connections drawn because I have no idea where that stuff is :)

There's also about 2 feet of foundation that the framing is built on that goes around the outer perimeter of the space. I added a picture you can see it in.
Quote:
if the fireplace is active and cannot be blocked up

It's typically not active, but the upstairs one is occasionally active. I was actually planning on figuring out some system where I could block up the fireplace opening but also easily remove the blocking if need be. Like some sort of assembly that fits in the opening with rubber seals and is held in place with something like a window sash lock. Otherwise I would block up the opening.
Quote:
the only problem is your left wall is shared between the control room and live room, which is a major flanking point.

The plan is to have this wall decoupled via genie clips on the live room side.
Quote:
at least the live room and iso booth. Fully decoupled framing everywhere and block up the fireplace.

This is the plan at the moment.


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PostPosted: Tue Mar 31, 2020 6:58 am 
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So what I mean by fully decoupled is free standing separate framing for your walls and ceiling. It will be much more effective than resilient channel.

The problem with resilient channel and genie clips etc is that even though the connection is highly buffered there is still a physical connection between the walls, and the cavity between the two walls is really minimal which means that you won’t have much isolation especially low frequency isolation.

Paul


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PostPosted: Tue Mar 31, 2020 12:00 pm 
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In this case, the main thing I'm concerned about with a full room-in-a-room assembly is significant loss of space. There's about 2 inches difference in the ceiling, which doesn't seem like much, but I'm already loosing about 3 inches from the 7'7"3/4 ceiling. So that would leave me with a ceiling around 7'2", plus any loss from treatments. (I'm clumsy and tall so that means frequent headstocks into the ceiling :) ) I would loose about 6 inchs on each wall instead or 3, which means a foot in each direction. It may make sense in the big room, but I don't think it would be practical in the other rooms.

Regarding the fireplace, if I block the opening, but leave the rest of the fireplace exposed (and seal the perimeter with backing rod/caulk), is that going to cause significant flanking?


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PostPosted: Tue Mar 31, 2020 8:24 pm 
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Brewbacca wrote:
In this case, the main thing I'm concerned about with a full room-in-a-room assembly is significant loss of space. There's about 2 inches difference in the ceiling, which doesn't seem like much, but I'm already loosing about 3 inches from the 7'7"3/4 ceiling. So that would leave me with a ceiling around 7'2", plus any loss from treatments. (I'm clumsy and tall so that means frequent headstocks into the ceiling :) ) I would loose about 6 inchs on each wall instead or 3, which means a foot in each direction. It may make sense in the big room, but I don't think it would be practical in the other rooms.

Regarding the fireplace, if I block the opening, but leave the rest of the fireplace exposed (and seal the perimeter with backing rod/caulk), is that going to cause significant flanking?



Yeah I completely understand that you want to preserve as much space as possible, it's always a battle.

The only real way of knowing whether or not you need that level of isolation is by getting a sound level meter, get some musicians to play in your live room as it stands now and then see how much you need to reduce the sound leakage by.

Once you have that information we can help you design a wall and ceiling assembly which will reach your goal. I don't remember if you mentioned it or not, but do you have neighbours you need to isolate from? If you do, and it turns out your current isolation plan will not be enough then you really have no choice - you'll have to sacrifice some extra space in order to not be a nuisance to them. If you don't have those kind of worries then happy days!

Paul


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PostPosted: Wed Apr 01, 2020 5:02 am 
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Thanks again for taking time to respond, but it seems like my actual questions are getting lost in the conversation.

The overall plan is to do as much isolation as I can without loosing too much real estate (which will involve a lot of compromises), so it seems that an SPL measurement isn't necessary. If there's still low freq leakage, I'll just have to work around that since this is a hobby space and not a professional space.

The main question regarding the overall structure is: will the fireplace structure (with the opening blocked off) cause enough flanking to nullify isolation? My impression is that it will cause some loss of isolation, but it's still worth it to do the isolation. I've added a couple pictures to show the current construction. The upstairs fireplace is directly above this.

Honestly, I'm actually much more interested in the air flow/baffle box questions I posted above.


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PostPosted: Wed Apr 01, 2020 6:17 am 
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I appreciate your anxiousness to get on to the exciting stuff but all the answers to your questions completely rest on how much isolation you need.

For example, right now you are basically saying "well, I'll do as much isolation as suits me... I don't want my walls to take up more space... if there's a problem after doing all that work then I'll just have to make do with it" you're doing a little isolation just to tick a box, and not really worried about the end result.

You cannot just hope to fluke this...

In my mind that is a complete waste of time, effort and money. If after doing your isolation plan and you can still hear a live band outside near your neighbours then all of that work was for nothing. At the same time you say that you're not really bothered about the result. And then you're asking if your isolation is going to be compromised by the fireplace... well, if you're not bothered about sound escaping through your newly isolated walls then what difference does it make whether it flanks through the fire place or not?...

Your baffle box sizing also depends on how good your isolation is... there's no point building excellent baffle boxes if the isolation around your walls is the weak spot...

If you want to do this properly then you need to tell us how much isolation you actually need. If the answer is "well, I'll make do with whatever the outcome is" then I would say don't bother wasting your time effort and money on doing any isolation at all.

Paul


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PostPosted: Wed Apr 01, 2020 12:04 pm 
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Quote:
"well, I'll do as much isolation as suits me... I don't want my walls to take up more space...

This is a mischaracterization of what I said. As posted in the first thread, I'm (at least) planning on using clips etc (a common practice with reasonable results). I'm willing to sacrifice some space, but am trying to balance isolation with ensuring that there's practical space in the room. I'm not just doing this as it suits me.

Quote:
little isolation just to tick a box, and not really worried about the end result.

This is totally unnecessary. I'm not just ticking a box and I certainly care about end results, or I wouldn't posting here, and I certainly wouldn't have ripped up my basement. Give me a break.

Quote:
If after doing your isolation plan and you can still hear a live band outside near your neighbours then all of that work was for nothing

I suppose, but if I follow typical guidelines, that seems unlikely.


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PostPosted: Fri Apr 03, 2020 8:31 am 
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If you are deciding to to clips + hat + drywall, cool. Do that. But make sure the entire room is done using those building materials. Yes, you will have flanking through the fireplace. So box it in and clip + hat + drywall over it too. Remember, a clip type system still follows the rules of a room in a room in that the outer leaf still needs to be sealed air tight and the outer leaf sheathing has to maintain your desired surface density.

For your silencer boxes, if you're doing just 1 for supply and 1 for return, I feel you're going to need at least 4 baffles per box and if possible, greater than twice the cross sectional area for the air path within the boxes.

Greg

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PostPosted: Fri Apr 03, 2020 9:23 am 
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Hey Greg, thanks for taking a look! My wife has forbidden walling off the fireplace, so I'll have to think about this some more it seems. I was kind of hoping that the mass of the bricks would counter some of the flanking if I did clips+hat+double drywall, but it sounds like there's no way of knowing how much the isolation would be compromised if I don't wall that off.

RE Baffle boxes:
I was confused more about the sizing of the ports of the baffle boxes. So lets say I'm running 6"x6" duct to the bafflebox, should the duct on the other side of the box have the same cross sectional area?


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PostPosted: Fri Apr 03, 2020 1:06 pm 
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Quote:
My wife has forbidden walling off the fireplace, so I'll have to think about this some more it seems. I was kind of hoping that the mass of the bricks would counter some of the flanking if I did clips+hat+double drywall, but it sounds like there's no way of knowing how much the isolation would be compromised if I don't wall that off.

If that's the case, as Paul mentioned above, I wouldn't bother trying to isolate at all.

Quote:
I was confused more about the sizing of the ports of the baffle boxes. So lets say I'm running 6"x6" duct to the bafflebox, should the duct on the other side of the box have the same cross sectional area?

If you're feeding it with a 6"x6" duct, that is 36 square inches. The inner path of your silencer would need to be greater than or equal to 72 square inches.

Greg

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PostPosted: Sat Apr 04, 2020 3:01 am 
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Okay, I understand the inner path part, but what about the duct or opening on the other side of the silencer. So lets say 36sqin duct -> silencer with 72sqin path -> 36sqin duct or 72sqin duct?

It seems like I've seen a number of designs where the opening size doesn't change, but in Rod Gervais book, he mentions that the second opening needs to be at least 2x the first opening or else it will act as a bottle neck.


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PostPosted: Sat Apr 04, 2020 5:02 am 
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Do you need ducting to run to certain places inside your rooms? You can just cut a hole in your baffle boxes and have the air spill out of them just like that - no need for ducting inside your room unless you have to run it to certain locations. In either case you should make the hole size the same as your baffle box inner CSA, provided that all of the other calculations are correct.

Looking at your ventilation plan it seems you have the stale air from one room being vented out into other rooms? I might be looking at it wrong, but you shouldn't have any stale air being exhausted into another space, and you should have a baffle box on every penetration in each leaf, so for one room that would be 4 boxes.

But, this may all be irrelevant; Does your wife mean you can't block up the chimney or, you can block up the chimney but leave the brick exposed? if you're not allowed to block up your fireplace then there's really no point trying to isolate your space, therefore your space will not be airtight anyway and so there's no need for ventilation silencer boxes.

There's massive benefits of not needing to isolate your space, here's a few:
- you'll save a whole load of money, time and effort, not to mention worry and stress.
- your rooms will be bigger
- you can fit deeper acoustic treatment if you need it, and at the same time you'll actually need LESS due to a lot of low end being able to escape through your walls.
- you can get up and running a lot faster and make music

The downsides are obvious:
- you risk annoying your neighbours and family
- external noise coming in may ruin a perfect take
- not much sound reduction between control room/live room

If you can deal with the first two downsides then the last one is a small compromise to pay for all of the benefits I mentioned.

Paul


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PostPosted: Sat Apr 04, 2020 6:20 am 
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Quote:
In either case you should make the hole size the same as your baffle box inner CSA, provided that all of the other calculations are correct

Great, so that leads me to my next question: If I have two baffle boxes on each side of a leaf, and lets say the first opening is 36sqin, then it would be 36sqin duct/hole -> baffle with 72sqin path -> 72sqin hole/duct -> WALL -> 72sqin hole/duct -> baffle with 144sqin path (??) -> 144sqin hole?

Quote:
Does your wife mean you can't block up the chimney or, you can block up the chimney but leave the brick exposed?
I can block up the fireplace hole but leave the brick exposed. I can't build a wall around the fireplace.

I hadn't considered some of the pros of not doing isolation (specifically around treatment). Thanks Paul!


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