John Sayers' Recording Studio Design Forum Archive

I’m in the design stages of building a new home that will enclose a music production work space. This forum has been an amazing resource and I haven’t had this much fun learning...well maybe ever. Every new stage has led me down another exciting rabbit hole, and I’ve always ended up back here to find solutions. I thought I’d take my first step towards asking for a little help here and truly appreciate any feedback I’d get. While at the same time hopefully being able to contribute to this forum with my lessons and detailed story (as it unfolds). I know there are many more factors than I will mention in this message, and I apologize if I skip something that is important. None the less, here is my best effort to be both concise and informative. Please note, I’m currently seeking some input towards the effectiveness of isolation only based on your experience. I have many more detail drawings, notes, and sketchup models. But before I dive into those, I thought I’d first get some input on the core isolation parameters onto which all other things will be built.

Parameters:
- Control room dimensions are: 20’ x 16’8” x 15’
- Live room dimensions are (an angled room): 51’5” (to 41’3”) x 20’4 x 15’
- the above dimensions will shift slightly as construction details become finalized
- height is from concrete foundation floor to the bottom of the concrete floor above
- they are located underground in a basement
- the space above is residential (my family) and is where the primary isolation requirements lie
- I am less concerned with extreme isolation between rooms within the basement for my style of working.
- due to it being family dwelling there is some flexibility to move to a different bedroom if noise levels are predicted to exceed certain thresholds during sleeping hours
- acoustic treatment features, electrical, HVAC distribution are not indicated here at all. Though I do have a set of drawings/plans in place that I’d love to share. Most of that takes place behind the interior false-wall and false-ceiling framing. That is all that is loosely indicated here.
- I’m relying heavily on the isolation properties of the outer concrete leaf and the earth damping to both reduce transmission to the exterior but also to hopefully reduce flanking to the room above.
- I have a plan for HVAC that includes air handlers outside of either room above the hallway, etc. With heavy duct silencers and other features to help reduce the impact of the duct penetrations of the inner leaf.

Level of Isolation:
- ideal levels in the residential environment would be a low of around 40dbC. Though approaching 45 to just under 50dbC is likely still adequate.
- typical listening levels in the studio are 85-95dbC measured at listening position (I try), and sustained peak recording levels may be around 115dbC. Most common will be just under 100dbC.

The design:
- I plan on building with a room-within-a-room approach as indicated.
- the overall layout is dictated by various factors. Including use of the adjacent rooms and that the live room serves as another creative space while not in use for sessions.
- I have full control over all aspects as none of this structure is currently built
- budget is not unlimited, however it is part of a complete home build and there is flexibility there and a desire to do as much as possible to avoid fixing issues later. I’m not sure if I need to divulge my complete home budget here, but I would say that I currently have $40k to dedicate to solutions specific to solving problems related to the studio. It’s hard to separate since much of this is common to the structure of the building as a whole.
- I would like to avoid building a floating concrete floor in the basement and hope that earth damping of the foundation goes a good way towards that desire.
- As is common, this will be built in stages. The design reflects some aspects that are necessary for that to happen.
- please ignore the elevator shaft transmission at the moment. The assembly surrounding that will be similar to or better than the interior leaf of Section A.

Alternative Options and future considerations:
- Some things have been designed with flexibility for change and expansion in mind.
- the interior false-wall framing is one of these features that may change/evolve after testing/evaluation. It's there only to indicate where it will be located in the assembly.
- I’m hoping that flooring could potentially be improved upon (at great expense) if flanking/street noise becomes an issue. Currently not planned (based on testing) and hopefully never necessary. The inner-leaf framing wouldn’t rest on it. I’m not certain whether this would cause significant flanking through the joint where the framing meets the foundation. Or whether decoupling there would be a good thing to do in order to “future proof” that aspect as well. I apologize for the amateur and incomplete thinking on this one.

Diagrams:
- the topographical area shows three points with cross sectional diagrams at those locations
- A: is the assembly at all studio walls next to the foundation
- B: is similar to A with the exception of the earth
- C: is the assembly where studio walls meet other normal walls in the basement (some detail missing here)
- the green foundation wall intersecting the live room and the control is a solid lead bearing wall. This may change to columns and beam depending on engineering. This is the more likely solution.

Questions:
- in your experience, what are your opinions of such an assembly regarding isolation to the space above (and given my rough parameters)?
- please point out my oversights and mistakes
- is there any significant advantage to decoupling the inner leaf framing assembly where it meets the foundation (under the base plates)? Also in terms of “future proofing" in the event that more decoupling (god forbid) is necessary due to the street noise mentioned above.
- This is the ambiguous one (I apologize): I am weighing the advantage of the decoupled 2” (or more) slab above (which also houses the radiant heating). Any input there is appreciated. Alternatively creating only a single 8” slab. I know this creates a sort of 3-leaf scenario, however tests I’ve researched can show a significant improvement with similar assemblies (though the reasons for this could be based on various things).

Thanks for your patience. I completely understand how hard it is to answer these kinds of questions without sufficient data. But I didn’t want to post too much and tried to be efficient in this first stage. Your help is truly appreciated.

Thanks in advance,

Marc

I realize this part of my question may be better suited for the Construction forum and I apologize for not having posted there if that's more appropriate. I'd like to share as much of the process as I can along the way with everyone. So I thought starting here and consolidating here would be best, but I could be wrong. Feel free to tell me I should delete and repost. I don't want to clutter the forums though. Thanks everyone.

Just updating with process. Feels like I'm being annoying since I haven't received responses, but I'm hoping eventually there will be

We're getting a soil test done this week. There's a chance the piling will be necessary but it's quite a variable environment. Fingers crossed there.

Also, costing the main structure is happening this week to get that started. So far, I'm going based off of my plans I've posted here for the main floor assemblies. Building interior rooms will come later.

I'm still a little hesitant about the sort of three leaf assembly in the ceiling. If anything it would be great to get feedback on even just that sole element. Like I mentioned earlier, I'm kind of referencing test cases at: http://www.kineticsnoise.com/arch/tests/concrete.html I know they don't show a lot of specific data. But the IIC impact and other factors seem to not negatively impact the STC qualities of the assembly. I apologize for my willingly naive thinking on this one.

Hi there "emkays", add WELCOME!!! I'm really not sure how I missed your thread for so long, but "better late than never", as they say...

While at the same time hopefully being able to contribute to this forum with my lessons and detailed story (as it unfolds).

Definitely! Build threads are the greatest asset of the forum, if you ask me...

- height is from concrete foundation floor to the bottom of the concrete floor above

15 feet of height! You luck, lucky fellow. This can be a GREAT studio, with those dimensions. Not just good, but great.

- acoustic treatment features, electrical, HVAC distribution are not indicated here at all. Though I do have a set of drawings/plans in place that I’d love to share. Most of that takes place behind the interior false-wall and false-ceiling framing.

"False wall"? "False ceiling"? Now you have me intrigued... I'll keep on reading to find out what is "false" about them, before I comment...

- I’m relying heavily on the isolation properties of the outer concrete leaf and the earth damping to both reduce transmission to the exterior but also to hopefully reduce flanking to the room above.

That's great, yes, but you only have one leaf there so far, even if it is well damped. I'm hoping that I'll soon be reading about the second leaf that isn't "false"...

Level of Isolation:
- ideal levels in the residential environment would be a low of around 35dbA. Though slightly more than that is likely still adequate.
- typical listening levels in the studio are 85-95dbA measured at listening position (I try), and sustained peak recording levels may be around 110dbA. More common will be around 100dbA.

You need to re-do your measurements: You did them with "A" weighting, which is no use for talking about studios. "A" weighting does not consider low frequencies at all. Use only "C" weighting for all your measurements. So please repeat your measurements with your meter set to "C" and "slow".

but I would say that I currently have $40k to dedicate to solutions specific to solving problems related to the studio.

That is probably a reasonable estimate, considering that most of the cost will actually be included in the cost of building the house itself. But like all estimates for studios, do build in a large "fudge factor" there, as there's always something unexpected that you need to take care of along the way...

- I would like to avoid building a floating concrete floor in the basement and hope that earth damping of the foundation goes a good way towards that desire

Correct. You do not need to do that. It would be a waste of time, money, and headroom.

- please ignore the elevator shaft transmission at the moment.

The shaft itself probably won't be an issue, but "elevator" conjures thoughts of large electric motors, drums, pulleys, gearboxes, and mechanical things that will be firmly attached to the building structure, and therefore potential sources of flanking noise that will be hard to get rid of...

- the interior false-wall framing

I'm still intrigued about those "false walls"...

- I’m hoping that flooring could potentially be improved upon

Plain old ordinary laminate flooring on a good acoustic underlay is an excellent floor for a studio. And you are correct: the inner-leaf walls are not built on it, and in fact do not even touch it: there's a slight gap between the edge of the flooring and the actual wall.

- in your experience, what are your opinions of such an assembly regarding isolation to the space above (and given my rough parameters)?

You have the right basic idea: What you are doing is a fully-decoupled two-leaf MSM system, which is indeed the best way to get good isolation at low cost with minimum loss of space.

- please point out my oversights and mistakes

One that I noticed is: lose the "soundlock". You do not need that. You will have a sound-lock on each entry anyway, since you have correctly shown the two-leaf walls. You will have a door in each leaf for each room (two doors, back to back), and that is your sound lock. You don't need more than that, if you build them correctly.

Also, you do have three-leaf walls in some places, but that is unavoidable due to the construction of the house itself. so you'll need to take that into account when you design the actual walls there. It probably wont be an issue.

- is there any significant advantage to decoupling the inner leaf framing assembly where it meets the foundation (under the base plates)?

Not really: You can if you want, but it's hard to do right, costs money, and isn't really needed unless you want extremely high isolation.

if flanking/street noise becomes an issue.

Why do you think street noise might be an issue? Is the street outside very busy? Does it carry heavy traffic, such as trucks and buses? Are there potholes, speed bumps, cracks or other unevenness in the surface that could cause impact noise from the wheels? What is it specifically that has you concerned?

I am weighing the advantage of the decoupled 2” (or more) slab above (which also houses the radiant heating). Any input there is appreciated.

That would help, yes, if done correctly. However, there's a lot of extra cost there, and we still have not figured out how much isolation you need, so it might not be necessary. It would only be needed if want very high levels of isolation.

I'm still a little hesitant about the sort of three leaf assembly in the ceiling. If anything it would be great to get feedback on even just that sole element.

It's not going to degrade your isolation, for two reasons: you have a huge amount of mass in two of those leaves, and the third one is a long way away from the other two. I would not worry about that at all. With two massive concrete slabs, the three-leaf effect will be practically none-existent. I thought you were asking about the need for doing that to get excellent isolation, not that you were worried about 3-leaf effect. Hence the comment above. So don't a sweat it: you will still get good isolation from that, if that's the way you want to build it.

- Stuart -

Hi Stuart,

Your message made my day! Thank you so much for responding. I’ve been hoping for some discussion here for a long time since I’ve learned so much from this forum already. And more since I posted the original message. I just wanted to address your notes.

- dbA measurements: Yikes. What an embarrassing oversight. Sorry about that. It’s a whole mess of values there really that I transcribed from my measurement spreadsheets in all sorts of wrong ways. I’ve corrected the post while at the same time updating them. It seems most of my measurements were dbC but some weren’t or were from something different while writing that post. It seems a minimum isolation of around 60db would be great.

- False Wall: judging by your notes, I think that became clear as you progressed through my long post. It’s mostly just referring to the cosmetic framing and the framing for the interior fabric surfaces (behind which things like trapping which will occur).This is completely loosely indicated and I didn’t mean to cause confusion. It should have very little impact on the isolation aspects (especially low frequency) since the surfaces will have nearly no mass and be very porous. Ideally doing it this way also minimizes penetrations of the the isolation envelope and perhaps some degree of flanking. I am working on more detailed acoustic details, but wanted to make sure my isolation shell was heading in the right direction first before getting into that.

- Elevator shaft: Indeed. Lots of scary things there I’m trying to leave all the mechanical aspects as decoupled from the studio walls as possible. There will always be flanking of course. But I’m taking care to, for instance, not attach the track hardware to common walls, etc. The wall surrounding is completely decoupled from the inside walls of the shaft. All mechanicals are also completely outside of either spaces. And lastly, as for noise when in use, it will never be used during critical times.

- Sound lock: Absolutely. This is not necessary at all. I had another design variation in mind that would aid in the reducing the propagation of sound up the stairwell. But the two standard doors should absolutely be adequate.

- 3 leaf walls: Yes. I’m trying to minimize that wherever possible but some structural aspects get in the way as you’ve noted.

- Street noise: since you asked, the only reason I mention it is that the neighbourhood is built on low quality fill from when the city was expanded many years ago. So there’s a slightly lower dampening effect (and movement) of the earth than you would expect. I only know this since I’ve been living and working here for my whole life essentially. I’m no longer worried about this for two reasons: 1-we are building so deep that the house will now rest on much more solid ground (as soil testing has shown recently) 2-the neighbourhood does not see a lot of this kind of heavy-load traffic and It’s just too small of an issue to outweigh the financial implications. The good news that came out of all of this though is that we don’t need the expensive Piling we were so afraid for the last year and a half!

- The crazy floor assembly above the studio: glad to hear you speak of it this way. This is the one area where I’m still balancing cost vs isolation implications. It may not be necessary to do the 2” concrete floor above the 6”. Instead perhaps going for a single 8” slab for instance. It was inspired by test data like: http://www.kineticsnoise.com/arch/tests/concrete.html which implied substantial improvements that tested beyond what would be expected and calculated from the mass increase alone. It’s pretty terrible observational pseudo science on my part there since there aren’t really any direct comparisons. Just wanted to be honest about what I’m finding

Thanks again for the response and thoughts. In addition to tuning this, I’m currently working on the HVAC situation which is turning out to be a bigger (but still fascinating) challenge than expected. Too many big holes in my nice walls/ceilings with my current approach. Trying a bunch of others.

Forgive me if I skipped something or misunderstood a comment.

Marc

Hey Marc, glad you are still around! With a thread that hadn't seen any action in a month, I wouldn't blame you at all if you had already left us and moved on...

Your message made my day!

we aim to please!

It seems a minimum isolation of around 60db would be great.

With your proposed techniques and materials, that is certainly feasible. That's getting close to what can be accomplished in a home studio without incurring large costs and complexity, but it's do-able.

- False Wall: judging by your notes, I think that became clear as you progressed through my long post. It’s mostly just referring to the cosmetic framing and the framing for the interior fabric surfaces (behind which things like trapping which will occur).

Ahhh!!!! They mystery is solved! I sort of thought that's what it was. In reality, you don't need that. It is possible to design the walls themselves to have most of the treatment incorporated into them, if you follow the "inside out" design concept. That sort of flips around your inner-leaf, so the drywall faces the cavity and the studs face the room. That gives you the stud bays to use for treatment.

I have designed quite a few rooms like that, and it works very well, if you do it right. As far as I know, John himself invented this way of doing walls, and it's a really good idea. It does make the inner leaf walls a bit harder to build, as they have to be built flat on the ground then raised into place, and they are heavy, but it isn't that complex. Two studios that I designed this way have recently been completed, one in Australia and one in the USA. The walls were raised by just one man working alone in the USA studio, and two men in the Australian one, in both cases using a system of winches. It works, it isn't as hard as it sounds, and the benefits are good.

As compared to building a "false wall", you'd save a lot of space and money by doing it "inside out" instead, since you are pretty much combining the two into just one.

Also, if you have a false wall that is basically fabric over a frame, you need to protect the fabric from people with some form of slats, or you end up with bumps, depressions, marks and tears in the fabric. You still need that on an inside-out wall, but it easier to do, and can be made part of the acoustic treatment itself, in the sens4e that the slats will be an active part of the acoustics, not just decorative wall guards...

Ideally doing it this way also minimizes penetrations of the the isolation envelope and perhaps some degree of flanking.

Not really. Even if you do a conventional wall (not "inside out"), you can still safely attach treatment to the wall. There is no problem with putting nails or screws through the drywall into the studs to support a treatment device. That is no different at all from putting in the nails or screws that hold the drywall itself in place. Since they go into the studs, there is not really any penetration, and no harm done to the isolation.

- 3 leaf walls: Yes. I’m trying to minimize that wherever possible but some structural aspects get in the way as you’ve noted.

It's not a big issue, in your case. As long as you keep the air gaps a bit larger, and double-check the math on your 3-leaf calculations to make sure you have the right resonant frequencies and sufficient isolation, you'll be fine.

This is the one area where I’m still balancing cost vs isolation implications. It may not be necessary to do the 2” concrete floor above the 6”. Instead perhaps going for a single 8” slab for instance.

Either way will work. An 8" slab has way plenty mass to keep you well isolated, provided that it is well sealed to the rest of the outer leaf. You'd be getting about 53 dB isolation just from that alone, purely with mass law, so adding in the second leaf and making it MSM, you'd have no problems hitting 60. Theoretically, according to a spreadsheet I've been working on for the last couple of years, you'd get 69 dB of isolation, and the system would isolate down to 22Hz, at least. You can't hope for better than that in a home studio!

Going the other way: 2" + 6" plus drywall, three-leaf: theoretically 65 dB, down to 27 Hz.

Either way, that's more than fine.

My spreadsheet is a "work in progress", and not all that accurate yet, but the basic answer both ways, either 2-leaf or 3-leaf is: that's one hell of a good isolation system!

So your decision on which way to go does not need to take into account the isolation. It only needs to consider whatever other factors you have in mind. Isolation is not a factor at all.

which implied substantial improvements that tested beyond what would be expected and calculated from the mass increase alone.

That's because it isn't just mass alone! For any two-leaf or three-leaf system, the MSM resonance becomes a major factor in the isolation. The actual isolation for a single-leaf wall goes up as mass law says, 6 dB per mass doubling. For a 2-leaf wall, it goes up 12 dB per mass doubling (at least between MSM resonance and the coincidence dip), and for a 3-leaf it goes up 18 dB per mass doubling, but you have to take into account both resonant frequencies there (f+ and f-) instead of just one, so the point where the greater increase takes over is way higher. So that's what you are seeing in those results. The increased isolation is due to the MSM system.

Also, that table shows mostly STC and IIC ratings, which are massively simplified attempts to apply a single number rating to a very complex system. STC, for example, is pretty useless for talking about studio isolation, since it does not consider the bottom two and a half octaves of the spectrum, and neither does it consider the top two and a half octaves! It's fine if you want to talk about isolation of typical office, shop or school noises, but terrible for talking about full-range music. I can build you two walls, one rated at STC-50 that does a lousy job of isolating music, and the other rated a STC-40 that does a much better job...

You can pretty much ignore STC, and only look at actual TL curves, for studio isolation. Especially if you need lots of low-end isolation, such as for thumping deep dance music, with major drums and bass lines.

I’m currently working on the HVAC situation which is turning out to be a bigger (but still fascinating) challenge than expected.

Oh yeah, and then some! Most people don't realize just how complex HVAC is. I often spend as much time designing the HVAC system for a studio as I do on designing all the rest of the entire building, acoustics included! It's a big thing...




- Stuart -

Thanks again for the reply Stuart. I excitedly read it as soon as you posted it. I apologize for the slow response on my part. There have been some delays and setbacks…as is the case with construction. But I just wanted to come back and say that things are on track and I’ll be updating this thread (and likely seeking more much appreciated advice). The issue was that we found our soil is quite terrible….though by some stroke of luck, going that depth alleviated some scary potential piling scenario. Still, our budget increased more than we ever thought but things are now moving forward again. Hurray!

I appreciate your notes too. And here I thought I was being clever and innovative by thinking of inside-out wall assemblies as a solution Fun to know that at least with my newbie inexperience I know my thinking is on the right path with people like yourself and John that are so far ahead of me. I’ve been building my own set of calculation spreadsheets too…though likely with many more errors than I can see yet. Bringing me closer to making sure I’m basing decisions on my best understanding of the science.

The newest major change is necessitating a move to precast concrete instead of slabs. Unfortunately this is lighter mass material so we’re going thicker (with a 2” concrete topper) to maintain around the 450kg/m2 mass that the original 6” poured slab was going to be. I might also simplify the original damped 2” concrete layer above the main slab and just go with a 4” topper right against the precast and leave it at that. Just doing the math to see where these options end up…while making sure the process of building is quick and cost effective. Particularly regarding resonant frequency and trying to drive that somewhere effective…or at least making sure it’s not somewhere unfortunate.

On the cooling front, we might have a chance to investigate helping that along with some radiant cooling (and perhaps even combining that with geothermal). Would be nice to lighten the load on forced air in order to drive duct sizes down.

In any case, thanks for your thoughts. Looking forward to being back here now that the cloud of fear on the soil has lifted. Moving ahead full force now!

Marc

I’ve been building my own set of calculation spreadsheets too…though likely with many more errors than I can see yet.

Great! Are you using the correct and complete versions of the MSM equations in there? And also the full Mass law equation, as well as the empirical one?

move to precast concrete instead of slabs. Unfortunately this is lighter mass material

Why? Concrete is concrete, unless it has some special weight-saving additives, or is aerated. But it would be unusual to use light-weight concrete for pre-cast structural slabs: What density was the old one going to be, and what density is the one going to be?

the 450kg/m2 mass that the original 6”

What type of concrete were you going to use for that?! To have a mass of 450 kg in 6" implies a density of over 3,000kg/m3. Why do you need concrete that dense? That's over 30% greater in density than normal concrete... That's getting into the realm of the type of concrete that is used to shield nuclear reactors... Why did you need it so dense? It must cost a fortune.... those high-mass aggregates are pretty expensive... I mean, I know you had some concerns with soil type, but that normally just implies larger footings, unless there is some type of gross instability... and even then, why would higher density concrete be necessary? I'm a bit confused.... Is that what your structural engineer said? That you would need ultra-high density concrete because of the soil issues?

Just doing the math to see where these options end up…while making sure the process of building is quick and cost effective.

Generally, pouring a simple monolithic slab-on-grade foundation and slab is the fastest, simplest, least expensive method. It also provides excellent isolation. It's very unlikely that you'd need more isolation than that.

Particularly regarding resonant frequency and trying to drive that somewhere effective…or at least making sure it’s not somewhere unfortunate.

For a slab-on-grade, you don't need to worry about that at all, since the damping is more than sufficient to take the coincidence dip of the concrete out of the equation completely.

Would be nice to lighten the load on forced air in order to drive duct sizes down.

You seem to be missing the point: you CANNOT decrease your duct sizes. For studios, duct sizes have no relationship at all to cooling needs. They are related only to ventilation needs, air velocity, and flow rates. You have to move enough air to meet the regulations, and you have to move it at a slow enough speed so as to not cause any air noise from the ducts or registers, and no turbulent flow in the ducts. So it does not matter how efficient your cooling or heating system is, there is till a minimum duct size that you cannot reduce, which is related only to the room volume, the RCPH figure, and the magic number of 300 FPS. You cannot go faster than that at the register, and preferably should keep it down to half of that. Any higher, and you'll be way high on the NR (or NC) curve, and the studio won't be usable as a studio.

we might have a chance to investigate helping that along with some radiant cooling (and perhaps even combining that with geothermal).

It does not really matter at all how you get rid of the waste heat on the outside of the building. What's important for the studio is that the AHU for actual internal HVAC system is the correct capacity, and has the ability to correctly handle the heating and cooling and dehumidification of the studio rooms. So sure, you could use any system you want on the outside, as long as it is compatible with the AGU and interior ducting system.

- Stuart -

Hi Stuart,

I think I may mistakenly been unclear and that’s causing confusion. The concrete I’m referring to is for the first floor (ceiling above the studio), not that on grade. Which is why we’re going with precast. When I say precast, I’m referring to the more typical hollow core variety. Drastically less expensive proposition for the first floor given the parameters of the space/building. Which also addresses why I’m calculating resonant frequencies and concerning myself with related things that seem strange given the misunderstanding. Indeed, that would be unnecessary for the slab on grade in my scenario Nothing to do with the soil either. Purely an economic labour consideration. Sorry for not being more clear about which concrete I was referring to. I think that should make some of the other comments a bit more logical.

And indeed, I seem to have made a mistake transcribing my table of thickness vs mass in my post. Another embarrassing oversight on the forum. I pulled the mass from the 8” column. I should have gone back to my actual calculation sheet when posting. We’re definitely not building a bunker…though the neighbours may think otherwise Definitely more standard density concrete ~ 2,200 kg/m3.

Regarding HVAC duct sizes: My early estimates point that I’m well above the minimum required for ventilation. And yes, I’m trying to get to the ideal 300FPM (I think that's what you were referring to by FPS if I'm not mistaken). That would be an amazing spec to get close to! These minimum ventilation requirements don’t seem to be too difficult to achieve. With substantial, but not crazy duct sizes. I definitely understand that I cannot suffocate people by driving this down The tricky part seems to come down to the numbers I’m getting beyond that in order to remove both the maximum potential sensible and latent heat loads (especially in the larger room). I could also be mistakenly grossly overestimating this load. That seems to be what’s driving the duct size into larger numbers beyond what’s necessary for ventilation. Other than the energy saving aspects of radiant, that’s the only reason I’m mentioning the Radiant cooling. To drive down the sensible load. Then the forced air system can provide ventilation and remove the latent load as well. I absolutely understand this has nothing to do with ventilation and that there is definitely a minimum requirement there regardless of temperature or humidity. At this point, I’m merely curious about this aspect. I haven’t investigated this to the point that I’m making a decision on it. There is definitely someone on board to handle the design of this system. It’s an interesting learning point for me though.

Once again, thanks for the discussion. Truly helpful to talk out loud. And I apologize for the confusing post that lead to all sorts of well-warranted questions on your end.

Once again, it seems there's a misunderstanding here: You can't remove the latent heat from your room air with one system, and the sensible heat with another system. At least, you can't do it separately in a reasonable manner! They are two interconnected, inter-joined, interleaved aspects of the air in your room, and your one single AHU unit will do both. It both cools and dehumidifies at the same time. Cooling is related to the sensible heat load, dehumidifying is related to the latent heat load, but they are both accomplished by the same single evaporator coil inside your AHU, and they both happen at once, intertwined. As the warm moist air passes over the coil, it gives up some of the heat that it contained (because the coil is cold), and that heat is removed by the refrigerant gas inside the coil, and because the air is cooled, it is forced to gives up some of the water vapor that it was "holding", which condenses out on the outside of the coil as water droplets, that is removed by a drain pipe that leads outside somewhere. Both of those actions take place at the surface of the coil, for one single reason: it is cold. It is not two individual things that the AHU is doing, just one: The cold coils cause both condensation and cooling of the air, which are related in complex ways. The simple action of cooling the air is what causes the air to release the water vapor. They happen together not separately.

So I'm not sure what you are intending to do when you say: "That’s the only reason I’m mentioning the Radiant cooling. To drive down the sensible load. Then the forced air system can provide ventilation and remove the latent load as well.". It simply does not work like that. The ventilation system does not "remove the latent heat load" in any shape or form. All it does is to move air. the ventilation system does not heat the air, it does not cool the air, it does not add humidity to the air, and it does not remove humidity from the air: it just moves the air. It is the coils inside the AHU that do the heating (or cooling, as needed) and remove excess humidity.

What the ventilation system does is to suck air out of the room, pass it through the AHU then push that air back into the room again. It should also exhaust some of the stale air to the outside world, and add some fresh air form the outside world. But the ventilation system itself does not remove "latent heat load". That's what the AHU does: it heats/cools/dehumidifies the air passing through it. If you wanted to improve efficiency, you could also include an HRV or ERV in the ventilation duct system.

But the ventilation system itself is just a fan and a set of ducts. It has no way of removing or adding heat or humidity. That's the job of the AHU, and/or the HRV/ERV.

The concrete I’m referring to is for the first floor (ceiling above the studio), not that on grade.

Ahh! Ok, that makes sense. Now I get it.

Which also addresses why I’m calculating resonant frequencies

it's not the resonance of the concrete you need to worry about: it's the resonance of the entire MSM system. What matters here is to keep the surface density of each of the two leaves high enough, and the air gap large enough, and the damping effective enough, to keep the MSM resonance at least an octave lower than the lowest frequency you need to isolate. The MSM resonance is not related in any way to the resonant frequency of the concrete itself. That will affect the coincidence dip, yes, but since you'll already be getting pretty good isolation up there in that part of the spectrum, it's not going to be an issue.

I’m trying to get to the ideal 300FPM (I think that's what you were referring to by FPS

Yup! FPM. Correct. That's what I get for trying to think in metric and imperial at the same time... confusing myself!

- Stuart -

There definitely seems to be something I’m missing regarding HVAC. Sorry for posting premature initial thoughts, but it’s too late to turn back now Here’s where my thoughts are (and these are just really sample numbers at the moment to establish where my misunderstanding is):

Ventilation requirements
Total CFM (roughly estimated at 15CFM per person at maximum occupancy): ~100
Desired Velocity (fpm): 300
Required square duct size: 7”

Cooling requirements
Estimated load: 12,000 BTU
Based on a nominal airflow at the cooling coil of ~400CFM/ton
Total CFM: 400
Desired Velocity (fpm): 300
Required square duct size: 14”

So where my thinking was coming from was that if the radiant cooling system could (for example) remove 9,000BTU that it would mean I could run a less powerful air cooling system as part of the AHU. This example system would only need to remove 3,000 BTU. Which in return would be less demanding in terms of nominal airflow and the resulting duct size to enable that. Additionally, since the radiant system can’t remove latent loads the forced air system serves that purpose as well (which is all I was poorly trying to say with all my yammering there). So in this example, I would get away with leaning towards smaller ductwork (than the 14” minimum required by the more powerful air cooling spec). While still being large enough to adequately deliver the desired volume of fresh air and running through the lighter duty cooling of the AHU.

I also understand that I’m not factoring in many other things/loads, such as the loads of the fresh air itself, the fact that these are tight minimums, delivery system/branching, etc. I’m still trying to get the basics and build on them. In truth, I’m clearly still far from understanding this aspect and probably shouldn’t have gone into it yet publicly. I will come back once I’ve wrapped my head around this aspect a bit further.

I hope that makes sense.

At the moment, I just wanted to gauge feedback on the isolation aspect on the assembly above the studio space which has been very helpful and positive. Hugely appreciated! And yes, definitely trying to calculate the resonance of the whole MSM system. Fun playing around with materials/numbers now that it feels like these are going to be real things

Marc

Ventilation requirements
Total CFM (roughly estimated at 15CFM per person at maximum occupancy): ~100
Desired Velocity (fpm): 300
Required square duct size: 7”

You are looking at only one part of the issue, and not considering the big picture.

Take a look here: http://www.engineeringtoolbox.com/air-c ... d_867.html

According to that (which agrees with ASHRAE specs), you need an absolute minimum of 4 room changes per hour (air changes per hour), and probably more like 6 to 8. I normally use 6 as a starting point.

From your first post: " Control room dimensions are: 20’ x 16’8” x 15’ - Live room dimensions are (an angled room): 51’5” (to 41’3”) x 20’4 x 15’"
Therefore, the volume of your control room is roughly 5,100 cubic feet, and you will need to move 5100 ft3 x 6 per hour = 30,600 CFH of air through it, which is 510 CFM.

For the live room: your volume is 15,500 ft3, + 6 per hour = 92,700 CFH = 1,545 CFM.

So your total air exchange rate is roughly 2,000 CFM.

So your estimate of 400 CFM is off by a large margin. 400 CFM is about what you'd use for a typical kitchen in a house, or a couple of small bathroom.

You seem to be confusing your total HVAC requirements, with your make-up air requirements: http://www.engineeringtoolbox.com/venti ... d_115.html

But even then you are short. taking the minimum rate of 10 l/s per person, in one minute that person needs about 600 l. 600 l of air is about 22 cubic feet (roughly, assuming typical atmospheric conditions). So assuming the occupancy of your control room is five people, you'd need about 110 CFM of make-up air (fresh air coming in from outdoors). In other words, a bit more than 20% of your entire air flow volume for the control room (510 CFM) would need to be fresh air coming in. And obviously, you'd need to exhaust the same volume of stale air overboard (to the outdoors).

For the live room, assuming maximum occupancy of 15 people, you'd need 15x22=330 CFM of make-up air, which is also a bit more than 20% of the total air flow volume (1,545 CFM)

Therefore, you should be dimensioning your HVAC system to be able to move a total of around 2,000 CFM through the AHU, of which about 450 needs to be fresh air coming from outside (and also dumping 450 of stale air). That would cover the "worst case" scenario of having 5 people in the CR and 15 in the LR. Obviously, the control system would close down the fresh air intake (and stale air exhaust) dampers when there are fewer people in the rooms, to account for the reduced need for fresh air. It could also slow down the total air-flow rate if nobody is in there (of course, it cannot stop the air flow entirely, since this is a studio, and the temp/humidity must be held constant in the live room at all times, even when nobody is in there).

So, assuming 2,000 CFM, and max velocity at the registers of 200 fpm (instead of 300, to make the math easy), you need a total of 10 square feet of open area for your registers: 7.5ft2 in your LR, and 2.5 ft2 in your CR. That's about 1,100 in2 in the LR, and 360 in the CR. You'd need a couple of 6" x 30" (or maybe 12"x16") supply registers in the CR, with at the same for the return registers, and for the LR you'd need three times as many (in other words, six registers of 6x30, or 12x16, or something similar). You could have a larger number of smaller registers if you wanted, but that would be the minimum.

So the internal cross sectional area (open area) of your silencer boxes would need to be the same as that of the registers: about 180in2 for each final duct. The ducts that you use to connect the silencer boxes to the AHU, HRV, etc. could be whatever fits, within reason. If you used 12" ducts on the LR boxes, for example (450in2), then the air flow velocity in those ducts would be fine. A bit bigger would be better. You could use 8" ducts for the CR boxes. You wouldn't want to go smaller than that, as the static pressure would be too high.

So that's the VENTILATION part of the equation: the amount of air that you need to move through each room to meet ASHRAE recommendations (which are actual building code regulations in many places), as well as the amount of make-up air that you need to inject/exhaust, also to meet spec.

So now you know that you need an AHU capable of moving a total of 2,000 CFM, for ventilation, and if your total duct length is about 100 feet, it would need to be able to do that into a static pressure of about .75".

Now for the cooling (which is only indirectly related to the ventilation):

Cooling requirements: Estimated load: 12,000 BTU

Ummmm... Nope! Not sure where you got that number from, but 12,000 BTU/h is tiny! That would only just deal with the heat put out by your room occupants (assuming maximum occupancy of 15 in the LR and 5 in the CR), without even considering the equipment in the Cr, the equipment and instruments in the LR, the lighting, and anything else that produces heat or humidity. I have no idea what equipment you plan on using, nor what type of recording you'd be doing, what gear you'd have in the LR, what lighting you0d be using, whether or not you allow eating/drinking in the rooms, or any other factor that affects HVAC, but at a very rough estimate based on experience, I would assume about 18,000 BTU/h for the CR and 48,000 BTU/h for the LR, at the very least. So I would be dimensioning the AHU for at least 5 tons, and probably more like 6. I'm not even calculating the latent heat vs. sensible heat issue here, but assuming general rules of thumb, I would not go smaller than 6 tons on the AHU.

So for a facility like yours, if I were designing it, I'd spec an AHU of 6 tons, capable of moving 2000 CFM into a static pressure of 0.8, and an HRV (or ERV) capable of handling about 500 CFM, to recover the energy that would otherwise be lost to the outside world. I would also spec silencer boxes with in interior cross section of at least 1000 in2 for the LR and 350 in2 for the CR, at the registers. And I would spec branch ducts for the LR of at least 12" (maybe 14), and for the CR, it would be 8" min. (or maybe 10"), or the equivalent area if it is done with rectangular duct. I would also spec that all ducts and silencers shall be lined internally with 1" duct liner.

Finally, I would also specify an insertion loss figure for those boxes that is roughly the same as the isolation that you are wanting for the entire facility, which I assume is somewhere north of 40 dB.

But that's just me: others might calculate things differently...


- Stuart -

Thank you. You are absolutely right that I’m confusing "Air changes per hour of outdoor air" with "Air changes per hour supplied to room"! This has been the source of confusion on my part from the very start. I misunderstood this relationship and didn’t keep them separate. That clears up so much of this and immediately makes everything work out much more clearly and as expected!!! Quite embarrassing in hindsight, but thank you so much for pointing out my mistake.

I still don’t quite understand how they come to the overall system ACH values in those tables and why they are what they are (which I think is what led to my own confusion). Especially relating to airtightness, envelope efficiency, etc. I will research this further on my own before bugging you with it again. I already found a post by Mr. Gervais that is helping me understand that particular concept/approach here: http://forum.studiotips.com/viewtopic.php?t=2948

For now, it’s probably best that I just accept the suggested values though: Also, it seems the sources for a few things I was referencing are significantly lower than yours (even things like Wattage per person, etc.). I’ll be updating those with more reliable and verified sources.

Even just playing with the numbers now, things are adding up in a much more logical way. My prior BTU estimate was definitely incomplete and only representative of part of space/equipment/average occupancy. Didn’t mean that to cause confusion at this stage. I’ll post the more complete process at some point once I work through this properly and feel more confident about it. I’m still not quite coming up to 4 tonnes for the live room, but everything is closer and seems much more realistic now.

Thanks again Stuart. You made the clarity bell go off! Now I can finally explore further and that’s amazing!