Hi Nathan, and Welcome to the fourm!
You certainly have an interesting and complicated situation! But there is hope. It probably can be made very good, depending on what your specific goals are.
there is a fair amount of mechanical pipe through the ceiling, that may be a show stopper,
Not necessarily a show-stopper. You mentioned further on that some of that piping is not used and can be removed, but other parts are required by code, as part of the fire system. How much of a problem that is depends on how much isolation you need. How feasible the solution is, depends on how much you are prepared to spend to get that level of isolation.
If you only need moderate isolation, then this isn't too much of a problem. If you need high isolation then it is more of an issue, and would cost more to deal with. So it's really a trade-off of needs vs. cost.
We have two sound mixing spaces currently,
We tend to call those areas "control rooms", to standardize on terminology. It helps to avoid confusion.
Current recording room has 36dB ambient machine noise (not normal)
How was that measured? There's a big difference between "C" weighting and "A" weighting, and depending on the type of ambient noise, there can also be a big difference between "fast" and "slow" response settings.
Current mixing room has 39dB ambient machine noise, nothing but drop ceiling.
Same applies here: It is important to know if that is 39dBA or 39dBC (or maybe even something else?).
Also, ambient noise levels in studios are more commonly defined in terms of NC curves or NR curves, which tell you something about the noise spectrum as well as its level. 39 dB by itself does not tell you anything about the spectrum, which is just as important as the actual level. There's a big difference in how humans perceive a level 39 dB with most of the sound at around 4kHz, vs. 39 dB with most of the sound around 100 Hz.
Pipes are insulated, but obviously not enough?
Pipe insulation is for thermal purposes, not acoustic. Just putting insulation on a pipe does practically nothing to reduce sound transmission. It's a common misconception that insulation by itself makes a good sound barrier: in reality, it makes a lousy sound barrier. When used as part of an isolation SYSTEM, however, insulation can be very effective. The whole is greater than the sum of its parts.
Building manager tells me we currently have something dysfunctional in the boiler room which is the root cause of the noise,
Did he tell you what that "something" is, and in what way it is "dysfunctional"? That's important to know! It is by far cheaper and easier to solve sound isolation issues at the source, than at the destination. If you can found out what is causing that issue, then we can help you figure out how to deal with it right there, in the boiler room, rather than try to deal with it in the studio isolation plan.
None of the current spaces are serviced by the buildings HVAC
Would it be possible to tie in to the building HVAC system? Does the building HVAC system have the capacity to handle your rooms, in addition to the load it is already carrying? It might be cheaper to connect to that than to implement your own HVAC system. However, if the building system does not run 24/7, then you might need your own anyway: film studios often keep strange hours, well outside normal office hours, and building administrators often shut down HVAC systems at night and over weekends, either partially or completely. So I'd check if you can hook into that system, but also if it will be running at the times you need it!
there are moisture problems in the current sound room
That needs to be solved before you do anything else at all. You need to get an expert in to figure out where that humidity is comping from, and fix it completely, before you can do build the studio. Isolating a studio implies putting up hermetic walls would trap the humidity inside the wall cavities, where it will slowly but surely destroy the walls from the inside, and create numerous very expensive problems for you over time. This should be your number one priority: find the source of that moisture problem, and spend whatever it takes to fix it permanently.
we run a dehumidifier when room is not in use), so I would like to get it hooked up.
Sorry, but that isn't the solution. If you have to run a dehumidifier then the problem is serious, and implementing an HVAC system will not solve it. HVAC only addresses the rooms themselves, but not the cavities in the walls between them. That's where your fungus, mold, rot and other nasty issues will happen: inside the walls, where you will not be aware of them until it is way too late. HVAC is not the solution to humidity problems. HVAC is highly necessary, yes, but it is not the correct way to deal with the issue.
basement is partially below grade.
That might be part of the issue with the moisture: Are the walls or floor damp to the touch? Is there visible water or condensation anywhere? You need to get an expert in to figure out the reason for this problem, and do whatever repairs are needed before doing anything to the studio. Any money you spend building the studio would just be thrown in the trash basically, if the humidity problem is not located and fixed first.
students are using the space to mix sound for their film projects - using a target of between -12 and -6dB.
It looks like you forgot to complete that sentence! "-12 and -6 dB" relative to what? What levels are you referring to there?
004 is the current sound mixing and recording space.
Mixing is approx. 10’8 x 12’ x 7’6 (drop ceiling)
That's VERY small for a control room! And even worse, the ceiling is very low. Specifications from SMPTE Dolby, the AES, ITU and EBU regarding critical listening rooms all suggest a minimum of at least twice that floor area, with a 10 foot ceiling. It would not be easy to use that room for a decent control room.
ADR/Foley Recording is approx. 10’2 x 9’8 x 9’.
That's also VERY small for a Foley stage. Very little room to have a good selection of pits in there. Question: Do you have a water pit in there? That might be part of your humidity problem! If you do have a water pit, then that would need to be taken into consideration in the HVAC plan, since there would be a very large latent heat load issue in there, in addition the sensible heat load. Are your pits sunk into the actual concrete floor, or are they just boxes placed on top?
Isolating a proper Foley stage is a big deal.
Sound is dampened pretty good between the two spaces, but it isn’t completely sound proof. It doesn't necessarily need to
A true "Foley for film" stage
DOES need to be isolated, to a very high level. Foley implies recording very quiet things, then increasing the level hugely to add it it the sound track. Even slight background noises become a thundering roar in the mix, if the room isn't isolated to very high levels. A Foley stage is about the toughest possible thing to isolate. You really need something like NR-15 or lower (roughly the same as NC-15).
003 is the computer lab we’d like to change to a mixing space. Approx 26.5 x 18 x 10.5
That's a MUCH better size for a control room! That would be ideal.
The circle is a structural post, circular metal (iron?).
That's a problem, but not necessarily a big one. It can probably be moved. You'll need a structural engineer to take a look at that, and tell you what needs to be done to move that pole. It can be done: I have done it before, even for home studios. The cost doesn't have to be prohibitive either, but it absolutely must be done with the blessing and guidance of a qualified structural engineer.
004 Mixing space as you enter.
That needs fixing! If you plan to keep that room as a control room, then there are many issues with the current layout that would need to be dealt with, to make it usable.
004 View through ceiling - the people who designed and installed this room didn't think a mixing space needed to have ceiling insulation.
They also didn't think that a control room needs any isolation at all! That open panel shows that there is NO isolation for this room, and no treatment either!
004 Recording booth door view
You said that this is a Foley stage, but I don't see any signs of that in the photo: Where are the pits? Was that photo taken when the room was NOT set up for Foley work? Pits taken out and stored somewhere?
004 Detail of pipe insulation. This is a heating pipe coming from the boiler room.
That's purely thermal insulation. No acoustic isolation at all. Pretty much all noises in that pipe will be heard in the room, and any loud noises generated in the room could also potentially flank through those pipes to other rooms.
Simple plan for construction
I'm trying to mentally correlate that drawing with the previous drawing, but not having much success! The two areas appear to be different shapes and sizes...
Proper double leaf shell for 003.
I don't see that shown on the plan at all. Maybe you could highlight the inner and outer leaf for that room in different colors, to clarify the plan?
diffusion and reflection treatments may be done at a later time if budget doesn’t cover it.
That room is waaaaaay too small to need diffusion or reflective treatment! It will need mostly absorption. Practically all absorption, in fact. I could run the numbers for you to be certain, but at a rough guess you are going to need absorptive treatment on well over 50% of the wall and ceiling surfaces. Diffusion is out of the question for that room: numerically-based diffusers can only be used successfully in rooms that are much larger than that. The lobing artifacts make it untenable for small rooms.
The drop ceiling will be removed in both 003 and 004 mixing and new drywall with isolation treatment will be hung from the original lath ceiling.
Why? I mean, removing the drop ceiling is most certainly necessary, but if there's another ceiling up there already, then adding a new one below it would likely create a 3-leaf system. Not a good idea, if you need isolation for low frequencies.
004 probably needs a new wall between it and 003 - I think it's currently just a regular drywall construction.
This is where I'm confused about your isolation plan. A few paragraphs up you mentioned that 003 will get a proper two-leaf isolation wall, yet here you mention that in addition to that you think 004 will get a new wall! That doesn't make sense. A proper isolation system around 003 automatically implies modifying the wall to 004, which is adjacent! There's no other way of doing it.
if 003 could work as a stereo and 5.1 mixing space, that would be idea
That's possible, yes. If you plan to do 5.1 in there, then the room needs to be designed from the start for 5.1 Trying to retrofit a 2.0 or 2.1 room for 5.1 is not something you want to do, but there's no problem at all in doing 2.0 or 2.1 in a room designed for 5.1, even if the 5.1 systems is not yet installed.
Installing double leaf construction where required
There seems to be a misunderstanding or misconception here, about how double-leaf construction works. You can't just install it where you feel like: if you want to isolate one room properly, using two-leaf isolation, then the entire room needs to be isolated that way: all four walls, and the ceiling, and possible the floor too. That implies taking the point of view of someone standing inside the finished room, and then confirming that there are ONLY two leaves between that person and ALL of the adjacent rooms: Not one leaf, not three leaves, or four, or any other number: there can be two leaves, only two leaves, and nothing but two leaves, in all directions. One of those leaves will be the drywall facing the person inside that room, and the other leaf will be drywall (or brick) facing the person in the adjacent room. Period. End of story. So if you work your way through this mentally, and you count more than two leaves in any direction, then you did something wrong: you don't have an isolation system.
So for example, if we are talking about going upwards from your room to the one above: you have the ceiling in your room, plus the existing ceiling above, plus the floor right above that. That is THREE leaves, so there's a problem right there. Something wrong. And if you were to put a two-leaf wall around 003 plus also a 2-leaf wall around 004, then you would have FOUR leaves between the rooms: that's very wrong. A three leaf system or a 4 leaf system will have a much higher fundamental resonant frequency that than a two leaf system of the same mass and total thickness. Always. And if the resonant frequency is higher, then the low frequency isolation is worse.
Extending current electrical through new walls
That also isn't possible, if you want good isolation between rooms. There can be no holes at all in the leaves the define the rooms. You can allow just one single penetration to bring in the power feed, then all the wiring for the room must be done using surface-mount "trunking" systems. The electrician cannot, under any circumstances, cut holes in the drywall like he normally would to install boxes for outlets, switches, lights, etc. All of those can only be surface mounted.
1. two leaf for each enclosed space?
Yes. That's the only way to get good isolation at low cost. But it isn't done as "two leaves for each room". Rather, it is done such that "between the interior of each room, and the interior of the next room, there are only ever two leaves, in any direction".
2. can the spaces share a two leaf wall?
It's not they the "can" do so. Rather, it is that they HAVE TO do so! There is no alternative, with correct two-leaf construction. So between your control room and your live room, you have drywall on the control room side, drywall on the live room side, and a gap between them. That's it: two leaves. The same applies in all other directions.
3. Is more air space between the two rooms helpful?
Most definitely! The equations for calculating the resonant frequency of a two-leaf system have only three major variables. One of those is the depth of the air cavity. The larger the cavity, then lower the frequency. The other two variables are the mass of each of the leaves, and how much damping (insulation) is in the cavity. Increasing any of those gives you a lower frequency, and better isolation. So more mass, more damping, and more depth are all good things.
Can this be done in phases effectively? (can we build 003 as a decently isolated space and revisit 002 at a later date?
Possibly, but not easily, and not cheaply. Unless you go with your own very next suggestion below...
*Is it cheaper/better to demo the whole thing and start over (keeping our low budget in mind)
Very likely, yes. In the demo, if you do it carefully, you can probably re-use a lot of the materials. Complete demo and re-build would allow you to build all of the walls as proper two-leaf MSM systems without trying to retrofit bits and pieces, and without being restricted by existing walls, doors, windows and other items. You would likely also not need to move that pillar, since you could re-design the rooms so that the pillar ends up inside one of the walls, in the cavity between the leaves. With a full demo, you'd also have good access to all the pipes, electrical and HVAC, as well as to the existing ceiling above, to deal with the issues associated with that. It would also make it a lot easier to figure out where your humidity problem is coming from, and to fix it properly: There are a lot of "pros" to this approach, and very few "cons".
Layout (which items should I be aiming for? I've currently gone with #1 but I'm feeling like that's not the best):
1.Maximum air space
2.Golden Ratio
3.Angled walls
All of the above! And none of the above!
Sorry to be so cryptic, but studio design isn't about choosing one thing over another: it is about looking at all of the issues, getting the "big picture", then designating the best possible layout within that space, with as few compromises as possible. There will be compromises (there always are!), but there is no need to compromise any of the above. You can angle the walls that need it, at the best angles, and still have enough air space inside the walls to get the isolation you need, and also have a good room ratio. Those don't need to be traded off. There might be other trade-offs to get there, but these don't have to be.
Also, there is no such thing as a perfect "golden ratio" for a recording studio. That's a myth. In reality, there are many good ratios (a couple of dozen) that have be figured out be acousticians such as Sepmeyer, Louden, Bolt, Volkman, Bonello, and others. Each has its advantages and disadvantages, and each is suited to some studios better than to others: None of them is perfect, none of them is "golden", and none of them is better than any of the others for all situations. That's part of good studio design: choosing the ratio that makes the most sense for each project. Arguably, one could say that Sepmeyer's best ratio is preferably for most cases, but even then, that would not be accurate.
How much does a HVAC damper help to isolate sound?
Your picture does not show an HVAC damper. This is what HVAC dampers look like:
Damper for round duct:
typical-HVAC-damper-round.jpg
Damper for rectangular duct:
typical-HVAC-damper-rectangular.jpg
Your picture shows an HVAC silencer box, or baffle box, or muffler, but it is built incorrectly: the interior lining should only ever by done with proper duct liner, never with fluffy insulation. Over time the air flow will erode that, and you'll end up with fibers all over your studio...
But to answer your question: A well designed and well built HVAC silencer can isolate sound VERY well. It uses several acoustic principles at once to do so, and the insertion loss can be quite high. However, the rest of the HVAC system needs to be designed in conjunction with the silencer: Even the best silencer in the world won't do much if the rest of the system is lousy: For example, if the flow velocity is too high, then the silencer won't achieve much since all of the noise will come from turbulent flow in the ducts and registers. And if the transition from duct to silencer and back again is not sudden enough, or does not involve a large enough difference in cross-section, then you won't get the necessary impedance mismatch, so you won't get good isolation, even of the silencer itself is well designed. HVAC is a system, and all of it has to be designed correctly.
Is the design pictured below the sort of thing I should be aiming for?
Concept: Yes. Implementation? No. The idea is roughly correct, but that's not the right way to build one.
I wanted to include my sketchup model, but seem to have trouble uploading it directly
There's a limit on the size of files that can be uploaded to the forum, and many SketchUp models are bigger than the limit. So uploading externally then positing a link is the right way to do it.
I'm downloading it now, and I'll take a look. If I see anything additional, I'll add another comment later.
- Stuart -
At least there is a heavy brick structural wall, except of course all the pipes running through it to other parts of the building. 
