Hi guys,
I'm renovating a lower budget studio in Central Coast California, and wanted to get some air flowing into our live room. My plan was to use some kind of blower mounted outside the mix space (which is less noise critical), then ducted in with an 8" or so circular duct. I was then going to put a vent with silencer boxes in between the room between the live room and mix room (see attached drawings), and finally, an exhaust vent in the ceiling of the live room. My thinking is that the blower would positively pressurize the mix room, which would then push air into the live room, which would in turn push some of the stale air out of the ceiling. Tell me, gents, how far off the mark am I? Oh, by the way, the ceilings are 10' high and currently have double drywall with green glue in the live room and nothing more than pink stuff and 8mil canvas in the mix room (we're not concerned about outside sound getting in the mix room).
Low Cost HVAC in Mild Climate
Originally posted at johnlsayers.com, topic 19667.
You idea will work . How many air changes per hour do you need in you rooms? How many CFM are your fans? Depending on your needs 8" could be just right not enough or overkill.Hi guys, I'm renovating a lower budget studio in Central Coast California, and wanted to get some air flowing into our live room. My plan was to use some kind of blower mounted outside the mix space (which is less noise critical), then ducted in with an 8" or so circular duct.
That will work also. The air will flow from room to room, But I would change the location of the vents so you get air flow across the whole room.I was then going to put a vent with silencer boxes in between the room between the live room and mix room (see attached drawings), and finally, an exhaust vent in the ceiling of the live room. My thinking is that the blower would positively pressurize the mix room, which would then push air into the live room, which would in turn push some of the stale air out of the ceiling.
If all you have is pink stuff and 8 mil canvas in your mix room on single frame wall expect outside sound to easily get into your live room through that. Also unless your planning to mix exclusively on headphones, I can't see why you wouldn't care about outside sound you mix room.Tell me, gents, how far off the mark am I? Oh, by the way, the ceilings are 10' high and currently have double drywall with green glue in the live room and nothing more than pink stuff and 8mil canvas in the mix room (we're not concerned about outside sound getting in the mix room).
Hi there Vince, and welcome to the forum! :)
Your idea is basically correct, assuming that the room is well sealed already (which it must be, if it is isolating well). You can, indeed, use a single fan to keep the air flowing, as the pressure differential across the room will do the job nicely.
However, I normally recommend putting the fan on the exhaust duct, rather than the supply duct, for a couple of reasons. One of them is that if you open the door, then the fan will send your air out the door, not out the exhaust duct, if you are forcing air into the studio. On the other hand, if the fan is on the exhaust end, then it will simply suck air in through the open door, but still exhaust it correctly, which is a better situation. Also, having the fan downstream of the air flow tends to reduce fan noise a bit (if you have the fan on the inlet side, then the moving air is bringing fan noise into the room).
Don't forget that you need silencer boxes on BOTH ducts, not just the supply duct! The silencer is not just there to reduce fan noise, but rather to reduce ALL sounds flanking through the ducts. Basically, in order to provide the level of isolation you have right now, your room is a hermetically sealed unit, with solid massive walls around you on all sides. Putting an HVAC duct in means that you have to chop a huge hole in the isolation wall, thus negating your isolation! The purpose of the silencer box is to replace that hole with a system that keeps the sound isolated still, but also allows the air to move through. So you need one of those on each duct, but supply and exhaust (or "return", depending on how your system is set up).
There's another issue with your plan that you'll need to fix: most building codes do not allow you to exhaust the stale air from one habitable room into another habitable room, so you cannot have the exhaust vent from the live room leading into the control room. That won't pass inspection, and isn't a good plan even if it did: the odors from the musicians and their warm, stale air will end up in the CR! Not a pleasant thought... :) So you'll have to have two sets of independent ducts, one set for each room. You'll need four silencer boxes: one for the inlet to the LR, number 2 for the LR exhaust, number 3 for the inlet to the CR, and number 4 for the CR exhaust. The ducts can run in the MSM air gaps between the rooms, or above the ceilings, and the silencer boxes can probably be disguised as some type of treatment or structure.
Perhaps not right now, but you will be, once you knock a pair of eight inch holes in your walls! :shock: Those will let in truck loads of unwanted sound... One more point: Are you certain that 8" is the correct size? There's a bit of math you need to do here, to make sure: There are recommendations for the flow volume (cubic feet per minute) and flow velocity (feet per minute) for each room, which you calculate based on the room volume, occupancy and usage. You need to keep the velocity at the registers under 300 FPM, maximum, and preferably 100 FPM, so you have to check that 8" ducts will do that for you. You also need to calculate the static pressure of the entire duct system (including silencers) and select the correct fan that can move the right volume of air when loaded with that specific static pressure. And if you plan to use flex duct, instead of lined rigid duct, then you need to increase the diameter even more, since flex duct sags and kinks so easily that it will rob you of a large amount of flow. Finally, you should also realize that, while this vent system is very necessary and highly recommendable, it is only half the solution that you need. It will neither cool nor dehumidify the air as it flows through the rooms, so it won't make it a whole lot better from that point of view. I'd suggest that you add a small mini-split system to each room, to take care of those issues. That's a very common solution in small studios, and works very well. Once again, you need to do the math to figure out what cooling capacity you need for each unit, because they must be sized correctly: If you get a unit that is too small for the room, it will not cycle on and off correctly, as it will struggle to do the job... it will be on almost full time, wasting power, not achieving the goal, and burning out very early in its life, due to the overload. And if you use a unit that is too big, it will cost you more than you needed to pay, will cycle on just briefly to blast the room with an arctic freeze, then turn off for a long time while the room warms up again, so you'll get "roller coaster" cycles in both temperature and humidity, which is not good for your gear, mics, or musical instruments, and is uncomfortable for the people. So there's some calculations you need to do on both sides of the issue! It would be nice if it were just a matter of chopping holes in the walls, poking any old piece of duct in, then sticking any old fan on one end, but unfortunately it's a bit more complex than that! HVAC is a big subject. - Stuart -we're not concerned about outside sound getting in the mix room
Wow. Thank you so much for the willingness to share your experience and knowledge. Both of your posts have greatly helped me to understand some of the basic concepts involved with studio HVAC.
In response to macmanmatty's comments about exterior noise: We are in a semi-rural environment, far from the street and miles away from any highway, surrounded by trees and parking lots. In short, other than a mockingbird here and there, there really is no external noise to speak of. In it's current state, the room does a good enough job at keeping out everything that would interfere with our mixing. In fact, our lack of consideration for leakage to the outside also allows some unwanted bass to sneak out of the room, which may slightly help reduce our need for bass trapping. The ceiling in our live room is double drywalled with green glue in between and insulated above the ceiling, so as long as our separating wall (between the mix and live room) goes up all the way (to the pitch), we should have pretty decent isolation even with a canvas ceiling. The separating wall is only single stud construction, but is double drywall on one side, and drywall + green glue + mdf on the other, so it's not a terrible barrier.
Once again, thanks for the help. There are a few other major issues that need to get resolved in the build (which I will probably post about on this forum if that's alright with you kind gents), and if we have the budget for it, we will be doing the HVAC last, otherwise we may wait until we can save some money and close the studio for a week to retrofit a system. I don't want to half ass this thing now and regret it later.
Actually, that would make for a pretty poor isolation system! :) Not intuitive, but many things about acoustics are not intuitive at all, the first time you look at them. Isolation is an "all or nothing" situation. You have to isolate the entire room, on all six sides, including all aspects (walls, windows, doors, HVAC and electrical), or you don't get any isolation. I often use the analogy of an aquarium to explain this, since sound behaves a bit like water. If you want to build an aquarium, but think to yourself "I only need to look at them from the front of the tank, so I'll just put glass on that side and leave the others open"... well clearly that won't work at all! You have to close of ALL sides of the tank so that it will hold water. Ditto with sound: you have to isolate all sides of the studio to the same level. So you think about your fish tank again: "OK, so I'll use glass in the front, because its expensive, then I'll use cardboard on the sides and the back, because its cheap"... You can guess how well that will work! :) So you rethink again... "Cardboard isn't so good at holding water in: too thin and not hard enough. Ok! Drywall! Yeah, that's the stuff!" :shock: That ain't gonna work either! Eventually you'll come to the conclusion that the ONLY way to make your fish tank hold water is to use glass on all sides, even though you don't need it on the other sides, simply because that's the only way that works! If you use any other material that isn't just as water tight, heavy, and rigid as glass, then your tank won't hold water. And as soon as he water gets out through a "weak" side of the tank, it will splash out on the floor and spread in ALL directions, not just the direction of the side that leaked. Sound is exactly the same: all sides of your studio need to be isolate to the same level, NOT just the sides where you want to stop sound going out. If you only isolate one or two walls, then sound will simply "flank" around those two, ignoring them as though the weren't even there, and it will "spread out in all directions", not just the direction of the weak isolation. This is especially so for low frequency sounds, such as bass, drums, the low end of electric guitars and keyboards, etc. So the cheapest, easiest and most effective way to do it, is with "room in a room" construction, which basically means that you have the outer building shell where you want to gave your studio, and inside that you build a separate room, or a bunch of separate rooms (as needed), but each of those rooms is a complete five-sides structure that does not couch any of the other rooms, and also does not touch the outer build shell. Not even at one single point. There can be NO mechanical connections at all between the inner room(s) and the outer shell. Not even a single nail. In studio design language, this is referred to as "fully decoupled 2-leaf MSM system". What that means is that there are two "leaves" involved, where a "leaf" is just a bunch of typical building materials, such as plywood, drywall, MDF, OSB or some such that make up a "shell". So the outer shell of the original building is one "leaf", and the actual studio room that sits inside it is the other "leaf". The "MSM" part stands for "Mass-Spring-Mass", since that's the principle of physics that makes this whole thing work. Each "leaf" is a just a bunch of mass (heavy building materials) and the air space between them is the "spring". They create a resonant system, and that is what does the isolating at low cost, and very effectively. However, this only works if the spring is allowed to act as a spring, and that means the the two "mass" leaves cannot touch. If anything at all creates a mechanical path between the two leaves, then it "short circuits" the spring, and there is no isolation. That's the very long-winded explanation regarding why your isolation plan will not be effective. Your ceiling seems to be done correctly: "...double drywalled with green glue in between and insulated above..." (assuming that the drywall is mounted on resilient channel, or on hat channel plus RSIC clips), but your plan for the wall is not: " so as long as our separating wall (between the mix and live room) goes up all the way (to the pitch)". That implies that you want to extend your inner leaf (the wall) all the way up to the outer leaf (the roof). That cannot happen. The inner leaf must not even touch the outer leaf at any point. In technical parlance, extending the inner-leaf wall to the outer-leaf roof creates a "flanking path" that trashes your isolation. What you should do is to extend the inner-leaf wall only as far as that ceiling, and no further. The ceiling and the inner-leaf walls form your "room within a room", which is what gives you good isolation.The ceiling in our live room is double drywalled with green glue in between and insulated above the ceiling, so as long as our separating wall (between the mix and live room) goes up all the way (to the pitch), we should have pretty decent isolation even with a canvas ceiling.
Whoa! Hang on a sec! In one place you say the live room has a canvas ceiling, but in another place you say that it is "... .double drywalled with green glue in between and insulated above..." It can't be both! So which is it?pretty decent isolation even with a canvas ceiling.
Actually, that IS a terrible barrier! It is a fully coupled 2-leaf wall, where each stud creates a massive and very effective flanking path across the gap! Any vibration in the drywall on one side will be easily and efficiently transmitted to the drywall on the other side, making it vibrate too, and thus transferring sound through the wall. In order to actually isolate, all you need to do is to take the drywall off one side, put up resilient channel across the studs (or RSIC clips with hat channel), then put the drywall back again. The resilient channel or the clips effectively decouple the drywall from the studs, isolating it and preventing vibrations from being transmitted. That alone would triple the effective isolation of your wall.The separating wall is only single stud construction, but is double drywall on one side, and drywall + green glue + mdf on the other, so it's not a terrible barrier.
That's what we are here for! :) Feel free to ask away, as much as you want ... - Stuart -There are a few other major issues that need to get resolved in the build (which I will probably post about on this forum if that's alright with you kind gents
Sorry if this wasn't clear before. But yeah two different ceiling types depending on the room. Thanks for the decoupling tip! That makes perfect sense about not going all the way up to the pitch. As far as the dividing wall, we do not have resilient channels (the wall was pre-existing and already had a layer of drywall), but according to these tests (http://www.soundproofingcompany.com/lab ... s-testing/), the wall should be between 50-56 STC rating, and adding resilient channels seemed to only add 1 point to the STC rating (Test OL 05-0825 vs OL 05-0414). Looking at the crappy drawing I made though, I think we may have more issues with sound flanking through the slab + ceiling than anything though. Anyway, I guess this is starting to get somewhat off topic, but I've made two other threads if you get a chance to take a look: viewtopic.php?f=2&t=19666 viewtopic.php?f=1&t=19668the ceilings are 10' high and currently have double drywall with green glue in the live room and nothing more than pink stuff and 8mil canvas in the mix room
OK, so from what I see so far, it is not important at all for you guys to have the live room isolated, but it is important to have the control room isolated? In other words, there are no issues with neighbors close by that might be upset by drums, guitars, or other loud things in the live room, and also there are no loud sound sources close by that could trash your tracking sessions of soft instruments and vocals, such as aircraft / helicopters flying overhead, nearby street traffic, noise from those same neighbors, other sounds in the building such as doors opening/closing, footsteps, people talking, phones ringing, toilets flushing, water running in pipes, that kind of thing. Is that correct? None of that is important? The real important thing for you guys seems to be that the control room is isolated, so that sounds in the live room and outside the building don't disturb the mixing sessions. Is that about right? That's the way it looks from the current design, so I'm just trying to understand what is important for your situation, and what is not important.Sorry if this wasn't clear before. But yeah two different ceiling types depending on the room.
According to these tests (see link below), the issue isn't so clear at all! :) (And these ones were exhaustive, very extensive, impartial, conducted by an independent lab, fully documented in great detail, etc...) http://archive.nrc-cnrc.gc.ca/obj/irc/d ... /ir761.pdf That's sort of the "bible" on 2-leaf MSM walls. Your source also rates isolation in STC, which is useless for studios. STC tells you basically nothing about how well a wall isolates full-spectrum music, because it was never designed to do that. It nly tells you how well the wall isolates voices and typical office/house/school sounds. STC totally ignores the bottom two and half octaves of the spectrum, and also the top two and half octaves. It only considers the mid range. I can build you a wall rated at STC-50 that does a really lousy job of isolating a studio, and I can build you another wall rated at STC-40 that does a far better job at isolating the studio. STC is basically worthless as a measure of music isolation for studios. What you should be looking at is the transmission loss curves for different wall structures, and IR-761 does that for literally hundreds of different types of walls, including resilient channel. But using the COMPLETE data from your same source, the truth emerges. Firstly, there are no tests done there with resilient channel using 5/8" drywall: they were only done with 1/2", so not comparable to the tests done without RC, which did use 5/8". But even so, here are the actual transmission loss graphs for both cases: First, for the wall with no resilient channel but using the thicker, heavier 5/8" drywall: And then the test for the wall that DOES use resilient channel, but the drywall is much thinner, at only 1/2": So based on those two graphs of the REAL isolation offered by each wall, I think it's clear which one is better! :) Even though it has lower mass and thinner drywall.... :shock: Regardless of what the STC ratings say, clearly the wall with RC is superior, by a lot. There's way more than just a couple of dB improvement there. At a rough guess, the RC wall is probably about 10 dB better at isolating full-spectrum sound, despite its major handicap of thinner, lighter construction. If that would have been built with 5/8" drywall, I reckon it would have been at least 5 dB better still. The two tests you were mentioning cannot be compared, since OL 05-0414 uses 24"OC spacing but all the RC tests are 16"OC. So I compared OL 05-0825 vs OL 06-0635, which is the closest match.As far as the dividing wall, we do not have resilient channels (the wall was pre-existing and already had a layer of drywall), but according to these tests (http://www.soundproofingcompany.com/lab ... s-testing/), the wall should be between 50-56 STC rating,
This is on the ground floor, right? Slab on grade? If so, then the slab is not an issue at all. The flanking limit for a good slab on grade is something like 70 dB, so I wouldn't be worried about that. However, if this is on an upper floor, where the slab is over an empty air space below you, another room, basement, crawl space) then all bets are off. But even so, it is the ceiling that is the biggest problem, for sure. Especially in the live room: it basically has just a single-leaf, so the isolation to whatever is above is roughly 20 dB or so. The CR should be a bit better, as that one at least is a coupled two-leaf, so probably about 30 dB or so of isolation. The big question here is: How much isolation do you NEED? (In decibels, not in STC :) ) That's what defines the type of construction... - Stuart -Looking at the crappy drawing I made though, I think we may have more issues with sound flanking through the slab + ceiling than anything though.